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1、Report/January 2024Zero-Carbon Home Heating in Chinas Yangtze River Delta RegionHeat Pumps as a Core Solutionrmi.org/2About RMIRMI is an independent nonprofit founded in 1982 that transforms global energy systems through market-driven solutions to align with a 1.5C future and secure a clean,prospero

2、us,zero-carbon future for all.We work in the worlds most critical geographies and engage businesses,policymakers,communities,and NGOs to identify and scale energy system interventions that will cut greenhouse gas emissions at least 50 percent by 2030.RMI has offices in Basalt and Boulder,Colorado;Ne

3、w York City;Oakland,California;Washington,D.C.;and in Beijing,Peoples Republic of China.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION Authors and rmi.org/3AcknowledgmentsAuthors Yihan HaoXinxin HuTing LiGuangxu WangMeng WangOther ContributorsEdward Chen,

4、formerly from RMINianying WuAuthors listed alphabetically.All authors from RMI unless otherwise noted.ContactsMeng Wang,mwangrmi.org Guangxu Wang,gwangrmi.orgCopyrights and CitationRMI values collaboration and aims to accelerate the energy transition through sharing knowledge and insights.We therefo

5、re allow interested parties to reference,share,and cite our work through the Creative Commons CC BY-SA 4.0 license.https:/creativecommons.org/licenses/by-sa/4.0/Yihan Hao,Xinxin Hu,Ting Li,Guangxu Wang,Meng Wang,Zero-Carbon Home Heating in Chinas Yangtze River Delta Region:Heat Pumps as a Core Solut

6、ion,RMI,2023,https:/rmi.org/insight/zero-carbon-home-heating-in-chinas-yangtze-river-delta-region/.All images used are from iS unless otherwise noted.AcknowledgementsThe authors thank the following individuals for offering their insights and perspectives.Appearing on this list does not indicate endo

7、rsement of the reports findings.Brett Bridgeland,RMIYifeng Gao,Heat Pump Committee at China Energy Conservation AssociationStephanie Greene,RMIWenxing Shi,School of Architecture,Tsinghua UniversityZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION rmi.org/4Ab

8、breviationsChinas Yangtze River Delta Region Urgently Needs Better and Zero-Carbon HeatingChallenges of Home Heating in the Yangtze River Delta RegionDevelopment Trends of Home HeatingComparative Analysis of Distributed Home Heating Systems in the Yangtze River Delta RegionMajor Distributed Home Hea

9、ting Devices in the YRD Region Multidimensional ComparisonConclusions Heat Pumps for China and BeyondAppendix A:Building Simulation Input ParametersAppendix B:Concepts and Assumptions for Economic Analysis Major Challenges SuggestionsEndnotesTable of Contents5 6991111 14 23 Major Challenges and Sugg

10、estions to Promote Heat Pumps in the YRD Region 27 2831 33 34 35ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONZero-Carbon Pathway by Scaling Heat Pumps in the Yangtze River Delta Region 2327rmi.org/5AbbreviationsASHP Air source heat pumpEFH Electric floor

11、 heatingGSHP Ground source heat pumpHPFH Heat pump hydronic floor heatingMini-splits Ductless,mini-split system air conditionersPERH Portable electric resistance heaterWSHP Water source heat pumpYRD Yangtze River DeltaZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE

12、 SOLUTIONChinas Yangtze River Delta Region Urgently Needs Better and Zero-Carbon HeatingSpace heating improves peoples quality of life,but its also a major source of energy consumption and carbon emissions.In 2021,space heating and domestic hot water accounted for almost 15%of global final energy co

13、nsumption,resulting in about 2.45 billion tons of CO2 emissions.Given the growing global Exhibit 1:In China,residents of the northern regions have district heating service provided by the government,but residents of southern China still have a significant lack of heating facilities.Climate change is

14、 causing frequent extreme weather.i These changes,coupled with the higher living standard resulting from rapid economic growth,mean that effective heating facilities for indoor environments during the winter in southern China are more urgently needed than ever.Under Chinas ambitious climate target,p

15、rovinces have started to make plans to achieve their own carbon peaking and carbon neutrality goals.It is necessary to develop a customized zero-carbon heating pathway in the vast southern repopulationandimprovinglivingstandards,theheatedbuildingfloorareaispredictedtoincreaseby12%between 2021 and 20

16、30.1 Because the energy required for heating is provided mainly by fossil fuels such as natural gas,the increasing heated floor area will lead to a significant increase in the CO2 emissions of the building sector,which poses a huge challenge to global climate targets.gions.Location of the Yangtze Ri

17、ver Delta regionrmi.org/6Source:Zheng et al.,2022 2i Similar to the devastating Texas cold wave in February 2021,the average temperature in the first 10 days of January 2021 in Shanghai reached 1.2C,the lowest temperature recorded since 1987.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REG

18、ION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/7 The Yangtze River Delta(YRD)region is a triangle-shaped metropolitan area located in the lowerreaches of the Yangtze River in the eastern coastal area of China(see Exhibit 1,page 6).It covers a total area of 358,000 square kilometers,approximately the size

19、of Germany,and encompasses Shanghai as well as the provinces of Jiangsu,Zhejiang,and Anhui.A snapshot summarizing the basic information of the YRD region is presented in Exhibit 2.As one of the most densely populated and economically advanced city clusters,with climate characteristics typical of sou

20、thern China,the YRD region has the greatest potential to explore the zero-carbon heating pathway and become a role model for other regions in southern China.In addition,10%30%of the residents in the region do not use any heating equipment.3 As a result,the winter indoor environment in the YRD region

21、 is poor,with an average indoor temperature in the coldest month in winter falling below 15C.For comparison,nearly 90%of households in similar climate areas in developed countries have winter indoor temperatures exceeding 20C.The poor winter indoor environment due to the lack of sufficient heating f

22、acilities in the YRD region requires urgent improvements to home heating systems.Although the outdoor temperature inwinterisnotaslowasthatinthe north(see Exhibit3,page 8),the highairhumiditymakespeople feel significantly colder in winter.ii However,most of the home heating devices currently used in

23、the YRD region,primarily ductless mini-split system air conditioners(mini-splits)and small electric resistance heaters,are insufficient to create a comfortable indoor thermal environment.4Exhibit 2:A snapshot of the YRD regionPopulation:218 million(2020)Area:358,000 km2GDP:US$3,670 billion(2020)Clim

24、ate:o Humid subtropical climate according to the Kppen climate classificationo Extreme hot and humid summer,cold wintero High air humidity throughout the yearResidential building types:Most residents in the YRD region live in high-rise apartments.Home heating systems:o Distributed home heating syste

25、ms(devices or systems installed in the apartment by the homeowner or real estate developer)are the norm in the YRD region.(District heating is the main heating approach in northern China.)o More than 60%of residents use mini-splits(with heating function)for space heating in winter,and small electric

26、 resistance heaters are also widely used;10%30%of the residents still have no heat in winter.5 ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONii High air humidity in cold weather increases the conduction of heat from the body and weakens the insulating qua

27、lities of clothing.rmi.org/8The advanced economic development in the YRD region lays the foundation for upgrading home heating systems.The YRD region is the largest economic center of China,contributing more than 24%of the national GDP.In 2021,the per capita disposable income reached US$7,350 per ye

28、ar(49,000 RMB per year),1.5 times the national average.Residents of the YRD region are able and willing to pay for better home heating systems.With more than 200 million residents,the YRD region is home to 15%of Chinas population and is one of the most densely populated areas in the world.The huge d

29、emand for better space heating there may also help the rapid development of the home heating manufacturing industry.The development of zero-carbon home heating is critical for the zero-carbon transition in the YRD region.As Chinas economic center and one of the global manufacturing centers,the regio

30、n features high consumption and a high share of fossil energy,the majority of which is imported from other regions in China.The final energy consumption in the YRD region accounts for 17%of the national total,and the share of fossil energy is 89.4%of the total energy consumption.The rapid developmen

31、t of home heating in the YRD region will inevitably lead to the accelerated growth of energy demand.To achieve the regional zero-carbon transition,it is critical to develop the zero-carbon heating in the YRD region.In short,the YRD region combines rising incomes,a lack of heating facilities,and the

32、strong desire for better home heating systems.It is of vital importance for the YRD region to develop a zero-carbon home heating pathway,which would not only contribute to the regional zero-carbon energy transition,but also set a good example for other southern China provinces and global regions wit

