ENERGY AND EXERGY ANALYSIS OF GROUND SOURCE HEAT EXTRACTION TECHNOLOGY IN INDIA

Abstract

A geothermal heat pump (GHP) or ground source heat pump (GSHP) is the heart of the geothermal technology which in fact pumps the heat from the ground to the dwellings. This design takes advantage of the moderate temperatures of the ground to boost efficiency and reduce the operational costs of heating and cooling systems. Primarily, there are two independent loops working in heat extraction process i.e., ground loop and refrigeration loop. A mixture solution of antifreeze & water absorbs heat from ground and supplies to the refrigerant loop through heat exchanger. The refrigerant loop transmits this heat to a desuperheater that is interfacing the user load where accumulation of heat occurs. It also may be combined with a thermal or solar heating system with even greater efficiency. GHPs use the relatively constant temperature of the earth to provide heating and a small amount of electricity input is required to run a compressor; however, the energy output is of the order of many times of this input. Earlier in this project a vertical U-tube design of ‘geothermal heat exchange system’ has been used to provide a regulated preheated water supply to the existing central heating plant used for space heating to the dwellings. The outcomes of this project have been translated into ‘Geothermal Technology’ towards energy savings in the space heating in the Himalayan region as well as to the armed forces and also for futuristic energy plans of the country. Now, in this study the main focus is on increasing the overall efficiency of the system and for attaining this objective two approaches were taken. First, to evaluate the performance of the existing facility at Defense Geoinformatics Research iv Establishment (DGRE), Manali, in order to get the optimum parameters for further studies; Second, to do the energy and exergy analysis of the complete geothermal heating system to find out the COP, or first law efficiency, and exergetic efficiency, or second law efficiency. This analysis is performed in Engineering equation solver (EES) software. Parameters obtained in performance evaluation study like Pressure (Po), Dead state temperature (To) etc. has been utilized for the energy and exergy analysis. The refrigerant used for the analysis is R-134a.The COP calculated for the system is 5.851 and the exergetic efficiency obtained was 77%. Maximum destruction or Irreversibility obtained in compressor as compared to condenser and expansion valve.