April 2016 VOL.6

AHPNW
NEWSLETTERCONTENTS
1. Related News (General, Policy, Market)
2. The Key Points of Efficient Application of Ground Source Heat Pump System (China)
3. An inside story behind the advent of “Eco Cute” CO2 heat pump water heater forresidential use (Japan)

ASIAN HEAT PUMP & THERMAL STORAGE TECHNOLOGIES NETWORK

ABSTRACTS OF EACH PAPER

The Key Points of Efficient Application of Ground Source
Heat Pump System
Along with the encouragement and support of policy, increasing the scale of ground source
heat pump (GSHP) project, the application area of GSHP system is expanding in China.
However, the operation of some existing GSHP projects is poor. The effect of energy saving
is not obvious due to various reasons existed in the design, construction and operation. How
to improve the efficiency of the heat pump system has aroused wide concern. The key pointsof efficient application of GSHP system is discussed in this paper from the viewpoint ofsystem theory. It analyzes the low temperature heat source, heat pump units, transmission
and distribution system, auxiliary system, user terminal equipment.

An inside story behind the advent of “Eco Cute” CO2 heatpump water heater for residential use
More than ten years have passed since the “Eco Cute” CO2 heat pump water heater forresidential use was commercialized in May 2001 in Japan through the collaborative R&D
including CRIEPI. Its cumulative shipments are over 4.6 million at the end of March 2015.
There were two projects involving hot water supply heat pumps prior to the development of
the Eco Cute in CRIEPI, though neither went into commercial production. In this paper, thehistory and technical aspects of the advent of the Eco Cute, including the former two projects,
are introduced.

1

Related News

provided by exhibitors. HVAC&R Japan isdesigned to facilitate business opportunities
for exhibiting companies and to provide an
opportunity for exhibitors to disseminate
informationon
their
cutting-edge
technologies to the world.

GENERAL■HVAC&R Japan 2016 Preview‘ A Look at Heating and CoolingTechnologies
foran
IdealTemperature Future’

Source; JARN ,January 25, 2016

Japan
The
Japan
Refrigeration
andAir
Conditioning Industry Association (JRAIA)
is slated to hold the 39th Heating,
Ventilating,Air
Conditioning
andRefrigerating Expo (HVAC&R Japan 2016)
over the four-day period of February 23-26,
2016, at Tokyo Big Sight Exhibition Centerin Japan.
HVAC&R Japan has played a criticallyimportant role as Japan's only specialized
trade fair in the HVAC&R industry over the
past half-century, providing public relations
opportunities for the industry as well as avenue showcasing corporate technology
developments and new products. The
exhibition itself has developed over theyears in tandem with the industry. During
this period, Japan's HVAC&R equipment
industry has become one of the world's
technological leaders, particularly in thefield of highly efficient heat pumptechnology.
HVAC&R Japan 2016 is to focus on fourkey
themes:energy,environment,
temperature, and technology. Among thesefour
themes,JRAIA
believes
that
temperature is critically important inshowcasing corporate activities focused on
this technology— that connects the past, thepresent, and the future. For this reason,
JRAIA chose 'A Look at Heating andCooling Technologies for an IdealTemperature Future' as the overarchingtheme of the event.
HVAC&R Japan features multiple parallel
events: not only does it showcase world
leading technologies as well as the latest
equipment
andsystemsintheenvironmental field all in one place, it alsooffers various seminars and enables visitors
to gain insight into new products and trends■ENEX2016 Held in Conjunction
with Two Other Energy ExposJapan
The ENEX2016, concurrently with the
Smart Energy Japan 2016 and the New
Power and Energy Expo that was held forthe first time this year, took place on
January 27-29 at the East Halls of Tokyo
Big Sight. The number of visitors during thethree days reached 48,514 according to theorganizer.
ENEX is a comprehensive exhibition in
the field of energy conservation and newenergy. A large number of business
operators and officials from national andlocal governments wishing to promoteenergy conservation and to rationalize
energy use visited the exhibition.
Smart Energy Japan is a professional
exhibition in the field of design anddevelopment
concerningenergymanagement. It features all types of
elemental technology such as technologies
for energy conservation and power control,
information communication, and smart
networks.
New Power and Energy Expo is a
professional exhibition that covers a fullrange of all devices, systems, and services
concerning the power retail business,
including power supply and retail services inview of the introduction of full liberalization of
the retail electricity market in Japan from
April 2016.
The exhibitions focused on the demand,
supply, and management aspects, all ofwhich are necessary to effectively utilize
supply and demand and to facilitate theefficient use of energy in the future.
The three exhibitions were held under the
auspices of an overarching concept2Related News

supporting energy conservation and powersaving for all energy consumers, promoting
rationalization of energy use, and offering
opportunities for the creation of new services
resulting in energy conservation and new
power businesses.
In the context of full liberalization ofelectricity retailing staring in April this year inJapan, all leading electric power, gas andnew electricity related companies, including
Tokyo Electric Power, Tokyo Gas, Chubu
Electric Power, and Kanden Energy Solution,
showcased their products and services.
The main exhibits at the New Power andEnergy Expo 2016 included electric power
supply services, power supply/demand
management systems, demand response
services, power storage systems, andelectric power business backup consulting.
As in the past, the 'Energy Conservation
Grand Prize' winning products were also
exhibited in the Awards Corner.