33、h similar climate features.Exhibit 3:Average hourly temperature in Shanghai Source:WeatherSZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONChallenges of Home Heating in the Yangtze River Delta RegionDevelopment Trends in Home HeatingIt is evident that home

34、heating in the YRD region is growing rapidly,driven by multiple factors such as frequent extreme weather,increasing demand for better indoor environments,and population influx.Heating facilities are becoming standard in all new buildings,and residents of existing buildings are increasingly purchasin

35、g new heating equipment.Individual home heating devices instead of district heating systems will continue to be the dominant approach in the YRD region.iii The development trends of home heating in the YRD region are illustrated in Exhibit 4.Year)2Residential floor area(billion mbetween 2020 and 203

36、0Homes to be built system upgrade Homes with heating system upgrade Homes without heating BEFORE 2020Residential buildings built AFTER 2020Residential buildings built Homes without heatingiii Multiple studies have shown that central heating is neither cost-effective nor energy-efficient for large-sc

37、ale development in southern China due to the high investment required for infrastructure construction and the strong dependence on fossil energy.iv Heating demand refers to the amount of heat required to maintain a comfortable indoor thermal environment in winter.rmi.org/9Exhibit 4:Development trend

38、s in home heating in the YRD region(20202060)Source:RMI analysisIn the long term(20302060),as new building construction peaks and retrofits of existing buildings are accelerated,upgrades of heating devices in existing residential buildings will create major momentum for heating device purchases.Acco

39、rding to RMIs forecast,about 10 billion m2 of residential floor area is Inthe shortterm(20202030),the residentialbuildingfloorareainthe YRDregionisexpectedtoincrease by 2.5 billion m2,20%of the current residential floor area.More than 20 million residents,currently without home heating systems,will

40、be equipped with new heating facilities.By 2030,there will be an increase of more than 500 million gigajoules of heating demand in the YRD region,equivalent to 40%of 2020s total heating demand.ivHome heating devices for the new buildings and the existing homes currently without heating contribute mo

41、st to the growth.expected to be improved by upgrading home heating facilities.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/10 Challenge 1:Fossilfuelheating appliances are prevalentproductinthe YRDmarketAccording to RMI research,heating facilities

42、 have become standard in newly built residential buildings in the YRD region.Gasboilersare prevalent,used by about 80%ofthese newlybuiltresidentialbuildings.In existing residential buildings,an increasing number of residents are upgrading their home heating using gas boilers.The extensive use of gas

43、 equipment will bring challenges to the stability of the energy supply and the provincial climate goals in the YRD region.According to RMIs analysis,the total annual residential gas consumption in the YRD region could reach 26 billion m3 by 2030,about 2.5 times the total consumption in 2020,if new h

44、eating demand in the region is met entirely by gas-fired equipment.China has limited domestic gas production and consequently relies onimports.Demandforgasisalsoincreasingowingtotheimplementationof“coalswitch”policiesinrural northernareasv.Thelarge-scaleuseofgasheatingintheYRDregionwillthusexacerbat

45、ethetightdomestic gas supply.In addition,the surge of gas consumption in winter may pose major challenges to the extension of gas infrastructure in the YRD region.Furthermore,the increasing application of gas equipment will lead to more direct CO2 emissions in the building sector.If the current tren

46、d of gas domination in YRDs home heating continues,the emissions of residentialbuildingswillincrease,resultingin56milliontonsofdirectCO2emissionsfrombuildingscaused by residential gas use by 2030.In the long run,from a 2060 perspective,if the building envelope remains at the current efficiency level

47、,CO2 emissions caused by home heating by gas equipment will dramatically increase to120milliontons.Ifthe buildingenvelope isrenovated,itcouldsignificantlyreduce the building heating demand,leading to 45 million tons of CO2 emissions by 2060 with the gas equipment applied.As aresult,buildings remain

48、as a huge barrier to the achievement of the regional climate goal.Challenge 2:Heating facilities have a lock-in effect The lock-in effect of heating facilities means that the adoption of a certain type of heating facilities(such as gas boilers,heat pumps,or district heating systems)will lead to cont

49、inuing use of such equipment for a long period.The effect hastwo dimensions:The lock-inof energyconsumptionandcarbon emissionswithinthe service life ofthe heatingdevice:The service life ofaheatingdevice istypically10years.Once aheatingdevice isadopted,the energyuse andCO2emissionswillessentiallybefi

50、xedforadecade.TheCO2emissionsofelectricheatingdevicesmay decrease with the decarbonization of the power grid,but gas boilers will cause high carbon emissions during their whole service life.The lock-in of the heating pathway means that the large-scale adoption of a type of heating facility willleadt

51、opathdependencyowingtoincreasedproductawareness,correspondingpolicysupport,andinfrastructuredevelopment.Pathdependencywillalsoincreasethecostofswitchingtoanotherheating path.For example,the large-scale adoption of gas boilers will lead to the expansion of gas infrastructure and services,reduction in

52、 gas boiler costs,more supporting policies,and higher product awareness.These thingsinturnwillallowgasboilerstodominate the heatingmarketfordecades,exacerbatingthe negative impact on the energy supply and the regional carbon neutrality goal.To sum up,under the current trend of rapidly growing home h

53、eating demand in the YRD region,the extensive applicationofgasboilersanditslock-in effectwillbringchallengestothe local energysupply and the regional climate goal.Because the development of home heating is still at the early stage inthe YRD region,developing and promoting energy-saving and low-carbo

54、n heating devices will be key to addressing thischallenge.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONV Coal switch is a central governmentled policy aiming to decrease coal consumption and improve air quality by promoting equipment fueled by natural ga

55、s and electricity to replace small-scale coal-fred boilers and household coal-based heating and cooking systems,which are commonly used in rural areas in northern China.rmi.org/11Comparative Analysis of Distributed Home Heating Systems in the YRD RegionIdeally,a home heating system should be able to

56、 provide a safe and healthful indoor environment while reducing greenhouse gas emissions and costs.However,because of the lack of unified evaluation methods such as energy efficiency labels,it is extremely difficult for consumers(including homeowners and real estate companies)and relevant policymake

57、rs to choose the most appropriate home heating system from the diverse products on the market.Having a set of unified criteria is critical for the comparison and evaluation of the major distributed home heating systems in the YRD region.In this section,we introduce the most typical home heating syst

58、ems with their typical application scenarios in the YRD region,followed by a thorough comparison of the home heating systems from multiple dimensions.Major Distributed Home Heating Devices in the YRD Region Distributed heating(also called decentralized heating)means that each household is equipped w

59、ith one or more heating devices.As mentioned above,distributed heating currently is,and will continue to be,the most common means of heating in the YRD region.Distributed heating comes in various forms,including heat pump hydronic floor heating(HPFH)systems,mini-splits,electric resistance heaters,el

60、ectric floor heaters,and gas boilers.Among them,HPFH systems and mini-splits both belong in the heat pump category,whose working principle is fundamentally different from that of other heating devices.Heat pumps A heat pump is a device that can heat a building(or part of a building)by transferring h

61、eat(thermal energy)from low-temperature objects to high-temperature objects.Different from traditional home heating systems,which convert other forms of energy into thermal energy,a heat pump produces heat primarily by transporting the existing thermal energy in the environment.Its working principle

62、 is shown in Exhibit 5(page 12).A heat pump is characterized by the following key features:necessaryconditionfortheoperationofaheatpump,whichenablesthefunctionoftransportingheatfrom the low-temperature side to the high-temperature side.The energy efficiency of a heat pump is affected by the temperat

63、ure of the heat source.Air source heat pumps(ASHPs),which use the ambient air as the heat source,are the most common heat pump models;other types include ground source heat pumps(GSHPs)and water source heat pumps(WSHPs).waterfromalowpositiontoahighposition,heatpumpsneedinputenergy(normallyelectricit

64、y)totransfer heat from the low-temperature side to the high-temperature side.Gas heat pumps can be driven by a gas engine,and absorption heat pumps require an external(high-grade)heat source as a driver.by a heat pump(to the high-temperature side)comes mainly from the heat absorbed from the low-temp

65、erature side.Usually,1 kWh of electricity input can produce 3 kWh or more of heat(i.e.,the heat pump absorbs 2 kWh or more heat energy from the low-temperature heat source),making the heating by heat pumps highly efficient.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A

66、 CORE SOLUTION Being able to absorb heat from a low-temperature heat source:A low-temperature heat source is a Requiring input energy as the drive energy:Similar to water pumps that use electric energy to carry Havinghigh energy efficiency:Althoughheatpumpsare drivenby electricityinput,the heatprodu

