31

Res. Rep. Fac. Eng. Mie Univ., Vol. 29, pp. 31-64 (2004)

Original Paper

Phase Change Materials for Low Temperature Solar Thermal
Applications
Someshower Dutt SHARMA†, Hiroaki KITANO and Kazunobu SAGARA†(Dept. of Architecture)(Received September 17, 2004)

Abstract
Latent heat storage in a Phase Change Material (PCM) is very attractive because of its highstorage density with small temperature swing. It has been demonstrated that, for thedevelopment of a latent heat storage system, the choice of the PCM plays an important rolein addition to heat transfer mechanism in the PCM. The information on the latent heatstorage materials and systems is enormous and published widely in the literatures. In thispaper, we make an effort to gather the information from the previous works on PCMs andlatent heat storage systems. The paper contains a list of about 250 PCMs and more than 220
references.
Key words: Phase change material, Solar energy, Latent heat storage system
1. Introduction
Scientists all over the world are in search of new and renewable energy sources. One of the options is todevelop energy storage devices, which are as important as developing new sources of energy. Thermal energy
storage is essential for many processes. Latent heat storage is one of the most attractive because large amounts ofenergy can be stored in a small volume with a small temperature change in the media. Latent heat storage is arelatively new area of study and pioneered by Dr. Telkes in the 1940s [1]. It did not receive much attention
however until the energy crisis of late 1970s and early 1980s where it was extensively researched for use in solar
heating systems [1, 2]. When the energy crisis subsided much less emphasis was put on latent heat storage.
Although research into latent heat storage for solar heating systems continues [3, 4], it is increasingly being
considered for waste heat recovery and load leveling for power generation [5]. Latent heat storage can beaccomplished through solid-liquid, liquid-gas, solid-gas, and solid-solid phase transformations, but the only twoof practical interest are the solid-liquid and solid-solid. The solid-gas and liquid-gas systems are of limited utility
because of the large volumes required for such systems. Of the two practical systems, the solid-liquid system isthe most studied and most commonly commercially available. Solid-solid systems shows much promise, but are
only recently being studied [6]. Many phase change materials (PCMs) have been studied for practical use. This
paper is a compilation of much of practical information on different PCMs and system developed based on latent
heat storage technology.
2.0 Thermal Energy Storage
Thermal energy storage can be stored as a change in internal energy of a material as sensible heat, latent heatand thermo - chemical or combination of these.
In Sensible Heat Storage (SHS), thermal energy is stored by raising the temperature of a solid or liquid. SHS
system utilizes the heat capacity and the change in temperature of the material during the process of charging
and discharging. The amount of stored heat depends on the specific heat of medium, the temperature change andthe amount of storage material.

∫(

Q = mC p dT = mC ap T f − Ti)

† Department of Architectural Engineering, Osaka University, Suita, Osaka 565-0871, Japan

[1]

32

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Latent Heat Storage (LHS) is based on the heat absorption or release when a storage material undergoes a phasechange from solid to liquid or liquid to gas or vice – versa. The storage capacity of the LHS system with a PCM
medium is given by∫m

Q = mam ∆hm + mC p dT +i[f

∫ mC dTmp(= m am ∆hm + Csp (Tm − Ti ) + Clp T f − Tm

)]

[2]

LHS systems have certain benefits in comparison with SHS systems. The most important is the higher
energy density per unit mass and per unit volume.
Thermo chemical systems rely on the energy absorbed and released in breaking and reforming molecularbonds in a completely reversible chemical reaction. In this case, the heat stored depends on the amount ofstorage material, the endothermic heat of reaction, and the extent of conversion.
Q = ar m∆hr

[3]

Amongst above thermal heat storage techniques, latent heat thermal energy storage is particularly attractive
due to its ability to provide high energy storage density and its characteristics to store heat at constanttemperature corresponding to the phase transition temperature of phase change material (PCM). Phase change
may be in the following form: solid – solid, solid – liquid, solid – gas, Liquid – gas.
In solid – solid transitions, heat is stored when the material is transformed from one crystalline to another.
This transition generally has smaller latent heat and volume changes than solid – liquid transitions. Solid–solid
PCMs offer the advantages of less stringent container requirements and greater design flexibility [9]. Most
promising materials are organic solid solution of pentaerythritol, pentaglycerine, Li2SO4 and KHF2 [10]. Trombe
Wall with these materials could provide better performance than a plain concrete Trombe Wall.
Solid - gas and liquid – gas transition through have higher latent heat of phase transition but their large
volume changes on phase transition are associated with the containment problems and rule out their potential
utility in thermal storage systems. Large changes in volume make the system complex and impractical.
Solid – liquid transformations have comparatively smaller latent heat than liquid - gas. However, thesetransformations involve only a small change (of order of 10 percent or less) in volume. Solid- liquid transitions
have proved to be economically attractive for use in thermal energy storage systems. PCMs themselves cannot
be used as heat transfer medium. Heat transfer medium must me employed with heat exchanger in between totransfer energy from the source to the PCM and from PCM to the load. The heat exchanger to be used has to be
designed specially, in view of the low thermal diffusivity of PCMs in general. The volume changes of the PCMs
on melting would also necessitate special volume design of the containers to wholes PCM. It should be able toabsorb these volume changes and should also be compatible with the PCM used. Any latent heat energy storage
system must, therefore, posses at least following three properties: a suitable PCM with its melting point in thedesired temperature range, a suitable heat exchange surface and a suitable container compatible with the PCM.
3.0 Latent Heat Storage Materials
Phase Change Materials (PCM) is latent heat storage material. As the source temperature rises, the chemicalbonds within the PCM break up as the material changes phase from solid to liquid (as is the case for solid-liquid
PCMs which are of particular interest here). The phase change is a heat-seeking (endothermic) process andtherefore, the PCM absorbs heat. Upon storing heat in the storage material, the material begins to melt when thephase change temperature is reached. The temperature then stays constant until the melting process is finished.
The heat stored during the phase change process (melting process) of the material is called latent heat. The effectof latent heat storage has two main advantages: 1. It is possible to store large amounts of heat with only small
temperature changes and therefore to have a high storage density. 2. Because the change of phase at a constanttemperature takes some time to complete, it becomes possible to smooth temperature variations. They store 5 to
14 times more heat per unit volume than sensible storage materials such as water, masonry, or rock [14]. A large
number of PCMs are known to melt with a heat of fusion in any required range. The PCM to be used in thedesign of thermal storage systems should passes desirable thermo physical, kinetics and chemical properties [11,12].

PCMs for Low Temperature Solar Thermal Applications
Thermo physical properties
(i)
(ii)
(iii)
(iv)
(v)
(vi)

Melting temperature in the desired operating temperature range.
High latent heat of fusion per unit volume so that the required volume of the container to store agiven amount of energy is less.
High specific heat to provide for additional significant sensible heat storage.
High thermal conductivity of both solid and liquid phases to assist the charging and discharging ofenergy of the storage systems.
Small volume changes on phase transformation and small vapor pressure at operating temperatures
to reduce the containment problem.
Congruent melting of the phase change material for a constant storage capacity of the material witheach freezing/melting cycle.

Kinetic properties
(i)
(ii)

High nucleation rate to avoid super cooling of the liquid phase.
High rate of crystal growth, so that the system can meet demands of heat recovery from the storage
system.

Chemical properties
(i)
(ii)
(iii)
(iv)
(v)

Chemical stability.
Complete reversible freeze / melt cycle.
No degradation after a large number of freeze / melt cycle.
Non-corrosiveness to the construction materials.
Non-toxic, non-flammable and non-explosive materials for safety.
Moreover, low cost and large-scale availability of the phase change materials is also very important.
3.1 Classification of PCMs

A large number of phase change materials (organic, inorganic and eutectic) are available in any required
temperature range. A classification of PCMs is given in Fig. 1.

Fig.1: Classification of latent heat storage materials
There are a large number of organic and inorganic materials, which can be identified as PCM from the point ofview melting temperature and latent heat of fusion. Organic and inorganic types of PCMs are given in Table 1
and 2 respectively. As no single material can have all the required properties for an ideal thermal storage media,
one has to use the available materials and tries to make up for the poor physical property by an adequate systemdesign. For example metallic fins can be used to increase the thermal conductivity of PCMs, super cooling may
be suppressed by introducing a nucleating agent in the storage material and incongruent melting can be inhibitedby use of suitable thickness. For their very different thermal and chemical behavior, the properties of each subgroup, which affects the design of latent heat thermal energy storage systems using PCMs of that sub group, arediscussed in detail below.

33

34

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Table 1: List of organic PCMs [94 - 98]
Material

Melting point

Latent heat of

O

( C)

fusion (kJ/kg)

N-Tetradeca

5.5

226

Formic Acid

7.8

247

Material

Melting point

Latent heat of

O

( C)

fusion (kJ/kg)

N-Penta Cosane

53.7

164

Myristic Acid

54.0

199

N-Pentadeca

10.0

205

Oxolate54.3

178

Acetic Acid

16.7

273

Tristearin

54.5

191

N-Hexadeca

16.7

237

O-Xylene

55.0

121

Caprilone

40.0

260

β-Chloroacetic

56.0

147

Docasyle

40.0

201

N-Hexacosane

56.3

255

N-Henicosan

40.5

161

Nitro Naphthalene

56.7

103

Phenol41.0120α-Chloroacetic

61.2

130

N-Lauric

43.0

183

N-Octacosane

61.4

134

P-Joluidine

43.3

167

Palmitic Acid

61.8

164

Cynamide

44.0

209

Bees Wax

61.8

177

N-Docosane

44.5

157

Glyolic Acid

63.0

109

N-Tricosane

47.6

130

P-Bromophenol

63.5

86

Hydrocinna

48.0

118

Azobenzene

67.1

121

Cetyl

49.3

141

Acrylic Acid

68.0

115

O-Nitroanili

50.0

93

Dintro70.0111Camphene

50.0

239

Phenylacetic Acid

76.7

102

Diphenyl

52.9

107

Thiosinamine

77.0

140

Toluene3.11 Paraffins
The normal paraffins of type CnH2n+2 are a family of saturated hydrocarbons with very similar properties.
Paraffins between C5 and C15 are liquids, and the rest are waxy solids. Paraffin wax is the mainly usedcommercial organic heat storage PCM [1,14]. It consists of mainly straight chain hydrocarbons that have melting
temperatures from 23 to 67 °C [2]. Commercial grade paraffin wax is obtained from petroleum distillation and is
not a pure substance, but a combination of different hydrocarbons. In general the longer the average length ofhydrocarbon chain the higher the melting temperature and heat of fusion [13]. Properties of some paraffin are
given in Table 3. Paraffins are easily available from many manufacturers and are usually more expensive thansalt hydrates [1,14].
3.11.1 Advantages
Paraffin waxes show no tendency to segregate. They are also chemically stable although Lane [1] reports
slow oxidation when exposed to oxygen requiring closed containers. Sharma [8, 145] reports stable properties
after 1500 cycles in commercial grade paraffin wax. Paraffin waxes show high heats of fusion as shown in Table
3. They also have no tendencies to super cool, so nucleating agents are not necessary [1, 14]. Paraffin waxes aresafe and non-reactive [14,15]. They are compatible with all metal containers and easily incorporated into heatstorage systems [1]. Care however should be taken when using plastic containers as paraffin's have a tendency toinfiltrate and soften some plastics [1].
3.11.2 Disadvantages
Paraffins have low thermal conductivity in their solid state as can be seen from Table 4. This presents a
problem when high heat transfer rates are required during the freezing cycle. Velraj [16] reports that this problem
can be decreased through the use of finned containers and metallic fillers or through combination latent/sensible
storage systems. Aluminum honeycombs has been found to improve system performance [14]. Paraffins have ahigh volume change between the solid and liquid stages. This causes many problems in container design [15].
Paraffin's are flammable, this can be easily alleviated by a proper container [13 - 15]. Lane [1] also reports thatparaffins can contract enough to pull away from the walls of the storage container greatly decreasing heat storage
capacity. Unlike Salt Hydrates, commercial paraffins generally do not have sharp well-defined melting points.

PCMs for Low Temperature Solar Thermal Applications
Abhat [2] reports melting ranges of up to 43 °C. This is due to the fact that they are a mixture of materials and asolid-solid phase transformation in commercial grade parafffins immediately before melting that stores a greatamount of the latent heat capacity of the material [2]. This decreases the efficiency of the heat storage system, as
is no longer isothermal.
3.12 Non-paraffinsThis is the largest category of candidate’s materials for phase change storage. Lane et al [1, 18 - 19], Abhat[2] and Buddhi [12] have conducted an extensive survey of organic materials and identified a number of esters,
fatty acids, alcohol’s and glycol’s suitable for energy storage. These materials are flammable and should not be
exposed to excessively high temperature, flames or oxidizing agents. Non - paraffins are tabulated in Table 4.
3.13 Fatty acids
Fatty acids, characterized by the chemical formula CH3(CH2)2nCOOH, have much the same characteristics
as paraffins. Their advantages of sharper phase transformations are offset by the disadvantage of about threetimes the cost of parffins [15]. They are also mild corrosive. Some fatty acids of interest to low temperaturelatent heat thermal energy storage applications are tabulated in Table 5. Sharma [8, 145] reports stable properties
after 1500 cycles for stearic acid.
3.14 Salt hydrates
Salt hydrates are some of the oldest and most studied heat storage PCMs [1]. They consist of a salt and water,which combine in a crystalline matrix when the material solidifies. They can be used in alone or in eutectic
mixtures [2]. Properties of some salt hydrates are given in Table 6. There are many different materials that havemelting ranges from 15 to 117 °C [1]. Salt hydrates are the most important group of PCMs, which have been
extensively studied for their use in latent heat thermal energy storage systems. Three types of the behavior of themelted salts can be identified: congruent, incongruent and semi congruent melting.
3.14.1 Advantages
Low cost and easy availability of salt hydrates makes commercial attractive for heat storage applications.
Two of the least expensive and most available salt hydrates are CaCl2.6H2O and Na2SO4.10H2O [1]. Many salt
hydrates are sufficiently inexpensive for the use in storage [18]. Salt hydrates have a sharp melting point, thismaximizes the efficiency of a heat storage system. They have a high thermal conductivity when compared withother heat storage PCMs. This can increase heat transfer in and out of the storage unit. They have a high heat offusion to decrease the needed size of the storage system. Salt hydrates have a lower volume change than otherPCMs.
3.14.2 Disadvantages
Segregation is formation of other hydrates or dehydrated salts that tend to settle out and reduce the active
volume available for heat storage. Abhat [2] reports a decrease in heat of fusion of over 73% in Na2SO4.10H2O
after 1000 melt/freeze cycles. This problem can be eliminated to a certain extent through the use of gelled or
thickened mixtures [1] though this process negatively impacts the heat storage characteristics of the mixture andthe mixture still degrades with time [2]. Salt hydrates shows supercooling because of not able to start
crystallization at the freezing point of PCM. This can be avoiding using suitable nucleating materials to start
crystal growth in the storage media. Lane [1] offers a comprehensive listing of nucleating materials for mostcommon salt hydrates. Abhat [2] reports material degradation in CaCl2.6H2O after only two cycles when the test
sample was not hermetically sealed. Therefore it is necessary to design containers to contain the material without
letting water out. Another problem of salt hydrates is their tendency to cause corrosion in metal containers thatare commonly used in thermal storage systems [2]. Compatibility of PCM and container should always bechecked before use.
3.15 Eutectics
A eutectic is a minimum melting composition of two or more components, each of which melts and freezes
congruently [19]. Eutectic nearly always melts and freezes without segregation since they freeze to an intimate
mixture of crystals, leaving little opportunity for the components to separate. On melting both componentsliquefy simultaneously. A list of eutectic is given in Table 7.

