Abstract
The water heat pump systems by utilizing the existing snow-melting equipment were constructed to reduce heating costs in the snowy region. In addition, the effect of introducing these systems was evaluated by reducing heating costs and CO2 emission. The results are as follows:
(1)Groundwater temperature for snow melting is 8.9 ℃ on average without significant variation during the measurement period. The temperature was confirmed to be stable as heat source of water heat pumps.
(2)The temperature range in the greenhouse by using the water heat pump systems was controlled to be the same range obtained by using boiler system with a preset temperature of 20 ℃ and a corresponding oil consumption of 47.2 L/d.
(3)The results showed that the water heat pump systems could reduce 54.3 % at the maximum of the heating costs during the investigation period, comparing with the boiler system.
(4)Water heat pump systems could reduce 12.2 % of the running costs which include running costs for snow melting.
(5)The relationship between the benefit of the introduction of the systems and the operating time of snow melting (snow melting operation rate) was analyzed. The results showed that the maximum reducing rate of the running costs was 21.8 % when the COP and the snow melting operation rate were 3.38 and 70 %, respectively.
(6)The relationship between the benefit of the inｔroduction of the system and the monthly heating load was analyzed. The results showed that the maximum reducing rate of the running cost was 21.9 % when the heating loads was under 127.0 W per square meters and the snow melting operation rate was 95 %.
(7)The influence of the oil price on the benefit of the introduction of the systems was also analyzed. Regardless of the snow melting operation rate, it is found that the running cost in these systems is lower than in boiler system when the oil price is over 64 yen per liter.
(8)The results showed that the CO2 emission was reduced by 10.8 % by using present system, comparing with the boiler system.
Therefore, the above results show that the water heat pump systems constructed in this study are efficient for the greenhouse heating in the snowy region.
