Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
1Heat Pump Technology to Reduce CO2 Emissions andRunning Costs by Replacing Boilers

HISAO MIZUNO*1

KENGO SHIMAMURA*2

KAZUO AKITA*3

YUJI OKADA*4

Mitsubishi Heavy Industries, Ltd. (MHI) Group puts priority on contributing to theachievement of carbon neutrality through its business activities. Shifting the heat source from fossil
fuel combustion to electrified heat pumps is an effective way to achieve this. With this heat pumptechnology, MHI Group will market heat pump products with reduced running costs so that a wide
range of customers will use our heat pumps. As such, we intend to reduce CO2 emissions in society
as a whole and will continue to contribute to the realization of a carbon-neutral society through thedevelopment of technologies.

|1. Introduction
MHI Group has declared the realization of a carbon-neutral society through our businessactivities as a key management issue, aiming to achieve Net Zero by 2040. One of the ways toachieve this is to aggressively expand the use of heat pumps, not only to reduce CO2 emissions
through direct combustion as in the past, but also to actively utilize renewable energy sources bypromoting electrification. Most of the heat sources used for the industrial field, such as boilers, arefossil fuel-combustion. In order to expand the use of heat pumps in this market, it is effective toimprove the economic efficiency and convenience entirely from the heat source to the user side.
This report introduces the heat pump technology by presenting MHI Group's efforts to apply heatpumps to various applications as a replacement for boiler heat sources.

|2. Shifting from boiler to heat pump
Currently, most of the high-temperature heat sources used in the industrial field are provided
by boilers, and their total heat demand is estimated to be approximately 13,000 TWh in 2020.
Figure 1 shows the percentage of total heat demand by temperature range. The actual demandtemperature below 200°C accounts for 48% of the total demand, and in particular, below 100°C
accounts for one third of the total demand. The CO2 emissions from the heat sources for thedemand temperature range below 100°C are approximately one megaton CO2, assuming a boiler
system efficiency of 80% and gas combustion of 200 g/kWh.
Heat pumps have a characteristic that the smaller the temperature difference between the heatsource side and the use side, the greater their coefficient of performance (COP), and the more
efficient they can be in transporting heat. Therefore, MHI Group has been marketing products thatutilize heat pumps mainly for the demand temperature range of 100°C or lower among themainstream demand temperature range of 200°C or lower to promote the replacement of boilers,
thereby contributing to reductions in energy in a crude oil equivalent and CO2 emissions. If allboiler heat sources for the demand temperature range of 100°C or lower are replaced with heat
*1General Manager, Marketing Department, Mitsubishi Heavy Industries Thermal Systems, Ltd.

*2Senior Manager, Business Development Department, Growth Strategy Office, Mitsubishi Heavy Industries, Ltd.

*3Manager, Business Development Department, Growth Strategy Office, Mitsubishi Heavy Industries, Ltd.

*4Manager, Air-Conditioner Designing & Engineering Department, Mitsubishi Heavy Industries Thermal Systems, Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
2pumps powered by renewable energy, it would be possible to reduce approximately one third of theCO2 emissions resulting from the use of heat source device in the industrial field.
Figure 2 shows heat pump products that MHI Group brings to the market by the capacity
and temperature range. In the next chapter, we will introduce four cases of heat pump technology
using air heat sources, which are easy to be designed and installed, as examples of the heat pumptechnologies being worked on by the temperature range.

