NIST IR 7963

Evaluation of Energy Consumption 

Rating Methods for Thermoelectric 

Wine Chillers and Compact 

Refrigerators

David A. Yashar

Young-Jin Baik
NIST IR 7963

Evaluation of Energy Consumption 

Rating Methods for Thermoelectric 

Wine Chillers and Compact 

Refrigerators

David A. Yashar 

Young-Jin Baik

Energy and Environment Division

Engineering Laboratory

September 2013

U.S. Department of Commerce 

Penny Pritzker, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
ii

EVALUATION OF ENERGY CONSUMPTION RATING METHODS FOR 

THERMOELECTRIC WINE CHILLERS AND COMPACT REFRIGERATORS

David A. Yashar and Young-Jin Baik

National Institute of Standards and Technology

Gaithersburg, MD 20899

Abstract

Most types of refrigerating appliances are rated according to the HRF-1 test method 

developed by the Association of Home Appliance Manufacturers (AHAM) and their 

energy use is regulated by the US Department of Energy. These products generally use

vapor compression system to maintain a cold internal temperature. Recently, several

small products have emerged which use a thermoelectric cooling module instead, an 

alternate technology with a vastly different method of operation. This study examines 

whether the HRF-1 test method can be used to rate units that employ thermoelectric 

cooling modules. Three units were examined in this study and each one was incapable of 

maintaining the standardized compartment temperatures that are the basis for the rating 

method, indicating that the test is not applicable. An alternate rating method was 

explored, which measures the appliance’s energy consumption while it operates in a 

cooler environment than that prescribed in the test. Presented results show that this 

adjustment to the test method does allow the products to operate in a manner that makes 

it possible to characterize their performance.

Keywords: energy consumption, thermoelectric refrigerator, thermoelectric wine chiller
iii

Acknowledgement

This study was sponsored by the United States Department of Energy, Office of Energy 

Efficiency and Renewable Energy under the supervision of Lucas Adin. Dr. Harrison 

Skye of NIST and Dr. Detlef Westphalen of Navigant Consulting Inc. provided technical 

commentary on the draft of this report.
iv

Table of Contents

Abstract............................................................................................................................... ii

Acknowledgement ............................................................................................................. iii

Table of Contents............................................................................................................... iv

List of Figures......................................................................................................................v

List of Tables .................................................................................................................... vii

Nomenclature................................................................................................................... viii

1. Introduction......................................................................................................................1

2. Experimental Procedure...................................................................................................4

3. Thermoelectric 12-Bottle Wine Chiller...........................................................................5

4. Thermoelectric 28-Bottle Wine Chiller...........................................................................7

5. Thermoelectric Compact Refrigerator.............................................................................9

6. Summary and Conclusions ............................................................................................12

7. References......................................................................................................................14
v

List of Figures

1.1 Peltier Cooling Module..................................................................................................1

3.1 Thermoelectric 12-Bottle Wine Chiller .........................................................................5

4.1 Thermoelectric 28-Bottle Wine Chiller .........................................................................7

5.1 Thermoelectric Compact Refrigerator...........................................................................9

5.2 Compartment Temperature and Power Draw for Thermoelectric Compact 

Refrigerator........................................................................................................................10
vi

List of Tables

2.1 Measurement Uncertainty..............................................................................................4

3.1 Test Results for 12-Bottle Wine Chiller in 32.2 oC Test Room.....................................6

3.2 Test Results for 12-Bottle Wine Chiller in 22.2 oC Test Room ......................................6

4.1 Test Results for 28-Bottle Wine Chiller in 32.2 oC Test Room ......................................8

4.2 Test Results for 28-Bottle Wine Chiller in 22.2 oC Test Room ......................................8

5.1 Test Results for Thermoelectric Compact Refrigerator in 32.2 oC Test Room............10

5.2 Test Results for Thermoelectric Compact Refrigerator in 32.2 oC Test Room............10
vii

Nomenclature

α....................................................................................................... Peltier Coefficient [μVK-1]

I............................................................................................................Electrical Current [Amp]

Im .................................................................... Electrical Current for Maximum Cooling [Amp]

