Energy-saving Evaluation And Control Optimization Of An ASHP Heating System Based On Indoor Thermal Comfort

Indoor thermal comfort and energy conservation are the unity of opposites in residential buildings heating.Based on indoor thermal comfort,the energy-saving control of ASHP(Air Source Heat Pump)heating system is optimized.The PMV(Predicted Mean Votes)is amended by the thermal perception of rural residents in northwest China.Different ranges of indoor temperature and control operation strategies are set up.Energy consumption,system efficiency,operation cost and PMV are used to evaluate the system.The tested results show that the daily power consumption increases by 86.23%while the PMV rises by 1.09.When the PMV maintain between-0.03 and+0.26,the daily power consumption of intermittent operation is 14.97%lower than continuous operation.When the water temperature of tank is controlled at 40℃,the daily power consumption is 41.84%lower than at 50℃,the PMV can maintain in a comfortable range.It is suggested that the optimal control strategy of the ASHP heating system is intermittent operation.When the mean daily outdoor temperature is 0℃,the indoor temperature and the water temperature of tank should be controlled at 14 to 16℃and 38℃,respectively.It can provide a new control optimization method for ASHP heating system.In the early stage of heating design of civil buildings,we should choose the suitable and economical heating equipment by the design thermal index in order to improve the efficiency of heat pump and obtain the real energy saving.Based on the thermal comfort,different operation modes of ASHP heating system are set.The design index of heating load is modified.The measurement shows that when the indoor temperature is set at 14-16℃,the daily heating load is 70.9MW.The calculated design thermal index is 41.04 W/m~2,which is 48.19%less than the indoor temperature of 20-22℃.The daily heating load of intermittent operation is 70.9MW.The design thermal index is 35.18W/m~2,which is 40.18%lower than continuous operation mode.The heat source of space heating system presents diversified development.Space heating systems often suffer from economic loss and insufficient heat supply.We should choose a reasonable protection heating scheme.The design thermal index is revised.Based on the indoor thermal comfort,economic,energy consumption and environmental benefits evaluation,a comparative analysis of five space heating modes are made.The modes are coal combustion,ASHP,solar energy,wall hung gas boiler and electric heating.The feasibility of ASHP in"coal to electricity"project is explored.The heating area is 120m~2.The results show that the most comfortable heating terminal is floor radiation heating.In floor radiant heating,the two space heating modes with lower annual cost are solar heating and ASHP,which are 3626and 3095 yuan/year respectively.The traditional heating mode of bulk coal combustion is reformed.For a peasant household,the three space heating modes with short static payback period are ASHP,coal furnace and solar heating,which are 5.2,6.1 and 6.9 years respectively.For the actual energy consumption reduction of society,the converted coal consumption and environmental cost of gas furnace and ASHP are the most.The conservations of converted coal consumption are 4165 kg/year and2767 kg/year respectively.The environmental cost savings are 1594 and 1211yuan/year respectively.Based on the above four evaluations,it is considered that the ASHP combined with low temperature radiant floor heating is the best space heating mode for farmers in the cold regions of China.After selecting reasonable design thermal index and optimizing capacity matching and operation mode of ASHP heating system,the COP has been effectively improved.Compared with the traditional bulk coal combustion space heating,the ASHP can reduce the annual space heating cost by 2521 yuan,the actual annual space heating cost of the society by 3128 yuan,and the annual environmental cost by 1211 yuan.