Xu Wei, served as the chairman of the heatpump as the committee, and Professor Ma
Zuiliang from Harbin Institute of Technology
served as honorary director.
The establishment of each special
committee of National Society of HVAC air
conditioning, can not only accelerate theimprovement organization building, but also
promote and facilitate the professional ofthe
HVAC
industryanimportantmanifestation.

Policy■The industrial standard "Technicalspecifications for cool storage air
conditioning system" JGJ158- 2008
was formally implemented
China
The
industrial
standard"Technicalspecificationsfor
cool
storageair
conditioning system" JGJ158- 2008, wasformally implemented in 2008.

Source; JARN ,February 25, 2016

■ National Society of HVAC andrelated special committee was held inNanjing, Jiangsu ProvinceThis standard has played an important rolein the TES field in China during last 7 years.

China

On this April, the revision work of thisstandard has been formally started. 26
units took part in the revision work. The
establishment of the working group andpreparation of the first working groupmeeting was held in Beijing on April 13,
2015, the leader of the Ministry of Housing
and Urban-Rural Development Institutestandard quota, editor of China Academy of
Building Research Unit and Construction
Group Co., Ltd. The leader of Qingdao
Bohai, the Housing and Urban construction
Department of building environment andEnergyConservation
standardization
technical
Committee
standards
management staff and all members of thegroup prepared a total of 40 people
attended the meeting.
The revision work will be completed by theend of 2016.

On December 15-16 2015, the series of
National Society of HVAC (HVAC Branch of
the Architectural Society of China, China
Institute of Refrigeration Air-conditioning
professional committee) events weresuccessfully held in Nanjing, Jiangsu
Province.
The event is divided into two parts, one is toarrange the establishment of Heat Pump
Professional Committee, Air-conditioning
Professional Committee, and the YouthCommittee, according to the National
Institute of HVAC air conditioning eighthwork of the Council; the second isorganized by the National Academic heatpump technology in the same period will,
air-conditioning technology development
forum, Youth Science and technology
Forum three forums.

3

Related News

MarketPanasonic—received the Chairman Prize
of ECCJ for its WX series of air conditioners
featuring the company's Econavi function
and its cooling unit that uses photovoltaic
power generation.
The WX series of RACs provides
individualized air conditioning by adopting atechnology that, by means of a thermal
image sensor, can detect the heat or cold
felt by each user. They also realize
continuous heating operation without anelectric heater by collecting the heat ejectedfrom the outdoor unit's compressor in heatstorage material and effectively utilizing it
during defrost operation.
The cooling unit incorporates PanasonicEcology Systems' sensible resin heatexchange element and a high-efficiency
brushless DC (BLDC) motor. Adopting thiscooling unit to Daihen's power conditioner realizes efficient heat exchange between
low-temperature outside air and heated air
inside the housing to cool the conditioner
with less electric power while maintaining
airtightness.
HitachiAppliances—received
theChairman Prize of ECCJ for its largecapacity refrigerators in the Vacuum Chilled
series. This series was highly rated for its
energy-saving technologies, such as theindustry's first multi-valve control, whichmakes energy savings compatible with thecooling power required to realize larger
capacity.
Toshiba Carrier—received the Chairman
Prize of ECCJ for its heat pump heat source
units in the Universal Smart X3 series. The
Universal Smart X series already received
the Minister Prize of Economic, Trade andIndustry for 2011. The second award thistime was given in recognition of further
energy savings and higher added value.