67、cedHeat sourcermi.org/12Compressor(air,water,soil)circuitRefrigerantElectricity inputHeat releasing(Indoor environment)Heat sink Absorbing heatCondenserEvaporatorExpansion valveHeat pumps are commonly used for space and water heating in buildings.Among the different types of heat pumps(ASHPs,GSHPs,W

68、SHPs),ASHPs are the most widely used heat pumps due to their ease of installation.In this report,we focus on the ASHPs used in residential buildings.In the YRD region,HPFH sidetothehigh-temperatureside,andthehigh-temperaturesidebecomeswarmerasthelow-temperature side becomes cooler.Therefore,heat pum

69、ps can also be used for space cooling in summer.systems and mini-splits are the two most common types of ASHP used in residential buildings.Exhibit 5:Simplified schematic diagram of the heat pump working principleSource:RMIHeat pump hydronic floor heating systemHeat pump hydronic floor heating syste

70、ms,or HPFH systems,are an emerging heating approach in the YRD region.HPFH systems are a type of air-to-water heat pump.Exhibit 6(page 13)presents a simplified diagram of this kind of heating system.In summer,when the system is in the cooling mode,cold water(or the refrigerant)produced by the heat p

71、ump is sent to the indoor fan coil units to cool the indoor air.In winter,in the heating mode,the hot water produced by the heat pump is sent to the floor heating system.Thereisanotherformofair-to-waterheatpumpinwhichtheheatpumpsendsthehotwatertotheradiators installed in each heated room.In the YRD

72、region,floor heating is more popular than other forms that can be coupled with heat pump units because of the HPFH systems ability to provide greater indoor comfort.In addition,the heating hot water supply temperature of floor heating is typically 35C40C,lower than that of radiators(typically 50C).T

73、he lower supply water temperature will further enhance the energy efficiency of heat pump systems.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONBeingabletoprovidebothheatingandcooling:Theheatpumptransfersheatfromthelow-temperaturermi.org/13?C?Exhibit 6:Si

74、mplified system diagram of HPFH systemSource:RMIMini-splitMini-split refers to air conditioning equipment with both cooling and heating functions.It has two main components,anoutdoorunit andanindoorair-handlingunit.Asatypeofair-to-airheatpump,amini-split unit directly heats the air and sends it into

75、 the room.In the YRD region,mini-splits are designed primarily for the cooling mode in summer;hence,they are normally not suitable for heating use under extreme cold weather conditions(In fact,there are emerging mini-split products that are specifically designed for the extreme cold region,but they

76、are not the focus of this study).Mini-splits are also normally equipped with a supplementary electric resistance heating element to be able to provide sufficient heat,so their energy efficiency is lower than that of HPFH systems.There are also other types of air-to-air heat pumps,for example,ducted

77、heat pumps;however,these types are rarely seen in residential buildings in the YRD region.Our study is therefore focused on the mini-split unit,which typically meets the heating demand of only a single room.Other common distributed heating devicesGas boilerGas boilers burn natural gas to heat water

78、thats used for central heating or hot water.Gas boilers are most commonly connected with floor heating systems(in new buildings)and radiators(in retrofits of existing buildings).For the sake of better comparability with HPFH systems,gas boilers with floor heating systems are the focus of this study.

79、Gas boilers burn fossil fuels to produce heat,resulting in more direct carbon emissions in buildings than would be produced by electric heating devices.In addition,gas boilers can provide only heating;additional devices are needed for cooling.Electric floor heating system The electric floor heating(

80、EFH)system is a new type of floor heating.Unlike the abovementioned floor heating system that uses hot water as the heat medium,an EFH system uses heating cables laid below the floor to heat the room.Compared with water-based floor heating systems,an EFH system is fast-response(that is,it is able to

81、 heat the space quickly)and easier to maintain.However,EFH systems are often more expensive and more energy-intensive than heat pump systems.For YRD residential buildings,EFH system use around three times more electricity than heat pumps.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:

82、HEAT PUMPS AS A CORE SOLUTIONrmi.org/14?Geographic LocationBuilding EnvelopeFloor LevelApartment SizeHeating deviceMain variables for scenario definitionPortable electric resistance heater The term portable electric resistance heater(PERH)generally refers to small heating devices that convert electr

83、icity directly into thermal energy.Compared with other heating systems,PERHs are much cheaper andeasiertouse.However,they are normally unable to provide sufficient heat to the entireroom.Therefore,a PERH usually serves as a supporting heating device,heating just part of the space where people stay.I

84、n the YRD region,its very common for people to combine mini-splits and PERHs in their home.Multidimensional ComparisonTo evaluate and compare the abovementioned five typical home heating systems in the YRD region,we first defined 54 home heating scenarios typical in the region,and then modeled 1 yea

85、r of energy use for space heating to determine the carbon emissions and the 10-year net present cost of each scenario.The variables making up the 54 scenarios are shown in Exhibit 7.Given that the heating demand of residential buildings is determined primarily by geographic location,building envelop

86、e,floor level,and apartment size,we selected parameters related to these variables to define the most typical scenarios of home heating in the YRD region.For geographic location,we selected three cities Xuzhou in Jiangsu Province,Shanghai,and Wenzhou in Zhejiang Province to represent cold,mild,and w

87、arm winter climate types in the YRD region,respectively.In addition to carbon emissions and economics,we considered other factors closely related to the user experience,such as the ability to provide indoor thermal comfort and the complexity of installation and maintenance,enabling a more comprehens

88、ive analysis of the advantages and disadvantages of the five Typical building envelope,energy codecompliant building envelope,and enhanced envelope were selected to represent poor,normal,and excellent building thermal insulation conditions,respectively(the parameters of each envelope structure are l

89、isted in Appendix A).In addition,floor and apartment size have an impact on the heating demand of buildings.In this study,bottom floor,middle floor,and top floor were selected as variables,and the two most common apartment sizes in the YRD region were considered as well(see Appendix A).heating syste

90、m types.Exhibit 7:Home heating scenario characteristics in the YRD regionSource:RMIZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/15XuzhouShanghaiWenzhouXuzhouShanghaiWenzhou)2 emissions(tons CO210-year cumulative COLarge apartmentSmall apartmentre

91、sistance heaterPortable electric heatingElectric floor heatingGas boiler floor floor heatingHeat pump hydronic Mini-splitsvii The CO2 emissions of the home heating systems in this study are calculated under the assumption that the indoor temperature of the entire home is maintained at 18C in winter.

92、viii CO2 emissions per kWh of electricity generated(kg CO2/kWh).The regional average carbon intensity is used in this study.CO2 emissions comparisonThe carbon emissions of heat pumps for home heating are the lowest in all the 54 scenarios defined;the cumulative CO2 emissions are 30%70%less than emis

93、sions produced by the competitors within the 10-year life span.Furthermore,compared with gas boilers,heat pumps could further lower the CO2 emissions of home heating as the electric grid becomes greener.The cumulative emissions of heat pumps for home heating during 20202060 are 50%less than that of

94、gas boilers.Exhibit 8:10-year cumulative CO2 emissions of various home heating systems by Home heating contributes to CO2 emissions directly and indirectly.vii Gas boilers burn natural gas to generate heat,resulting in direct CO2 emissions.Indirect CO2 emissions come from power plants that burn foss

95、il fuel to generate electricity to power the electric heating devices.The indirect CO2 emissions of home heating systems are calculated by multiplying the amount of electricity used for home heating by the carbon intensity of the regional grid.viii Exhibit 8 shows the 10-year cumulative CO2 emission

96、s comparison of the five typical home heating systems in different cities and sizes of apartment.The impact of envelope structure and floor is presented by the error bars(vertical line on the bars)in the exhibit.The CO2 emissions of home heating are strongly affected bythelocationandtheapartmentsize

97、:largerapartmentsizeandcolderclimateleadtosignificantincrease inCO2emissionscausedbyhomeheating.However,inallthescenariosmodeled,theCO2emissionscaused by heat pumps,including mini-splits and HPFH systems,were lower than those caused by other home heating systems.The CO2 emissions of HPFH systems are

98、 the lowest among the five typical heating systems thanks to the high energy efficiency of those systems.Taking a large apartment in Xuzhou as an example,home heating using the HPFH system created just 70%of the CO2 emissions of a gas boiler floor heating system,and about 30%of the emissions of an e