35

36

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA
Table 2: List of inorganic PCMs [1, 2, 12, 94 - 98]
NameMelting point

Latent heat of(OC)

fusion (kJ/kg)

Name

Melting point

Latent heat of(OC)

fusion (kJ/kg)

H2O

0.0

333

BI3

31.8

10

POCl3

1.0

85

SO3(β)

32.3

151

D2O

3.7

318

TiBr4

38.2

23

SbCl5

4.0

33

H4P2O6

55.0

213

H2SO4

10.4

100

SO3 (γ)62.1

331

IC l (β)

13.9

56

SbCl3

73.4

25

MOF6

17.0

50

NaNO3

307

172 - 199

SO3(α)

17.0

108

KNO3

333 - 380

116 - 266

IC l (α)

17.2

69

KOH

380

149

P4O6

23.7

64

MgCl2

714 - 800

452 - 492

H3PO4

26.0

147

NaCl

800 - 802

466 - 492

Cs

28.3

15

Na2CO3

854

275

Ga

30.0

80

KF

857

452

AsBr3

30.0

38

K2CO3

897

235

Table 3: Melting point and latent heat of fusion of paraffins [1, 2, 12, 94 - 99]
Name

No. of "C"

Melting point

Atoms

O

Density( C)(kg/m )

n - Dodecane

12

-12

750

n - Tridecane

13

-6

756

n - Tetradecane

14

4.5 - 5.6771

n - Pentadecane

15

10

768

0.17
S

3

Thermal Conductivity

Latent heat of(W/mK)

fusion(kJ/kg)
n.a.

0.21S

n.a.
231

n - Hexadecane

16

18.2

774

n - Heptadecane

17

22

778

0.21

n - Octadecane

18

28.2

814S[14], 775L

n - Nonadecane

19

31.9

207
238
215

0.35S [14], 0.149L[14]

245
222

n - Eicosane

20

37

247

n - Heneicosane

21

41

215

n - Docosane

2244

n - Tricosane

23

47

234

n - Tetracosane

24

51

255

912S, 769L

n - Pentacosane

25

54

Paraffin Wax

n.a.

32

785S[15],

0.21S

249

238
0.514S[15], 0.224L[15]251[15]n - Hexacosane

26

56

770

257

n - Heptacosane

27

59

773

236

n - Octacosane

28

61

n - Nonacosane

29

64

0.21S
S

L

910 , 765

255
240

n - Triacontane

30

65

252

n - Hentriacontane

31

n.a.

n.a.

n - Dotricontane

3270

n - Tritricontane

33

71

S: solid; L: liquid; n.a.: not available

930S, 830L

n.a.
189

37

PCMs for Low Temperature Solar Thermal Applications

Table 4: Melting point and latent heat of fusion of non - paraffins [1, 2, 12, 94 - 99]
NameMelting point

DensityLatent heat of fusion(OC)(kg/m3)(k J/ kg)

Formic Acid

7.8

1226.715C

247

Acetic Acid

16.7

105020C

187

17.9

20C

198.7

Glycerin

1260

Lithium Chloride Ethanolate

21

n.a.

188

Polyethylene Glycol 600

20-25

110020C

146

D – Lattic Acid

26

124915C

184

1-3 Methyl Pentacosane

29

n.a.

197

Camphenilone

39

n.a.

205

Docasyl Bromide

40

n.a.

201

Caprylone

40

n.a.

259

Heptadecanone

41

n.a.

201

1-Cyclohexylooctadecane

41

n.a.

218

4-Heptadacanone

41

n.a.

197

Cyanamide

44

20C

1080

79C

209

Methyl Eicosanate

45

851

3-Heptadecanone

48

n.a.

218

230

2-Heptadecanone

48

n.a.

218

Camphene

5084254C238

9-Heptadecanone

51

n.a.

213

Methyl Behenate

52

n.a.

234

Pentadecanoic Acid

52.5

n.a.

178

Hypophosphoric Acid

55

n.a.

213

Chloroacetic Acid

56

20C

130

20C

1580

Trimyristin

33-57

862

201-213Heptaudecanoic Acid

60.6

n.a.

189

Bee Wax

61.8

950

177

Glycolic Acid

63

n.a.

109

Oxazoline-Wax-TS 970

74

n.a.

Arachic Acid

76.5

n.a.
81C

227

Bromcamphor

77

1449

174

Durene79.3

83820C

156

Acetamide

81

1159

241

Methyl Brombrenzoate

81

n.a.

126

1095

98.7C

Alpha Napthol

96

163

Glautaric Acid

97.5

1429

156

p-Xylene Dichloride

100

n.a.

138.7

Methyl Fumarate

102

1045

242

Catechol

104.3

137015C

207

Quinone

115

131820C

171

Acetanilide

115

12104C142

Succinic Anhydride

119

1104

204

Benzoic Acid

121.7

126615C

142.8

Stibene124

116415C

167

Benzamide

127.2

1341

169.4

Phenacetin

137

n.a.

136.7

38

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA
Alpha Glucose

141

1544

174

Acetyl – p- Toluidene

146

n.a.

180

Phenylhdrazone Benzaldehy

155

n.a.

134.8

Salicylic Acid

159

144320C

199

Benzanilide

161

n.a.

162

O-Mannitol

166

148920C

294

Hydroquinone

172.4

20C

1358

258

p- Aminobenzoic Acid

187

n.a.

153

Table 5: Melting point and latent heat of fusion: Fatty acids [1, 2, 12, 94 - 99]
NameMelting point

Density

Thermal conductivity

Latent heat of fusion(OC)(kg/m3)(W/mK)(kJ/kg)Propyl Palmiate

10

n.a.

n.a.

186

Isopropyl Palmiate

11

n.a.

n.a.

100

13.5 - 16.3

86360Cn.a.

n.a.

14 - 19

n.a.

n.a.

140 - 142

Caprylic Acid

16

90130C

0.14939C

148

Butyl Stearate

19

n.a.

n.a.

140

Dimethyl Sabacate

21

n.a.

n.a.

120 - 135

Myristic Acid + Capric

2488825C, 10181C

0.16439C, 0.15461C

147.7

27 - 29

n.a.

n.a.

122

Oleic Acid
Isopropyl Stearate

Vinyl Stearate
Methyl Palmitate

29

n.a.

n.a.

205

Capric Acid

32

87845C

0.15338.5C

152.7

Erucic Acid

33

85370C

n.a.

n.a.

60C

n.a.

178

42 - 44

Elaidic Acid

47

85179C

n.a.

218

Pelargoinc Acid

48

n.a.

n.a.

n.a.

n.a.

205

Myristic Acid862

, 100724C

Lauric Acid

55C

49 - 51

861

65C

68.4C

185.4

Palmitic Acid

64

850

0.162

Stearic Acid

69

84870C0.17270C

202.5

Valporic Acid

120

n.a.

n.a.

n.a.

Table 6: Melting point and latent heat of fusion of salt hydrates [1, 2, 12, 94 - 99]
NameMelting

Density

Thermal Conductivity

Latent Heat

Melting

Point (OC)(kg/m3)(W/m K)(kJ/kg)Behaviora [13]LiClO3.3H2O

8

n.a.

n.a.

253

c

NH4Cl.Na2SO4.10H2O

11

n.a.

n.a.

163

n.a.

K2HO4.6H2O

14

n.a.

n.a.

108

c

NaCl.Na2SO4.10H2O

18

n.a.

n.a.

286

n.a.

KF.4H2O

18

n.a.

n.a.

330

c

K2HO4.4H2O

18.5

144720C, 145518C,

n.a.

231

n.a.

Mn(NO3)2.6H2O

25

173820C[12],

n.a.

148

n.a.

LiBO2.8H2O

25.7

n.a.

n.a.

289

n.a.

FeBr3.6H2O

27

n.a.

n.a.

105

n.a.

CaCl2.6H2O

29 - 30

LiNO3.3H2O

30

1562

32C

24C

, 1802

n.a.
24C

0.561

61.2C

23C

170 - 192

ic

n.a.

, 1.008

189 - 296c

Na2SO4.10H2O

32

1485

0.544

251 - 254

ic

Na2CO3.10H2O

33 - 36

1442

n.a.

247

ic

KFe(SO4)2.12H2O

33

n.a.

n.a.

173

ic

39

PCMs for Low Temperature Solar Thermal Applications
CaBr2.6H2O

34

195635C, 219424C

n.a.

115 - 138n.a.

LiBr.2H2O

34

n.a.

n.a.

124

ic

Na2HPO4.12H2O

35

1522

n.a.

256 - 281ic

134 - 147

c

1828

36C

24C

, 1937

,

0.464

39.9C

61.2C

Zn(NO3)2.6H2O

36, 0.469

Mn(NO3)2.4H2O

37

n.a.

n.a.

115

n.a.

FeCl3.6H2O

37

n.a.

n.a.

223

c

CaCl2.4H2O

39

n.a.

n.a.

158

ic

CoSO4.7H2O

40.7

n.a.

n.a.

170

n.a.

CuSO4.7H2O

40.7

n.a.

n.a.

171

n.a.

KF.2H2O

42

n.a.

n.a.

162 - 266c

MgI2.8H2O

42

n.a.

n.a.

133

n.a.

CaI2.6H2O

42

n.a.

n.a.

162

n.a.

Ca(NO3)2.4H2O

43 - 47

n.a.

n.a.

106 - 140c

Zn(NO3)2.4H2O

45

n.a.

n.a.

110

n.a.

K3PO4.7H2O

45

n.a.

n.a.

145

n.a.

Fe(NO3)3.9H2O

47

n.a.

n.a.

155 - 190

ic

Mg(NO3)3.4H2O

47

n.a.

n.a.

142

n.a.

Na2SiO3.5H2O

48

n.a.

n.a.

168

n.a.

Na2HPO4.7H2O

48

n.a.

n.a.

135 - 170

ic

Na2S2O3.5H2O

48

1600

n.a.

209

n.a.

K2HPO4.3H2O

48

n.a.

n.a.

99

n.a.

MgSO4.7H2O

48.4

n.a.

n.a.

202

n.a.

Ca(NO3)2.3H2O

51

n.a.

n.a.

104

n.a.

Na(NO3)2.6H2O

53

n.a.

n.a.

158

n.a.

Zn(NO3)2.2H2O

55

n.a.

n.a.

68

c

FeCl3.2H2O

56

n.a.

n.a.

90

n.a.

CO(NO3)2.6H2O

57

n.a.

n.a.

115

n.a.

Ni(NO3)2.6H2O

57

n.a.

n.a.

168

n.a.

MnCl2.4H2O

58

n.a.

n.a.

151

n.a.

CH3COONa.3H2O

58

n.a.

n.a.

270 - 290

ic

LiC2H3O2.2H2O

58

n.a.

n.a.

251-377n.a.

MgCl2.4H2O

58.0

n.a.

n.a.

178

n.a.

NaOH.H2O

58

n.a.

n.a.

272

n.a.

Na(CH3COO).3H2O

58

n.a.

n.a.

n.a.

n.a.

Cd(NO3)2.4H2O

59

n.a.

n.a.

98

n.a.

Cd(NO3)2.1H2O

59.5

n.a.

n.a.

107

n.a.

Fe(NO3)2.6H2O

60

n.a.

n.a.

125

n.a.

NaAl(SO4)2.12H2O

61

n.a.

n.a.

181

ic

FeSO4.7H2O

64

n.a.

n.a.

200

n.a.

Na3PO4.12H2O

65

n.a.

n.a.

168

n.a.

Na2B4O7.10H2O

68

n.a.

n.a.

n.a.

n.a.

Na3PO4.12H20

69

n.a.

n.a.

n.a.

n.a.

LiCH3COO.2H2O

70

n.a.

n.a.

150 - 251

c

Na2P2O7.10H2O

70

n.a.

n.a.

186 - 230

ic

Al(NO3)2.9H2O

72

n.a.

n.a.

155 - 176

ic

Ba(OH)2.8H2O

78

193784C, 207024C,

0.65385.7C, 0.67898.2C,

265 - 280c

Al2(SO4)3.18H2O

88

n.a.

n.a.

218

ic

Sr(OH)2.8H2O

89

n.a.

n.a.

370

ic

162 - 167c

Mg(NO3)2.6H2O

89 - 90

94C

1550

25C

, 1636

0.490

95C

110C

, 0.502,

40

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA
KAl (SO4)2.12H2O

91

n.a.

n.a.

184

n.a.

(NH4)Al(SO4).6H2O

95

n.a.

n.a.

269

n.a.

Na2S.51/2H2O

97.5

n.a.

n.a.

n.a.

n.a.

LiCl.H2O

99

n.a.

n.a.

212

ic

CaBr2.4H20

110

n.a.

n.a.

n.a.

n.a.

Al2(SO4)2.16H2O

112

n.a.

n.a.

n.a.

n.a.

MgCl2. 6H2O

115 - 1171450120C, 144278C,

0.570120C, 0.598140C,

165 - 169

n.a.

NaC2H3O2.3H2O

137

1450

n.a.

172

n.a.

n.a..: not available; c: congruent melting; ic : incongruent melting

3.16 Cross-linked polyethylene
Cross-linked Polyethylene is much like the polyethylene used in plastic bottles except for the fact that it islightly cross-linked to prevent it from turning into a liquid when it melts. Like a liquid-solid PCM it storesenergy in the forming and breaking of crystalline structure. Properties of two cross-linked polyethylene areshown in Table 8. Unlike a liquid-solid PCM, it has a stable form and can be used without encapsulation.
3.16.1 Advantages
Although higher cost than other PCMs, Therefore, low cost is required for entire heat storage system andmore feasibilities than other PCMs [1]. Cross-linked polyethylene is nontoxic and mostly chemically inert.
3.16.2 Disadvantages
The operating temperatures of 110 to 140 °C are too high for some applications such as space and water
heating. To the author’s knowledge no company has commercially developed cross-linked polyethylene for heatstorage applications at this time.
3.17 Polyalcahols
There has also been research done in playschools [1]. Polyalcahols store energy in a structure change from aheterogeneous state at lower temperatures to a face centered cubic form at higher temperatures [6]. Polyalcahols
have many advantages over solid-liquid PCMs such as small volume change, no leaking, and no degradation of
the material [6]. These advantages come with the disadvantages of low latent heat, high phase change
temperatures, and higher cost. Wang [6] reports a system of combining polyalcahols to adjust working
temperatures. Some of his results are shown in Table 8 for Neopentyl Glycol (NPG)/ Penaerythritol (PE) andNeopentyl Glycol (NPG)/Trihydroxy Mthyl-Aminomethane (TAM) systems.
Table 7: List of organic and inorganic eutectics [1, 2, 10, 12, 94 - 99]
Composition (wt %)Melting point (OC)Latent Heat of fusion (k J/ kg)

Na2SO4+NaCl+KCl+H2O

31+13+16+40

4

234

Na2SO4+NaCl+NH4Cl+H2O

32+14+12+42

11

n.a.

C5H5C6H5+ (C6H5)2O

26.5+73.5

12

97.9

Na2SO4+NaCl+H2O

37+17+46

18

n.a.

Na2S4+MgSO4+H2O

25+21+54

21 - 24n.a.

C14H28O2 + C10H20O2

34 + 66

24

147.7

Ca(NO)3.4H2O + Mg(NO)3.6H2O

47 + 53

30

136

-

46

95

NH4 NO3

61.5 +38.4

52

125.5

Mg(NO3)2.6H2O + MgCl2.6H2O

58.7 + 41.3

59

132.2

Mg(NO3)2.6H2O + Al(NO3)2.9H2O

53 +4761

148

Mg(NO3)2.6H2O + MgBr2.6H2O

59 + 41

66

168

Napthalene + Benzoic Acid

67.1 + 32.9

67

123.4

AlCl3+NaCl+ZrCl2

79+17+4

68

234

Name

NH2CONH2 + NH4 NO3
Mg(NO3)2.6H2O +41

PCMs for Low Temperature Solar Thermal Applications
AlCl3+NaCl+KCl

66+20+1470

209NH2CONH2 + NH4Br

66.6 + 33.4

76

151

LiNO3 + NH4 NO3 + NaNO3

25 + 65 + 10

80.5

113

AlCl3+NaCl+KCl

60+26+1493

213

AlCl3+NaCl

66+34

93

201

NaNO2+NaNO3+KNO3

40+7+53

142

n.a.