■Energy Conservation Grand Prize
Ceremony for 2015
Japan
At ENEX 2016 held at the Tokyo Big Sight
convention center at the end of January, aceremony to award the 2015 Energy
Conservation Grand Prize for excellent
energy-efficient equipment was held. The
prize is organized by the Energy
Conservation Center, Japan (ECCJ), withthe aims of contributing to increased
awareness, activities, and steps towardsaving energy and promoting the use ofenergy-saving products.
Daikin—received the Minister Prize of
Economic, Trade and Industry, the highest
prize, for its 'Promotion of energy
conservation through worldwide expansionof high efficiency of HFC-32 air
conditioners.' The company was highly
recognized for having contributed to theprevention of warming on a global scale byadopting HFC-32 refrigerant, which can
reduce equipment's impact on global
warming.
Daikin also received the Chairman Prize
of ECCJ for its VRF air conditioners. These
VRFs reduce annual power consumption by
adopting a new scroll compressor that
achieves higher efficiency during low-load
operation as well as new technology that
automaticallycontrols
refrigerant
temperature according to the load duringcooling and heating operation. The
technologies incorporated into this series
can contribute to the realization of net zeroenergy buildings (ZEBs).
Mitsubishi Electric—received the Minister
Prize of Economic, Trade and Industry, thehighest prize, for its room air conditioners(RACs) in the Kirigamine Advance FZ
series. These innovative, state-of-the-art air
conditioners make high energy-savings
compatible with comfort by completely
redesigning the indoor unit structure for the
first time inabout 50 years andincorporating the world's first personal twin
flow fans.

Source; JARN ,March 25, 2016

■ Japanese Manufacturers Keeping
Pace with R32 Use in PACs

4

Related NewsJapan
A leading edge knowledge hub for ductless
air conditioner technology, the 39th Heating,
Ventilating,Air
Conditioning
andRefrigerating Expo Japan (HVAC&R
JAPAN) 2016 was held from February 23 to
26 at Tokyo Big Sight. HVAC&R JAPAN isorganized biennially by the Japan
Refrigerating and Air Conditioning Industry
Association (JRAIA). This year's exhibition
was the attracted 188 exhibitors and 27,383
visitors during the four-day event.
Although this exposition is not large inscale, the latest technologies and productsin the field of HVAC&R are displayed. Major
HVAC&R manufacturers exhibited a wide
range of products for residential andcommercial applications. Products intended
for industrial uses also stood out.
At this year's exposition, almost all
Japanesemanufacturers
exhibitedpackaged air conditioners (PACs) using thenext-generation refrigerant R32. They
focused on R32 PACs ranging from 3 hp to6 hp for light commercial use. At theprevious exposition held two years ago,
Japanese manufacturers displayed models
demonstrating that the manufacturers were
keeping pace with R32 use in room air
conditioners (PACs).
Source; JARN ,March 25, 2016

5

ChinaThe Key Points of Efficient Application of Ground Source
Heat Pump System
Lingyan Yang, Wei Xu, China Academy of Building Research, China

ABSTRACT (Initial CAPS, 11-pt Arial font, bold)
Along with the encouragement and support of policy, increasing the scale of ground source
heat pump (GSHP) project, the application area of GSHP system is expanding in China.
However, the operation of some existing GSHP projects is poor. The effect of energy saving
is not obvious due to various reasons existed in the design, construction and operation. How
to improve the efficiency of the heat pump system has aroused wide concern. The key pointsof efficient application of GSHP system is discussed in this paper from the viewpoint ofsystem theory. It analyzes the low temperature heat source, heat pump units, transmission
and distribution system, auxiliary system, user terminal equipment.
KEY WORDS: Ground source heat pump (GSHP), Energy efficiency, Emissionreduction
INTRODUCTION
The maximum average concentration in 24h was 766 μg／m3. So, the pressure on energy
saving and emission reduction was unprecedented. Under this background, the GSHP, as akind of energy-saving technology, driven by the relevant policies in recent years, has
acquired widespread application, the project size has been increasing rapidly simultaneously.
Furthermore, some projects have already obtained successful results on energy
conservation and emission reduction. While at the same time, due to a variety of reasons
existed in the processes of preliminary scheme, design, construction, operation and finalperiod management, some problems have happened to part of the GSHP systems
engineering which affected its normal use, even worse, part of the systems could not work. It
directly lead to not only the waste of the owners’ investment and the state’s subsidies, butalso the doubts for applying the GSHP system from the users or even the workers. Therefore,
the improvement of the GSHP system energy efficiency makes its application a current
concern. By participating in the design and test of a series of GSHP researches forinvestigation and analysis, we analyze several essential problems for the efficient applicationof GSHP system from the low temperature heat source to the user terminal system.
LOW TEMPERATURE HEAT SOURCE---ensure the heat balance of absorbing andreleasing, avoid the accumulation
As the heat source in winter and heat sink in summer for the heat pump, the essence of soil
is energy storage. The heat absorption and rejection of the heat exchanger depends on theheat transfer processes of both building system and soil source heat exchanger.
To get the cumulative total of the absorption and rejection of heat, we must do hourly
coupling calculation for both heat transfer processes.
It is unreasonable to determine the number of boreholes by estimating heat transfer rate permeter during the system design process. Heat transfer rate per meter is obtained by the heattransferred which is tested by experiment in 48 hours divide the depth of borehole. The test
results only represent the heat transfer rate under the condition that only run the test