99、lectric floor heating system,which has the highest CO2 emissions due to that systems low efficiency.apartment size and citySource:RMI analysisZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/16/kWh)2Carbon intensity(kg CO)2 emissions(tons CO210-year

100、cumulative COCarbon intensity of the electricity consumed in buildingsPortable electric resistance heatersElectric floor heatingfloor heatingGas boilerfloor heatinghydronic Heat pump Mini-splitsExhibit 9:Annual CO2 emissions of home heating using various home heating systems considering the decarbon

101、ization of the power grid from 2020 to 2060Source:RMI analysisEconomic analysisHeat pumps have the advantage of low operating costs.However,the overall cost-effectiveness of heat pumps depends mainly on the up-front costs.As a type of heat pump,mini-splits have the best cost-effectiveness among the

102、five home heating systems in the YRD region thanks to the low equipment costs.High up-front costs make HPFH systems less cost competitive in the YRD region.To evaluate the cost-effectiveness of the various home heating systems,we calculated and compared the life-cycle cost of the five different home

103、 heating systems in the predefined 54 home heating scenarios.The life-cycle cost includes capital cost,operating cost(energy bills for home heating in winter),maintenance cost,and salvage value of the devices.The definition of each cost and the assumptions used in this study appear in Appendix B.For

104、 the sake of comparison,the life-cycle cost is presented as the 10-year net present value and the equivalent annual cost in this study.x This corresponds to the annual expenditure on home heating.x Present value is the value of future cash flows converted to the present.The total present value of al

105、l cash flows over the life cycle is the net present value.The equivalent annual cost is the annual value of the net present value during the life cycle.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONix Given the rapid deployment of distributed solar photov

106、oltaic panels(PVs),such as rooftop PVs,in the building sector,we predict that electricity used in buildings will become zero carbon by 2060.Exhibit 9 shows the annual CO2 emissions of various home heating systems taking into account the decarbonization of the power grid from 2020 to 2060.In 2020,eve

107、n with the current grid carbon intensity in the YRD region,the CO2 emissions of HPFH systems were lower than those of gas boilers.With the rapid decarbonization of the power grid,HPFH systems advantage in emissions reduction will become more prominent;they will achieve net zero by 2060 once zero-car

108、bon electricity is used by buildings.ix On average,HPFH systems could reduce CO2 emissions by more than 50%compared with gas boiler heating.The savings would be even higher when compared with electric floor heating and electric resistance heaters.heatingElectric floor resistance heatersPortable elec

109、tric Mini-splitsfloor heatingHeat pump hydronic floor heatingGas boiler Large apartmentSmall apartmentXuzhouShanghaiWenzhouXuzhou ）RMB/year（ShanghaiWenzhouEquivalent annual cost0000,10009,0008,0007,0006,0005,0004,0003,0002,0001,0rmi.org/17Exhibit 10:Equivalent annual costs of various home heating sc

110、enariosSource:RMI ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION Exhibit 10 shows the equivalent annual costs of various home heating scenarios.(The error bars in the exhibit represent the variances created by the envelope structure and floor.)In most ana

111、lyzed scenarios,HPFH systems cost more than the other home heating systems,whereas mini-splits have the best cost-effectiveness.In small apartments,the equivalent annual cost ranges from 4,670 to 5,450 RMB(US$689toUS$804)forHPFHsystemsand1,040to1,970RMB(US$153toUS$290)formini-splits.Inlargerapartmen

112、ts,theannualcostrisesto5,520to7,430RMB(US$814toUS$1096)and1,440to3,710RMB(US$212toUS$547),respectively.Theaverageequivalentannualcostofgasboilerfloorheatingandelectricfloorheatingisalsolower butfluctuates more than that of HPFH systems(see error bars in Exhibit 10).In some scenarios,the life-cycle c

113、ostofgasboilerfloorheatingand electricfloorheatingmeetsor exceedsthatofHPFHsystems.The cost-effectivenessofheatpumpsimproveswithincreasedheatingdemand.Asmini-splits have already shownthebesteconomicsamongallthecomparedsystems,wecomparedthethreefloorheatingsystems(HPFH,gas boiler floor heating,and EF

114、H)to showcase how the heating demand affects the economics ofthe floor heating systems with different heat sources.In the modeled scenario with the largest heating demand,the equivalentannualcostofaHPFHsystemisabout7,432RMB(US$1,101),muchlowerthanthe 9,214 RMB(US$1,365)of an electric floor heating s

115、ystem,and close to the 7,366 RMB(US$1,091)of a gas boiler floor heating system(seeExhibit 11,page 18).Multiple factors contribute to the increase in heating demand,including lower winter temperatures,less insulated envelope,larger apartment sizes,and floorlevel.Ouranalysisshowsthatthe life-cycle cos

116、tofHPFHsystemswillbecome lowerthanthatofgasboilerfloor heating systems when annual heating demand exceeds 11,500 kWh,equivalent to an annual gasconsumptionof1,500m3 for heating use.rmi.org/18floor heatingGas boiler heatingElectric floor floor heatingHeat pump hydronic ApartmentSmall(Middle Floor)Lev

117、el 3 EnvelopeEnhanced (warmer)WenzhouApartmentLarge(Bottom Floor)Level 1 EnvelopeTypical(colder)Xuzhou Equivalent annual cost(RMB/year)Max Load ScenarioMin Load Scenario10,0009,0008,0007,0006,0005,0004,0003,0002,0001,00009,2141,8987,3662,920Exhibit 11:Comparison of equivalent annual costs in lowest-

118、and highest-heating-7,4324,667demand scenariosSource:RMI analysisHeat pumps have considerably lower operating costs;however,the overall cost-effectiveness is determined primarily by their up-front costs.Among all analyzed home heating systems,HPFH systems have the lowest operating cost.However,the o

119、perating cost savings are unable to offset the huge up-front cost difference,resulting in an overall higher life-cycle cost for a HPFH system compared with its competitors(see Exhibit 12).Mini-splits enjoy both low operating costs and low up-front costs,making them the most cost-effective home heati

120、ng system in the YRD region.heatingElectric floor resistance heatersPortable electric Mini-splitsfloor heatingHeat pump hydronic heatingGas boiler floor Present value of cost(RMB)Salvage valueOperationMaintenanceUp-front cost500,0040,00030,00020,00010,000010000-Source:RMI analysisExhibit 12:Breakdow

121、n of the life-cycle costs of the five home heating systemsZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/1950%Increase100%IncreaseUp-front cost:heat pump indoor systemUp-front cost:heat pump outdoor unitValley electricity chargePeak electricity cha

122、rgeDiscount rateHeat pump COP%05%04%03%02%01%0%01-(Not Realistic)Change in equivalent annual costxi The discount rate expresses the time value of money in discounted cash flow.To further clarify why the HPFH system costs more than its competitors and how to improve its cost-effectiveness,we conducte

123、d a sensitivity analysis(see Exhibit 13).It considered the potential impact of factors such as up-front cost,electricity rates,discount rates,and the efficiency of heat pumps on the life-cycle costs of HPFH systems.Key findings are as follows:impact on the life-cycle cost-effectiveness.The impact of

124、 the outdoor unit price exceeds that of the indoor system.the operating cost of the HPFH system.However,the operating cost accounts for a much smaller share of the life-cycle cost of the HPFH system than does the up-front cost.Source:RMI analysisExhibit 13:Change in equivalent annual cost when selec

125、ted variables increase(in the scenario of a large apartment with typical building envelope in Shanghai)ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION The up-front cost of the HPFH(including outdoor units and indoor systems)has the most significant An incr

126、eased discount rate significantly reduces the cost competitiveness of HPFH systems.xi Electricity rates have a limited impact on the economy of HPFH systems.The power price mainly affects Increasing the COP has a limited impact on improving the cost-effectiveness of HPFH systems.rmi.org/201.7 m1.7 m

127、2.7 m2.7 mWarmCoolColdWarmFloor heating(HPFH,etc.)Forced air systems(mini-splits)Comfort and healthHPFH systems are the healthiest and most comfortable heating choice considering temperature,humidity,noise,and air quality.HPFH systems,gas boiler floor heating,and EFH can provide more uniform tempera

128、ture distribution,a better humidity level,and better heating comfort.HPFH systems can also provide better indoor air quality than gas boiler floor heaters.Temperature,humidity,and noise are the most critical factors affecting indoor comfort.We considered these three factors in evaluating the perform

129、ance of home heating systems in terms of indoor comfort in winter.Indoor air quality(including elements such as allergens,dust,and CO2 concentration)also needs to be taken into consideration,as it affects not only indoor comfort but also occupants health.Source:Stephanie Cernivec,2018The heat transf

