HISTORY AND LATEST TRENDS OF

DOMESTIC HOT WATER HEAT

PUMP TECHNOLOGIES

2019.08.27

JAPAN NATIONAL TEAM

WASEDA University Kiyoshi Saito

International congres of refrigeration, August, 24-30, 2019

INTRODUCTION

2

Heat pump technologies are promising ones to reduce CO2 emissions.

Recently new technologies appeared for DHW heat pump technologies

I would like to introduce the followings.

1. History of development – How systems have changed?

2. Components and system technologies

3. Kinds of refrigerant

4. End-user and installer focused technologies

5. Water quality and saving management technologies

6. Smart technologies(ZEB, smart grid, smart energy)

International congres of refrigeration, August, 24-30, 2019

MARKET OF HEAT PUMP SYSTEMS

3

In Japan,

2001: CO2 refrigerant heat pump system was

started to put on market

2018: 6 million systems were going into

market.

Figure: Development of hot water heat pumps sales in Switzerland

In Switzerland,

1919 - 1950： heat pumps for space heating and

domestic hot water heating were developing

from rare first prototypes to a reliable,

efficient and even economically viable

heating device.

2009-2015: the sales numbers of hot water heat

pumps has increased from 364 in 2009 to

4919 units in 2015.

Figure: Development of hot water heat pumps sales in Japan

International congres of refrigeration, August, 24-30, 2019

HEAT PUMP CYCLE

4

200 300 400 500600

700

800

900

1000

2000

3000

4000

5000

6000

60

Specific enthalpy kJ/kg

Pre

ssu

re k

Pa

T = 0 oC

4020 80 100

R 410A1

23

4

Conventional Freon system CO2 system

Condenser

Compressor Expansion Valve

Evaporator

Gas cooler

Compressor Expansion Valve

Evaporator

International congres of refrigeration, August, 24-30, 2019

COMPONENT TECHNOLOGIES

5

R134a miniature turbocompressor

Figure 20: Oil free miniature turbo compressor, Left: 3D flow simulation, Middle: Manufactured impeller with 20

mm diameter, Right: Compression unit with impeller, bearings and electromotor (Schiffmann 2005).

Two-phase compressor

Figure 21: Left: T-s diagram of R290 (propane) as an example, illustrating the process with the two-phase compressor

(evaporation temperature 0°C, condensation temperature 40°C), a conventional compressor and an ideal Carnot

process, Right: CAD model of the compressor test stand (Friedl et al. 2012).

International congres of refrigeration, August, 24-30, 2019

COMPONENT TECHNOLOGIES

6

Development of DENSO Development of MITSUBISHI

New compressor for CO2 refrigerant

International congres of refrigeration, August, 24-30, 2019

COMPONENT TECHNOLOGIES

7 DAIKIN

Water side heat transfer enhancement for CO2 gas cooler

International congres of refrigeration, August, 24-30, 2019

COMPONENT TECHNOLOGIES

8

MITSUBISHI

ELECTRIC

New gas cooler

International congres of refrigeration, August, 24-30, 2019

COMPONENT TECHNOLOGIES

9 DENSO

Ejector with flow control

International congres of refrigeration, August, 24-30, 2019

COMPONENT TECHNOLOGIES

10

"Uretank"

Changes in the hot water storage unit of Hitachi's Eco Cute

Glass wool Styrofoam Styrofoam

+ vacuum

insulation material

※Standard type

Urethane foam

Urethane foam + vacuum

insulation material

※Mainly high-efficiency type ※High-efficiency type

2003 ～ 2007 ～ 2012 ～ 2014 ～

History of thermal storage tank development

To prevent legionella, we have to heat up to more than 65 ℃. That’s why insulation of thermal storage is very important.

International congres of refrigeration, August, 24-30, 2019

SYSTEM TECHNOLOGIES

11

Solar assisted system

International congres of refrigeration, August, 24-30, 2019

SYSTEM TECHNOLOGIES

12

Fig. Hybrid system with Gas heater

Hybrid system with gas water heater

International congres of refrigeration, August, 24-30, 2019

SYSTEM TECHNOLOGIES

13

Compact Thermo Acoustic Heat Pump for the Built Environment (CTWB)

Project goal is to develop a prototype compact TAWP

for decentralized heating and cooling of buildings with

a COP of 3.5 to 4.0 (air / water) and a thermal capacity

of 1kW. This contributes to compact, inexpensive and

efficient developments in the field of heat pump

technology in the built environment.