Table 8: Melting point and latent heat of fusion of some selected solid - solid PCMs [1, 2, 10, 94- 99]
Name
38.2%NPG/61.8%PE
38.2%NPG/61.8%TAM
76.4%NPG/33.6%TAM
76.4%NPG/33.6%PE
91%NPG/9%PE
91%NPG/9%TAM
Neopentyl Glycol(NPG)
Diamnopentacrythritol
2-Amino - 2 - Methyl - 1, 3 - Propanediol
2 - Methyl - 2 - Mtro - 1, 3 - Propanediol
Trumethylolethane
Pentaglycerin
2-Hydroxymethyl-2-Methyl-1, 3 - Propanediol
Monoaminopentaerythritol
Cross-Linked Polyethylene
Tris(Hydroxymethyl)Acetic Acid
2-Amino-2-Hydroxymethyl-1, 3 - Propanediol
Cross-Linked HDPE
2,2-Bis(Hydroxymethyl) Propionic Acid
38.2%NPG/61.8%PE
Penterythritol(PE)Melting point (OC)Latent heat of fusion (kJ/kg)

26 - 32
22 - 35
28 - 38
31 - 37
31 - 36
30 - 39
43
68
78
79
81
81
81
86
110 - 115
124
131
125 - 146
152
170
185

18 - 75
27 - 33
75 - 80
35 - 4668
143 - 150
130
184
264
201
192
192
192
192
125 - 146
205
285
167 - 201
289
147
303

4.0 Latent Heat Storage Systems
The intermittent and dynamic nature of solar irradiance and the need to utilize solar energy systems in acontinuous and static load, make the use of storage systems essential in most of the potential uses of solar energy.
Amongst the various heat storage techniques of interest is latent heat storage in comparison to sensible heatstorage. The use of phase change materials (PCMs) can be found in solar energy storage systems for water
heating, green houses, heating and cooling of buildings, cooking and waste heat recovery systems.
4.1 Solar water heating
Solar water heater is getting popularity [21-23] since they are relatively inexpensive and simple to fabricate
and maintain. Prakesh et al. [24] analyzed a built in storage type water heater containing a layer of PCM filled at
the bottom (Fig. 2). During the sunshine hours, the water gets heated up which in turn transfers heat to the PCM
below it. The PCM collects energy in the form of latent heat and melts. During off sunshine hours, the hot wateris withdrawn and is substituted by cold water, which gains energy from the PCM. The energy is released by the
PCM on changing its phases from liquid to solid. This type of system may not be effective due to the poor heattransfer between PCM and water.

42

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Fig.2: Built -in storage type heater with PCM layer
A cylindrical storage unit in the closed loop with a flat plate collector (Fig.3) has been theoretically studied
by Bansal and Buddhi [25] for its charging and discharging mode. As a result, a theoretical model for cylindricallatent heat storage system was developed. The calculations for the interface moving boundary and fluid
temperature were made by using paraffin wax (p-116) and stearic acid as phase change materials. Tiwari et al.
[26] presented an analysis of a PCM storage for water heater by incorporating the effect of water flow through aparallel plate placed at the solid-liquid interface. In order to reduce the night heat losses from the exposed
surface, movable insulation has been made. They concluded that the hot water (temperature 15 –20 °C > Ta) can
obtain throughout the day and night, and the fluctuations in water temperature decrease with an increase in themelted region of the PCM water heater. Tayed et al. [27] developed a system for domestic hot water using
Na2SO4.10H20 as a PCM and compared with the simulation model which gives the optimum flow rate of theinlet water supply required to maintain the constant-temperature water at outlet. Font et al. [28] conducted apreliminary study for the design of a device for domestic water using solid - solid PCM. Numerical simulation
has been made using unidirectional model and verified with the experimental results. The concordance between
both experimentally and simulation results shows that this model is available to study the heat transfer
phenomenon in the PCM in order to optimize the design of the device.

Fig.3: A domestic hot water system with separate PCM heat
Chauarsia [29] and Gu [32] reported that paraffin wax could be used as a storage system for solar water heating.
Baran and Sari [30] reported the eutectic (melting point 52.3 OC, latent heat of fusion 182 kJ/kg) of palmitic acid(64.2wt%)+ stearic acid (35.8 wt%) is suitable for domestic water heating application. Bhargava [31] utilized the
PCM in solar water heater and concluded that the efficiency of the system and the outlet water temperatureduring the evening hours increases with the increase in the thermal conductivity of the solid-liquid phases of thematerials. Hasan et al. [33] has investigated some fatty acids as a phase change materials for domestic water
heating. They recommended that myristic acid, palmitic acid and stearic acid, with melting temperature between
50 OC - 70 OC are the promising phase change materials for water heating. Thermophysical properties ofidentified PCMs were determined using differential scanning calorimeter (DSC). They concluded that the little
reduction of the latent heat was found after 450 heating cycles (20–80°C), while a reduction of up to one-third of
the latent heat was found after 21 heating cycles (20–150°C).

PCMs for Low Temperature Solar Thermal Applications
Kurklu et al. [34] developed a new type of water - PCM solar collector and its short-term thermal
performance was investigated (Fig.4). The solar collector consisted of two adjoining sections one filled withwater and the other with a PCM (Paraffin Wax, 45–50 OC). The results of the study indicated that the watertemperature exceeded 55 OC during a typical day of high solar radiation and it was kept over 30 OC during thewhole night. The present solar collector was much advantageous over the traditional solar hot water collectors in
Turkey in terms of total system weight and the cost in particular. This type of collector might use of PCM–watersolar panels on the south faces of buildings for energy storage applications.
PCM relief and filling connection
Water relief pipe
Water outlet for domestic use
Water store
PCM store
3 mm glass
Water supply
PCM evacuation(if necessary)
Insulation

Fig.4: Water - PCM solar collector
4.2 Heating
Jurinak and Khalik [35, 36] have studied the effects of PCM on the performance of an air-based solar
heating system. Their main conclusion was that the PCM should be selected based on its melting temperature,
rather than its latent heat, i.e. melting temperature has a significant effect on system performance. They also
reported that systems utilizing Na2SO4.10H20 requires roughly the one-half storage volume of a conventional
water tank system. An effective heat capacity for the latent heat storage unit was also obtained as a function of its
mass, latent heat, specific heat, and melting temperature. Acquired effective heat capacity could used to estimate
the thermal performance of the system utilizing PCM. Klein and Beckman [37] presented a simulation study forclosed-loop solar thermal system, which could use for a variety of applications including space heating,absorption air conditioning, and certain types of process heating. This design method can be used to estimate thelong-term performance of such type systems. Bulkin et al. [38] suggested a mathematical model for designing asolar heating and hot-water supply system on the basis of solar absorbers and a heat pump with twothermal-storage tanks, taking into account the system’s interaction with the outside climate and with the room
being served. Ghoneim [39] has studied the effect of assumptions in the models of earlier studies on both thefraction of the load met by solar energy, and the required storage capacities.
Kaygusuz et al. [40] developed an experimental model to determine the dynamics of solar-assisted heatpump, collectors, dryer, and energy storage tank used for drying grains. Kaygusuz [41] investigated theperformance of a dual-source heat pump system for residential heating (Fig.5). In the dual-source configuration,
the evaporator is designed so that it can receive energy from either the atmosphere or from the solar-energy store.
He concluded that the dual source system could save more energy than the parallel and series system. Kaygusuz[42] also conducted an experimental and a theoretical study to determine the performance of phase-change
energy storage materials, and the variation of the outlet fluid temperature with different values of NTU (thenumber of transfer units of the storage unit) for water based solar heating systems (Fig.6). This system consistsof the solar collector, energy storage tank, water-to-air heat exchanger, auxiliary electrical heater, water
circulating pump and other measuring and control equipment.

43

44

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Fig.5: Solar -assisted heat pump system linked to energy storage tank
Whenever solar energy is available, it is collected and transferred to the energy storage tank that is filled by1500 kg encapsulated phase change material (PCM) and the heat transfer fluid (water) flows parallel to them(Fig. 7). From the experimental and theoretical investigations, they concluded that heat storage is an importantcomponent in moderate climatic conditions (i.e. Trabzon, Turkey), and for this purpose, CaCl2.6H20 or
Na2SO4.10H2O can be used as a PCM and would provide a desirable alternative to rock and water storage
systems. PCM storage is more preferable as a heat source than the water and rock storage for a heat pumpbecause the energy storage temperature of the PCM is around 25-35°C for either CaCl2.6H20 or Na2SO4.10H2O.
This temperature range is suitable for solar-assisted heat pump applications in Turkey. Mehmet [43] also
investigated the thermal performance of a solar-aided latent heat storage used for space heating with heat pumpusing 1090 kg encapsulated PCM (CaCl2.6H2O). He concluded that the shorter and thinner pipe should be used
for effective heating in the beginning of the experiments.
Fath et al. [44] developed a simple solar air heater integrated with thermal energy storage system shown in Fig.
8. Heat storage materials were filled in the tubes and set as an absorber of the collector. Paraffin Wax (melting
point 50 OC, latent heat of fusion 190 kJ/kg) and Na2SO4.10H20 (melting point 32 OC, latent heat of fusion 251
kJ/kg) are used as PCMs. These systems increase the heat transfer area; coefficient and reduce theradiation/convection losses. Based on a simple transient analysis, explicit expressions for the heater absorber andglass cover temperatures, effective heat gained, outlet air temperature, and the heater efficiency have beendeveloped as a function of time. For the system with built-in PCM, the heat load could be provided for the 24
hrs/day, at almost constant temperature. The daily average efficiency, with paraffin wax, is about 63.35% ascompared to 59% with sand as the storage material and 38.7% for the conventional flat plate heater system.
Strith et al. [45] used TIM (Transparent Insulation Material) and translucent PCM in the wall for heating the
air for the ventilation of the house. Paraffin wax (melting point 25-30 oC, latent heat of fusion 150 kJ/kg) wasused as a PCM and 60 kg was filled in a panel for space heating. The efficiency of solar energy absorbed into the
PCM and transferred to the ventilation air was 45% on average. Manz et al. [46] also conducted same study withanother PCM (CaCl2.6H2O). He developed a numerical simulation which agrees well with experimental results.
He also reported that maximum time ratio parameter could be reached with a mean melting temperature of
approximately 20 to 21OC when building does not lose energy through the south facing TIM-PCM wall.
Arkar et al. [47] also designed a solar assisted ventilation system based on PCM storage. He recommended
that paraffin - spherical encapsulations provide homogeneous porous effect in ventilation duct which can
improve the thermal conductivity of paraffin. He reported that ambient air could be cooled for 3 to 4 K in a clear
summer night.

Fig.6: Schematic diagram of the base solar energy system

PCMs for Low Temperature Solar Thermal Applications

45

Fig.7: Schematic configuration of latent heat storage tank
A theoretical model of a shell-and-tube PCM storage unit was reported by Ismail and Alves [48]. Energy
equation for the PCM is written in terms of the enthalpy. The numerical results show the effects of the Biot
number, the relative diameters of the tubes, and the inlet fluid temperature on the thermal performance of the unit.
Visser [49] developed a component model for numerical description of two different short term heat storage
vessels. In both vessels, the energy is stored as the latent heat of PCMs. The transient simulation program wasused to determine the performance of the cylindrical energy storage tank that can be used in the solar assisted
domestic heating by heat pump system. Yimmer et al. [50] also developed a numerical model for optimizing abasic 1-D, shell-and-tube, thermal energy storage system. Again, an enthalpy approach was adopted for the PCM.
A parametric study was then conducted to assess the effects of the inner tube and outer shell radii and of theliquid phase thermal conductivity of the PCM on the performance of the unit. Lacroix [51] developed atheoretical model to predict the transient behavior of a shell-and-tube storage unit with the PCM on the shell sideand the HTF circulating inside the tubes. Then, parametric studies are performed to assess the effects of various
thermal and geometric parameters on the heat transfer process and on the behavior of the system.
Sagara et al. [52] estimated the long term performance of an air based solar heating system using a PCM.
Theoretical heat transfer models within a spherical capsules enclosed the PCM were studied. Effect on theoverall COP was studied with respect to the capacity of the PCM storage tank, melting temperature, collector
area and air flow rate. They reported that the simple uniform temperature model is useful for long term systemsimulations. Sari and Kaygusuz [53] developed a eutectic (lauric acid 75.5 wt% + stearic acid 24.5 wt%) for
space heating. Developed eutectic melts at 37 OC with latent heat of 183 kJ/kg, thus, these properties make it an
attractive PCM used for passive solar space heating applications such as building and greenhouse heating withrespect to the climate conditions. Vakilaltojjar [54] developed computer models for the evaluation of thermalenergy storage system for space heating and cooling applications. The effect of PCM slab thickness and fluidpassage gap on the storage performance was investigated. He filled the PCMs (CaCl2.6H2O and KF.4H2O) inthin flat containers and air is passed through gaps between them. He concluded that the air velocity profile at theentrance does not affect the heat transfer characteristics and the outlet air temperature considerably. Usingsmaller air gaps and thinner PCM slabs can obtain better performance, however, this increases the number of
PCM containers and the total volume of the storage system which will lead to higher-pressure drop across thestorage system.
4.3 Cooling
The most common storage media for space cooling are water, ice and PCMs, commonly known as eutectic
salts. PCMs have been used for various heat storage applications since the 1800s, but they have only recently
been used as a storage media for space cooling. So far, most of the PCMs for cool storage are inorganic salt
hydrates, organic paraffin waxes and mixtures of these. Literatures available on thermal storage at a temperature
below the ambient, other than for ice are limited. A theoretical simulation of cool storage was reported by
Solomar et al. [55]. BoHe et al. [56] investigated the potential for using cool storage systems using PCMs andstatic and dynamic cool storage process are discussed. They reported that the Rubitherm RT5 (melting point 7 OC,
latent heat of fusion 158.3 kJ/kg) appears to be an excellent candidate as a PCM for cool storage because of its
economical cost, congruently melting, self-nucleation property, no super cooling and stable during a number ofcooling and heating cycles.

46

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Fig.8: Solar air heater configuration with set of PCM tubes
A search for literature on commercial chemical products on PCMs for cool storage for the temperature range
15 - 23 OC was carried out [57]. Nagano et al. [58] investigated the thermal characteristics of manganese (II)nitrate hexahydrate (melting point 25.8 OC, latent heat of fusion 125.9 kJ/kg) as a PCM for cooling systems.
They reported that almost all chlorides were effective in modulating the melting point of Mn(NO3)2.6H2O.
MnCl2 .4H2O was an effective additive with respect to modulation of melting point, reduction of super coolingand quantity of the heat of fusion. The temperature differences required for melting and solidification from themelting point measured by DSC are about 6 OC for melting process and 4 OC for solidification process for the
mixture of Mn(NO3)2.6H2O and 4.0 wt% of MnCl2 .4H2O The indoor air at temperature of 28 OC in daytime andthe outside cool air at night below 16 OC can be utilized to melt and solidify this mixture. Farid et al. [59] studied
the feasibility of cool storage using dimethyl-sulfoxide (melting point 16.5 OC) as a PCM in rectangularcontainer. Based on the experimental results and the model predictions, dimethyl-sulfoxide can be used as a
PCM for cool storage. The results also show that, cooling extraction period depends on the amount of solidified
PCM. The cool extraction period was completed when the outlet air temperature from the PCM section reachedat 25 OC. This temperature is considered the highest temperature at which the human may feel comfortable.
Saitoh and Hirose [60] studied the thermal characteristics of an encapsulated thermal storage tankexperimentally and theoretically. They used Na2HPO4.12H2O as PCM to fill cylindrical capsules with an inside
diameter of 70.7 mm. They concluded that the main factors affecting the charging process were the capsule size,
coolant flow rate, coolant temperature, and capsule material. Kondepudi et al. [61] discussed the effect of Biot
number, Stefan number and Fourier number on the thermal performance of cold storage. Laybourn [62] utilized aconcept of thermal resistance, which embraced the convective resistance, wall resistance, and ice layer resistanceto calculate the cold storage of the tank with rectangular capsules. Arnold [63] analyzed the heat transfer during
the freezing and melting process by performing a series of charging and discharging experiments. Chen [64 -66]
developed a general lump model to predict the thermal performance of a cold storage system. The results showedthat the lump model is a convenient and simple method to determine the thermal performance of cold storage
system. Ryu et al. [67] used a rectangular storage tank with copper tube container and conducted a series ofexperiments using both vertical and horizontal tank to investigate the heat transfer characteristics. In the area of
subcooling of water, Chen [68] conducted a series of experiments to investigate the subcooling phenomenon andthe freezing probability of water with and without nucleation agents inside a cylinder. They verified that theaddition of nucleation agents is one of the approaches to improve the subcooling phenomenon effectively. Chenet al. [69] experimentally investigated the pressure drop of an encapsulated thermal storage tank during thecharging process. The cylindrical capsules inside the thermal storage tank utilize water added with nucleation
agents as PCM, and the coolant is the aqueous solution of ethylene glycol. They concluded that high cold storage
could obtain by using the lower inlet coolant temperature with high flow rate. The heat transfer coefficientincreases as the coolant flow rate increases. The pressure drop flowing through tank is enlarged as the coolant
flow rate increases during the charging process.