130、er methods of heating systems have important impacts on the above factors.Among the five common distributed home heating systems,HPFH systems,gas boiler floor heaters,and EFH systems heat the space with floor heating,whereas mini-splits use a forced air system.The following sections will compare and

131、 evaluate the impact of different home heating systems on comfort and health.Temperature distribution is very important in indoor comfort.Exhibit 14 compares the impact of forced air systems(applied by mini-splits)and floor heating(normally applied by HPFH systems,gas boiler,and EFH systems)ontemper

132、aturedistribution.Withfloorheating,thehumanbodycanreachtheidealtemperature for optimal thermal comfort.This is determined by the different heating approaches of the two systems:floor heating can form a comfortable indoor temperature distribution through radiative heat dissipation,warming residents f

133、eet first;mini-splits,which heat the room by blowing hot air into it,could cause the uncomfortable feeling of warm head and cool feet because the air outlet is typically located near the ceiling and warmer air also flows upward.xii6Exhibit 14:Comparison of comfort levels of mini-splits and floor hea

134、ting xiiMany of the mini-splits manufacturers have been working on developing more advanced mini-split products that are able to provide higher indoor comfort(e.g.,by adjusting the airflow pattern).However,the most typical mini-splits on the YRD market currently are still confronting the problem of

135、indoor discomfort.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION rmi.org/21Noise is another important consideration.Hydronic floor heating and electric resistance heaters operate quietly,avoiding the noise created by mini-splits air supply.Similarly,EFH s

136、ystems are very quiet.In In terms of humidity,typical existing home heating systems cannot adjust indoor humidity in heating mode.Furthermore,mini-splits often cause a drier feeling indoors since they use forced top-down air distribution.This supplies strong air flow toward the occupants head and ac

137、celerates evaporation of the moisture in the air and from the skin.In contrast,hydronic floor heating and radiators heat the room through radiation,which greatly reduces the dry parison,the outdoor units of HPFH systems and gas boilers both produce a certain amount of noise,but the impact is limited

138、 since these devices are typically installed far away from the bedrooms and living rooms(the unit of heat pumps that produces noise is installed outdoors;the gas boiler is typically installed in the kitchen).The advantages and disadvantages of various distributed home heating systems in terms of com

139、fort and Introducing fresh air is an important measure in improving indoor air quality.At present,most zone-level home heating systems do not have fresh air systems.Fresh air comes in through infiltration and open windows,which not only is insufficient but also introduces outdoor pollutants.Some of

140、the more advanced HPFH systems can be equipped with a mechanical ventilation module that may help improve indoor air quality.Mechanical ventilation systems equipped with filter(HEPA/MERV)devices can effectively filter outdoor air pollutants.More accurate mechanical control could ensure sufficient fr

141、esh air.More advanced mini-splitsonthemarkettodayalsocanprovidefresh air ventilation butthefreshairintakeisusuallysmall,leading to limited improvement of indoor air quality.health are shown in Exhibit 15.Exhibit 15:Source:RMI Comparison of comfort and health levels of different heating optionsCompar

142、ison dimensionsTemperatureHumidityNoiseMini-SplitCould lead to unevenly distributed temperature;feeling of blowing air could lead to poor comfort level as wellAir system may lead to feeling of drynessGas boileHPFH Air system may generate noisesystemrEFHPERHUnevenly distributed temperature leads to p

143、oor comfort Ideal temperature distribution and high comfort level,but the heating process is relatively slowlevel Doesnt include air system so theres no feeling of blowing air and less feeling of drynessLow noiseLow noiseMinimal noiseMinimal noiseOptional fresh air ventilation and dehumidification m

144、odule could improve indoor air Some models may provide fresh air,which improves Air Q Qualityindoor air qualityquality;dehumidificationNormally doesnt have fresh air ventilationmodule could improve indoor air quality ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE

145、SOLUTIONrmi.org/22Other dimensionsEase of installation and compatibility with future energy systems are also important factors in the choice of home heating systems.These dimensions affect energy consumption and carbon emissions in addition to the above-discussed three major comparison dimensions(CO

146、2 emissions,economics,and comfort).This section will consider the dimensions of ease of installation and power system compatibility.Ease of installationHydronic floor heating is hard to install.Installation of gas boiler floor heaters,HPFH systems,and EFH systems includes laying pipelines or heating

147、 cables and supporting facilities under the floor,greatly increasing the complexity of construction,which will affect users choices to a certain extent.Smaller appliances such as mini-splits and electric resistance heaters are significantly easier to install,especially in existing buildings,where us

148、ers are likely to choose“plug and play”types of heating systems without retrofitting their homes.Moreover,HPFH systems usually require large volumes of outdoor units,making them impossible to install in old residential buildings in the YRD region due to spatial and structural constraints.Compatibili

149、tywiththe powersystemOnthe pathtoafuture zero-carbon energysystem,electrificationhasbeenconsideredasone ofthe most viable and efficient approaches.Compared to the industry and transportation sectors,the buildings sector could be considered easier to electrify,as electrified equipment is already avai

150、lable in the market as an alternative to gas boilers/stoves.Due to its high energy efficiency and heat storage capacity,the HPFH system is most compatible with the power system compared with other common home heating options in the YRD region.In addition,improving the flexibility of the power system

151、 is becoming critical given the increasing share of renewable energy generation such as solar PV and wind in the power system.Demand response is often a more economical approach to providing flexibility than deploying more energy storage facilities on the supply side(such as battery storage).In the

152、HPFH system,the floor can also serve as heat storage and reduce the electricity peak of the grid.This can be accomplished by running the hydronic system in advance of the peak period of power demand or when renewable generation is abundant,then releasing the stored heat energy when needed.In this wa

153、y,demand-side load management(load shifting)can be Electrifying all heating systems in the YRD region would lead to a substantial increase in regional power consumption and peak power load,resulting in an increase in indirect carbon emissions and a challenge to the stable operation of the power grid

154、.To deal with this problem,using highly efficient heat pumps would lead to lower electricity demand and provide the same amount of heat,resulting in less impact on the power system compared with less efficient electric resistance heaters and EFH systems.accomplished at a very low cost without sacrif

155、icing indoor comfort.The shifting and adjustment of demand-side load using heat pumps has become one of the hot research topics in recent years.Studies showed that load shifting can be achieved for up to six hours by installing additional thermal buffering in heat pump systems.7The flexibility provi

156、ded by retrofitting old buildingenvelopes and the adoption of heat pump technology can greatly reduce the cost of installing requiredenergystorage forthe newpowersystem.8ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/23Conclusions We comparedfive c

157、ommonlyusedhome heatingsystemsinthe YRDregion(see Exhibit16)alongmultipledimensions and found that heat pumps(including HPFH systems and mini-splits)were the better choice thatisinline for the trendofupgradinghome heatingsystemsandpursuingthe zero-carbontransition.Its carbon emissions are significan

158、tly lower than those of other systems.The HPFH systemsare capable ofprovidingdemandresponse to ease the burdenonfuture powersystems.However,HPFHsystemsalso face certain challenges,including being economically inefficient owing to their high up-front investment,havingacomplicatedinstallationprocess,a

159、ndofferinglowheatingflexibility.the power systemCompatibility with Ease of installationdimensionsOther Cost-effectiveness emissions reduction2COComfort and healthGas boilerEFHPERHMini-splitsHPFH systemOther systemsHeat pumpsExhibit 16:Multidimensional comparison of five home heating systemsNote:More

160、 solid stars indicate more significant advantages over other choices in this comparison dimension.Source:RMIIn practice,occupants needs can often be divided into two categories:o Users who are relatively insensitive to indoor comfort:Mini-splits and electric resistance heaters are two home heating s

161、ystems used by users who are less sensitive to indoor comfort.Electric resistance heaters are relatively cheaper and more flexible;however,they are not suitable to be used as a major home heating system owing to their low energy efficiency.o Users who have higher requirements for indoor comfort:User

162、s with higher requirements for comfort are more inclined to choose radiant home heating systems(HPFH systems,gas boilers,and electric floor heaters),and HPFH systems are the best option.HPFH systems have significant advantage in energy saving and carbon emissions reduction,HPFH systems provide a bet

163、ter indoor thermal environment than the other two floor heating systems because they can provide both heating and cooling.HPFH can also bring in fresh air and control humidity.For homes with higher heating demand(larger indoor area,relatively colder climate,and closer to the top or bottom floor of t