6

Chinaborehole in a specific time period. So there are obvious deviations using such values toestimate the heat of absorbing and rejecting in the operating process of GSHP system.
According to the new standards in GB50366-2005 (2009), the demand for soil thermal
physical property test, through the test, we can obtain the complex thermal conductivity
coefficient and the soil specific heat at local condition, the project is located by fitting
calculation. It can be more close to the actual operation by employing these two parameters
to calculate the absorbing and rejecting heat in GSHP system.
Finally, the arrangement of the boreholes is also important, it may decrease the thermal
disturbance as the increase of the distance between each other. Therefore, it is positive toincrease the distance of heat exchangers under the conditions which areas is allowed. For
large-scale GSHP systems, the boreholes should be arranged by separated partitions. In theoperation, it should supply energy in separated areas by turns. In this way, it’s better for the
long-term efficient operation.
UNIT CONTROLAND TRANSMISSION---improve the level of unit auto-control, optimize
the hydraulic transmission system, reduce the heat loss
1) Improve the level of unit auto-control to ensure the system is also operated
efficiently under partial load
The heat pump unit is the core equipment for the heat pump system. Various kinds of heatpump units can be chosen to satisfy the different types of heat pump systems. Almost every
equipment manufacturer has produced the GSHP units. For GSHP, the water temperature of
the borehole outlet in winter is below 15 ℃ , the load demand is maximal while thetemperature of the outlet water is lowest. The same problem also exists in summer. The heatpump units always focus on the max load conditions, most of time, the capacity of units is toolarge, and the efficiency is lower under partial load. To improve the efficiency of GSHP
system, heat pump units should be decided by the end of the building load calculation hourly
and coupling calculation for the ground heat exchangers, at the same time, according to theload frequency, choosing the higher COP heat pump units under the high frequency load.
2) Water distribution system should be designed scientifically and constructed
rigorously
The GSHP system includes numerous ground heat exchangers, and the hydraulictransmission system is more complicated. So only the scientific design for the ground heatexchangers and rigorous construction can ensure the system’s efficient operation. Thatmeans in the design process, the number, spacing and the effective depth of heatexchangers should be calculated scientifically for GSHP based on soil thermal physicalparameters and meteorological parameters where the project is located, and meanwhile, acomprehensive detailed hydraulic balance calculation should be taken.
In the process of construction, the work should be finished strictly in accordance with thedrawings combined the situation of construction, after the construction, the comprehensive
hydraulic balance of debugging should be carried out.
From some current GSHP system, we find that the effective length of ground heatexchangers is reduced due to the poor construction condition.
Some other projects have no hydraulic balance of debugging after construction. The
measured datas of a GSHP project is shown in Table 1. From the Table we can see that theflow doesn’t increase as the numbers of heat exchangers, part of the heat exchanger in Area
2 is blocked.
In addition, the complexity of the ground heat exchange system needs more careful
arguments for GSHP hydraulic system.
The selection of pumps and the settings of operation should be adapted to ground heatexchanger system, this is very important, especially for large-scale systems.

7

ChinaSome projects can take turns to use ground heat exchangers in separated areas if possible,
at this time, the pump is chosen as the exchangers of each area. Frequency conversion ofpump should be taken in to reduce the system distribution energy consumption under partial
load and in this way make the system’s efficiency higher.
Besides, detailed hydraulic calculation, monitoring system, using the double pump like shownin Figure 1, etc. can be taken into consideration. Hydraulic transmission system aims to
improve the flexibility of the adjustment and control, make it better to adapt to changes insystem load, reduce the energy consumption of distribution system, and improve the energy
efficiency of the system under the premise that the system is stable.

Table1 Buried side flow meter
Area
Area 1
Area 2
Area 3
Area 4

Number of
Borehole
57
80
135
215

The flow（m3/h）
137
115.6
164.3
212

Fig.1 Double pump hydraulic distribution system
diagram3) Energy loss of circuit headers should be avoided.
For more and more large-scale system, it is important to reduce the heat loss of system andensure energy distributing efficiently to the users.
At present, in the design of large-scale GSHP system, circuit headers of ground heatexchangers which are considered in the condition of heat insulation [3] are not contained in
the length of the heat exchanger.
However, in the actual project, circuit headers are all directly buried without thermal
insulation. This part of the heat loss can be ignored in small-scale systems, but for the largescale GSHP system, it can't be ignored.
Till now, there are few heat loss researches of circuit header for borehole system.
The author took one office building in Beijing as an example, carried out the simulation
results on the energy loss problem of circuit headers and draw the conclusion that the energy
loss of circuit headers in the different length in the winter did have effect on the unit COP,
recommendations for horizontal headers in different length were also proposed [4]. For otherprojects in other places, the similar methods can be employed to obtain relevant conclusions.
3 AUXILIARY SYSTEM---The energy should be used according to the quality, adapted
to local conditions
Auxiliary system is stetted to avoid the imbalance between absorption and rejection of heaton the low temperature reservoir of soil which is due to the user’s deferent demanding fortemperature.
It is effective to adapt to the variety of the areas which the heat pump of current soil source
are applied to, and it’s also an important part of the heat pump system for the hybrid soil
source.