PCMs for Low Temperature Solar Thermal Applications
4.4 Green house heating
Solar agricultural greenhouses have been widely used in the past two decades in order to increase plantquality and productivity and to reduce consumption of fossil fuels for heating and cooling. The most effective
greenhouses require control of temperature, humidity, solar irradiance and internal gas composition with rational
consumption of energy. Research work in this area, involving studies of new materials, heat storage and heatexchange devices resulted in some interesting demonstration units followed by rapid commercial applications.
The most frequently used PCM for these purposes is CaC12.6H2O, Na2SO4.10H2O, PEG, and paraffins.
Nishina and Takakura [75] conducted a research applying Na2SO4.10H20 with some additives to prevent
phase separation and degradation for heating a greenhouse in Japan. Fig. 9 shows the general view of theexperimental set-up. This study concluded that although 8°C target inside was achieved, only 40-60% of thelatent heat potential of the PCM was realized which indicated that almost half of the PCM was not usedefficiently during the energy exchange processes. Takakura et al. [70] tested polyethylene glycol and
CaCl2.6H2O as a PCMs in greenhouse heating for 7.2 m2 ground area. They compared conventional greenhousewith PCM storage type greenhouse. Efficiency of the greenhouse with PCM storage integrated with solar
collector was 59 % and able to maintain 8°C inside the greenhouse at night, when the outside temperature
dropped to - 0.6°C. A microcomputer control system has been developed in order to establish more accurate andmore sophisticated control for solar greenhouse systems.
CNRE-France conducted a study using a glass-covered multi-span greenhouse with 500 m2 ground area,
dedicated to rose production, by utilizing 13.5 tons of CaC12.6H20 (melting at 28°C) by Jaffrin and Cadier [66]and by Jaffrin [71, 72]. Thermal and crop performance of this greenhouse was compared with an air-bubble
double plastic-covered and a conventional greenhouse. Figure 10 shows the arrangement of the PCM containers
in underground. The containers were placed in concrete shelves with five layers in semi-circular tunnels and air
was used to transfer heat. The outcome of this study was that with this system, propane gas savings of 80 and
60% in comparison with the conventional and double-covered greenhouses, respectively, was obtained.
Electricity consumption of the fans was determined to be less than 10% of the heating load of the greenhouse.
Levav and Zamir [73] tested CaC12.6H20 in greenhouse. They reported that required air temperature in thegreenhouse was achieved without any increase in the relative humidity. It was stressed that the most important
drawback of the system was the $1.1/kg cost of the PCM. Furthermore, they indicated that the 24°C melting
temperature of the PCM could be high for some crops.
Kern et al. [74] used CaC12.6H20 as a PCM in aerosol cans to investigate energy storage possibilities both
inside and outside a 36 m2-ground area greenhouse covered with fiberglass. Results of this study indicated thatwhile the external unit released about 80-90% of the energy absorbed, this was 60-80% for the internal energy
storage unit. Paraffin's have also been used for energy storage in greenhouses. A study performed by Bagetinelik
et al. [78] was the only work in literature using paraffin (48 - 60 OC , Latent Heat of Fusion 190 kJ/kg ) for
greenhouse heating.

Fig.9: General view of phase change energy storage system
The latest studies on the Na2SO4.10H20 based PCM applications in greenhouses were those of Ktirklti et al.
[76, 77]. In their study, two types of a similar PCM, one with a melting range of 22 - 25°C and the other with
about 8°C, were employed, the former for the reduction of peak temperatures towards summer and the latter for
frost prevention in both greenhouses.

47

48

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Fig.10: Underground tunnel: equipped with a PCM
Figure 11 shows the experimental set-up for both applications. Results revealed that about 2.5 - 3°C
temperature difference existed between the PCM greenhouse and the control one throughout the experimental
period, and that solar collection efficiency on an outside solar radiation basis was 29% for the experiments with
the PCM with higher melting temperature. Similarly, the temperature difference and solar collection efficiency
was found to be about 22°C and 30%, respectively during the frost prevention experiment, and frost occurrence
was prevented on 7 out of 9 frosty occasions. Most applications were carried out in either double-covered
greenhouses or greenhouses with one or more layers of thermal screens. The only study that barely defined theeffect of the PCM store on the environmental parameters of a greenhouse seemed to be those of Kuruklu et al.
[76, 77]. However, all studies imply that PCMs could be used for both energy storage and humidity control ingreenhouses, in a way for energy management, effectively given the right choice and design of the whole system.

Fig.11: General view of the storage used for energy management in greenhouse
4.5 Solar cooking
Solar cookers are used to cook rice, vegetables, meat, bake cakes, etc. The detailed design, testing, theory
and utility of box-type solar cookers are well developed [79 - 86]. The use of these cookers is limited because
they do not have any storage, i.e. these cookers cannot be used on cloudy days or in late evening. The use of
PCMs for storing the heat in the form of latent heat has been recognized as one of the areas to provide a compact
and efficient storage system due to their high storage density and constant operating temperature [80, 81].
A box type solar cooker with latent heat storage has been designed and fabricated for the composite climaticconditions of India by Buddhi and Sahoo [87]. Commercial grade stearic acid (melting point 55 OC, latent heat offusion 161 kJ/kg) used as a latent heat storage material. Fig. 12 shows the sketch of a box-type solar cooker for
one vessel having a PCM to store the solar energy. The cooker consists of an aluminum-absorbing tray ‘A’. In
the center of the absorbing plate, a cylindrical container of 0.165 m diameter and 0.02 m in depth has been
welded (shown in Fig. 1by ‘C’), and the cooking pot is to be kept tightly in it. This container will provide a heattransfer from the absorbing plate and PCM. Moreover, aluminum fins were also provided at the inner side of the
tray and cylindrical container. The outer tray ‘B’ is also made from the same aluminum sheet. The distance
between tray ‘A’ and tray ‘B’ was kept at 0.025 m on the bottom side. Tray ‘B’ was filled with 3.5 kg ofcommercial grade Stearic Acid (PCM) and it was made sure that the PCM should be in good contact with thebottom side of tray ‘A’. The space between tray ‘B’ and the casing was filled with glass wool to provide thermal
insulation to the bottom and sides of the solar cooker. A flat glass mirror was fixed in an aluminum cover toPCMs for Low Temperature Solar Thermal Applications

49

serve as a booster and as a cover for the glass lid when the cooker is not exposed to solar radiation. The
aluminum tray ‘A’, cooking pot and its cover were painted with a dull black paint on the outside. The
experimental results demonstrate the feasibility of using a phase change material as the storage medium in solar
cookers, i.e. it is possible to cook the food even in the evening with a solar cooker having latent heat storage. It
also provides a nearly constant plate temperature in the late evening.
Domanski et al. [88] investigated the possibility of cooking during off-sunshine hours using phase changematerials (PCMs) as storage media. They designed the storage-cooking vessel for off sunshine hours (Fig. 13).
For this purpose, two concentric cylindrical vessels (0.0015 m thick), made from aluminum, are connected
together at their tops using four screws to form a double-wall vessel with a gap between the outer and inner walls.
The outer and inner vessel has a diameter of 0.18 m and 0.14 m. The annular gap between the outer and inner
vessels is 0.02 m. This gap is covered with a removable aluminum cover into which three circular holes were
drilled to allow inserting of thermocouples and permit direct visualization during filling or removing of the
PCMs. A circular aluminum cover is used as the lid for the inner vessel.

Fig.12: Schematic diagram of the box of a solar cooker with PCM storage
The outside surfaces of the outer vessel and the covers are painted using ordinary black paint for maximum
absorption of available solar radiation. The gap between the outer and inner vessels is filled with 1.1 kg of stearicacid (69 OC, 95% pure), or 2 kg of magnesium nitrate hexahydrate (89 OC, 99% pure), which leaves sufficientspace for expansion of the PCMs on melting. They concluded that the cooker performance evaluated in terms ofcharging and discharging times of the PCMs under different conditions. He reported that performance depends
on the solar irradiance, mass of the cooking medium, and the thermo physical properties of the PCM. The overall
efficiency of the cooker during discharging was found to be 3-4 times greater than that for steam and heat-pipe
solar cookers, which can be used for indoor cooking. In such type of design, the rate of heat transfer from the
PCM to the cooking pot during the discharging of the PCM is slow, and more time is required for cooking theevening meal.
Sharma et al. [89] designed and developed a cylindrical PCM storage unit for a box type solar cooker tocook the food in the late evening. Since this unit surrounds the cooking vessel, the rate of heat transfer between
the PCM and the food is higher, and cooking can be faster. For this purpose, a PCM container to hold thecooking vessel was designed and fabricated as shown in Fig. 14. It has two hollow concentric aluminum
cylinders of diameter 18 cm and 25 cm and 8 cm deep of 2 mm thickness. The space between the cylinders wasfilled with acetamide (melting point 82 OC, latent heat of fusion 263 kJ/kg) as a PCM. The dimensions of thevessel used for cooking were 17.5 cm and 10 cm in diameter and height, respectively, and it can be inserted
inside the PCM container for cooking purposes. To enhance the rate of heat transfer between the PCM and theinner wall of the PCM container, 8 fins (1x3 cm) were welded at the inner wall of the PCM container. They
reported that by using 2.0 kg of Acetamide as a latent heat storage material, the second batch of food could becooked if it is loaded before 3:30 P.M. during the winter season. They recommended that the melting
temperature of a PCM should be between 105 and 110 oC for evening cooking. Therefore, there was a need to
identify a storage material with appropriate melting point and quantity, which can cook the food in the lateevening. To store a larger quantity of heat in a PCM, more input solar radiation would be required. Hence,
Buddhi and Sharma [90] used a latent heat storage unit for a box type solar cooker with three reflectors. They
used acetanilide (melting point 118 oC, latent heat of fusion 222 kJ/kg) as a PCM for night cooking. To conduct
the cooking experiments with the PCM storage unit, a double glazed (glass covers) box type solar cooker having
50 cm x 50 cm aperture area and 19 cm deep was used. In this solar cooker, three reflectors were provided, i.e.
the middle reflector was mounted with a hinge and had rotation only about the horizontal axis. The other two
reflectors were fixed by a ball and socket mechanism in the left and right sides of the reflector. This pair of50

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

reflectors has three degrees of freedom, i.e. they can have movement about the horizontal axis and vertical axis
and can rotate about both the axes. By these mechanisms, efforts were made to keep the reflected solar irradianceon the absorber surface to enhance the incident solar radiation on the glass cover during the course of the sun
exposure experiments.
Following Sharma et al. [90], a cooking vessel with latent heat storage was designed and fabricated to cook
the food in night / late evening. The unit has two hollow concentric aluminum cylinders of diameter 20 and 30
cm and 12.5 cm deep of 2 mm thickness. The space between the cylinders was filled with 4.0 kg of PCM to
conduct the cooking experiments with all three reflectors. The dimensions of the vessel used for cooking were 19
and 15 cm in diameter and height, respectively, and it can be inserted inside the PCM storage unit for cooking
purposes. To enhance the rate of heat transfer between the PCM and the inner wall of the PCM container, 8 fins
(1 cm x 3 cm) were welded at the inner wall of the PCM container. From the experimental results one canconclude that the cooking experiments were successfully conducted for the evening time cooking up to at 8 P.M.
with 4.0 kg of PCM during winter season in India.

Fig.13: Solar Cooker with PCM Cooking Container
Sharma et al. [91] developed a solar cooker based on Evacuated Tube Solar Collector (ETSC) with PCM
storage, as shown in Fig. 15. It consists of an ETSC, a closed loop pumping line-containing water as Heat
Transfer Fluid (HTF), a PCM storage unit, cooking unit, pump, relief valve, flow meter and a stainless steel
tubing heat exchanger. PCM storage unit has two hollow concentric aluminum cylinders, and its inner and outer
diameters are 304 mm and 441 mm respectively and 420 mm deep with 9 mm thickness (Fig. 16). The space
between the cylinders was filled with 45 kg erythritol (melting point 118 OC, latent heat of fusion 339.8 kJ/kg)
used as the PCM. A pump circulates the heated water (HTF) from the ETSC through the insulated pipes to the
PCM storage unit by using stainless steel tubing heat exchanger that wraps around the cooking unit by closed
loop. During sunshine hours, heated water transfers its heat to the PCM and stored in the form of latent heatthrough stainless steel tube heat exchanger. This stored heat is utilized to cook the food in the evening time orwhen sun intensity is not sufficient to cook the food. They concluded that two-time cooking (noon and evening)
was done in a day. Noon cooking did not affect the cooking in evening and evening cooking using PCM storage
was found faster than noon cooking. Experiments and analysis indicated that the prototype solar cooker yieldedsatisfactory performance in spite of low heat transfer, the modified design of heat exchanger in the thermal
storage unit will enhance the rate of heat transfer in the present set-up.
20 cm

12.5 cm

PCM

30 cm

Fig.14: A schematic diagram of the latent heat storage unit

PCMs for Low Temperature Solar Thermal Applications
Ramadan et al. [92] designed a simple flat-plate solar cooker with focusing plane mirrors using energy
storage materials. In his design, a jacket of sand (1/2 cm thick) around the cooking pot has improved the cooker
performance tremendously. They concluded that six hour per day of cooking time has been recorded.
Approximately three hours per day of indoor cooking has been achieved. An overall energy conversion
efficiency up to 28.4% has been obtained. The possibility of using a PCM as a storage medium to obtain longer
cooking periods was studied. A thin layer of the salt hydrate Ba(OH)2·8H2O as a jacket around the cooking pot
was suggested. Bushnell [93] presented a prototype for solar ovens, which employs pentacrythritol as asolid-solid PCM. He described the performance from efficiency measurement and determination of figure of
merit.

Fig.15: Outline of the prototype solar cooker based on evacuated tube solar collector with PCM storage unit

Fig. 16 (a): Sectional view of the PCM storage unit

Fig. 16(b): Vertical view of the PCM storage unit

51

52

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

4.6 Waste heat recovery systems
Air conditioning system ejects (sensible and latent) heat, in which sensible heat accounts for about 15‐20%of the total exhausting heat [101]. The exhausting temperature of compressor is relatively high (< 65 OC) whenusing Freon as refrigerant. Therefore, it can be recovered using an accumulator and gets heat of higher
temperature. Zu et al. [32] developed a heat recovery system using PCM to recover the ejected heat of air
conditioning system and producing low temperature hot water for washing and bathing. They concluded that theheat recovery system decreases not only the consumption of primary energy for heating domestic hot water but
also the calefaction to the surroundings due to the rejection of heat from air conditioning systems. It wasobserved that the efficiency ratio of the system is improved effectively when all the rejected (sensible and latent)
heat from air conditioning systems is recovered. The technical grade paraffin wax and the mixtures with liquidparaffin and lauric acid qualify as PCM for heat recovery of air conditioning system.
An effective utilization of urban waste heat from co-generation systems, typically available at temperaturesof 60 - 100 OC. Kakiuchi et al. have investigated erythritol (Melting point 118 OC; Latent heat of fusion 339.8
kJ/kg) [102, 103] that can be used for relatively high temperature industrial waste heat processes. Several studies
have been done on stearic acid [104, 105]. This material has a melting point between 60 - 70 OC and is expensive.
It has only found of limited use in waste heat systems. Nagano et al. [106] proposed a mixture ofMg(NO3)2.6H2O as a base material with MgCl2·6H2O as an additive to modulate the melting point. They
reported that addition of 5‐10 wt% of MgCl2·6H2O can set the Mg(NO3)2.6H2O (melting point 80 OC, latent heatof fusion 150 kJ/kg). Increasing the mix ratio had little effect on heat of fusion, but allowed the melting point tobe reduced to about 60 OC. No degradation in the melting point and latent heat of fusion was observed after 1000
accelerated thermal cycles. Yagi et al [107] conducted fundamental studies on heat transfer for developing a heatstorage process by latent heat for recovering the high temperature waste heat over 500 K. Heat transfer
experiments were attempted for a single encapsulated phase change materials and for a packed bed. The metal
PCMs were found to be excellent for heat storage because of uniform temperature in the capsule. Simulation
results shows that the concurrent flow for heat storage and release showed better result for effective use of storage
heat than counter-current flow.
Buddhi [108] designed and fabricated a shell and tube type heat exchanger for low temperature waste heatrecovery using stearic acid (melting point 59 OC, latent heat of fusion 198 kJ/kg) was used as a PCM for thisstudy. Thermal performance of this system was evaluated for charging and discharging process of PCM fordifferent mass flow rates. Schematic diagram of the shell and tube heat exchanger is shown in Fig. 17. Used PCM
has poor thermal conductivity, to enhance the effective thermal conductivity of the system, the radial distance
between the tubes was kept 3 to 4 cm. Shell was filled with 50 Kg commercial grade stearic acid being used aslatent heat storage media. Flowing hot water through HTF tubes started the energy-charging test, and the stored
energy was extracted by passing cold water in the HTF tubes. Ambient temperature, flow rate and PCM
temperatures of the heat exchanger were also measured simultaneously at an interval of 15 minutes. He concluded
that the experimental results show the feasibility of using PCM as storage media in heat recovery systems. Due topoor thermal conductivity of the PCM the overall heat transfer coefficient is quite low and fins should be provided
to increase the effectiveness of the heat exchanger. Distance between tubes, fins and mass flow rates should beselected carefully in order to optimize the performance of the heat exchanger. Paraffin wax (melting point 54 OC,
latent heat of fusion 184 kJ/kg) was also used in shell and tube type heat exchanger for waste heat recovery [109].
Fins were also used for effective heat transfer.

