A Ground Source Heat Pump (GSHP) system heats and cools building by using earth as a heat source or heat sink. The system either extracts thermal energy out of the ground or transfers thermal energy from buildings to the ground. Moreover, heat energy stored during the summer season could be extracted out during winters to heat the ambient spaces. On average, 46% of the total solar energy received is stored. At 4-6 meters below ground surface, temperatures are more or less constant. Heat could be pumped in during summers to the ground, where the temperature is lower than the ambient temperature. GSHP system has three major components:
Depth below ground surface where temperatures are nearly constant is valid for India. It varies by latitude.
|The system has high EE (50 – 70%) and provides heating, cooling and hot water||More suitable for composite climate as continuous pumping of heat to ground could make the ground saturated|
|Low maintenance requirement as well as operates at a lower cost||It requires an intense concept design stage research to check the feasibility of the system on the individual site|
|Uses renewable source of energy||Requires skilled labour for designing and installing the system|
|Government approval may not be available for all states|
|High initial investment|
|Case study||Central University of Rajasthan|
|Location||Ajmer, Rajasthan, India|
|Climate Type||Hot and dry|
|Building Type||Residential – student hostel|
|System Description||Geothermal hybrid cooling system
Water from the boreholes is used to cool the air before introducing the same in the indoor spaces. Heat exchange between water from boreholes and supply air takes place inside specially designed AHUs. Air is further cooled after this through a two stage evaporative cooling system. The system uses 100 percent fresh air and is designed to reduce temperature of the supply air by around 10 °C. Design temperature for the hostel rooms is 29°C.
|System Performance||Average outlet water temperature from the boreholes is recorded at 25 °C. Outlet temperature in winter is around 19 °C.
Energy Performance Index was measured to be approximately 78 kWh/m2/year (2012).