164、he building),the cost-effectiveness of HPFH systems also improves significantly owing to the higher energy efficiency.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONPursuing a Zero-Carbon Pathway by Scaling Heat Pumps in the Yangtze River Delta Regionrmi.o

165、rg/24Home heating in the YRD region is in the early stages of development and transition,and choosing energy-saving and low-carbon heat pump systems(rather than gas-fired systems)will be a key enabler for the zero-carbon transition of home heating in the region.Research by RMI shows that the adoptio

166、n of heat pumps in the YRD region could save nearly 600 million tons of CO2 cumulatively by 2060 compared with using gas-fired heating.To analyze the total emissions reduction potential of heat pump heating in the YRD region,this study sets two scenarios for home heating:a reference scenario and a z

167、ero-carbon scenario.In the reference scenario,gas-fired systems will be widely used in new buildings,followed by rapid expansion,finally forming a home heating pattern dominated by gas in 2060.In the zero-carbon scenario,the promotion of heat pump systems in new buildings deters large-scale deployme

168、nt of gas-fired systems,enabling heat pumps to gradually replace and finally phase out existing gas-fired systems.A comparison of heating choices in the two scenarios is shown in Exhibit 17.YearYearBoth heat pumps possibleNo heatingDistrict heating EFHGas boilerHPFH systems）supported by PERH（Mini-sp

169、lits)2Residential floor areas(billion m(Heat pumps as the dominant heating device)Zero-carbon scenario(Gas boiler as the dominant heating device)Reference scenarioExhibit 17:Adoption of equipment in reference scenario and zero-carbon scenario(202060)Source:RMI analysisAs shown in Exhibit 18(page 25)

170、,under the reference scenario,the overall carbon emissions of home heating will rise at first,then decline and finally flatten.During 202030,the widespread adoption of gas-fired systems in new buildings will be the main reason for the increase of carbon emissions from home heating.During 203040,when

171、 gas-fired systems have not been widely promoted in existing buildings ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONYearTotal CO2Emissions reduction potential of residential buildings Emissions reduction potential of residential buildings built afer 2020

172、built before 2020 emissions of YRD home heating:reference scenario CO2Total CO2 emissions of YRD home heating:zero-carbon scenario emissions(million tons/year)rmi.org/25and most still use mini-splits for heating,xiii the overall carbon emissions of home heating will decline with the retrofit of buil

173、ding envelopes and the reduction of the grid carbon intensity.During 204060,the share of gas-fired heating systems in existing buildings will gradually increase due to the scale effect,and the emissions reduction enabled by retrofits will gradually be offset by the emissions growth caused by the use

174、 of gas.By 2060,home heating in the YRD region will still create about 45 million tons per year of CO2 emissions.Under the zero-carbon scenario,the overall carbon emissions of home heating will be flat at first,followed by continual decline.During 20202030,as HPFH systems are adopted as the major he

175、ating systems in new buildings,the overall carbon emissions of home heating will be flat due to the offset of increasing heating demand and decreasing carbon intensity of the power grid.During 20302060,the carbon emissions of home heating will decrease thanks to the upgrade of building envelopes and

176、 the popularization of heat pumps.The large-scale adoption of heat pumps and the gradual decarbonization of the power system make zero-carbon home heating possible by 2060.Compared with the reference scenario,the zero-carbon scenario will cumulatively reduce CO2 emissions by about 600 million tons f

177、rom 2020 to 2060.Of that reduction,200 million tons will be contributed by buildings built after 2020 and 400 million tons by buildings built before 2020.Exhibit 18:Overall carbon emissions of home heating in the YRD region under different scenariosSource:RMI analysisAt present,the rapid development

178、 of gas-fired heating systems(especially in new buildings)is bringing great challenges to the zero-carbon transition of home heating in the YRD region.The key to solving this problem is to accelerate the promotion of heat pump systems for home heating as soon as possible,rolling them out in differen

179、t types of buildings in stages.Based on the above scenario analysis,the promotion of heat pumps for home heating in the YRD region can be roughly divided into the following three stages:xiii ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONIn the assumptions

180、 of home heating scenarios in the YRD region,mini-split refers to the heating mode that takes mini-split air conditioners as the main source of heating and electric resistance heaters as supplementary heating.Because electric resistance heaters are often used as supportive heating devices,they are n

181、ot listed as a separate system in the analysis.rmi.org/26xiv Centralized heating includes district heating that uses urban heating networks and the heating approach that uses a unified heat source to provide heating to a community.Under the zero-carbon scenario,centralized heating should adopt zero-

182、carbon heat sources such as central heat pumps,industrial waste heat,and biomass boilers to ensure the decarbonization of home heating.StageI:Theinitialstageofthehomeheatingsystemtransition(202030).Theheatedresidential floor area and heating market continues to grow,promoting the adoption of heat pu

183、mps for heating in new buildings.In this stage,households in new buildings and existing buildings without heating are faced with the choice of new home heating systems.Preventing these users from choosing gas-fired systems is the primary task in this stage.Efforts should be made to vigorously promot

184、e the adoption of HPFH systems in new buildings and encourage households in existing buildings without heating to use mini-splits instead of gas boilers.By 2030,all residents in the YRD region will have access to heating,with about 20 million residents installing home heating systems from nothing.Ab

185、out 17%of residents in the region will adopt heat pumps for heating,15%more than the 2020 level.The expansion of gas boilers will be curbed and maintained at the 2020 level of about 10%.Stage II:The mid-stage of the home heating system transition(203045).Heat pumps will be widely promoted in existin

186、g buildings,reducing the share of gas-fired heating systems.In this stage,replacementofexistingsystemsbecomesthe drivingforce inthe home heatingsystemtransition.Gas-firedsystemswillbe graduallyreplacedbyHPFHsystemsastheyapproachtheendoftheirlife span,and their share of the home heating sector will d

187、ecline to less than 5%by 2045.Meanwhile,with more buildingsbeingretrofittedandthe increasingrequirementforthe indoorthermalcomfort,HPFHsystemswillalso replace some of the mini-splits in existing buildings and become a mainstream home heating system.Stage III:The final stage of the home heating syste

188、m transition(204560).Gas-fired heating systemswillbecompletelyphasedout,andthegoalofzero-carbonhomeheatingwillbeachieved.In this stage,gas-fired heating systems and less-efficient electric floor heaters will be completely replaced by heat pumps.Except for a small number of residential buildings with

189、 centralized heating,all home heating demand in the YRD region will be met by heat pumps.xiv With the decarbonization of electricity used by buildings,zero-carbon home heating will be achieved by 2060.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION rmi.org

190、/27Major Challenges and Suggestions to Promote Heat Pumps in the YRD RegionIn response to Chinas national climate pledge and rising demand for better indoor comfort in the YRD region,heat pumps are the best solution.However,the large-scale adoption of heat pumps still faces many challenges.Based on

191、previous analysis,this section will summarize the challenges of promoting heat pumps for heating in the YRD region and then provide suggestions for multiple stakeholders.Major ChallengesHighpurchasecostisthebiggestbarriertotheuseofHPFHsystems.AccordingtoRMIsanalysis,installationofheatingsystemsinnew

192、residentialbuildingshasbecomeamainstreampracticeintheYRD region,with real estate developers playing a decisive role in the choice of home heating systems.The purchase cost of a gas-fired floor heating system is about 15%lower than that of an HPFH system,which is the main reason gas systems are curre

193、ntly the preferred heating approach.If there is no preferential policy for heat pump promotion,developers tend to choose to install the cheaper system.Low public awareness of HPFH hinders the use of heat pumps.Many users are not aware of heat pumps at all,because of the products lower penetration ra

194、te compared with other home heating devices.Some users may have heard of heat pumps but are not fully aware of their advantages in terms of comfort,environmental benefits,and low operating costs.In addition,the lack of convenient online/offline purchasing channels constrains users adoption of heat p

195、umps.Inadequate adaptability of the HPFH system with certain buildings is a challenge.The installation of the outdoor unit of HPFH systems requires a large space;the limited reserved space of high-rise apartment buildings constrains the ability to install HPFH systems at these buildings.In addition,

196、potential users are concerned about the complex installation and maintenance of the HPFH system.Furthermore,because outdoor air in the YRD region is relatively humid,the outdoor heat exchanger may frost during the operation of heat pumps,which may lead to problems such as decreasing heating capacity