Tc ................................................................................................Cold Junction Temperature [K]

Th................................................................................................. Hot Junction Temperature [K]

K..............................................................................................Thermal Conductivity [Wm-1

K-1]

R...........................................................................................................Electrical Resistance [Ω]

w........................................................................................................................Power Input [W]

wm................................................................... Power Input at Maximum Cooling Capacity [W]

q .............................................................................................................Heat Transfer Rate [W]

qm ......................................................................................... Maximum Heat Transfer Rate [W]

Z................................................................................................................. Figure of Merit [K-1

]

Subcripts

n ....................................................... Properties associated with n-type semiconductor material

p ....................................................... Properties associated with p-type semiconductor material
1

1: Introduction

The energy consumed by most domestic refrigerating products sold in the United States 

is regulated by the U.S. Department of Energy; and beginning in 2014, this regulation 

will be based on the test methods outlined in Appendix A of Subpart B of 10CFR430 

(2010), which incorporates the test methods outlined in the Association of Home 

Appliance Manufacturers (AHAM) HRF-1-2008. This test is based on steady state 

operation of the unit with no door openings or user interaction in order to maintain a 

repeatable and reproducible test result. In order to compensate for the lack of interaction, 

the test is performed in a warm (32.2 oC (90 oF)) environment. Most domestic 

refrigerating appliances employ a vapor compression based system to extract heat from 

the internal cabinet of the appliance. This is because vapor compression systems offer a 

range of benefits for this application including reasonable efficiency, scalability, and cost. 

The power consumption and cooling capacity of these products are well suited to 

properly function in an environment that is warmer than typical household conditions. 

In recent years, however, some smaller niche products have come to market which 

employ thermoelectric cooling modules to maintain a cool cabinet. While thermoelectric 

cooling offers certain benefits such as no moving parts, no fluorinated refrigerants, and 

compactness, the limits of refrigerating capacity and efficiency for these modules are 

much smaller than that which can be obtained with a vapor compression system operating 

in the same range of temperature. In light of this, it is suspected that thermoelectric 

systems may not operate well enough in the warmer ambient conditions used for rating 

purposes. Therefore, the focus of this study was to examine whether such units can be 

tested according to the current rating method or if an alternative method is needed.

The physics governing the operation of thermoelectric modules is quite complicated. It is 

useful, however, to describe some key aspects of their operation; a more detailed 

discussion can be found in Goldsmid (2010). Thermoelectric cooling is based on the 

Peltier effect, which was discovered by J. Peltier in 1834 when he observed that if he 

passed an electrical current through the junction of two dissimilar materials, he could 

absorb or reject heat at the junction depending on the direction of the current. A sketch 

of a single junction thermoelectric cooling module is shown below in Figure 1.

Figure 1.1 Peltier Cooling Module
2

When a current is passed through a junction, the amount of Peltier cooling (q) at the heat 

absorption junction is proportional to the difference in the Peltier coefficients of the 

materials (αp, αn), the applied current (I) and the temperature of the cold junction (Tc). 

However, there are two other factors that need to be considered when examining the total 

obtainable cooling effect. The first factor is caused by the fact that heat will be 

transferred through the module via conduction from the hot junction to the cold junction 

because of the temperature difference generated by the process; this reduces the useful 

cooling effect by a term proportional to the thermal conductivity of the module (K) and 

the temperature difference between the hot and cold junctions. The second factor is 

caused by the fact that heat will be generated in the module simply because the circuit is 

made up of real materials which have electrical resistance; this further reduces the useful 

cooling effect by another term proportional to the square of the applied current and the 

resistance (R) in the circuit. The resulting expression for the obtainable cooling capacity

of a thermoelectric module is shown in equation 1.

q = �αp − αn�ITc − K(Th − Tc) − 1

2

I2R (1)

The form of this equation is a concave down quadratic with respect to the applied current, 

I; therefore, there exists a maximum cooling capacity that can be obtained from a module. 

By setting the first derivative of this equation equal to zero, the maximum cooling 

capacity is obtained at the current Im.

