The aim of this study is to understand the effects of the precooling and preheating operation of convection systems (air conditioner, AC) and radiant systems (floor cooling/heating and radiator, RAD) on the self-consumption rate by photovoltaic (PV) power generation and on thermal comfort. To evaluate the effect of the precooling and preheating operation, we measured indoor environmental factors, energy consumption, and skin surface temperature and heat loss using thermal manikins under 10 cases (4 cases in summer, 6 cases in winter) with different air-conditioning operations in a ZEH. In addition, the energy evaluation according to the daytime operation of HP water heater was conducted via simulation.
The following were reported in this article.
1) With regard to thermal comfort, precooling and preheating of AC and RAD was effective in stabilizing the indoor thermal comfort (PMV) at the time of returning home (18:00) and during evenings (18:00~23:00). Especially during evenings in winter, the PMV of Case5 (6-h RAD preheating operation) was stable at a slightly warm range; however, the other cases were stable at a slightly cool range. In addition, the comparison between PMV meter and Thermal manikin PMV shows that temperature unevenness occurred in AC cases. Regarding the heat loss of thermal manikin, the amount of heat loss of RAD cases was smaller than that of AC cases, and the amount of heat loss stabilized over time.
2) With regard to the energy evaluation, the RAD cases of precooling and preheating decreased the total energy consumption for cooling and heating by AC PMV control during evenings (18:00~23:00). Especially in winter, the RAD preheating operation cases were stabilized at a comfort range without heating by the AC PMV control. In the case of the 6-h RAD preheating operation, the energy consumption by the PV generation increased by 2.1 kWh. On the other hand, the energy consumption by the BT discharge and purchased power was reduced by 3.9 kWh. This shows a large heat storage effect, and it was suggested that the energy consumption could be reduced by RAD preheating operation. Regarding the self-consumption rate, when the AC system was the same, the energy consumption of the 6-h precooling/preheating was increased by about 15% in summer and about 14% in winter, compared to that of the 3-h precooling. In addition, when the precooling/preheating operation time was the same, the energy consumption of the RAD cooling/heating system was increased by about 2% in summer and about 13% in winter, compared to that of the AC system.
3) With regard to the energy evaluation for the daytime operation of HP water heater, the daytime operation of HP water heater is more effective in reducing the trading power and increasing the self-consumption rate. In winter, the self-consumption rate of AC preheating cases was higher than that of RAD preheating cases, because AC preheating cases have more surplus power than the RAD case.