Figure 1 Total global heat demand (13,000 TWh) bytemperature range

Figure 2

Our heat pump product line

|3. Technologies for products MHI Group is working on by supply
temperature range
3.1(1)

Hot wind generator "Neppu-ton"(1)Product technology overview
This product is a heat pump that generates 90°C hot wind using an air heat source, andwas developed to replace boilers and electric heaters used as a heat source for drying device.
Obtaining high-temperature hot wind or hot water by general heat pumps requires a system thatrecovers heat from factory waste hot water to reduce the temperature difference between theheat source device and the hot wind generator. Such a system requires water piping to circulate
waste hot water, and therefore there arise issues that the system is complicated, the cost is high,Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
3and ensuring the installation space is difficult. To solve these issues, this product was designed
to consist of two components like ordinary air conditioners: a heat source unit (an outdoor unit)that draws heat from the atmosphere and a hot-wind generator (an indoor unit) that can directly
generate hot wind. This product design made it possible to install the hot wind generator nearfactory device where hot wind is used. Since the waste hot water piping is no longer necessary,it is easy to install additional device to increase the capacity of the factory, which allows theheat pump system to be used more widely in the industrial field. Furthermore, this productadopts a highly efficient system with a two-stage compression cycle, which makes it possible toblow hot wind at 90°C even though air is used as the heat source.
(2) CO2 emissions reducing effect
In the example case of applying this product to hot wind supply system for a drylaminator, this product was introduced as a replacement for a conventionally used heating
device that generated hot wind of 70°C to 80°C using a steam coil. Figure 3 shows a system
diagram of the hot wind supply device to which our product was introduced. New ducts wereinstalled upstream of the existing steam coil, and the hot wind generator was installed to supply
hot wind of 70°C to 80°C as intake air preheating. Even when the output of the heat pump heatsource unit drops due to defrosting operation, the temperature supplied to the dry laminator ismaintained at a constant level by bypassing the heat pump heat source through the existing
ducts and using the steam coil for heating. Similarly, in the event of a heat pump failure, theexisting ducts are used to secure an airflow path, allowing the dry laminator to continue
operation.

Figure 3

Hot wind supply system for dry laminator

Figure 4 shows an example of estimating the effect of introducing this system, andTable 1 shows the estimation conditions. In addition to the unit energy cost and CO2 emissions,
Table 1 also shows the value obtained by converting the electricity used by this system toprimary energy. As a result of the demonstration test conducted for approximately one monthfrom late November to late December, energy consumption, CO2 emissions, and running costs
were all reduced by approximately 50% compared to the conventional steam heater. These
positive results are because this system is located close to the place of use in addition to theefficiency improvement due to the heat pump, whereas the boiler is not installed close to theplace of use and its efficiency drops to about 0.6 when heat loss in the piping is included. This
demonstration test confirmed the achievement of both environmental load reduction and higheconomic benefits in winter, and we expect this system to be even more effective on an annualbasis.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
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Figure 4

Example of estimating effect of introducing developed system

Table 1

Conditions for estimating effect of introducing developed system

ItemUnit calorific value of city gas
Primary energy equivalent of electricity
Electricity
CO2 emissions
City gas

UnitMJ/Nm3
MJ/kWhkgCO2/kWh
kgCO2/Nm3

Value
45.0
9.76
0.496
2.29

Source:- Unit calorific value of city gas: Value set in Act on Promotion of Global WarmingCountermeasures- Primary energy equivalent of electricity: Value set in Act on the Rational Use of Energy- CO2 emissions (Electricity): Tokyo Electric Power Company Holding, Inc.'s emissions
factor for submission in 2017 (adjusted emissions factor),
https://www.env.go.jp/press/106320.html- CO2 emissions (City gas): Values published by Tokyo Gas Co., Ltd. (Tokyo Gas website),https://www.tokyo-gas.co.jp/network/gas/shurui/index.htm

3.2
(1)