Im = �αp−αn�Tc

R (2)

The amount of power used to operate a thermoelectric device, shown in equation 3, 

consists of the power used to drive the cooling effect plus the amount of energy that is 

ultimately turned into heat by passing an electrical current through a resistive material.

w = �αp − αn�I(Th − Tc) + I2R (3)

Therefore, the Coefficient of Performance (COP) of the system, obtained by dividing 

equation 1 by equation 3, is expressed in equation 4.

q

w = �αp−αn�ITc−K(Th−Tc)−1

2

I2R

�αp−αn�I(Th−Tc)+I2R (4)

The Coefficient of Performance (COP) at the current which provides the maximum 

cooling output is the parameter that is of most interest when considering thermoelectrics

cooling devices. By substituting equation 2 into equation 4 and separating out all of the 

terms that consist of material properties, equation 5 is obtained.

qm

wm

= ZTc

2

2 −(Th−Tc)

ZThTc

 (5)
3

where:

z = �αp−αn�

2

R (6)

The term Z, called the figure of merit, consists solely of material properties and has units 

of [K-1]. Since the figure of merit varies with temperature, it is often expressed as a 

nondimensional value being multiplied by the temperature, denoted ZT. Significant

research has been performed recently to identify materials with a large figure of merit for 

materials that may potentially be used for thermoelectric cooling. Further research into 

materials have used various deposition and doping methods to enhance the figure of merit 

for candidate materials (Goldsmid, 2000). At the present day, alloys based on the Bi2Te3

system stand out as those with the largest figure of merit and are the state of the art for 

modern thermoelectric cooling systems. The dimensionless figure of merit (ZT) for these 

systems at 300 K, within the expected range of operation for a domestic refrigerating 

appliance, is typically on the order of 0.95 (Encyclopedia of Materials, 2002; Terasaki, 

2005; Tervo et al., 2009), although some researchers have indicated the possibility of 

pushing this value up to 1.1 (Yamashita et al, 2005). Using this value the maximum 

obtainable COP for a thermoelectric module operating between a -17.8 oC (0 oF) heat 

source and a 32.2 oC (90 oF) heat sink (the internal and external temperatures expected for 

a refrigerator-freezer under rating conditions) is 0.22. For comparative purposes, the 

theoretical COP limit for a vapor compression system operating under these conditions is

5.1 and most commercially available domestic refrigerators achieve an efficiency of 

approximately 20 % to 25% of this limit; i.e. with a COP in the range of 1.0 to 1.5. 

The recent influx of thermoelectric products was driven by the introduction of dedicated 

wine storage cabinets which are a relatively new product class. Wine chillers are 

described as cooled cabinets whose sole purpose is the storage of wine. They are 

required to maintain an internal storage temperature of 12.8 oC (55 oF) during energy 

consumption tests (AHAM, 2008) which is significantly warmer than most other 

refrigerating products and therefore requires a much lower amount of cooling capacity. 

Since this internal compartment temperature is an achievable condition for a 

thermoelectric unit operating in a home, where the expected ambient temperature is 

approximately 22.2 oC (72 oF), several dozen models of thermoelectric wine storage 

cabinets are now commercially available. Thermoelectric compact refrigerators, whose 

purpose is to maintain a cabinet temperature of 3.9 oC (39 oF) are also beginning to 

emerge as a commercially available product. In this study, three such units were

examined with the intent of evaluating the appropriateness of energy testing according to 

existing methods.
4

2: Experimental Procedure

The test setup was constructed in accordance with the Department of Energy’s test 

procedure outlined in 10CFR430, Subpart B, Appendix A, 2010; details of the 

environmental chamber and data acquisition system can be found in Yashar and Park

(2011). All of the temperature data were gathered using a personal computer and a 

multiplexed data acquisition unit. Table 2.1 below lists the measured quantities and the 

uncertainty associated with the 95 % confidence level. All of the uncertainties reported 

in this document were calculated based on the measurement uncertainties listed in 

Table 2.1 and the equations listed in the Appendix of Yashar and Park, 2011, and are 

expressed at the 95 % level of confidence.