Fig. 17: Shell and tube type heat exchanger with latent heat storage material

PCMs for Low Temperature Solar Thermal Applications

53

5.0 Latent Heat Storage Exchanger
Latent heat storage systems mainly depends on heat storage material investigations and on the developmentof heat exchangers that assure a high effective heat transfer rate to allow rapid charging and discharging. Heatexchanger with high temperature PCM not only has a high capacity to store thermal energy, but also can makethe stored energy to be highly applicable. It is always a problem to get a sufficient rate of heat transfer from thelatent thermal energy storage systems due to the poor design of heat exchanger. So far, some different types ofheat exchangers have been developed to overcome this shortage. Double pipe heat exchanger for latent thermalenergy storage has been studied [110]. This research suggested that heat transfer rate can be enhanced byincreasing the air inlet temperature, air mass flow rate and heat exchanger length. Single full-length heatexchanger exhibited better thermal effectiveness than two half-length and equal capacity parallel heat exchangers.
A direct contact heat exchanger with an immiscible heat transfer fluid moving in the PCM has eliminated thepermanent heat exchange surface and has been confirmed to prevent phase separation of the PCM [111 - 113].
Classical double-pipe or shell-and-tube heat exchangers have been applied in the storage energy systems anda relevant theoretical and experimental analysis of the phase-change phenomenon has been restricted togeometry of a cylindrical capsule [114], an annulus gap, spherical or rectangular enclosures [115]. Another novel
configuration includes the use of three types of PCMs with different melting temperature [116]. This allows for
maximum use of the HTF energy. Use of plate heat exchangers was thought to provide more efficient andcompact heat exchange configuration [117]. Erk and Dudukovic [118] presented a novel energy storage system
consisting of n-octadecane retained by capillary forces in a porous silica support. This configuration eliminates
the expensive heat exchange surface, provides higher energy density, and gives higher rates of energy storage
and release. Lecomte et al [119] presented a design method for sizing a shell-and -tube latent heat exchanger fora thermal system under thermodynamic conditions. They concluded that high flow rates could not deliversignificant heat from PCM to the load. Discharging of heat from PCM to the load depends on the performance ofthe heat exchanger and thermophysical properties of the PCM. Bathelt [120] studied the heat transfer during
melting from a horizontal cylindrical heat source with a uniform surface heat flux and a uniform surface
temperature by circulating a fluid through a multipass heat exchanger embedded in n-heptadecane andn-octadecane. The instantaneous shape of the melt volume was recorded photographically and local heat transfer
coefficients at the solid - liquid interface were determined. For quasi-steady melting, the local and average heattransfer is correlated in dimensionless form. Using the correlation, the solid-liquid interface position was
calculated and found to be in good agreement with experimental data.
Saxena et al. [121] presented a preliminary model for estimating possible thermal energy storage in shell andtube heat exchanger. Effect of various parameters such as thermal and physical properties of PCM andconvective fluid, heat exchanger dimensions and heat transfer fluid flow rates both in laminar and turbulent
regime on energy storage times are discussed. El - Kassaby et al. [122] simulated the behavior of a
low-temperature PCM in a heat exchanger for short-term storage. An excellent agreement was obtained for theoutlet air temperature when compared with the experimental measurements, and differences did not exceed
0.5°C over the simulated period. This simulation approach can be used for any PCM with known thermophysicalproperties and able to predict the transient moving front for freezing or melting, mass fraction of either liquid or
solid phase to the total PCM mass.
Kamimoto et al. [123] developed a latent heat thermal storage exchanger using form-stable high-density
polyethylene. In their design, the hot fluid entered into the exchanger from the top end during the charging
process, whilst cold fluid entered into the exchanger from the bottom end during the discharging process. No
explanation was given as to why such an operation mode was adopted. Bellecci et al. [124] numericallysimulated the cyclic thermal processes in a shell-and-tube latent heat thermal storage exchanger. In their design
the hot and cold fluids were introduced from the same end of the storage exchanger for the successive charge anddischarge processes. Gong et al. [125] tried to find, which operation mode is better in-between Kamimoto [123]and Bellecci et al. [124]. They developed a finite element model to simulate the cyclic thermal process occurringin a shell-and-tube latent heat thermal storage exchanger. This exchanger consists of a tube, which surrounds byan external coaxial cylinder made up of a PCM. A heat-transfer fluid flows through the tube to store or extract
thermal energy from the PCM. Numerical experiments indicated that introducing the hot and cold fluid from thesame end of the storage exchanger is more desirable than introducing the hot and cold fluid from different endsof the storage exchanger. Numerical results also provide the guidance for selection of the appropriate mode. The
results are limited to only conduction-controlled melting/freezing heat transfer in the PCM.
Hasan[126] developed a simple tube-in-tube heat exchanger for thermal energy storage with stearic acid as a
PCM. He found that the melting front moves in the radial direction inward as well as in the axial direction fromthe top toward the bottom of the PCM tube. Melting front speed was enhanced by a convection heat transfer

54

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

mechanism in the melted PCM. Phase transition can also be fast by placing the heat exchanger in a horizontal
position rather than a vertical one. He et al. [127] presented a theoretical analysis and experimental tests on anovel shell-and-tube latent heat exchanger which provides a basis for optimal design and operation of the heatexchanger. They reported that some parameters, such as the inlet temperature, the velocity of fluid, the thicknessof the PCM and the length of the flow channel have visible effects on the heat transfer performance of the unit.
Stable heat output can be obtained by increasing the entrance temperature of heat transfer fluid, PCM thickness,and flow channel length. Banaszek et al. [128] used a spiral heat exchanger in latent heat storage unit.
Compactness, enhanced heat transfer due to centrifugal forces, easy sealing, large heat transfer surface, and ashorter undisturbed flow length are the most appealing features of this system. Qarnia et al. [129] presented amathematical model for simulating the thermal behavior of a cross - flow heat exchanger with layers of PCM
sandwiched between the hot and cold air streams to prevent frosting. Mathematical model was validated withexperimental data. It was found that thermal resistance affects the exchanger performance by reducing thedimensionless outlet temperature of the cold air stream.
6.0 Measurement Techniques of Thermo-physical Properties
The different measurement techniques presently used for latent heat of fusion and melting temperature of
PCMs may be classified as (i) Drop Calorimeter (DC) (ii) Differential Thermal Analysis (DTA) (iii)
Differential Scanning Calorimeter (DSC). The DC method requires a long time and the accuracy of the results is
also not good [21]. In DSC & DTA techniques sample and reference materials are heated at constant rate. The
temperature difference between them is proportional to the difference in heat flow between the two materials andthe record is called the DSC curve. The recommended reference material is Alumina (Al2O3). Latent heat offusion is calculated using the area under the peak and melting temperature is estimated by the tangent at the pointof greatest slope on the face portion of the peak. Lots of researchers have been used DSC for measuring thethermo physical properties of the PCMs (Flaherty, 1971; Giavarini et al., 1972;Cantor et al., 1978; Elder et al.,
1980; Salyer et al, 1986; Bukovec N. et al., 1989; Dunn J.G. et al., 1989; Aboul-Enein et al., 1991; Takahashi Y.
et al., 1991; Babich M.W. et al., 1992; Richardson M.J. et al, 1993, Gibbs et al, 1986; Feldman D. et al., 1996; Li
W. et al., 1999; Sharma S.D. et al., 1999; Sharma, A. et al. 2002; Liu et al. 2001) [130 - 146].
The above methods are, in general, appreciated as an accurate means in measuring the heat of fusion. But thethermophysical properties of a very small amount (1-10 mg) of the sample PCM might be different from those of
the bulk materials including heterogeneous additives. As another method for determining thermo physicalproperties of PCM, Zhang's proposed a T-history method [147] to be able to overcome the above limitation of
DSC. Because this method does not take a small amount of sample, it is very convenient when a cycle test is
carried out with sealed tubes containing newly developed PCMs. Nevertheless, the original T-history method has
a restriction on accuracy of thermophysical properties owing to introduction of some invalid physicalassumptions. Hong et al. [148] tried to improve the accuracy of T-history method for measuring heat of fusion ofvarious materials. Marin et al. [149] also improved the Zhang et method to determine temperature dependent
properties. They reported that using this method it is possible to obtain both properties and curves in a simple way
which will be of great help in selecting heat storage material and in the subsequent design of a thermal energy
storage system. The enthalpy–temperature curves represent an advance to obtain average properties of thematerials since they enable an evaluation of the variation of the thermal properties against temperature.
7.0 Thermal Cycles
For latent heat storage, commercial-grade PCMs with a purity of about 95% is preferred due to theirlarge-scale availability and low cost. In general, the thermo physical properties and behavior of commercial-grade
materials are found to be very different from those quoted in the literature for laboratory-grade materials (purity
more than 99%). Since limited data are available on the effect of thermal cycling on commercial grade PCMs, it isimportant to study the effects of thermal cycling on the melting temperature, latent heat of fusion and the specificheat of commercial grade PCMs. Sharma et al. [144, 145] conducted accelerated thermal cycle test for stearic acid,acetamide and paraffin wax. They concluded that commercial grade PCMs have shown no regular degradation in
their melting points during repeated 1500 thermal cycles. Acetamide and paraffin wax have shown reasonably
good stability for the cycling process and can be considered as promising PCMs. It is recommended that before
employing a commercial grade material as PCM, its thermal cycle test should be conducted as the behavior may
change. Ting et al. [150] conducted accelerated cycle tests on a PCM unit having (Na2SO4 .nH2O) at different
ratios by weight. They studied the effect of 1000 thermal cycles on the container tube, but did not analyze its effecton the thermophysical properties of the PCM. Fernanda [151] has also studied the thermal reliability of salt hydrate
PCMs with melting temperatures between 15 and 32OC by measuring latent heat of fusion and melting temperature
after subjection to repeat cycles.

PCMs for Low Temperature Solar Thermal Applications
Sharma et al. [152] tested the effect of thermal cycling on urea and noticed that it did not melt after a several
cycles. They suggested that urea should not be used as a PCM. Hadjieva [153] calculated the enthalpy of threeparaffin mixtures and found the dependence on their oil content and the distribution of atoms defined bychemical and gas chromatographic analyses. Thermal cycle testing also carried out for the mixture of technicalgrade paraffins and found stable after repeating 900 heating/cooling cycles. Gibbs [141] reported that paraffinshows excellent thermal stability. Kimura and Kai [154] used NaCl to improve the stability of CaCl2.6H2O,
containing slightly more water than the stoichiometric composition. The salt was found to be very stable after
repeating more than 1000 heating/cooling cycles. Porisino [155] studied the thermal reliability of salt hydrate
PCMs by measuring the latent heat of fusion and melting temperature after subjection to repeated cycles. Wadaet al. [156] investigated the decreasing heat storage capacity of CH3COONa.3H2O during thermal cycling andperformed calorimetric measurements on three kinds of samples. Hasan and Sayigh [157] investigated thethermal properties of some saturated fatty acids using the DSC technique after a middle term period that includes
heating‐cooling cycles of 450 times. The thermal energy storage capacity of Na2SO4.10H2O was investigatedwith respect to thermal cycling by Marks [158]. Zhang et al. [159] studied the solid - liquid phase transitions inlauric, palmitic and stearic acids and their binary systems. They also investigated the stability of the thermal
properties after many times of heating - cooling cycles, such as 30, 50, 80, and 100. Sari [160, 161] conducted1200 accelerated thermal cycle tests to study the thermal reliability of lauric, myristic, palmitic, and stearic acid.
Thermal cycling tests have also been conducted for 24 wt% PCM impregnated wallboards. The samples showedno tendency of the PCM (paraffin) to migrate within the wallboard, and there was no observable deterioration in
the thermal energy storage capacity [162].
8.0 Corrosion of the PCMs
The corrosion of some salt hydrates and salt eutectics to different materials of container and their thermal
stability were tested by Porosini [155] and Groll et al. [164]. Recently, Cabeza et al. [165 - 168] studied corrosion
resistance of five common metals (aluminum, brass, copper, steel and stainless steel) in contact with molten salt
hydrates (zinc nitrate hexahydrate, sodium hydrogen phosphate dodecahydrate, calcium chloride hexahydrate,sodium carbonate, potassium hydrogen carbonate, potassium chloride, water, sodium acetate trihydrate, andsodium thiosulphate pentahydrate) in an immersion corrosion test. Recently, Sari et al. [169] investigated thecorrosion resistance of some construction materials to the fatty acids (stearic, palmitic, myristic and lauric acid)over a long period. The materials containers were stainless steel (SS 304 L), carbon steel (steel C20), aluminum(Al) and copper (Cu). It can concluded that stainless steel (SS304L) with chromium oxide (Cr2O3) surface layer
and aluminum (Al) metals with aluminum oxide (Al2O3) layer surface are essentially compatible with theinvestigated fatty acids based on gravimetric and metallographic corrosion tests results. Carbon steel (Steel C20)and copper (Cu) metals, as storage container materials are preferentially compatible.
9.0 Heat Transfer Enhancement
In a latent heat storage system, the solid‐liquid interface moves away from the heat transfer surface duringphase change. During this process, the surface heat flux decreases due to the increasing thermal resistance of thegrowing layer thickness of the molten/solidified medium. In the case of solidification, conduction is the onlytransport mechanism, and in most cases it is very poor. In the case of melting, natural convection can occur inthe molten layer and this generally increases the heat transfer rate compared to the solidification process (if thelayer is thick enough to allow natural convection to occur). However, the generally low heat transfer rate can beincreased considerably by using a suitable heat transfer enhancement technique. There are several methods toenhance the heat transfer in a LHTS system. The use of finned tubes with different configurations has been
proposed by various researchers as an efficient means to improve the charge/discharge capacity of a LHTS
system [170 - 179]. Other heat transfer enhancement techniques for LHTS systems are having the PCM inserted
in a metal matrix [180 - 185], using PCM dispersed with high conducting particles [186], microencapsulation of
PCM [187 - 188], embedded graphite matrix [189 - 190], carbon fiber brushes with a high thermal conductivity(190 W/mK) [191], exfoliated graphite (EG) for improving the thermal conductivity of the form-stable P/HDPE
composite PCMs [192], copper plates inserted in spherical capsules for n- octadecane PCM [193], using metal
screens/spheres placed inside the PCM [194]. Erik and Dudukovic [195] presented a novel energy storage
system consisting of n-octadecane retained by capillary forces in a porous silica support. This configuration
eliminates the expensive heat exchange surface, provides higher energy density, and gives higher rates of energy
storage and release. Leoni and Amon [196] employed aluminum foam to enhance the heat transfer process inlatent heat storage system.