Commercial-use water heater "Q-ton"(2)Product technology overview
This product was developed to replace boilers that use fossil fuels and electric heater-typewater heaters. Conventional air source heat pumps have a problem in that their heating capacity
decreases when the outside air temperature is low, and they have not been widely used in cold
regions. To solve this problem, this product employs a two-stage compression gas injection
cycle that increases the amount of gas cooler refrigerant circulating at low outdoor temperaturesby using a two-stage compression process for CO2 refrigerant, which is a natural refrigerant,
and injecting gas refrigerant at the intermediate pressure. As a result, the same capacity as therated capacity is maintained at the inlet water temperature of 17°C and the outside airtemperature of -7°C, and more than 70% is maintained at the outside air temperature of -20°C.
Furthermore, hot water of 90°C can be produced at a lower outside air temperature of -25°C. Inaddition, the use of CO2 with a GWP (Global Warming Potential) of 1 as a refrigerant has also
been highly evaluated, and the use of this product is spreading to hotels, hospitals, food service
centers, and other facilities in cold regions.
(2) CO2 emissions reducing effectFigure 5 shows example cases in which this product was installed in existing hot watersupply device using a boiler. The system installed in east Hokkaido mainly supplies hot water
for machine washing, and the system installed in north Iwate Prefecture supplies hot water forsanitary use. Both of these demonstration tests were conducted in some of the coldest regions inJapan, and it was confirmed that our product could supply hot water without any problems evenin winter.
Figure 6 shows examples of estimating the effect of introducing this system, and Table 2
shows the estimation conditions. Compared to a boiler assuming a system efficiency of 80%,
the primary energy consumption could be reduced by slightly less than 20%, the running costby slightly more than 50%, and CO2 emissions by slightly less than 30%, clearly demonstrating
the superiority of this technology over boilers.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
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Figure 5

Diagram of introduced Q-ton systems

Figure 6

Examples of estimating effect of introduced Q-ton systems
Table 2

Conditions for estimating effect of introduced Q-ton systems

Location
North Iwate
Prefecture

Electricity

East
Hokkaido

Electricity

Kerosene

Fuel oil A

Unit price
Summer: 11.65 yen/kWh
Other seasons: 10.70 yen/kWh90 yen/LNight time: 6.5 yen/kWhDaytime: 13.0 yen/kWh
84 yen/LCO2 emissions

Primary energy
equivalent

0.546 kg-CO2/kWh

9.76 GJ/103 kWh

2.49 kg-CO2/L

36.7 GJ/kL

0.680 kg-CO2/kWh

9.76 GJ/103 kWh2.71 kg-CO2/L

39.1 GJ/kL* Other conditions: System efficiency of existing boiler is 80%
Source:- CO2 emissions (Electricity):

Tokyo Electric Power Company Holding, Inc.'s emissions factor
for submission in 2017 (adjusted emissions factor),
https://www.env.go.jp/press/106320.html
CO2 emissions (Kerosene and fuel oil A): Ministry of the Environment's website, Greenhouse Gas Emissions
Calculation, Reporting, and Publication System
List of Calculation Methods and Emissions Factors for Calculation,Reporting, and Publication System,
https://ghg-santeikohyo.env.go.jp/calc- Primary energy equivalent (Electricity): Value set in Act on the Rational Use of Energy
Primary energy equivalent (Kerosene, fuel oil A): Agency for Natural Resources and Energy's website, List ofstandard calorific values by energy source (2005)
https://www.enecho.meti.go.jp/statistics/total_energy/carbon.html

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
63.3

Water chiller/heater MSV (Mitsubishi Smart Voxcel)

(3)

(1)