Table 2.1 Measurement Uncertainty

Measured Quantity Measurement Device Uncertainty at 95 % 

confidence 

Temperature Thermocouples ± 0.1 °C (0.2 °F) 

Power Digital Power Meter Max (± 0.5 %, ± 0.06 W)

A series of tests were conducted to characterize the energy consumed by each 

thermoelectric appliance operating in two different ambient conditions. First, the energy 

consumption of each unit was measured in accordance with the existing test procedures 

for wine chillers and all refrigerators. 

The AHAM test method requires that an elevated ambient temperature condition of 

32.2 oC (90 oF) be maintained during the measurements. The elevated ambient test 

condition is used to compensate for the effects of the lack interaction (door openings, 

insertion of warm foodstuffs, etc.) that the unit would see during field use. However, 

with thermoelectric cooling modules, the temperature difference prescribed in the test 

method may require cooling loads that are beyond the maximum capacity of the modules. 

Therefore, the possibility of measuring the annual energy consumption with the same 

setup and control settings for each test subject, but with a more typical household 

ambient temperature 22.2 oC (72.0 oF) was examined. The results for each test subject 

are described in the following chapters of this report.
5

3: Thermoelectric 12-Bottle Wine Chiller

The first unit studied was a small 33 liter (1.2 cubic foot) thermoelectric wine chiller 

designed to store 12 bottles of wine, shown in Figure 3.1. The cooled compartment 

consists of three-bottle storage at the bottom of the cabinet and three moveable metal 

racks designed to store three bottles of wine each. The temperature in the cabinet is 

controlled by an externally accessible thermostat controlling the thermoelectric module 

and air is circulated in the compartment by a small fan located at the rear.

Figure 3.1 Thermoelectric 12-Bottle Wine Chiller

The internal compartment of the wine chiller was outfitted with three weighted 

thermocouples constructed in accordance with AHAM HRF-1-2008, which can be seen 

in the figure. The compartment temperatures reported are equal to the average of the 

three temperature measurements. We monitored the unit’s power draw and the 

temperatures maintained in the compartment during steady state operation. The AHAM

test procedure requires two measurements with different thermostat settings with the 

results bounding the prescribed target temperature of 12.8 oC (55 oF); this is generally 

accomplished by performing the first test at the median thermostat position and the 
6

second test at either the warmest or coldest thermostat position based on the results of the 

first test.

It should be noted that these units operate with variable power input to the cooling 

module and therefore run at a constant part-load condition for any given thermostat 

setting. Because of this, the system does not cycle on and off in the same way that most 

other systems operate. Each test period used in this analysis was defined to be 3 hours of 

steady state operation since the power draw and internal temperatures remained constant 

throughout. The results of the measurements in the 32.2 oC (90 oF) test room are shown 

in Table 3.1.

Table 3.1 Test Results for 12-Bottle Wine Chiller in 32.2 oC Test Room

Thermostat Setting Compartment Temperature Average Power Draw

Test 1 Mid 17.0 ± 0.1 oC 46.7 ± 0.2 W

Test 2 Cold 17.2 ± 0.1 oC 46.6 ± 0.2 W

These results showed no measurable difference in operation due to the change in 

thermostat setting. This is because the cooling system in this unit is not powerful enough 

to meet the set point temperature when operating in a 32.2 oC (90 oF) environment. The 

cooling module was operating at its maximum output during both tests resulting in 

similar measurements of the compartment temperature and power draw. It is not 

appropriate to use the data acquired using the AHAM test method since that test method 

requires the unit maintain a 12.8 oC (55 oF) internal condition in a 32.2 oC (90 oF) ambient 

condition.

For the second set of tests, the ambient temperature in the test chamber was maintained at 

22.2 oC (72 oF), a more conventional temperature that would be realized during field use. 

The results of these tests are shown in Table 3.2.