55

56

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

10.0 New PCM Innovations
Ravankar [197] presented a new testing method for satellite power using latent heat storage. PCM becomes
liquid under high temperature, which then freezes during hours of cold darkness and released its latent heat. The
released heat can used to generate electricity by driving thermoelectric units. John et al. [198] designed a novel
ventilation nighttime cooling system (a novel combination of PCM and heat pipes) as an alternative to air
conditioning. The system offers substantial benefits in terms of reducing or eliminating the need for air
conditioning. Microencapsulated PCMs can be included within textile fibers; composites and clothing to provide
greatly enhanced thermal protection in both hot and cold environments [199]. Cabeza et al. [200] reported that
the PCM can be used for transporting temperature sensitive medications and food because the PCMs capability
to store heat and cold in a range of several degrees. Several companies are engaged in the research oftransporting temperature sensitive PCMs for various applications [201 - 205].
Vasiliev et al. [206] developed the latent heat storage module for motor vehicle because the heat is stored
when the engine stopped, and can be used to preheat the engine on a new start. It is possible to reach an
optimized working temperature within the engine in a much shorter time using the heat storage than without heatstorage. Pal and Joshi [207, 208] recommended the PCM to restrict the maximum temperature of electronic
components. Tan et al. [209] conducted an experimental study on the cooling of mobile electronic devices, andcomputers, using a heat storage unit (HSU) filled with the phase change material (PCM) of n-eicosane inside thedevice. The high latent heat of n-eicosane in the HSU absorbs the heat dissipation from the chips and canmaintain the chip temperature below the allowable service temperature of 50 OC for 2 h of transient operations of
the PDA.
Climator [210] has developed a cooling vest for the athletes for reducing the body temperature. PCMs also
proposed for cooling the newborn baby [211]. Koschenz et al. [212] developed a thermally activated ceiling
panel for incorporation in lightweight and retrofitted buildings. It was demonstrated, by means of simulation
calculations and laboratory tests, that a 5 cm layer of microencapsulated PCM (25% by weight) and gypsum
surface to maintain a comfortable room temperature in standard office buildings. Heptadecance were tried as
PCM in this prototype set-up. Naim et al. [213] constructed a novel continuous single-stage solar still with PCM.
They reported that the productivity of a solar still can be greatly enhanced by the use of a PCM integrated to thestill. Huang et al. [214] used PCMs for thermal regulation of building-integrated photovoltaic. Depending on
ambient conditions, a PV/PCM system may enable the PV to operate near its characterizing temperature (25 OC).
They developed PV/PCM simulation model and validated with experimental results. The improvement in thethermal performance achieved by using metal fins in the PCM container is significant. The fins enable a more
uniform temperature distribution within the PV/PCM system to be maintained. An extensive experimental test
has been undertaken on the thermal behavior of a phase change material, when used to moderate the temperaturerise of PV in a PV/PCM system [215 - 217]. Use of PCM with photovoltaic (PV) panels and thermoelectricmodules (TEMs) in the design of a portable vaccine refrigerator for remote villages with no grid electricity was
proposed by Tavaranan et al. [218]. TEMs, which transfer heat from electrical energy via the Peltier effect,
represent good alternatives for environmentally friendly cooling applications, especially for relatively low
cooling loads and when size is a key factor. Thermoelectric refrigeration systems employing latent heat storage
have been investigated experimentally by Omer et al. [219]. Duffy and Trelles [220] proposed a numericalsimulation of a porous latent heat thermal energy storage device for thermoelectric cooling under different
porosities of the aluminum matrix. They used a porous aluminum matrix as a way of improving the performanceof the system, enhancing heat conduction without reducing significantly the stored energy.
Weinlader et al. [221] used PCM in double-glazing façade panel for day lighting and room heating. A facadepanel with PCM shows about 30% less heat losses in south oriented facades. Solar heat gains are also reduced byabout 50%. Facade panels with PCM improve thermal comfort considerably in winter, especially during
evenings. In summer, such systems show low heat gains, which reduces peak cooling loads during the day.
Additional heat gains in the evening can be drawn off by nighttime ventilation. If a PCM with a low melting
temperature of up to 30 OC is used, thermal comfort in summer will also improve during the day, compared to
double glazing without or with inner sun protection. Ying et al. [222] developed the test standards for PCM
fabrics. Three indices have been proposed to characterize the thermal functional performance of PCM fabrics.
The index of thermal regulating capability can described the thermal regulating performance of PCM fabrics,
and is strongly dependent on amount of PCM. Khateeb et al. [223] designed a lithium-ion battery employing anovel phase change material (PCM) for thermal management system in electric scooter. Developed Li-ion
battery was suggested in order to replace the existing lead–acid battery in the electric scooter with the Li-ion
battery without introducing any mechanical changes in the battery compartment.

PCMs for Low Temperature Solar Thermal Applications
11.0 Conclusion
This review will help to find the suitable PCM for various applications, different techniques for themeasurement of thermo physical properties of PCM, suitable heat exchanger with ways to enhance the heattransfer and provide the various designs to store the heat using PCM for different applications i.e. heating,cooling, cooking, greenhouse, water heating and waste heat recovery systems. Study on thermal cycles andcorrosion of the materials for long term stability is discussed. Recent innovations on PCM applications areincluded for the awareness about new applications. More applications are yet to be discovered.
Acknowledgement
Dr. Someshwer Dutt Sharma is very grateful to Japan Society for the Promotion of Science for funding thepost doctoral fellowship for the year 2003 - 2005.

Nomenclature
am
ar
∆hm
∆hr
m
Ta
Tf
Ti
Tm
Cp
Cap
Clp
Csp
Q

Fraction melted
Fraction reacted
Heat of fusion (kJ/kg)
Endothermic heat of reaction (kJ/kg)
Mass of heat storage medium (kg)Ambient air temperature (OC)Final temperature (OC)Initial temperature (OC)Melting temperature (OC)Specific heat (kJ/kg K)
Average specific heat between Ti and Tf (kJ/kg K)
Average specific heat between Tm and Tf (kJ/kg K)
Average specific heat between Ti and Tm (kJ/kg K)
Quantity of heat stored (kJ)Abbreviations
c
CASE
EG
ETSC
HDPE
HTF
ic
LHS
L
n.a.
NPG
PCM
PE
PHPS
PV
SHS
S
TAM
TEM

Congruent melting
Compressed air energy storage
Exfoliated graphite
Evacuated tube solar collector
High density polyethylene
Heat transfer fluid
Incongruent melting
Latent heat storage
Liquid state
Not available
Neopentyle glycol
Phase change material
Penaerythritol
Pumped hydro power storage
Photovoltaic
Sensible heat storage
Solid state
Trihydroxy methyl aminomenthane
Thermoelectric module

References
1.
2.
3.
4.
5.

Lane, G., 1983, "Latent heat materials", Volume 1, CRC Press, Boca Raton, Florida.
Abhat, A., 1983, "Low temperature latent heat thermal energy storage: heat storage materials", Solar Energy, 30, 4,
313-331.
Kaygusuz, K., 1999, “The viability of thermal energy storage”, Energy Sources, 21, 745-755.
Sari, A. and Kaygusuz, K., 2000, “Energy and exergy calculations of latent heat storage systems,” Energy Sources, 22,
117-126.
El-Dessouky, H. and Al-Juwayhel, F., 1997, “Effectiveness of a thermal energy storage system using phase-changematerials", Energy Conversion and Management, 38, 601-617.

57

58
6.

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

Wang, X., Lu, E., Lin, W., Liu, T., Shi, Z., Tang, R. and Wang, C., 2000. “Heat storage performance of the binary
systems neopentyl glycol/pentaerythritol and neopentyl glycol/trihydroxy menthyl-aminomethane as solid phase changematerials,” Energy Conservation and Management, 41, 129-134.
7. Kauranen, P., Peippo, K. and Lund, P.D, 1991, “An organic PCM storage system with adjustable melting temperature,”
Solar Energy, 46, 275-278.
8. Sharma, S.D., Buddhi, D. and Sawhney, R.L., 1999, “ Accelerated thermal cycle test of latent heat-storage materials,”
Solar Energy, 66, 483-490.
9. Pillai, K.K. and Brinkwarth, B.J.,1976, "The storage of low grade thermal energy using phase change materials,"
Applied Energy, 2, 205-216.
10. Garg, H.P., Mullick, S.C. and Bhargava, A.K., 1985, "Solar thermal energy storage", D. Reidel Publishing Co.
11. Abhat, A., 1978, "Investigation of physical and chemical properties of phase change materials for space heating/coolingapplications", Proc. of the International solar energy congress, New Delhi, India.
12. Buddhi, D. and Sawhney, R.L.,1994, "Proc: Thermal energy storage and energy conversion", School of Energy andEnvironmental Studies, Devi Ahilya University, Indore, India
13. Hiran, S., Suwondo, A., Mansoori, G.,1994, “Characterization of alkanes and paraffin waxes for application as phasechange energy storage medium”, Energy Sources, 16, 117-128.
14. Hale, D.V., Hoover, M.J., and O'Neill, M.J., 1971, " Phase change materials", Hand Book, Marshal Space Flight Center,
Alabaa.
15. Hasnain, S., 1998, “Review on sustainable thermal energy storage technologies, Part I: heat storage materials andtechniques,” Energy Conservation and Management, 39, 1127-1138.
16. Veraj, R., Seeniraj, B., Hafner B., Faber, C. and Schwarzer, K.,1998, “Heat transfer enhancement in a latent heat storage
system,” Solar Energy,65, 171-180.
17. Abhat, A., 1981, " Development of a modular heat exchanger with an integrated latent heat storage", Report No. BMFTFBT 81-050, Germany Ministry of Science and Technology Bonn.
18. Lane, G.A., 1978, " Macro–encapsulation of PCM", Report No. oro/5117-8, Dow Chemical Company, Midland,Michigan, 152.
19. Lane, G.A., 1989, " Hand book of thermal design, Chapter 1:Phase change thermal storage materials’, Edited by C.
Guyer, McGraw Hill Book Co.
20. Gustafsson, M., Bo He and Seterwall, F.,1998, "Paraffin waxes and their mixture as phase change materials (PCMs) for
cool storage in district cooling system", IEA Annex 10, 45 – 56, Turkey.
21. Buddhi, D., Sawhney, R.L., Seghal, P.N., and Bansal, N.K., 1987, " A simplification of the differential thermal analysis
method to determine the latent heat of fusion of phase change materials", J. Physics D., Applied Physics, 20, pp
1601-1605.
22. Tanishita, I., 1970, "Present situation of solar water heaters in Japan", Int. Solar Energy Society Conference, Melbourne.
23. Richards, S.J., and Chinnery, D.N.W., 1967, CSIR Res. Rep. 237, South.
24. Prakesh, J., Garg, H.P., and Datta, G., 1985, " A solar water heater with a built – in latent heat storage", Energy Convers
Mgmt., 25, 1, 51-56.
25. Bansal, N.K., and Buddhi, D., 1992, " An analytical study of a latent heat storage system in a cylinder", Solar Energy,
33, 4,235-42.
26. Tiwari, G.N., Rai, S.N., Santram and Singh, M., 1988, "Performance prediction of PCCM collection-cum-storage water
heater:Quasi-steady state solution", Energy Conversion and Management, 28, 3, 219-223.
27. Tayeb, A.M.,1993, "A simulation model for a phase change energy storage system: experimental and verification",
Energy Conversion and Management, 34, 4, 243-250.
28. Font, J., Muntasell, J., and Cardoner, F., 1994, " Preliminary study of a heat storage unit using a solid-solid transition",
Solar Energy Materials and Solar Cells, 33, 2, 169-176.
29. Chaurasia, P.B.L., 1986, "Study of solar energy storage in paraffin wax storage system up to two night duration", India
Energy Abstract, 5(3-4), 14.
30. Baran, G., and Sari, A, 2003, "Phase change and heat transfer characteristics of a eutectic mixture of palmitic and stearic
acids as PCM in a latent heat storage system", Energy Conversion and Management, 44,3227-3246.
31. Bhargava, A.K., 1983, "Solar water heater based on phase changing material", Applied Energy, 14, 3, 197 -209.
32. Gu, Z., Liu, H., and Li, Y., 2004, "Thermal energy recovery heat recovery system calculation and phase change material
development", Applied Thermal Engineering (in press).
33. Hasan, A., and Sayigh, A.A., 1994, "Some fatty acids as phase change thermal energy storage materials", Renewable
Energy, 4, 1, 69 - 76.
34. Kurklu, A., O' Zmerzi, A., and Bilgin, S., 2002, "Thermal performance of a water- phase change material solar
collector", Renewable Energy, 26, 391 - 399.
35. Jurinak, J.J., and Abdel Khalik, S.I., 1978, " Properties optimization for phase change energy storage in air based solar
heating systems", Solar Energy, 21, 377.
36. Jurinak, J.J., and Abdel Khalik, S.I., 1979, " Sizing phase change energy storage units for air based solar heating
systems", Solar Energy, 22, 355.
37. Klein, S.A., and Beckman, W.A., 1979, " A general design method for closed loop solar energy systems", Solar Energy,
22, 269.
38. Bulkin, S.G., Vyrlan, P.M. and Pleshka, M.S., 1988, "Mathematical model of a solar assisted heat pump system withsolar absorbers and two thermal storage tank", Applied Solar Energy, 21, 41.
39. Ghoneim, A.A., 1979, "Comparisons of theoretical models of phase change and sensible heat storage for air and water
based solar heating systems, Solar Energy, 42, 209.

PCMs for Low Temperature Solar Thermal Applications
40. Kaygusuz, K., Comakli, O., and Ayhan, T., 1991, "Solar assisted heat pump systems and energy storage", Solar Energy,
27, 383.
41. Kaygusuz, K., 1995, "Performance of solar assisted heat pump system", Applied Energy, 51, 93.
42. Kaygusuz, K., 1995, "Experimental and theoretical investigations of latent heat storage for water based solar heating
system", Energy Conversion and Management, 36, 315.
43. Mehmet, E., 2000, " Thermal performance of a solar-aided latent heat store used for space heating by heat pump, Solar
Energy,69, 1, 15-25.
44. Fath, Hassan, E.S.,1995, "Thermal performance of a simple design solar air heater with built-in thermal energy storage
system", Energy Conversion and Management, 36, 10, 989-997.
45. Strith, U., Novak, P., 2002, "Thermal storage of solar energy in the wall for building ventilation", IEA, ECES IA Annex
17, Advanced thermal energy storage techniques - Feasibility studies and demonstration projects 2nd Workshop, 3-5 april
2002, Ljubljana, Slovenia
46. Manz, 1997, "TIM-PCM external wall system for solar space heating and daylighting", Solar Energy, 61, 6, 369-379.
47. Arkar, C., Medved, S., 2002, "Enhanced solar assisted building ventilation system using sphere encapsulated PCM
thermal heat storage", IEA, ECES IA Annex 17, Advanced Thermal Energy Storage Techniques – Feasibility Studies
and Demonstration Projects 2nd Workshop, Ljubljana, Slovenia.
48. Ismail, K.A.R. and Alves, C. L. F., 1986, "Analysis of shell-and-tube PCM storage system", Prec. 8th Int. Heat Transfer
Conf.,SanFrancisco, 1781-1786.
49. Visser, H., 1986, "Energy storage in phase-change materials-development of a component model compatible withTRNSYS", Final Report. Contract No. 2462-84-09 El) ISPNL. Delft Univ. of Technology, Department of Applied
Physics, Delft.
50. Yimmer, B. and Adami, M., 1989, "Parametric study and optimization of phase change thermal energy storage systems",
National Heat Transfer Conference, HTD, Multiphase Flow, Heat, and Mass Transfer 109, 1 - 8.
51. Lacroix, M., 1993, "Numerical simulation of a shell- and - tube latent thermal energy storage unit", Solar Energy, 50, 4,
357 - 367.
52. Sagara, K.K., Hisano, K. and Terashima, T., 1994, "Performance of latent thermal storage for solar heating system", Mie
Academic Press, Mie University, Japan, B2, 83 - 88.
53. Sari, A., and Kaygusuz, K., 2002, "Thermal performance of a eutectic mixture of lauric and stearic acids as PCM
encapsulated in the annulus of two concentric pipes", Solar Energy, 72, 6, 493-504.
54. Vakilaltojjar, S.M., and Saman, W., 2001, "Analysis and modeling of a phase change storage system for air conditioning
applications", Applied Thermal Engineering, 21, 249-263.
55. Solmar, A., Persson, J. and Loyd, D., 1989, "Field testing and simulation of a cool storage at a warehouse", 9thInternational Congress on Energy and Environment, Miami, USA.
56. Bo He, Seterwall, F., 2002, "Technical grade paraffin waxes as phase change materials for cool thermal storage and coolstorage systems capital cost estimation", Energy Conversion and Management, 43, 1709–1723.
57. Kinds of chemical products in Japan, Kagaku-Kougyou-Nippou-Sha (in Japanese), 1998, Chemical Industry Daily
Report Corp., ISBN 4-87362-267-4, Tokyo.
58. Nagano, K., Moochida, T.,Takeda, S., Domanski, D. and Rebow, M., 2003, "Thermal performance of maganese (II)nitrate hexahydrate as a phase change materials for cooling systems, Applied Thermal Engineering, 23, 2, 229 - 243.
59. Farid, M.M., Hamad, F.A. and Abu-Arabi, M., 1998, "Phase change cool storage using dimethyl-sulfoxide", Energy
Conversion and Management,39, 8, 819-826.
60. Saitoh, T., Hirose, K.,1986, "High-performance phase-change thermal energy storage using spherical capsules", Chem.
Eng. Commun. 41, 39 - 58.
61. Kondepudi, S., Somasundaram, S., Anand, N.K., 1988, " A simplified model for the analysis of a phase-changematerial-based thermal energy storage system", Heat Recovery System. CHP 8 (3), 247 - 254.
62. Laybourn, D.R., 1988, " Thermal energy storage with encapsulated ice", ASHRAE Trans. 94 (1), 1971 - 1988.
63. Arnold, D., 1990, "Dynamic simulation of encapsulated ice stores-Part I: The model", ASHRAE Trans. 97 (2), 1170 1178.
64. Chen, S.L., 1991, "An experimental investigation of cold storage in packed capsules with solidification", Int. J. Exp.
Heat Transfer, 4, 263 - 280.
65. Chen, S.L., Yue, J.S., 1991, "A simplified analysis for cold storage in porous capsules with solidification", ASME J.
Energy Resources. Technol, 113, 108 - 116.
66. Chen, S.L., Yue, Y.S., 1991, "Thermal performance of cool storage in packed capsules for air conditioning", Heat
Recovery Syst. CHP, 11, 6, 551 -561.
67. Ryu, H.W., Hong, S.A., Shin, B.C. and Kim, S.D., 1991, "Heat transfer characteristics of cool-thermal storage systems",
Energy,16, 4, 727 - 737.
68. Chen, S.L., Wang, P.P., Lee, T.S., 1999, "An experimental investigation of nucleation probability of supercooled water
inside cylindrical capsules", Experimental Thermal and Fluid Science, 18, 299 - 306.
69. Chen, S.L., Chen, C.L., Tin, C.C., Lee, T.S. and Ke, M.C., 2000, "An experimental investigation of cold storage in an
encapsulated thermal storage tank", Experimental Thermal and Fluid Science, 23, 3-4, 133 - 144.
70. Takakura, T. and Nishina, H., 1981, "A solar greenhouse with phase change energy storage and a microcomputer control
system", Acta Hort. (Energy in Protected Cultivation), 115, 583-590.
71. Jaffrin, A. and Cadier, P., 1982, "Latent heat applied to horticulture--la baronne solar greenhouse", Solar Energy, 38, 4,
313-321.
72. Jaffrin, A., Cadier, P. and Venard, M., 1987, "La baronne solar greenhouse of CREAT-CNRS", In REUR technicalseriesI--Greenhouse Heating With Solar Energy, CNRE, pp. 192-194.