Product technology overview
This product is a versatile air-cooled heat pump chiller designed to meet the demand not
only for air conditioning applications using fan coil units, but also for the replacement offactory boilers used for heating parts washing tanks in factory manufacturing processes. Many
washing tanks need to be heated so as to maintain the temperature at 55°C to 60°C throughout
the year. Conventional air-cooled heat pump chillers have issues that the heating temperature islimited by an excessive increase in the refrigerant pressure and operation under high outside airtemperature conditions, which tend to cause an increase of the refrigerant pressure, isimpossible due to the large absorption. This product enables heating operation up to 60°C andcontinuous operation at an outside air temperature of 43°C by optimizing control of therefrigerant flow rate to the condenser and controlling the blower of the evaporator, making it
possible to meet the demand for replacement of industrial boilers.
(2) CO2 emissions reducing effectFigure 7 shows a system that assumes the introduction of this product into a washingprocess for machine parts. This system mainly uses a heat pump to heat the washing solution in
the washer, from using only steam from a boiler. Since the washing solution is corrosive, thesystem provides heating thereto via an indirect heat exchanger in a newly installed hot water
circulation piping circuit. We estimated the effect of the introduction of the system assuming aheating load of 150 kW, a temperature increases from 55°C to 60°C, and an operating time of3,840 hours per year.
Figure 8 shows an example of estimating the effect of the introduction, andTable 3 shows the estimation conditions. The annual electric energy consumption
calculated by integrating the amount of electricity used during winter, summer,
and the intermediate period resulted in an approximately 44% reduction in runningcosts and an approximately 40% reduction in CO2 emissions compared to the boiler,
indicating that this technology is expected to be superior to the boiler. An
equivalent system is currently in operation at MHI Group.

Figure 7

Example of introducing our product to part washing process

Figure 8 Example of estimating effect of introducing our productto part washing processMitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
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Table 3

Conditions for estimating effect of introducing our product to part washing process

Load condition

Heating load
Heating temperature
condition
Operating hours

Unit price

Estimation
conditions

ElectricityGas

Electricity Basic charge:
1,800 yen/kWh
Summer:11.65 yen/kWh
Other seasons:10.70 yen/kWh
94.09 yen/Nm3

150 kW
55°C -> 60°C
Operating hours 3840 hours/year(16 hours/day x 240 days/year)
CO2 emissions

Primary energy
equivalent(Daytime)

0.494 kg - CO2/kWh

2.29 kg - CO2/Nm3

9.97 MJ/kWh(Nighttime)
9.28 MJ/kWh
45.0 MJ/Nm3 (HHV）* Other conditions
COP of heat pump: (Winter: 5.6°CDB) 2.50, (Mid-season: 18.1°CDB) 2.90, (Summer: 26.3°C DB) 3.20
System efficiency of existing boiler: 70%
Source:- CO2 emissions (Electricity): Tokyo Electric Power Company Holding, Inc.'s emissions factor for
submission in 2017 (adjusted emissions factor),
https://www.env.go.jp/press/106320.html
CO2 emissions (City gas): Values published by Tokyo Gas Co., Ltd. (Tokyo Gas website),https://ghg-santeikohyo.env.go.jp/calc- Primary energy equivalent (Electricity): Value set in Act on the Rational Use of Energy
Primary energy equivalent (City gas): Value set in Act on Promotion of Global Warming Countermeasures
https://www.enecho.meti.go.jp/statistics/total_energy/carbon.html

3.4
(1)

Circulation heating heat pump "Q-ton Circulation"(4)Product technology overview
In some cases, the temperature of hot water used in the degreasing process after cutting
and the parts cleaning process in machine parts factories and for the cleaning of manufacturing
device in food factories is around 70°C, which is higher than the supply temperature of thewater chiller/heater mentioned above, and it is necessary to select a refrigerant suitable for suchtemperature and employ a high-efficiency cycle. This product is an air source circulation
heating heat pump for these applications, and can provide 75°C hot water (inlet/outlet
temperature difference 5°C) under ambient air temperatures from -20°C to 43°C. The use ofthis air source heat pump eliminates the need to prepare waste hot water and avoids
complicated system design and installation during the introduction. In order to enable acirculation hot water supply function with high temperature and a small difference between theinput and supply water temperatures, R454C, a low-GWP refrigerant, is used. On the otherhand, since air source heat pumps have the characteristic that the heating capacity decreases as
the outside air temperature decreases, a two-stage compression gas injection cycle is used toaddress this issue, similarly to Neppu-ton and Q-ton.
(2) CO2 emissions reducing effectFigure 9 shows an example of using this product for heating a washing tank in a foodfactory. The conventional system circulate-heats hot water from the existing open tank througha heating plate that uses heat from a fossil fuel-combustion steam boiler. For introducing thisproduct, a circulation circuit for heating by the heat pump was newly added to the open tank toheat the water to 70°C.
Figure 10 shows an example of estimating the effect of introducing the product on
reduction of annual running costs and CO2 emissions based on the operation data from
September 2018 to March 2019, and Table 4 shows the estimation conditions. The electricity
rates were calculated from the actual measured electricity consumed by the product. Therunning cost before the introduction of this product was calculated by back-calculating the fuelconsumption of the existing boiler based on the heating capacity of this product to compare theenergy-saving effects. As a result, a reduction of approximately 50% was achieved in energy
consumption, CO2 emissions, and running costs.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
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Figure 9