Table 3.2 Test Results for 12-Bottle Wine Chiller in 22.2 oC Test Room

Thermostat Setting Compartment Temperature Average Power Draw

Test 1 Mid 13.8 ± 0.1 oC 14.4 ± 0.1 W

Test 2 Cold 10.4 ± 0.1 oC 29.6 ± 0.1 W

During this set of tests, the unit was capable of lowering the cooled compartment’s 

temperature down to the set point during each measurement. Therefore this unit was able 

to vary the compartment temperature in response to the thermostat setting and the results 

of these two tests bounded the target temperature of 12.8 oC (55 oF). The prescribed test 

method requires that these results are linearly interpolated to determine the power draw at 

the target temperature, which yielded 19.0 ± 0.1 W, or in alternate units 167 ± 1 kWh/yr.
7

4: Thermoelectric 28-Bottle Wine Chiller

The second unit studied is a 65 liter (2.3 cubic foot) thermoelectric wine chiller designed 

to store 28 bottles of wine, shown in Figure 4.1. The cooled compartment consists of 

four-bottle storage at the bottom of the cabinet and six metal racks designed to store four

bottles of wine each. The temperature in the cabinet is controlled by variable power input 

to the thermoelectric module and air is circulated in the compartment by a small fan 

located at the rear.

Figure 4.1 Thermoelectric 28-Bottle Wine Chiller
8

The internal compartment of the wine chiller was outfitted with three thermocouples, 

which can be seen in the figure and a similar set of experiments to those performed on the 

12-bottle unit was performed. Similar to the other tests, the test periods were all

truncated to 3 hours due to the steady nature of operation. The results of the 

measurements in the 32.2 oC (90 oF) test room are shown in Table 4.1.

Table 4.1 Test Results for 28-Bottle Wine Chiller in 32.2 oC Test Room

Thermostat Setting Compartment Temperature Average Power Draw

Test 1 Mid 18.0 ± 0.1 oC 66.8 ± 0.3 W

Test 2 Cold 18.1 ± 0.1 oC 66.8 ± 0.3 W

These results also showed no measurable difference in operation due to the change in 

thermostat setting. Again, the cooling system in this unit is not powerful enough to lower 

the cabinet temperature to satisfy the thermostat set point when operating in a 32.2 oC 

(90 oF) environment. The cooling module was operating at its maximum output during 

both tests resulting in similar measurements of the compartment temperature and power 

draw. For the second set of tests, the ambient temperature in the test chamber was 

maintained at 22.2 oC (72 oF). The results of these tests are shown in Table 4.2.

Table 4.2 Test Results for 28-Bottle Wine Chiller in 22.2 oC Test Room

Thermostat Setting Compartment Temperature Average Power Draw

Test 1 Mid 15.6 ± 0.1 oC 14.7 ± 0.1 W

Test 2 Cold 12.9 ± 0.1 oC 24.0 ± 0.1 W

During this set of tests, the unit was capable of varying the compartment temperature in 

response to the thermostat setting. It is interesting, however, that the unit did not meet 

the target temperature of 12.8 oC (55 oF) at the coldest setting, although it came very 

close. Although it is possible that this unit could attain the 12.8 o (55 oF) condition in the 

22.2 o (72 oF) environment, it is more likely that the unit’s controller did not allow it to 

bring the cabinet below this temperature since the results of the first round of tests 

suggest that it has more capacity since it can operate with a much larger power draw. In 

any regard, interpolating (or extrapolating in this case) the results of these tests to 

determine the power draw at 12.8 oC yields 24.6 ± 0.1 W, or in alternate units 

216 ± 1 kWh/yr.
9

5: Thermoelectric Compact Refrigerator

The final unit examined is a 71 liter (2.5 cubic foot) compact refrigerator, shown in 

Figure 5.1. The unit has a single compartment which included two moveable wire racks. 

It was outfitted with three thermocouples for testing. 

Figure 5.1 Thermoelectric Compact Refrigerator

A set of tests was performed according to the DOE test procedure for compact 

refrigerators. The unit was operated in a 32.2 oC (90 oF) environment and its power draw 

and internal temperature were recorded. Before examining the data, it is interesting to 

note that this unit’s user manual stated that it included an automatic defrosting system. 