59

60

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

73. Levav, N. and Zamir, N., 1987, "Phase change materials for heat storage in greenhouse", In REUR technical seriesl--Greenhouse Heating With Solar Energy, CNRE, 163-166.
74. Kern, M. and Aldrich, R. A., 1979, "Phase change energy storage in a greenhouse solar heating system", Paper presented
at the summer meeting of ASAE and CSAE, June 24--27, University of Manitoba, Winnipeg.
75. Nishina, H. and Takakura, T., 1984, "Greenhouse heating by means of latent heat storage units", Acta Hort. (Energy inProtected Cultivation Ill), 148, 751-754.
76. Kfirklfi, A., Ozmerzi, A., Wheldon, A. E. and Hadley, P., 1996, "Utilization of a phase change material (PCM) for the
reduction of peak temperatures in a model greenhouse", Paper presented at Agritech 96, International workshop on
Greenhouse Technologies for Mild Climates, 12 15 May, BetDagan.
77. Kfirklti, A., Wheldon, A. E. and Hadley, P., 1997, "Use of a phase change material (PCM) for frost prevention in amodel greenhouse",J. Enging. Sci. Univ. Pamukkale.
78. Bagetinelik, A., Demirel, Y., Paksoy, H. O. and Oztfirk, H. H., 1994, "Greenhouse heating with solar energy stored byphase change material", 15th National Agricultural Mechanisation Congress, September 20-22, Antalya, 698-705.
79. Telkes, M., 1959, "Solar cooking ovens", Solar Energy, 3, I, 1 - 11.
80. Hoda, M. M., 1977, Proceedings of ISES-UK Conference, London, 817.
81. Garg, H. P., Mann, H. S. and Thanvi, K. P., 1978, Sun: Mankind’s Future Source of Energy, 3, 491.
82. Rommel, M., Stahl, W. and Wittwer, 1996, V., Sun at Work in Europe, l, 3.
83. Mullick, S. C., Kandpal, T. C. and Saxena, A. K., 1987, "Thermal test procedure for box type solar cookers", Solar
Energy, 39, 4, 353-360.
84. Thulasi Das, T. C., Karmakar, S. and Rao, D. P., 1994, "Solar box cooker: Part 1 Modeling", Solar Energy, 52, 3,
265-272.
85. Abhat, A.,1980, "Short term thermal energy storage", Revue Physique Applique, 15, 477 - 501.
86. Buddhi, D.and Sharma, S.D.,2000, "Thermal performance studies of a latent heat storage unit for night cooking",
TERRASTOCAL, Proc. of 8th International conference on thermal energy storage, Stuttgart, Germany, 2, 615 - 618.
87. Buddhi, D., and Sahoo, L.K., 1997, "Solar cooker with latent heat storage: design and experimental testing", Energy
Conversion and Management, 38, 5, 493 - 498.
88. Domanski, R., El-Senaii, A.A., and Jaworski, M., 1995, "Cooking during off - sunshine hours using as storage media",
Energy,20, 7, 607 - 616.
89. Sharma, S.D., Buddhi, D., Sawhney, R.L. and Sharma, Atul, 2000, "Design development and performance evaluation oflatent heat storage unit for evening cooking in a solar cooker". Energy Conversion and Management, 41, 1497 - 1508
90. Buddhi, D., Sharma, S.D., and Sharma, A., 2003, "Thermal performance evaluation of a latent heat storage unit for lateevening cooking in a solar cooker having three reflectors", Energy Conversion and Management, 44, 809 - 817.
91. Sharma, S.D. and Sagara, K., 2004, "Solar cooker for evening cooking using latent heat storage material based on
evacuated tube solar collector", IEA, ECES IA Annex 17, Advanced thermal energy storage through phase changematerials and chemical reactions - feasibility studies and demonstration projects. 6th Workshop, Arvika, Sweden.
92. Ramadan, M.R.I., Aboul-Enein, S., and El-Sebaii, A.A., 1987,"A model of an improved low cost indoor solar cooker in
Tanta", Solar &Wind Technology, 5, 4, 387 - 393.
93. Bushnell, DL., 1988, "Performance studies of solar energy storing heat exchanger. Solar Energy 41, 6, 503 -12.
94. Farid, M.M., Khudhair, A.M., Razack, S.A.K and Al-Hakkaj, S., 2004, "A review on phase change energy
storage:materials and applications", Energy Conversion and Management, 45, 1597 - 1615.
95. Zalba, B., Marin, J.M., Cabeza, L.F. and Mehling, H., 2003, "Review on thermal energy storage with phasechange:materials, heat transfer analysis and applications, Applied Thermal Engineering, 23, 251 - 283.
96. Sharma, S.D., 1999, "Study of thermal energy storage in phase change materials for low temperature solar applications",
Ph.D. Dissertation, Devi Ahilya University, Indore, India.
97. Hasnain, S.M., 1998, "Review on sustainable thermal storage technologies, Part 1:Heat storage materials andtechniques", Energy Conversion and Management, 39, 11, 1127 - 1138.
98. Hale D. V., Hoover M.J. and O’Neill, M.J., 1971, "Phase change materials Hand Book", Report no.
HREC-5183-2LMSC-HREC D225138. NASA, Marshal Space Flight Center, Alabama.
99. http://silipids.com
100. Nicolas, S., "Latent heat phase change materials for thermal storage", University of Wisconsin - Platteville, WI 53818.
101. J. Zhang, 1999, "Energy saving technology of refrigeration devices", Mechanical Industry Press, Beijing.
102. Ona, E. P., Zhang, X, Kyaw,K., Watanabe, F., Matsuda, H., Kakiuchi, H., Yabe, M., Chihara,S., 2001, "Relaxation ofsupercooling of erythritol for latent heat storage", J. Chem. Eng. Japan. 34, 3, 376 - 382.
103. Kakiuchi, H., Yamazaki, M., Yabe, M., Chihara, S., Terunuma, T., Sakata, Y. and Usami, T., 1998, "A study of erythritol
as phase change material", IEA Annex 10- PCMs and chemical reactions for thermal energy storage, 2nd Workshop,
November 11-13, Sofia, Bulgaria.
104. Buddhi,D., Sharma, S.D., 1999, "Measurements of transmittance of solar radiation through stearic acid: a latent heatstorage material,Energy Conversion and Management 40, 1979 - 1984
105. Sari,A., Kaygusuz, K., 2001., "Thermal energy storage system using stearic acid as a phase change material", Solar
Energy 71, 6, 365 - 376.
106. Nagano, K., Ogawa, K., Mochida, T., Hayashi, K. and Ogoshi, H., 2004, "Thermal characteristics of magnesium nitratehexahydrate and magnesium chloride hexahydrate mixture as a phase change material for effective utilization of urban
waste heat", Applied Thermal Engineering 24, 221 - 232.
107. Yagi, J. and Akiyama, T., 1995, "Storage of thermal energy for effective use of waste heat from industries", Journal of
Materials Processing Technology 48, 793 - 804
108. Buddhi, D., 1997, "Thermal performance of a shell and tube PCM storage heat exchanger for industrial waste heatrecovery", Proc. ISES Solar World Congress.

PCMs for Low Temperature Solar Thermal Applications
109. Buddhi, D., 2003, "Experimental thermal performance evaluation of a heat exchanger having PCM for storage of wasteheat", IEA, ECESIA Annex 17,Advanced thermal energy storage through phase change materials and chemical
reactions – feasibility studies and demonstration projects, 4th Workshop, 21-24 March 2003, Indore, India.
110. Fath, H.E.S., 1991, "Heat exchanger performance for latent heat thermal energy storage system", Energy Conversion andManagement, 31, 2, 149 - 155
111. Farid M. and Yacoub K., 1989, " Performance of direct contact latent heat storage unit", Solar Energy, 43, 4, 237 –51.
112. Abhat, A., 1988, Proc. of the l&h ASME Sol. Rnergy‘Con: Cola .
113. Sokolov, M. and Keizman, Y., 1991, "Performance indicators for solar pipes with phase change energy storage", Solar
Energy 47, 5, 339- 346.
114. Domanski, R., El-sayed, O.A., Jaworski, M., 1994, " Experimental study for the melting of PCM inside concentrichorizontal cylindrical annuli", Proceedings of 6th International Conference on Thermal Energy Storage, Espoo, Finland,503 - 511.
115. Dietz, D., 1984, "Thermal performance of a heat storage module using calcium chloride hexahydrate", Trans. ASME
106, 106 - 111.
116. Watanbe T, Kikuchi H, Kanzawa A., 1993, " Enhancement of charging and discharging rates in a latent heat storage
system by use of PCM with different melting temperatures", Heat Recov Syst CHP, 13, 1, 57- 66.
117. Bansal NK, Buddhi D., 1992, "Performance equations of a collector cum storage system using phase change materials",
Solar Energy 48, 3, 185 - 194.
118. Erk HF, Dudukovic MP., 1996, "Phase-change heat regenerators: modeling and experimental studies", AIChE, 42, 3,
791 - 808.
119. Lecomte, D. and Mayer, D., 1985, " Design method for sizing a latent heat store/ heat exchanger in a thermal system",Applied Energy, 21, 1, 55 - 78.
120. Bathelt, A.G.and Viskanta, R.,1980, "Heat transfer at the solid-liquid interface during melting from a horizontal
cylinder", International
Journal of Heat and Mass Transfer, 23, 11, 1493 - 1503.
121. Saxena, S., Subrahmaniyam, S. and Sarkar, M.K., 1982, " A preliminary model for phase change thermal energy storage
in a shell and tube heat exchanger", Solar Energy, 29, 3, 257 - 263.
122. El-Kassaby, M.M. and Ahmed, A.E., 1993, " Modeling of a heat exchanger utilizing a phase change material for
short-term storage",Renewable Energy, 3, 8, 857 - 865.
123. Kamimoto, M., Abe, Y., Sawata, A., Tani, T. and Ozawa, T., 1986, " Latent thermal storage unit using
form-stablepolyethylene; part II: performance of the storage unit". ASME Journal of Solar Energy Engineering, 108,287- 290.
124. Bellecci, C. and Conti, M., 1993, " Phase change thermal storage: transient behaviour analysis of a solar receiver/storage
using the enthalpy method", International Journal of Heat and Mass Transfer, 36, 2157- 2163.
125. Gong, Z. X. and Mujumdar, A.S., 1997, " Finite-Element Analysis Of Cyclic Heat Transfer In A Shell-And-Tube Latent
Heat Energy Storage Exchanger", Applied Thermal Engineering, 17, 6, 583-591.
126. Hasan, A., 1994, " Thermal energy storage system with stearic acid as phase change material", Energy Conversion andManagement, 35, 10, 843 - 856.
127. He, Q. and Zhang, W., 2001, " A study on latent heat storage exchangers with the high-temperature phase-changematerial", International Journal of Energy Research, 25, 331 - 241.
128. Banaszek, J., Domanaski, R., Rebow, M. and El-Sagier, F., 1999, " Experimental study of solid - liquid phase change ina spiral thermal energy storage unit", Applied Thermal Engineering 19, 1253 - 1277.
129. Qarnia,H. El., Lacroix, M. and Mercadier,Y., 2001, "Use of a Phase Change Material to Prevent Frosting in a Compact
Cross-Flow Air Exchanger", Energy Conversion and Management 42, 1277 - 1296.
130. Flaherty, B., 1971, " Characterisation of waxes by differential scanning calorimetry", J. Appl. Chem. Biotechnol. 21131. Giavarini, C., Pochetti,F., 1972, " Characterization of petroleum products by DSC analysis", J. Thermal Anal, 5, 83–94.
132. Cantor, S., 1978, "Applications of differential scanning calorimetry to the study of thermal energy storage",
Thermochemica Acta, 26, 1- 3, 39 - 47.
133. Elder, J.P., 1980, " Thermal energy storage materials - a DSC study", Thermochemica Acta, 36, 1, 67 - 77.
134. Salyer, I.O., Sircar, A.K., Chartoff, R.P., 1986, "Analysis of crystalline paraffinic hydrocarbons for thermal energy
storage by differential scanning calorimetry; Part 1, Pure hydrocarbons", 15th North American Thermal Analysis
Society Conference, Cincinnati, OH
135. Bukovec, N., Bukovec, P. and Arbanas, V., 1989, "TG and DSC investigation of CaCl2.6H2O a phase change material,
Thermochemica Acta, 148, 281- 288.
136. Dunn, J.G., Smith, H.G. and Willix, R.L., 1984, "The supercooling of acetamide", Thermochemica Acta, 80, 343 - 353.
137. Aboul-Enein, S. and Olofa, S.A., 1991, "Thermophysical properties of heat-of-fusion storage materials for coolingapplications", Renewable Energy, 1, 5 - 6, 791 - 797.
138. Takahashi, Y., Neigishi, A., Abe, Y., Tanaka, K. and Kamimoto, M., 1991, "Thermoanalytical Investigation Of Fluoride
Composites For Latent Thermal Storage", Thermochemica Acta, 183, 299 - 311.
139. Babich, M.W., Hwang, S.W. and Mounts, R.D., 1992, "The search for novel energy storage materials using differential
scanning calorimetery", Thermochemica Acta, 210, 83 - 88.
140. Richardson, M.J., 1993, "The derivation of thermodynamic properties by DSC: free energy curves and phase stability",
Thermochemica Acta, 36, 1, 67 - 77.
141. Gibbs, B.M., Hasnain, S.M., 1995, "DSC study of technical grade phase change heat storage materials for solar heating
applications", Proceedings of the 1995 ASME/JSME/JSEJ International Solar Energy. Conference. Part 2.
142. Feldman, D. and Banu, D., 1996, "DSC analysis for the evaluation of an energy storing wallboard", Thermochemica
Acta, 272, 243 -251.
143. Li, W., Zhang, D., Zhang, T., Wang, T., Ruan, D, Xing, D. and Li, H., 1999, "Study of solid-solid phase change of(n-CnH2n+1NH3)2MCl4 for thermal energy storage", Thermochemica Acta, 326, 183 - 186.

