Scope and Implementation of Ground Source Heat Extraction Technology in India for Multiple Energy Saving Applications

Abstract

India is a country of diverse geography comprising the world’s highest mountain ranges to large plains, peninsular plateau, deserts and coastal areas, where climatic conditions are highly variable and extreme. Therefore, both heating and cooling are essential requirements for the inhabitants throughout the year, and in this perspective, it is envisaged that there is tremendous scope of ground heat extraction technology in India for multiple energy saving applications. Present work deal with the implementation of a ground source heat pump system, installed at one of the SASE establishment near Manali (HP) in India, and its performance evaluation towards energy saving purposes along with reduction in GHG emissions. Prior to the design of the GSHP system, a geothermal investigation of the project site was carried out. Our study revealed that relatively a higher geothermal heat flux is present in this region as compared to its reported global average value, which may likely be due to the proximity of the project site to the tectonic fault line passing across. Through drilling of a test bore hole of depth more than 100 m, the geological strata of the site shows a heterogeneous formation which was composed of small pebbles of granite, dolomite, shale and sand. The test bore hole thermal test indicates higher values of thermal conductivity relative to their documented values for above geological structures. For erection of the ground source heat exchanger, vertical U-bent closed loop comprising nearly 5200 m long HDPE/MDPE pipe networks inserted into 27 numbers of boreholes (dia. 125 mm, with total running depths more than 2500 m), is coupled to a 100 kW capacity GHP system. In this work, the antifreeze fluid is prepared using mono ethylene glycol (by 25% with water) for ground loop circuit; however, refrigerant R410a is used in GHP loop. An intermediate heat exchanger is coupled to the existing central heating plant to transfer the heat from GHP to user load side. After installation of the complete GSHP based system, its performance was evaluated in terms of energy saving. Our results show that the CoP thus achieved is about to 3.1 for peak loading of 100 kW, yielding an energy saving up to 67%. Further, during peak winter load of the existing heating plant, the GHG emission has substantially reduced below 5%. This pilot study has opened new fronts of geothermal energy in India to provide a significant energy saving as well as environmental protection.