197、 and unstable operation,negatively impacting users experiences.Unsatisfactory heating comfort is the major challenge for mini-splits.Although many of the mini-splits manufacturers have been developing more advanced products being able to provide higher indoor thermal comfort,the mainstream mini-spli

198、t heat pump products on the YRD market still adopt a top-down air flow pattern in the heating mode,resulting in poor thermal comfort.Research shows that about 50%of mini-split users complain about the“slow heating process and poor heating performance”of the product.5ZERO-CARBON HOME HEATING IN CHINA

199、S YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION rmi.org/28SuggestionsFor usersGet to know heat pumps and prioritize them over gas boilers as the home heating device.HPFH systems can provide excellent indoor comfort in both summer and winter.HPFH systems low operating cost also makes their

200、 whole-life cost close to or even lower than that of gas boilers.For mini-split products,with the improvement of the product,both the heating capacity and the heating comfort(through the adjustment of the air flow pattern)will be improved.These improvements,combined with lower cost and simpler purch

201、ase and installation,are making mini-splits a recommended choice for more home heating,especially for households that are sensitive to up-front investment and older residential buildings that are not suitable for HPFH system installation.Retrofit residential buildings to install heat pumps.Older res

202、idential buildings may encounter difficultiesininstallingtheoutdoorunitsofHPFHsystems,includinginsufficientspace,unstableexternal walls,and low load-bearing capacity.To address these problems,households in older residential buildings may consider sharing a set of heat pump devices(similar to the cen

203、tralized HVAC heating,ventilation,air conditioning systems in commercial buildings).These households can install the outdoor unit on the ground or rooftop in a way that does not affect the wall structure.Even in these cases,however,retrofits are needed to improve older residential buildings insulati

204、on and thus reduce the overall heating demand,so that heat pumps with lower heat capacity and lower price could be installed.For policymakersSupport heat pump manufacturers and retailers with subsidies.Targeted subsidies are critical to narrowing the cost gap between heat pumps and other home heatin

205、g devices.Subsidies at the production end can directly benefit heat pump manufacturers and boost heat pump industry development.Such subsidies can take various forms,including research and development subsidies,product subsidies,and tax credits.Acceleratepoliciesthatencourageormandatetheuseofheatpum

206、psforheatinginnewresidential buildings.Policies could mandate some aspects of the installation of home heating systems in new residential buildings,such as not encouraging the use of fossil fuel systems or requiring heat pumps.In a softer approach,policies could provide incentives to real estate dev

207、elopment projects that choose to adopt heat pumps,such as relaxing restrictions on the salable floor area ratio.Incorporate heat pumps into the voluntary emissions reduction certification system.Using heat pumps for heating and cooling offers great potential in carbon reductions.Monetizing the envir

208、onmental attributes of heat pumps by permitting the issuance of China Certified Emission Reductions(CCER)for heat pump emissions reduction projects may help reduce heat pump costs.Improve public awareness of heat pumps.At present,lack of public awareness of heat pumps is a major barrier to their gro

209、wth.To increase the public awareness of heat pumps,relevant authorities,social organizations,and heat pump manufacturers need to work together.Publicizing the advantages of heat pumps,including user comfort,economic benefits,and positive environmental impacts,will help potential users realize that h

210、eat pumps are not only a comfortable and economical choice for heating,but also a key enabler of the national climate goals.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION rmi.org/29For real estate developersEstablish long-term cooperation with heat pump s

211、uppliers.Through cooperation with heat pump manufacturers or retailers,real estate developers could simplify the purchase process of heat pumps,accelerating the scale of their adoption.Developers can also help connect users and heat pump suppliers with convenient access to heat pump product purchase

212、 and after-sales service,to attract more potential users.Explore innovative business models to apportion the up-front cost of heat pumps.In view of the high up-front investment of HPFH products,developers should explore innovative business models to help users apportion the early costs with approach

213、es such as providing loans for the purchase of the Develop heat pump friendly and heat pump ready homes.During the project planning and design stages,developers should consider the conditions required for heat pump installation,such as setting aside a platform and space for the installation of outdo

214、or units.whole system and receiving paybacks by charging heating fees and property fees.For manufacturers and retailersOptimize heat pump products customized specifically for the climate of the YRD region.Due to the implementation of the“coal switch”policy in recent years,heat pump products develope

215、d for rural users in northern China have been the focus of many heat pump manufacturers.However,heat pump products for southern China residents need further improvement.Optimizations could be undertaken in the following areas:heatingcomfortofmini-splits,effortscouldbemadetooptimizetheairsupplypatter

216、n,suchasimproving temperature distribution in the heating mode of wall-mounted mini-splits by increasing the volume of air supply and blowing air downward.Tower type air conditioners could also be optimized to develop a separated air supply pattern that blows cooling air from the top and heating air

217、 from the bottom.humidity may cause the problem of frost in the outdoor unit of the heat pump system,which will lead to lower heating performance and higher energy consumption,reducing heating comfort and increasing themainreasonsforthehighpurchasecostofHPFHsystemsisthehigh nominal capacity ofthemai

218、nstream heat pump products,which typically have a heat generation capacity above 10 kW.These products are suitable for larger apartments but are too large for the small and medium-sized apartments typical of the YRD region,resulting in many smaller homes being equipped with large HPFH systems and an

219、 unnecessarycost burdenforusers.Therefore,wesuggestheatpumpmanufacturersdesignandpromote products with a smaller capacity(nominal capacity below 8 kW with single-fan outdoor unit),which would be easier to install for small and medium-sized apartments.cost.This problem should be better addressed duri

220、ng the heat pump R&D process.Develop and promote multifunctional heat pumps able to provide cooling,heating,and domestic hot water.In addition to the heating and cooling functions of HPFH systems,multifunctional products are able to provide domestic hot water.At present,users of HPFH systems need to

221、 install separate ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION Optimizing the heating function of mini-splits to improve heating comfort:Developing and promoting smaller HPFH systems for small and medium-sized apartments:One of In view of the poor Solvi

222、ng the frost problem caused by the high air humidity in the YRD region:High outdoor air rmi.org/30domestic water heaters.In contrast,gas boilers usually have both heating and domestic hot water functions,which is one of the reasons users choose gas boilers rather than HPFH systems.Therefore,the deve

223、lopment of multifunctional heat pumps will greatly increase the competitiveness of heat pumps.In addition,multifunctional heat pumps can further contribute to energy savings and emissions reductions via heat recovery devices in summer.Develop heat pumps with low-GWP refrigerants.xv The heat transfer

224、 medium known as refrigerant is crucial for heat pump operation.A wide range of refrigerants with high GWP(e.g.,R410a,R134a,etc.)has been extensively used in heat pump products,and would contribute to global warming if leaked.Shifting heat pumps toward low-GWP refrigerants(e.g.,natural refrigerants

225、including ammonia,carbon dioxide,etc.)would make heat pumps more environmental-friendly.Disseminate and demonstrate successful installation and use of heat pumps.At present,residents in the YRD region have limited chances to learn about heat pumps.Providing successful case studies of heat pump insta

226、llation and use through cooperation with heat pump suppliers and developers would Provide whole-system service for home heating system upgrades.A whole-system approach means making envelopes more air-tight and improving the insulation alongside the equipment upgrade.With improved envelopes,the home

227、heating demand can be reduced,further lowering the operation cost.And smaller heat pumps that are less expensive and easy-to-install can be applied.help increase awareness and confidence among potential customers.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLU

228、TION xv Global warming potential(GWP)is the heat absorbed by any greenhouse gas in the atmosphere,as a multiple of the heat that would be absorbed by the same mass of carbon dioxide(CO2).GWP is 1 for CO2.rmi.org/31Heat Pumps for China and BeyondHeat pumps are considered a key technology for addressi

229、ng global warming,and they have been widely used around the world because of their advantages of high energy efficiency and low emissions.Many countries are developing policy measures to accelerate the promotion and deployment of low-carbon home heating systems:in the European Union,the RePowerEU pl

230、an released in March 2022 proposed targets of(1)doubling annual sales,(2)adding 10 million heat pumps in the next five years,and(3)adding a total of 30 million heat pumps by 2030;in the United States,the Inflation Reduction Act signed in August 2022 proposed to encourages residents to purchase heat

231、pumps for heating with significant rebates and tax incentives.About 190 million heat pumps are currently used for space heating in buildings around the world,covering 10%of heating demand in the building sector,according to an International Energy Agency report,butthe deploymentrate ofheatpumpsissti