61

62

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

144. Sharma, S.D., Buddhi, D., Sawhney, R.L., 1998, "Accelerated thermal cycle tests of industrial grade phase changematerials", Proc. National solar energy convention-97: towards commercialization of clean energy. Chennai. India. Anna
University 73-77.
145. Sharma, A., Sharma, S.D. and Buddhi, D., 2002, " Accelerated thermal cycle test of acetamide, stearic acid and paraffin
wax for solar thermal latent heat storage applications", Energy Conversion and Management, 43, 1923 - 1930.
146. Liu, Z. and Chung, D.D.L., 2001, "Calorimetric evaluation of phase change materials use as thermal interface materials",
Thermochemica Acta, 366, 135 - 147.
147. Zhang Y, Jiang Y., 1999, "A simple method, the T-history method, of determining the heat of fusion, specific heat andthermal conductivity of phase-change materials", Measurement and Science Technology, 10, 201–5.
148. Hong,H.,Kim,S.K.and Kim, Y.S., 2004, "Accuracy improvement of T-history method for measuring heat of fusion ofvarious materials", International Journal of Refrigeration, 27, 360–366.
149. Marin, J.M., Zalba, B., Cabeza, L.F. and Mehling, H., 2003, " Determination of enthalpy–temperature curves of phasechange materials with the temperature-history method: improvement to temperature dependent properties", Meas. Sci.
Technol, 14,184–189.
150. Ting, K. C., Giannakakas, P. N. and Gilbert S. G., 1987, "Durability of latent heat storage tube sheets", Solar Energy ,39, 2, 79–85.
151. Fernanda, G. P., 1988, "Salt hydrates used for latent heat storage: Corrosion metals and reliability of thermal
performance", Solar Energy, 41, 2, 193–197
152. Sharma, A., Sharma, S.D., Buddhi, D. and Sawhney, R.L., 2001, "Thermal cycle test of urea for latent heat storage
applications",Int. J. Energy Res, 25, 465 - 468.
153. Hadjieva,M., Kanev, S., Argirov,J., 1992, "Thermophysical properties of some paraffins applicable to thermal energy
storage", Solar Energy Mater.Solar Cells 27, 181–187
154. Kimura, H., Kai, J., 1984, "Phase change stability of CaCl2.6H2O. Solar Energy 33, 557 - 63
155. Porisino, F.G., 1988, "Salt hydrates used for latent heat storage corrosion of metals and reliability of thermal
performance", Solar Energy, 41, 193 - 7.
156. Wada, T., Yamamoto, R., Matsuo, Y., 1984, "Heat storage capacity of sodium acetate trihydrate during thermal cycling",
Solar Energy,33, 3 -4, 373–375.
157. Hasan, A., Sayigh, A.A.M., 1994, "Some fatty acids as phase change thermal energy storage materials", Renewable
Energy 4, 69 -76.
158. Marks, S., 1980, "An investigation of the thermal energy storage capacity of Glauber’s salt with respect to thermal
cycling", Solar Energy, 25, 255 - 8.
159. Zhang, J.J., Zhang, J.L., He, S.M., Wu, K.Z., Liu, X.D., 2001, " Thermal studies on the solid–liquid phase transition inbinary systems of fatty acids", Thermochemica Acta, 369,157 - 60.
160. Sarı, A., Kaygusuz, K.,2003, "Some fatty acids used for latent heat storage: thermal stability and corrosion of metals
with respect to thermal cycling", Renewable Energy, 28, 939 - 48.
161. Sarı, A., 2003, "Thermal reliability test of some fatty acids as PCMs used for solar thermal latent heat storage
applications", Energy Conversion and Management, 44, 2277 - 87.
162. Khudhair A, Farid M, Ozkan N, Chen J., 2003, "Thermal performance and mechanical testing of gypsum wallboards
with latent heat storage", In:Proceedings of Annex 17, advanced thermal energy storage through phase change materials
and chemical reactions ‐‐feasibility studies and demonstration projects (www.fskab.com/annex17), Indore, India.
163. Heine, D., 1981, "The chemical compatibility of construction materials with latent heat storage materials", Proceedingsof the International Conference on Energy Storage, Brighton, UK.
164. Groll, M., Brost, O., Heine, D., 1990, "Corrosion of steels in contact with salt eutectics as latent heat storage materials:
Influence of water and other impurities", Heat Recovery Systems & CHP 10, 567 - 72.
165. Cabeza, L.F., Illa, J., Roca, J., Badia,F., Mehling, H., Hiebler, S., Ziegler,F., 2001, "Immersion corrosion tests on
metal-salt hydrate pairs used for latent heat storage in the 32 to 36 OC temperature range", Mater. Corros, 52, 140 - 146.
166. Cabeza, L.F., Illa, J., Roca, J., Badia,F., Mehling, H., Hiebler, S., Ziegler,F.,2001, " Middle term immersion corrosion
tests on metal-salt hydrate pairs used for latent heat storage in the 32 to 36 OC temperature range", Mater. Corros., 52,
748 - 754.
167. Cabeza, L.F., Badia, F., Illa, J., Roca,J., Mehling, H., Ziegler, Z., 2001, "Corrosion experiments on salt hydrates used asphase change materials in cold storage", IEA ECES IA Annex 17 Kick-off Workshop, Lleida (Spain).
168. Cabeza, L.F., Mehling, H., Hiebler,S. Immersion corrosion tests on metal-salt hydrate pairs used for latent heat storage
in the 48 to 58 OC temperature range", Mater. Corros., in press.
169. Sari, A., Kaygusuz, K, 2003, "Some fatty acids used for latent heat storage: thermal stability and corrosion of metals
with respect to thermal cycling", Renewable Energy, 28, 939 - 948.
170. Velraj R, Seeniraj RV, Hafner B, Faber C, Schwarzer K., 1997, "Experimental analysis and numerical modellingof
inward solidification on a finned vertical tube for latent heat storage unit",.Solar Energy, 60, 5, 281 - 290.
171. Morcos, V.H., 1990, "Investigation of a latent heat thermal energy storage system", Solar Wind Technol, 7, 197 - 202.
172. Costa M, Buddhi D, Oliva A., 1998, " Numerical simulation of a latent heat thermal energy storage system withenhanced heat conduction", Energy Convers Mgmt, 39, 319 - 30.
173. Padmanabhan, P.V., Murthy, M.V., 1986, "Outward phase change in a cylindrical annulus with axial fins on the innertube", Int J Heat Mass Transfer, 29, 1855 - 68.
174. Lacroix, M., 1993, "Study of the heat transfer behavior of a latent heat thermal energy storage unit with a finned tube",
Int.J. Heat Mass Transfer, 36,2083 - 2092.
175. Sparrow, E.M., Larsen, E.D., Ramsey, J.W., 1981, "Freezing on a finned tube for either conduction-controlled or naturalconvection controlled heat transfer", Int. J. Heat Mass Transfer, 24, 273 - 284.
176. Smith, R.N., Koch, J.D., 1982, "Numerical solution for freezing adjacent to a finned surface", Proceedings of theSeventh International Heat Transfer Conference, Munich, Germany, 69–74.

PCMs for Low Temperature Solar Thermal Applications
177. Eftekhar, J., Sheikh, A.H., Lou, D.Y.S., 1984, "Heat transfer enhancement in a paraffin wax thermal storage system",J.
Solar Energy Eng., 106, 299 - 306.
178. Choi, J.C., Kim, S.D., 1992, " Heat-transfer characteristics of a latent heat storage system using MgCl2.6H2O", Energy,
17, 8, 1153 - 64.
179. Bauer, C., Wirtz, R., 2000, "Thermal characteristics of a compact, passive thermal energy storage device" In:
Proceedings of the 2000 ASME IMECE, Orlando, USA.
180. Kamimoto, M., Abe, Y., Kanari, K., Swata, S., Tani, T., Ozawa, T., 1986, "Heat transfer in latent heat thermal storage
units using pentarythritol slurry thermal energy storage", World Congress of Chemical Engineering, Tokyo, Japan.
181. Hoogendoorn, C.J., Bart,C.C.J., 1992, " Performance and modeling of latent heat stores", Solar Energy, 48 , 53 - 58.
182. Tong, X., Khan, J., Amin, M.R., 1996, " Enhancement of heat transfer by inserting a metal matrix into a phase changematerial", Num Heat Trans Part A Appl, 30, 2, 125 - 41.
183. Khan, M.A., Rohatgi, P.K., 1994, "Numerical solution to a moving boundary problem in a composite medium",
Numer.Heat Transfer, 25, 209 - 221.
184. Stovall, T.K., Arimilli, R.V., 1988, "Transient thermal analysis of three fast-changing latent heat storage configuration
for a space-based power system", Proceedings of the 23rd Inter Society Energy Conversion Engineering
Conference,Denver, Colorado,171 - 177.
185. Hafner, B., Schwarzer,K., 1999, "Improvement of the heat transfer in a phase-change-material storage", Proceedings ofthe IEA, ECES IA Annex 10, 5th Workshop, Benedikbauern, Germany.
186. Siegel, R., 1977, "Solidification of low conductivity material containing dispersed high conductivity particles", Int. J.
Heat Mass Transfer, 20, 1087 -1089.
187. Mulligan, J.C., Colvin, D.P., Bryant, Y.G., 1996, "Microencapsulated phase-change material suspensions for heattransfer in spacecraft thermal systems", J. Spacecraft Rockets, 33, 2, 278 - 284.
188. Bedecarrats,J.P., Strub, F.P., Falcon, B., Dumas,J.P., 1996, "Phase-change thermal energy storage using sphericalcapsules: performance of a test plant", Int. J. Refrig., 19, 3, 187–196,
189. Mehling, H., Hiebler, S., Ziegler, F., 1999, "Latent heat storage using a PCM-graphite composite material: advantages
and potential applications", In:Proceedings of the 4th Workshop of IEA ECES IA Annex 10, Bendiktbeuern, Germany.
190. Py, X., Olives, S., Mauran, S., 2001, "Paraffin/porous graphite matrix composite as a high and constant power thermal
Storage material", Int J Heat Mass Transfer, 44, 2727 - 37.
191. Fukai, J., Hamada, Y., Morozumi, Y., Miyatake, O., 2003, "Improvement of thermal characteristics of latent heat
thermal energy storage units using carbon-fiber brushes: experiments and modeling", Int. J. Heat and Mass Transfer,46, 4513 - 4525.
192. Sari, A., 2004, " Form-stable paraffin/high density polyethylene composites as solid–liquid phase change material forthermal energy storage:preparation and thermal properties", Energy Conversion and Management, 45, 2033 - 2042.
193. Koizumi, H., 2004, " Time and spatial heat transfer performance around an isothermally heated sphere placed in a
uniform, downwardly directed flow (in relation to the enhancement of latent heat storage rate in a spherical capsule)",Applied Thermal Engineering (in press)
194. Ettouney, H.M., Alatiqi, I., Al-Sahali, M., Al-Ali, S.A., 2004, "Heat transfer enhancement by metal screens and metal
spheres in phase change energy storage systems", Renewable Energy, 29, 841 - 860.
195. Erk, H.F., Dudukovic, M.P., 1996, " Phase-change heat regenerators: modeling and experimental studies", AIChE, 42, 3,
791 - 808.
196. Leoni, N., Amon, C.H., 1997, "Transient thermal design of wearable computers with embedded electronics using phasechange materials", ASME HTD, 437, 5, 241–250.
197. Revankar, S., 2001, Purdue University News Bulletin <http://news.uns.purdue.edu>.
198. John, T., David, E. and David, R. , 2000, "A novel ventilation system for reducing air conditioning in buildings: Testing
and theoretical modeling", Applied Thermal Engg., 20, 1019 - 37.
199. Colvin, D.P. and Bryant,Y.G., 1998, " Protective clothing containing encapsulated phase change materials", Proceedingsof the 1998 ASME International Mechanical Engineering Congress and Exposition, Anaheim, CA, USA, 23–32.
200. Cabeza, L.F., Roca, J., Nogues, M., Zalba, B., Marın, J.M., 2002, "Transportation and conservation of temperaturesensitive materials with phase change materials: state of the art", IEA ECES IA Annex 17 2nd Workshop,Ljubljana(Slovenia).
201. Available from <www.va-q-tec.de>202. Available from <www.rubitherm.de>203. Available from <www.sogrigam.com>
204. Available from <www.tcpreliable.com>
205. Available from <www.pcm-solutions.com>
206. Vasiliev, L.L., Burak, V.S., Kulakov, A.G., Mishkinis, D.A., Bohan, P.V., 2000, "Latent heat storage modules forpreheating internal combustion engines: application to a bus petrol engine", Appl. Thermal Eng., 20, 913 - 923.
207. Pal,D., Joshi,Y., 1996, "Application of phase change materials for passive thermal control of plastic quad flat packages:
a computational study", Numer. Heat Transfer, Part A .30,19 - 34.
208. Pal, D., Joshi, Y.,1997, "Application of phase change materials to thermal control of electronic modules: a computation
study", Trans. ASME, 119, 40 - 50.
209. Tan, F.L. and Tso, C.P., 2004, "Cooling of mobile electronics devices using phase change materials", Applied ThermalEngineering, 24, 159 - 169.
210. Ulfvengren, R., 2004, " Will PCM help athletes in the olympic games in athens 2004?", IEA ECES IA Annex 17 6thWorkshop,Arvika, Sweden.
211. Olsson, L., 2004, " Cooling of newborn baby with PCM", IEA ECES IA Annex 17 6th Workshop, Arvika, Sweden.
212. Koschenz, M., Lehmann, B., 2004, "Development of a thermally activated ceiling panel with PCM for application inlightweight and retrofitted buildings", Energy and Buildings, 36, 567 - 578.

63

64

Someshower Dutt SHARMA, Hiroaki KITANO and Kazunobu SAGARA

213. Naim, M.M., Kawib, M.M.A.E., 2002, " Non-conventional solar stills Part 2. Non-conventional solar stills with energy
storage element", Desalination, 153, 71 - 80.
214. Huang,M.J.,Eames,P.C.and Norton,B.,2004, " Thermal regulation of building-integrated photovoltaics using phasechange materials", International Journal of Heat and Mass Transfer, 47, 2715 - 2733.
215. Huang, M., Eames, P.C. and Norton, B., 2001, "An experimental study into the application of phase change materials tolimit the temperature rise in build integrated photovoltaic systems", in: Proceedings of Renewable Energy in Maritime
Island Climates, September, Belfast, UK, 143–150.
216. Huang, M., 2002, "The application of CFD to predict the thermal performance of phase change materials for the controlof photovoltaic cell temperature in buildings", Ph.D. Thesis, University of Ulster, UK.
217. Huang, M., Eames, P.C. and Norton, B., 2000, "The application of computational fluid dynamics to predict theperformance of phase change materials for control of photovoltaic cell temperature in buildings" Proceedings of VI
World Renewable Energy Congress, July, Brighton, UK, 2123–2126.
218. Tavaranan, S., Das, A., Aurora, P., Trelles, J.P., 2002, " Design of a standalone portable solar powered Thermoelectric
vaccine refrigerator using phase change material as thermal backup", Solar Engineering Program, University of
Massachusetts Lowell, USA.
219. Omer, S.A., Riffat, S.B., Ma, X., 2001, "Experimental investigation of a thermoelectric refrigeration system employing aphase change material integrated with thermal diode (Thermosyphons)", Renewable Energy, 21, 1265 - 1271.
220. Trelles,J.P., Duffy, J.P., 2003, " Numerical simulation of porous latent heat thermalenergy storage for thermoelectriccooling", Applied Thermal Engineering, 23,1647 - 1664.
221. Weinlader,W., Beck,A. and Fricke, J., 2004, " PCM-facade-panel for day lighting and room heating", Solar Energy (inpress)
222. Ying, Bo-an, Kwok, Yi - lin, Li, Yi., Zhu, Q.Y., Yeung, C.Y., 2004, "Assessing the performance of textiles
incorporating phase change materials", Polymer Testing, 23, 541–549.
223. Khateeb, S.A., Farid, M.M., Selman, J.R., Al-Hallaj,S., 2004, "Design and simulation of a lithium-ion battery with aphase change material thermal management system for an electric scooter", Journal of Power Sources, 128, 292–307.