| Domestic water heaters can satisfy the demand of hot water for people,which has been an important household appliance in contemporary family.Currently,the sales and holdings of water heater in China kept increasing,promoting the development of water heater industry.However,the production of water heater was accompanied by the consumption of resources and the discharge of pollutants.The energy consumption in the use process accounted for a large proportion in household appliances,which is closely related to the environmental conditions and energy efficiency levels.The regional differences in the environmental impacts of different types of water heaters in China,as well as the cost and energy saving benefits within the service life and the future development directions are all worthy of in-depth exploration.This study took the electrical water heaters(EWH),gas water heater(GWH),evacuated tube solar water heater(ETSWH),flat panel solar water heater(FPSWH)and air-source heat pump water heater(AHPWH)as the research objects.Considering the influence of climate types,energy supplyment(solar radiation,electricity and natural gas)and the energy efficiency level,the life-cycle environmental impact assessment model and cost analysis mode of water heaters were built.The main contributions are summarized as follow.(1)The production of raw materials and use stages contributed the most to the life cycle environmental impact of water heaters,of which the former had a great influence on resource consumption and toxicity indexes,and the latter made a great contribution to energy consumption and common environmental impacts.The environmental benefits of recycling process on ozone destruction,acidification and photochemical oxidation were obvious.The focus of improving the environmental impacts of water heaters are reducing the use of toxic materials,improving the actual energy efficiency of the process,and optimizing the recycling patterns and technologies.(2)The environmental impact of GWH and ETSWH were relatively small in every region.The energy consumption of EWH was the highest,mading most environmental impacts largest,in addition to energy consumption,ozone detruction and toxicity impacts.AHPWH had higher energy efficiency and lower environmental impacts in hotsummer and cold winter areas.Ozone destruction and toxic effects caused by the production of refrigerant and copper materials were the main concerns.The energy consumption of the solar water heater was low,especially in areas with abundant solar radiation,but the consumption of stainless steel tank,carbon steel shell and heating copper tube were large,resulting in the prominent resource consumption and toxic impact.(3)The results of the total cost analysis of water heaters showed that the initial investment of the EWH was low,but the high energy consumption led to the rapid increase of life cycle cost.The energy consumption and initial investment of GWH were low,and the total cost was the lowest in severe cold region,cold region,and hot summer and cold winter region.Total cost of the AHPWH were the highest except for the hot summer and cold winter region.The pay-back period of the FPSWH and ETSWH were 7-8 years 3-4 years,respectively on basis of the EWH.When the EWH with the energy efficiency level of 1 reached the service life,it saves 159.27-348.81 yuan,439.45-859.52 yuan,954.63-1583.18 yuan and 1866.24-2837.64 yuan,respectively,compared to the EWH with the energy efficiency level of 2 to 5.(4)The heating supply cost of the GWH,EWH,AHPWH,ETSWH and FPSWH were 0.13-0.19 yuan/MJ,0.16-0.25 yuan/MJ,0.12-0.17 yuan/MJ,0.14-0.18 yuan/MJ and 0.15-0.21 yuan/MJ,respectively.The GWH and ETSWH cost less in the severe cold region,cold region as well as hot summer and cold winter region.The ETSWH and FPSWH have economic advantages in the mild region as well as hot summer and warm winter region. |
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