Upon examination of the test data, it was obvious that this defrost system merely 

implemented a shutdown of the cooling module for one hour every day and a half. Test 

data from this unit is shown Figure 5.2, the left vertical axis corresponds to the internal 

temperature (blue dashed line) and the right vertical axis corresponds to the power draw 

(red solid line). Nevertheless, a three hour steady state portion of the data was used for 

the analysis and the data recorded during the ‘defrost’ periods were excluded. The results 

of the measurements in the 32.2 oC (90 oF) test room are shown in Table 5.1.
10

Figure 5.2 Compartment Temperature and Power Draw for Thermoelectric Compact 

Refrigerator

Table 5.1 Test Results for Thermoelectric Compact Refrigerator in 32.2 oC Test Room

Thermostat Setting Compartment Temperature Average Power Draw

Test 1 Mid 10.8 ± 0.1 oC 69.5 ± 0.3 W

Test 2 Cold 10.8 ± 0.1 oC 69.5 ± 0.3 W

Once again, these results showed no measurable difference in operation due to the change 

in thermostat setting because the cooling system in this unit is not powerful enough to 

meet the selected set point when operating in a 32.2 oC (90 oF) environment. The cooling 

module was operating at its maximum output during both tests resulting in similar 

measurements of the compartment temperature and power draw. For the second set of 

tests, the ambient temperature in the test chamber was maintained at 22.2 oC (72 oF). The 

results of these tests are shown in Table 5.2.

Table 5.2 Test Results for Thermoelectric Compact Refrigerator in 22.2 oC Test Room

Thermostat Setting Compartment Temperature Average Power Draw

Test 1 Mid 5.3 ± 0.1 oC 32.5 ± 0.2 W

Test 2 Cold 2.7 ± 0.1 oC 56.1 ± 0.3 W
11

During this set of tests, the unit was capable of varying the compartment temperature in 

response to the thermostat setting. The defrost behavior for these tests was identical to 

that which was recorded during the tests in the 32.2 oC (90 oC) environment. 

Interpolating the results of these tests to determine the power draw at 3.9 oC (39 oF) 

yields 45.2 ± 0.6 W, or in alternate units 396 ± 5 kWh/yr. 
12

6: Summary and Conclusions

In this study, the performance of three small thermoelectric refrigerating appliances was 

examined to determine whether or not the existing test methods could be used to rate 

these products. In each case, it was obvious that the current test method cannot be used 

for these products because the prescribed temperature difference between the internal 

compartment of the cabinets and the environment is too large for the thermoelectric units 

to overcome and they simply are not capable of achieving the test conditions. 

For this reason the possibility of an alternate test condition was examined which 

decreased the difference between the required internal cabinet temperature and the 

temperature of environment where the cabinet is installed. When testing each of these 

products in a cooler environment, they were able to achieve the required storage 

temperatures; therefore this could be used as the basis for an alternative rating method for 

thermoelectric products. 

Two thermoelectric wine chillers were examined as part of this study. Presently, the US 

Department of Energy does not regulate the energy consumption associated with wine 

chillers and therefore there is no federally mandated maximum energy standard for these 

products. However, a test method does exist in AHAM HRF-1-2008 and is regulations 

are in place in California and Canada. The rating method outlined in AHAM HRF-1-

2008 requires that the energy consumption of a wine chiller be rated while operating in a 

32.2 oC (90 oF) environment and maintaining a 12.8 oC (55 oF) internal temperature. 

Since the thermoelectric wine chillers were unable to achieve this condition, an ambient 

temperature of 22.2 oC (72 oF) was selected as an acceptable alternative condition. 

While exploring this alternative method, however, it is important to keep sight of the fact 

that the elevated ambient test condition was established for all other refrigerating 

products, and reducing the ambient temperature to rate these products will result in test 

measurements that are not comparable to measurements on other products that were rated 

using the existing test method. Therefore, if an approach using a lower ambient 

temperature is employed, the results should be scaled by an appropriate penalty factor in 

order to estimate the energy consumption that would be measured if the unit were capable 

of achieving the conditions prescribed in the test. Only then can the results of a test using 

the alternative method be compared to those of a unit tested with the conditions in 

AHAM HRF-1-2008.