8

ChinaThe key of realizing efficiently running of the heat pump system for the hybrid soil source isthe energy should be used according to the quality and adjust measures to local conditions.

Users, who use the renewable energy such as solar energy and air source as the auxiliary
system, can be considered according to actual operation condition, if the direct power ofrenewable energy cannot meet the user’s demand, it can be used as a supplement ofunderground temperature field. While if the boiler or cold machine and cooling tower system
is used as the auxiliary system, we should give priority to the users directly. In this way it can
avoid the high-quality energy be used inefficiently due to putting back the high-quality energy
to underground temperature field after heating or cooling.
4 THE USER TERMINAL SYSTEM—Select the appropriate terminal system “improving
the cooling temperature and reducing the heating temperature”.
In the ideal heat-pump cycle, improving the evaporating temperature or reducing condensing
temperature will improve the COP value. The ideal heat pump cycle which uses several
kinds of common refrigerants changes as Figure 2, the COP values will improve as shown in
Table 2.

（a）the ideal heat pumpcycle（b）reduce thecondensing temperature（c）increase thevaporization point

Figure 2 the ideal heat pump cycle and the pressure enthalpy diagram after adjustment
According to the results, we can know that reducing heating water temperature in winter andincreasing cooling water temperature in summer under the ideal conditions can improve theenergy efficiency of the heat pump cycle significantly. In practical engineering applications,
the EER is less than ideal conditions as a result of the heat pump cycle’s irreversible process
and friction loss. But under the two different conditions, changing the evaporating
temperature and condensing temperature both enhance energy efficiency, this trend isunchanged. Therefore, we can obtain the direction for the optimization by analyzing this ideal
cycle.

Refrigerant

R22
R134a

Table2 conditions COP calculation comparison table in the ideal
After reduce theincrease thereduce thecondensing
vaporization
the ideal
increase thecondensing
temperaturepoint increase
heat pump
vaporization
temperature
Increase thethe vaporization
cycle COP
point COP
COP
percentage ofpoint COP
COP
4.46
5.96
33.6%
5.85
31.2%
4.44

5.98

34.7%

9

5.87

32.2%

China
R407C

4.26

5.82

36.7%

5.63

32.2%

We should take the low-temperature heating terminal equipment in winter and hightemperature cooling terminal equipment in summer actively. In general, conventional airconditioning mode will bring a series of new problems, while reducing winter heating
temperature and increasing in summer temperature cooling, such as heat and moisture loadcannot all be met with, etc.
Currently, the application of independent temperature-humidity control air conditioning
system provides a new opportunity for the application of highly efficient heat pump terminal
devices.
The heat pump system can only supply the sensible heat, operate safely and keep a higher
level of energy efficiency. Heat pump system should take priority of the “High temperature
cooling and Low temperature heating terminal system devices”.
5 OPERATION AND MANAGEMENT--Strengthen the operation of monitoring,
management and maintenance
GSHP system should not only maintain long-term efficient operation, but also strengthen themonitoring and management and maintenance.
Through setting the monitoring system, the soil temperature, water temperature and flow of
the GSHP system should be monitored.
It is convenient to check the heat exchange capacity of the system which has run for years,
and adjustment operation strategy appropriately according to monitoring data.
Especially for hybrid GSHP system, by monitoring and timely adjusting supplements of theauxiliary energy immediately can not only ensure the effective application of auxiliary energy
and energy supply of the terminal, but also make the soil source system achieve long-term
efficient operation.
We should choose a reasonable position for the monitoring device buried, which should be
as close to the regional centers as well, then the values can be measured objectively andreflect the actual temperature of the soil conditions. If the monitoring devices are disposed in
the outer region of the heat exchanger as inconvenient location for construction and someother reasons, the value of the testing temperature is greatly reduced, which cannot reflect
the actual situation accurately.
The management of electricity systems and hydraulic transmission and distribution systems
should be strengthened in order to avoid local faults which may affect the whole system
operation.
The daily maintenance is important, and particular attention should be paid on the drainageof the distributed-centralized water chambers. Especially after rain and snow, more attention
should be drawn on maintenance of the valves and insulating layers. Drainage should avoid
creating new point of energy loss.
CONCLUSION
GSHP system is an effective way of using renewable energy，the effective application
depends on reliable thermal physical properties of test data, the scientific simulation analysis,
systematic design process, the correct construction debugging and effective management
and maintenance. We hope that the analysis in this article can draw the attention of theprofessionals, promote the effective application of GSHP and make the GSHP system givefull play to its role in energy saving and emission reduction.
REFERENCES

10

China・List all the references document as followed.
1.