Example of introducing our product for heating washing tank in food factory

Figure 10 Example of estimating effect of introducing our product for heating washingtank in food factory
Table 4Conditions for estimating effect of introducing our product for heating washingtank in food factory

ItemLower calorific value of city gas
Primary energy equivalent of electricity
Electricity
CO2 emissions
City gas

Unit
MJ/Nm3
MJ/kWhkgCO2/kWhkgCO2/Nm3

Value
40.6
9.76
0.496
2.29

Source:- Lower calorific value of city gas: Values published by Tokyo Gas Co., Ltd. (Tokyo Gas website) for gas
having a unit calorific value of 45 MJ/Nm3
https://www.tokyo-gas.co.jp/Press/20041018-1.html
Estimated lower calorific value from Iwatani Corporation's fuelcomparison chart (Iwatani website)
https://www.iwatani.co.jp/jpn/business/energy/basic-knowledge/fuel/- Primary energy equivalent of electricity: Value set in Act on the Rational Use of Energy- CO2 emissions (Electricity): Tokyo Electric Power Company Holding, Inc.'s emissions factor forsubmission in 2017 (adjusted emissions factor)
https://www.env.go.jp/press/106320.html- CO2 emissions (City gas): Values published by Tokyo Gas (Tokyo Gas website)
https://www.tokyo-gas.co.jp/network/gas/shurui/index.html|4. Conclusion
This report presented examples of heat pumps that have already been commercialized as oneof MHI Group's top priority technologies for achieving carbon neutrality worldwide.
This report mainly focused on the products of MHI Thermal Systems, Ltd. andintroduces our efforts in the supply temperature range of 100°C or lower and output ofless than 100 kW; MHI Group, however, is also working on heat pump technologies inthe supply temperature range of 100°C or higher and large output. For example,Turboden S.p.A. (Italy), an MHI Group company, is working on high-temperature,large-scale applications of 3 to 30 MW per unit up to 200°C for district heating andindustrial process applications.
With energy prices continuing to soar, it is expected that combustion will be further replacedby heat pumps because heat pumps are also effective in reducing running costs. MHI Group will
extend the range of temperatures and capacities of our heat pump products in order to solve theirissues and expand the range of applications to contribute to achieve carbon-neutrality.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
9References
(1)
(2)
(3)
(4)

Takayuki Kobayashi et. al, Development of "Neppu-ton" Hot Wind Generator Using High-efficiency Air
to Air Heat Pump，Mitsubishi Heavy Industries Technical Review Vol. 54 No. 2 (2017), p.23～28
Shigeru Yoshida, The Commercial CO2 Heat Pump Water Heater available to Cold Regions,
REFRIGERATION, Vol.89 No.1039, p28～31
Takuya Okada et. al, "Mitsubishi Smart Voxcel (MSV)” Heat Pump Module Chiller Supplies 60℃ HotWater for Industrial Use, Mitsubishi Heavy Industries Technical Review Vol. 54 No. 2 (2017), p.29～33
Yuji Okada et. al, "First in Japan" Development of an Air source Heat Pump Using R454C Refrigerants toHeat Circulation Water, Mitsubishi Heavy Industries Technical Review Vol. 56 No. 4 (2019)