Vapor compression based wine chillers operate across a 19.4 K (35 oF) temperature 

difference [32.2 oC (90 oF) ambient and 12.8 oC (55 oF) internal] during their energy 

consumption test. The alternative test condition described in this report for 

thermoelectric units would require operation across a 9.4 K (17 oF) temperature 

difference [22.2 oC (72 oF) ambient and 12.8 oC (55 oF) internal], which requires a 

significantly smaller cooling load and therefore results in a significantly lower value for 

the energy consumption. Since the heat transfer into the cabinet from the ambient and the 

efficiency of the thermoelectric cooling module are both proportional to this temperature 

difference, the ratio of these two numbers (equation 7) is an obvious starting point for 

determining an appropriate penalty factor. Multiplying this penalty factor by the 
13

thermoelectric unit’s power draw would result in a reasonable estimate of the amount of 

energy that the unit would consume if it were capable of meeting the required internal 

compartment temperature in a 32.2 oC (90 oF) ambient temperature.

32.2 °C−12.8 °C

22.2 °C−12.8 °C = 2.06 (7)

The data collected for the 12-bottle wine chiller and the 28-bottle wine chiller show that 

the energy consumption for these units operating in a 22.2 oC (72 oF) environment is 

167 ± 1 kWh/yr and 216 ± 1 kWh/yr, respectively. Therefore, applying this penalty 

factor would result in rated values of 344 ± 2 kWh/yr and 445 ± 2 kWh/yr, respectively, 

for these units.

We also examined a thermoelectric compact refrigerator. Unlike wine chillers, compact 

refrigerators are currently regulated by the US Department of Energy and the maximum 

allowable energy consumption for the size unit examined here is currently 326 kWh/yr. 

The thermoelectric compact refrigerator tested here had similar issues to those seen with 

the wine chillers, and again we verified that testing in a 22.2 oC (72 oF) environment was 

a possible alternative. Even in this relaxed test condition, the thermoelectric unit 

consumed more than 20 % above the energy limit. However, in order to properly 

compare it to regulated vapor compression units of the same size we would have to 

multiply the measured energy consumption by an appropriate penalty factor. Using the 

same assumption as for the wine chillers, this factor should be:

32.2 °C−3.9 °C

22.2 °C−3.9 °C = 1.55 (8)

which would result in a total rated value of 614 ± 8 kWh/yr, nearly twice the regulated 

limit for these products.
14

7: References

AHAM, 2008. ANSI/ HRF-1-2008, Association of Home Appliance Manufacturers, 

Energy and Internal Volume of Refrigerating Appliances, Washington, DC.

Energy Conservation Program for Consumer Products: Test Procedures for 

Refrigerators, Refrigerator-Freezers, and Freezers; Final Rule and Interim Final Rule, 

Title 10 Code of Federal Regulations, Part 430, Subpart B, Appendix A (16DEC2010).

Goldsmid, H. J. Recent Trends in Thermoelectric Materials, Semiconductors and 

Semimetals Vol. 69, Ch.1 (Academic, 2000).

Goldsmid, H. J. Introduction to Thermoelectricity, Springer 2010 DOI 10.1007/978-3-

642-00716-3.

K. H. Jürgen Buschow, Robert W. Cahn, Merton C. Flemings, Bernard Ilschner (print), 

Edward J. Kramer, Subhash Mahajan, and Patrick Veyssière (updates), Encyclopedia of 

Materials: Science and Technology, 2001. ISBN: 978-0-08-043152-9 .

Terasaki, I. Introduction to Thermoelectricity (Ch 13). Materials for Energy Conversion 

Devices, J. Woodhead Publishing in Materials, Cambridge, 2005, pp. 339–357.

Tervo, J., Manninen, A., Ilola, R., and Hanninen, H., State-of-the-Art Thermoelectric 

Materials Processing, VTT 2009, ISBN 978-951-38-7184-0.

Yamashita, O. and Sugihara, S., High-performance bismuth-telluride compounds

with highly stable thermoelectric figure of merit, Journal of Materials Science 40(2005) 

pp. 6439-6444.

Yashar, D. and Park, K.J., 2011. Energy Consumption of Automatic Ice Makers Installed 

in Domestic Refrigerators, NIST Technical Note 1697, NIST Gaithersburg, MD USA.