2.

3.
4.

China National Environmental Monitoring Centre. In January, 2013, 74 urban air
quality monthly report. 2013.(in Chinese)
Dong Fei, Ni Long, Yao Yang etc. Shallow rock and soil energy storage combinedwith shallow geothermal energy substainable low source of ground source heat.
HVAC 2009,39（2）：70-72. (in Chinese)
PRC National Standard. Technical code for ground-source heat pump system(GB50366-2005(2009)). (in Chinese)
Yang Lingya, Zhu Qingyu, Xu Wei. Energy loss simulation of horizontal circuit header
in ground-source heat pump systems in Beijing. HVAC 2013,43（3）：36-40. (inChinese)11

JapanAn inside story behind the advent of “Eco Cute” CO2 heatpump water heater for residential use
Michiyuki Saikawa
Central Research Institute of Electric Power Industry (CRIEPI)

SummaryMore than ten years have passed since the “Eco Cute” CO2 heat pump water heater forresidential use was commercialized in May 2001 in Japan through the collaborative R&D
including CRIEPI. Its cumulative shipments are over 4.6 million at the end of March 2015.
There were two projects involving hot water supply heat pumps prior to the development of
the Eco Cute in CRIEPI, though neither went into commercial production. In this paper, thehistory and technical aspects of the advent of the Eco Cute, including the former two projects,
are introduced.
1.

IntroductionMore than ten years have passed since the “Eco Cute” CO2 heat pump water heater forresidential use was commercialized in May 2001 in Japan through the collaborative R&D ofTokyo Electric Power Company (TEPCO), Denso Corporation (DENSO) and Central
Research Institute of Electric Power Industry (CRIEPI). It has become widespread byintroduction of subsidy by Japanese government, market entry of new manufactures andgrowing interest in environmental problem. Its cumulative shipments are over 4.6 million at
the end of March 2015 as shown in Fig. 1[1].
There were two projects involving hot water supply heat pumps prior to the development of
the Eco Cute in our institute, CRIEPI, though neither went into commercial production. On
this occasion, the history and technical aspects of the advent of the Eco Cute, including theformer two projects, are introduced.
2.

History of research & development of heat pumps in CRIEPIThe R&D activities of heat pumps in CRIEPI began when it was entrusted to a part of theSuper Heat Pump development project, which was a national project and started in 1984.
Because the heat pumps work on the same principle of the thermal power generation cycle,
a staff member of the thermal power section who was senior to me was assigned to play acentral role in this research project. The CRIEPI decided to hire a new employee for the
project, which led to me being hired to join in 1986.
Not only to do the entrusted research but also to have started the original research in CRIEPI,
the sector in which the introduction of a heat pump could bring about a large energy saving
effect was investigated. As results, it was found that major energy savings were possible if ahighly efficient heat pump could be developed and introduced for domestic tap water heating.
The demand for hot tap water accounts for about 30% of residential final energy
consumption, but most of this demand is met by direct combustion of fossil fuel.
Under such a circumstances, a new system named the “two-stage compression and cascadeheating heat pump water heater (TS-HPWH)” was invented by my senior staffer based on his
knowledge and experiences in the field of the thermal power generation cycle. This system
was later issued as a patent of Japan.
For a normal refrigerant such as Fluorocarbon, water or air is heated by a refrigerant thatcondenses at a constant temperature on the high pressure side of the heating cycle. For this12

