Abstract
This paper described the heating performance evaluation of an agricultural air-conditioning system using groundwater in winter and the reduction of the groundwater consumption for this system. This system consisted of an air-conditioning room for horticulture in a greenhouse and a water circulation system of groundwater. The pumped groundwater is passed through the heat exchange panels and then discharged as sewage. Although it has been confirmed that this system can be sufficiently heated in winter, it has an issue of wasting underground aquifer resources. Therefore, we have improved the system by water recirculation in the air-conditioning room to solve this problem. Results showed that the room temperature could be successfully maintained up to 20°C during the daytime when the outside temperature is 5°C, and above 5°C even during the nighttime when the temperature is below freezing in winter during a three days experiment. The experiment was conducted in Yamanashi prefecture. Whereas, the heating performance decreased when the circulating water was used at night. Therefore, we used groundwater from 10p.m. to 10a.m. The results showed that the room temperature at night was about 3°C higher than when using the circulating water in same outdoor temperature. Thereby, the consumption of underground aquifers per day would be reduced by 50% while maintaining sufficient heating performance. In addition, we measured the room temperature of the system when it was in operation and when it was not in operation, and found that the room temperature during the daytime when the system was not in operation exceeded 35°C despite winter conditions.