232、llshortofthatrequiredbythe 2050net-zerocarbon goal.9Further efforts are needed by all stakeholders to accelerate the adoption of heat pumps.The promotion of heat pumps for home heating in Chinas YRD region not only contributes to the zero-carbon heating in this region,but also accelerates the adopti

233、on of heat pumps globally to achieve zero-carbon heatingon alarger scale.Promoting zero-carbon home heating in other regions of ChinaThe zero-carbon transition of home heating by heat pumps in the YRD region can serve as a model for other southern regions of China,such as Hunan,Hubei,Sichuan,and Cho

234、ngqing in the middle and lower reaches of the Yangtze River.Similar to the YRD region,these regions also have hot summers and cold winters,and rely on distributed devices for heating.These less-developed regions can learn from the promotion of heat pumps in the YRD region.In northern China where hea

235、ting demand is higher,low ambient temperature ASHPs have been adopted.For example,in rural areas of Beijing,Tianjin,and Hebei,heat pumps are the main device installed in the national program of the“coal switch”initiative supported by government subsidies.Government subsidies have been playing the ce

236、ntral role in promoting heat pumps in these regions.As a result,the real market and the corresponding sales model for heat pumps havent been fully established.In contrast,home heating systems used in the YRD region are mostly purchased by users themselves or real estate developers.The successful pro

237、curement models in this region could provide valuable experience for northern China.Contributing to global zero-carbon home heatingAs the worlds manufacturing powerhouse,China is also the worlds largest exporter of ASHPs.In recent years,Chinas export of these products has experienced rapid growth,wi

238、th export volume reaching 4.86 billionRMB(US$721million)in2021,nearlyquadruplethelevelof2017.10 Inthepursuitofcombatingclimate change,the demand for heat pumps is growing rapidly.In 2021,global heat pump sales grew by 13%,and the European heat pump market even reached a new record with 35%growth.In

239、2023,the energy crises in Europe due to the Russia-Ukraine conflict continued to further stimulate demand for heat pumps.ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONThe demand for heat pumps will continue to increase for years,providing abundant space f

240、or the growth of Chinas heat pump exports.Therefore,the large-scale promotion of heat pumps in the YRD region will provide valuable market experience and user feedback for Chinese manufacturers,improving the competitiveness of Chinese heat pumps in the international market.Around the world,there are

241、 many regions with subtropical humid climates similar to that of the YRD region(see Exhibit 19),and about 15%of the worlds population lives in these regions.The valuable experience of promoting heat pumps for heating in the YRD region will provide a reference for residents in these regions and contr

242、ibute significantly to the global zero-carbon home heating effort.Exhibit 19:Regions with climate similar to that of the YRD regionSource:Kppen climate classificationZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/32Appendix A:Building Simulation In

243、put ParametersExhibit A1:Envelope parametersScenarioTypical building envelopeEnergy codecompliant envelope11 Advanced building envelopeHeat transfer coefficient of external walls(W/m2-K)Heat transfer coefficient of roof(W/m2-K)Heat transfer coefficient of windows(W/m2-K)Solar heat gain of external w

244、indows(W/m2-K)(SHGC)Air tightness(ACH)1.140.60.530.930.40.482.82.51.710.750.670.6710.50.5Apartment sizeLargeSmallArea(m2)10870Apartment size3 bedrooms+2 living rooms+2 bathrooms2 bedrooms+2 living rooms+1 bathroomThree-generation family(retired elderlies+working parents+child;5 persons)Typical famil

245、y(working parents+child;Living room:08:0012:00,14:00Living room:18:00Bedroom 1:12:0014:00,22:003 persons)08:00Bedroom 2:22:0008:0022:00Bedroom:22:008:0022:00Living room:08:0012:00,14:00Bedroom:12:0014:00,22:0008:0023:00Bedroom:12:0014:00,23:0008:00Family membersPeople in room on weekdays(Mon.Fri.)Pe

246、ople in room on weekendsExhibit A2:Apartment parametersZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTIONrmi.org/33Living room:08:0012:00,14:0022:00Up-front purchase costThis includes the costs of purchasing and installing the heating system.Up-front purchase

247、 costs used in this study were collected from multiple sources,including manufacturers online stores and interviews with manufacturers.For general home users,different heating systems are purchased in different ways.For example,mini-splits and electric resistance heaters can be purchased in manufact

248、urers online and offline stores,with installation service provided by manufacturers.For systems with more complicated installation,such as HPFH systems,gas boilers,and EFH,manufacturers normally arrange for local Appendix B:Concepts and Assumptions for Economic Analysisretailers to assist users in d

249、esign,device selection,and installation.The purchase costs of heating systems in scenarios other than HPFH and mini-splits also include the purchase costs of cooling systems.For these systems,the price of a home air conditioner(mini-splits)is used as the referential cost of the cooling system.Mainte

250、nance costThis is the cost of repair,parts replacement,and device maintenance during the service life of the home Operating costThisincludesthecostofelectricityorgasusedforheating.Formoredetailedanalysis,ourstudyadopted the average peakvalley electricity price in the YRD region.12 We also adopted th

251、e average civil gas price in36largeandmedium-sizedcitiesacrossthecountry.13 Theoperatingcostsofcoolingarenotincluded.heating system.The maintenance cost in this research was determined mainly through market surveys.rmi.org/Salvage valueSalvage value refers to the residual value of the home heating s

252、ystem at the end of its service life.Salvage values are considered only for devices with a service life longer than 10 years.For example,the service life of a floor heater system is generally 50 years.This research adopts the straight-line depreciation approach to calculating the amount of depreciat

253、ion after 10 years of service and calculates the salvage value by subtracting the amount of depreciation from the purchase cost.The salvage value is expressed as a positive cash flow after 10 years.34ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION Endnotes

254、1 International Energy Agency,Heating,2022,https:/www.iea.org/reports/heating.2 Yuan Zheng et al.,Developing GreenBuilding Design Strategies in the Yangtze River Delta,China,through a Coupling Relationship between Geomorphology and Climate,Land,2022.3 Shan Hu et al.,A Survey on Energy Consumption an

255、d Energy Usage Behavior of Households and Residential Buildings in Urban China,Energy and Buildings,Vol.148,pp.366378,2017.4 US Energy Information Administration,Residential Energy Consumption Survey,2015,https:/www.eia.gov/consumption/residential/data/2015/.5 Building Energy Conservation Research C

256、enter of Tsinghua University,Annual Report on China Building Energy Efficiency,Beijing:China Architecture&Building Press,2021.6 Stephanie Cernivec,Answering Some of Electric Floor Heatings Most Frequently Asked Questions(FAQs),2018,https:/ J.Hong et al.,Assessing Heat Pumps as Flexible Load,Proceedi

257、ngs of the Institution of Mechanical Engineers,Part A:Journal of Power and Energy,Vol.227.1,2013.8 Arthur Rinaldi et al.,What Adds More Flexibility?An Energy System Analysis of Storage,Demand-Side Re-sponse,Heating Electrification,and Distribution Reinforcement,Renewable and Sustainable Energy Revie

258、ws,Vol.167,2022.International Energy Agency,Heat Pumps,2022,https:/www.iea.org/reports/heat-pumps.10 China Heat Pump Association,China Heat Pump Heating Annual Market Review,2021.rmi.org/11 Ministry of Housing and UrbanRural Development,General Code for Energy Efficiency and Renewable Energy Applica

259、tion in Buildings,Beijing:China Architecture&Building Press,2021.35ZERO-CARBON HOME HEATING IN CHINAS YANGTZE RIVER DELTA REGION:HEAT PUMPS AS A CORE SOLUTION12 Source:State Grid app.13 Source:CEIC,Price Monitoring Center of National Development and Reform Commission.Yihan Hao,Xinxin Hu,Ting Li,Guan

260、gxu Wang,Meng Wang,Zero-Carbon Home Heating in Chinas Yangtze River Delta Region:Heat Pumps as a Core Solution,RMI,2023,https:/rmi.org/insight/zero-carbon-home-heating-in-chinas-yangtze-river-delta-region/.RMI values collaboration and aims to accelerate the energy transition through sharing knowledg

261、e and insights.We therefore allow interested parties to reference,share,and cite our work through the Creative Commons CC BY-SA 4.0 license.https:/creativecommons.org/licenses/by-sa/4.0/All images used are from iStock unless otherwise noted.RMI Innovation Center 22830 Two Rivers RoadBasalt,CO 81621www.rmi.org January 2024 RMI.All rights reserved.Rocky Mountain Institute and RMI are registered trademarks.