Japanreason, good efficiency can be gained if the heating temperature range is small, as seen in
the cycle for air conditioning. On the other hand, for hot water supply, water of 10 °C needs
to be heated up to 65 °C, thus requiring a heating process with a high temperature rise. Fig.
2 (a) shows the heating process wherein water at 65 °C is made by a simple heat pumpcycle. As shown in the figure, there is a section in which low temperature water at about
20 °C is heated by condensing refrigerant at about 70 °C, which results in large loss. A
heating temperature of about 30 °C suffices to heat the water at 20 °C.
While the TS-HPWH we had invented, it was intended to decrease the irreversible loss by
preparing two condensation pressures through its two-stage compression. By doing so it
could achieve proper heating suitable to the temperature level as shown Fig. 2(b). Next,
whether this system could actually be put into practical use should have been examined, andwhat kind of elemental technology should have been adopted for it. On this account, an
experimental apparatus of the system was manually fabricated as shown in Fig.3. Using thisapparatus, feasibility of its cycle was verified and good results were obtained.
The collaborative R&D with electric power companies and a manufacturer was conductedfrom 1988 to 1992 for developing the air conditioning & hot water supply heat pump forresidential use based on the TS-HPWH. The development progressed smoothly, evolved toactual field tests. Despite these efforts, this apparatus was not made into a commercial
product. The reasons were lower hot water supply efficiency than expected and its
unattractiveness in terms of price, size and so forth. Rather than a multifunctional heat pump,a heat pump equipped with only a hot water supply function was to be developed.
Having learnt the experience, the development of the TS-HPWH for business use in hotels
and other facilities was conducted from 1990 to 1996. The prototype was made as shown in
Fig.4. For commercializing it, the collaborative development with a manufacturer and ageneral contractor was done. In the collaboration, a basic system for business use wasestablished and its elemental technology was developed. Unfortunately, the system was notcommercialized because of issues surrounding Fluorocarbon. The developed system wasvery good from a technical standpoint, particularly because it was designed specifically for
hot water supply. However, the development was underway at an inopportune time.
Thus, two collaborative developments were made but neither resulted in commercialization.
Two younger colleagues joined us, so four employees engaged in the R&D project at the
CRIEPI, with some funds being invested into the ongoing project. Accordingly, R&D of heatpumps was under increasing pressure in-house, being questioned as to the degree ofprogress of our research on the heat pump.
3.

Investigation of natural refrigerants and encounter with CO2 refrigerant

One of the main reasons for the failure of the commercialization of the two-stagecompression system for business use was an issue surrounding the use of Fluorocarbon.
CFC12 was used for the heat pump. At that time, the refrigerants of the HFC family had
become promising alternatives to the conventional refrigerants in Japan and the UnitedStates. In Europe, the move was toward examining natural refrigerants. Considering thesefacts, our investigation was started in 1993 with the idea that examination of naturalrefrigerants should be done from a long-term viewpoint.
Among natural refrigerants, CO2 was focused on because it has unique properties. Basicstudies began in 1995. It was confirmed that a higher COP can be theoretically obtained from
CO2 than any other refrigerant when making hot water. The reason is described in Fig. 2. It
can be seen from Fig. 2(c) that CO2 does not condense, unlike normal refrigerants, and thatits temperature decreases gradually as water is heated. For this reason, irreversible loss is
reduced, bringing about a higher COP than Fluorocarbons. Though the two-stagecompression system had been invented previously, the use of CO2 enabled us to achieve analmost ideal hot water heating.
Back in those days, R&D of CO2 refrigerants was already underway in Europe, but not inJapan. So a basic experiment loop for a CO2 heat pump was designed, fabricated and13

Japaninstalled (Fig. 5) in March 1996. At that time, there was no compressor able to operate on thepressure of CO2. For this reason, a company that was small in size but specialized in highpressure gas processes was found and it made the compressor for the loop despite its
misgivings. Using the experiment loop, the feasibility of the CO2 cycle, its control method
and heat transfer were investigated. As a result, it became certain that CO2 is a promisingrefrigerant for hot water supply.
4.

Joint development of CO2 heat pump water heater

In March 1998, when it had been found that the CO2 refrigerant could be put into practicaluse and was a promising refrigerant for hot water supply, a sales representative fromTEPCO visited CRIEPI for inquiry into natural refrigerant technologies for use in air
conditioning. Introducing that CO2 is a good refrigerant for hot water supply, he understoodthe excellent properties of CO2 as a refrigerant for heat pump water heater. In this way,
making in-house arrangements for the development on both companies was started.
However, it is true that only a manufacturer can actually produce a product, so it wasnecessary to find a manufacturer to be able to participate in our development.
In May of the same year, 1998, an international conference on natural refrigerants was heldin Europe. CRIEPI participated in the conference and made a presentation about the resultsof basic studies of CO2 heat pump. DENSO from Japan also presented the development of a
CO2 car air conditioner. While listening to the presentation, it was convinced that DENSO
could develop the CO2 heat pump water heater. During the conference, meetings between
CRIEPI and DENSO were held intermittently. In July, a representative from TEPCO visitedthe DENSO and discussed about a joint development. Its first reaction was not so good
because DENSO was a car air conditioner maker. During the course of the explanation of thedevelopment technology, however, DENSO agreed to the offer. In effect, the joint
development project began from October.
During the joint development, a wind tunnel for testing a prototype of CO2 heat pump water
heater was installed in CRIEPI as shown in Fig. 6(1999). Using the wind tunnel, a lot of tests
on the prototype (Fig. 7) were carried out. Measuring, analyzing and evaluating COP and
efficiencies of elements were done. Development issues were abstracted and measures for
performance improvement were investigated. Improved components were sent to CRIEPI by
DENSO. These components were assembled, tested and evaluated, and then results werereturned to DENSO. This cycle was repeated over and over again. Finally it was confirmedthat our initial goal for the developed technology could be achieved.
Anyway, after going through many ups and downs, the “Eco Cute” was commercialized forthe first time in the world in May 2001. As they say, "third time lucky" applies to CRIEPI. Past
experiences of previous two failed attempts at commercialization contributed greatly to thesuccess of this development project.
5.

