Agri-environmental System Engineering and Energy : Original Article ; Analysis on Heating Effects of the Vertical Type Geothermal Heat Pump System

Purpose: This paper is aimed at analyzing the heating performance of the vertical closed loop type Geothermal Heat PumpSystem (GHPS) distributing the farm site and providing basic data of the GHPS. Method: Seedling greenhouse heating wasmade from October 2012 to May 2013. The seedling greenhouse was divided into 4 sectors (A, B, C and D zone, total 3,300m2) with different temperatures. It was heated from 5PM to 8AM, and during the night the greenhouse was covered bynon-woven fabric thermal curtains along the upper 2m of the greenhouse for temperature maintenance. In order to analyzethe heating performance of the GHPS, power consumption and operating time of the GHPS, inlet and outlet watertemperature of the condenser, temperatures of each zone of the greenhouse, and ambient temperature were measured. Results: When operating only one heat pump unit, heat generated in the condenser decreased as the experiment progressedand power consumption increased correspondingly. However, the heating coefficient of performance decreased from 3.3 to2.0 rapidly. Also, when operating two heat pump units, heat generated in the condenser decreased and power consumptionincreased. Heating coefficient of performance decreased from 4.5 to 3.7 rapidly. When the set temperature of thegreenhouse was 13.7~20.1°C and minimum ambient temperature was -20.8~4.8°C, the annually accumulated heat andpower consumption were 520,623 kW, 142,304 kW, respectively. Conclusion: When the set temperature of the greenhousewas 13.7~20.1°C and the minimum ambient temperature was 20.8~4.8°C, the annually accumulated heat and powerconsumption were 520,623 kW, 142,304 kW, respectively. When operating only one heat pump unit, the heating COP was2.0~3.3, and when operating 2 heat pump units, it was 3.7~4.5. If several heat pumps are installed in one GHPS, it issuggested that all heat pumps be operated except in special cases. Because the scale of the water pumps are set to the scaleof when all heat pump units are operating, if even one unit is not operating, the power consumption will increase. Thatbecomes the cause of COP decrease.