Blue Heart heat pumps are closed systems that are

filled with Helium under pressure.

Electrical driven drivers send an acoustic wave

through the pump.

At the point where Helium is compressed heat is

exchanged by a heat exchanger.

Between the two heat exchangers a regenerator is

located. Within the regenerator a thermal cycle arises.

In this way the regenerator creates a temperature

difference or a so called thermal pump or heat pump.

At the point where the helium is expanded, heat from

the source is added using a second heat exchanger.

The heat exchangers (2) and (4) are connected to either

the source or heatsink, depending on the demand of the

consumer. Either heating or cooling.

International congres of refrigeration, August, 24-30, 2019

SYSTEM TECHNOLOGIES

14

Prediction

of demand

Prediction of

solar energy

Optimum control of

battery and heat pump

Battery

Heat pump

Thermal storage

Grid

Demonstration Image of the project

International congres of refrigeration, August, 24-30, 2019

SYSTEM TECHNOLOGIES

15

Absorption and adsorption technologies

International congres of refrigeration, August, 24-30, 2019

REFRIGERANTS

16

• In most of the countries, R410a, R134a, R407c were used for

DHW heat pump.

• In Japan, refrigerant of most of DHW is CO2. Recently, R32 and

HC(R290) system has been just put on market.

• Recently, HFOs are investigated for the refrigerants of DHW heat

pump

International congres of refrigeration, August, 24-30, 2019

END-USER FUCUSED TECHNOLOGIES

17

Multi function type

Hot water supply + floor heating + space heating

Floor

heating

International congres of refrigeration, August, 24-30, 2019

END-USER FUCUSED TECHNOLOGIES

18

Figure 23: Left: New components of the wall unit THERMOS, Right: Renovated

bathroom with integrated wall unit THERMOS (Swissframe AG) (Büchel et al. 2016).

Front wall installation system in bathroom

International congres of refrigeration, August, 24-30, 2019

INSTALLER FOCUSED TECHNOLOGIES

19

A plug and play concepts for existing and new

domestic buildings. A special integrated unit has been

developed combining heat pump technologies with

solar energy.

The complete installation is built pre-fab at the

factory, avoiding potential installation failures with

‘new technologies’.

International congres of refrigeration, August, 24-30, 2019

WATER QUALITY MANAGEMENT TECH.

20

Bubble cleans up piping between heat pump and bathtub

International congres of refrigeration, August, 24-30, 2019

WATER SAVING TECHNOLOGIES

21

With a classic shower, 10 minutes of showering

takes about 70 to 90 litres of water. The water

used during showering corresponds

approximately to 30% of the total water use.

The rain shower grows in popularity as comfort

shower in modern bathrooms, but a rain shower

uses 15 to 30 litres per minute! By recirculation

more than 85% less water and thus 70% less

energy is used. Each drop is recycled 9 times

via a unique system that cleans water based on

UV light

International congres of refrigeration, August, 24-30, 2019

SMART TECHNOLOGIES

22

HEMS controller controls heat pump water heater, air-conditioner, lights, refrigerator

and so on simultaneously - 16 systems can be connected -.

International congres of refrigeration, August, 24-30, 2019

CONCLUDING REMARKS

23

The recent R&D of heat pump system are introduced.

Especially in Japan, to develop DHW heat pump that uses CO2 as a

refrigerant, many new technologies appeared.

From now, still some developments of new technologies will be

needed for DHW heat pump. For example,

• Smart use of DHW heat pump with other systems in domestic use.

• DHW heat pump that self-consumes solar energy optimally.

• DHW heat pump that uses lower GWP refrigerants but whose cost

is lower

Anyway, heat pump technologies contribute a lot to reduce the CO2

emissions. We have to do our best to expand this technologies.