Conclusion

In this paper, mainly our hard-luck story prior to the advent of Eco Cute was introduced.
Looking back on the development of Eco Cute, it really got started in a timely fashion withgood connections between people, each of whom had their own role to play. In the end agood outcome was achieved through each of us aiming at the same goal. Finally the Eco
Cute that was installed in my home was introduced in Fig. 8. Taking responsibility as adeveloper, it was purchased in 2004 and has been used more than 10 years. In heavy snowof February 2014, it had failed. But after repair it again started producing hot water.
Besides, detailed hydraulic calculation, monitoring system, using the double pump like shownin Figure 1, etc. can be taken into consideration. Hydraulic transmission system aims to
improve the flexibility of the adjustment and control, make it better to adapt to changes insystem load, reduce the energy consumption of distribution system, and improve the energy
efficiency of the system under the premise that the system is stable.

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JapanAcknowledgements
The author would like to thank Mr. Tomoaki Kobayakawa (TEPCO), Mr. Kazutoshi Kusakari(TEPCO), Mr. Masahiko Ito (DENSO) and Mr. Hisayoshi Sakakibara (DENSO) as membersof the joint development of CO2 heat pump water heater. The author also would like to thankDr. Teruhide Hamamatsu, Mr. Toshio Mimaki, Mr. Tetsushiro Iwatsubo, Mr. Hiromi
Hasegawa and Dr. Katsumi Hashimoto as bosses or colleagues of CRIEPI.
Reference[1] http://www.jraia.or.jp/english/excel/shipments_fy_e.xls

Fig.1 Cumulative shipments of “Eco Cute” CO2 heat pump water heater for residential use in Japan[1](Made from the statistical data, such as JRAIA )Fig.2 Comparison of heating cycle（Temperature - Enthalpy Diagram）

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JapanHeating capacity 4kW, installed in 1987
Fig.3 Experimental apparatus of two-stage compression system

Heating capacity 150kW, installed in 1991
Fig.4 Prototype of two-stage compression system for business use

Heating capacity 4kW, installed in 1996
Fig. 5 Basic experiment loop for CO2 heat pump16

JapanHeating/cooling capacity 5kW, installed in 1999
Fig.6 Test chamber for prototype of CO2 heat pump water heater

Heating capacity 4kW, installed in 1999
Fig.7 Prototype of CO2 heat pump water heater for residential use

Heating capacity 6kW, tank capacity 460L, 2004 model
Fig.8 Eco Cute of my home17

Asian Heat Pump Thermal Storage Technologies Network
To promote energy savings and combat global warming, there is an urgent need to spread efficientheat pump and thermal storage technologies on the demand side. Countries in Asia, which areenjoying rapid economic growth, should coordinate with one another to spread this technology.
Five to ten years from now, Asia will become a global economic powerhouse and heat pumptechnologies will play a considerable role in all sectors. Asian countries will therefore need toaddress common issues and problems that have already been faced in Europe and North America.
Concerning the building of connections and networks among countries, it is essential to share
information on diffusion policies, technology trends, applications, etc., and then to make incremental
improvements. Further, situations which can or should be handled through collaboration should be
handled flexibly, on a case-by-case basis, with the collaboration of all countries.
In order to encourage the use and development of heat pump and thermal storage technologies in
Asian countries we have established AHPNW in 2011.

Participating Countries and Entities
CHINA: China Academy of Building Research (CABR)INDIA: The Energy and Resources Institute (TERI)JAPAN: Heat Pump and Thermal Storage Technology Center of Japan (HPTCJ)KOREA: Korea Testing Laboratory (KTL)VIETAM: Hanoi University of Science and Technology (HUST)THAILAND: King Mongkut’s University of Technology Thonburi (KMUTT)INDONESIA: Heating, Cooling & Thermo Fluids Technology Indonesia (HCTFTI)

Please visit our website for more information.
⇒http://www.hptcj.or.jp/e/ahpnw/tabid/571/language/en-US/Default.aspx

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