Heating and cooling of residential annual application using DMS transcritical CO2 reversible system and traditional solutions: An environment and economic feasibility analysis

Dedicated mechanical subcooling (DMS) transcritical CO2 system for annual residential space heating and cooling is compared with traditional heating/cooling solutions. Environmental and economic analysis model is established to study the system feasibility and performance, and eight typical Chinese cities are selected as the evaluated scenarios. The annual primary energy consumption (PEC) can be considerably reduced by introducing DMS to CO2 system, which is up to 8.65, 15.66, and 55.41% in comparison with baseline (BASE) CO2 system, coal-fired boiler (CFB) + traditional air conditioner (TAC), and direct electric heating (DEH) + TAC system, respectively. The PEC is higher for the severe cold and the cold region, and it is the lowest when small temperature difference fan-coil unit (STD-FCU) is utilized as heating/cooling terminal. The PEC can be reduced by 47.90% when the energy-saving potential for the building envelope is 65%. The gaseous and solid particulate matter emissions can also be significantly decreased by 3.80-9.75% in comparison with BASE CO2 system. The life cycle cost (LCC) performance is improved, and a lowest levelized annual total revenue requirement (TRRL) of 7924.93 CNY is obtained when DMS CO2 system with STD-FCU is used in Guangzhou, which is 4.51-14.04% lower compared with BASE system. CO2 compressor and electricity price have significant impact on the LCC and payback period. DMS CO2 system is a promising solution for annual space heating and cooling with the help of feed-in tariff and CO2 compressor price reduction.