1. Introduction to Geothermal Energy
Geothermal Energy is heat stored in earth crust and being used for electric generation and also for direct heat application worldwide since beginning of last century. USA, Philippines, Indonesia, Turkey, and New Zealand are leading countries availing commercial exploitation with worldwide installation of 12800 MW at end of 2017 .
(i) Power Production
Geothermal electricity generation is site and technology specific and India is in Low Geothermal Potential Region with low/medium heat enthalpy. Government is planning to encourage the industry lead demonstration projects at the first stage to assess the technical viability of the project before going to the commercial models.
Various resource assessments carried out by GSI, NGRI & CEA estimated the potential of approx. 10000 MW spread over 300 hot springs across seven geothermal provinces/11 states. As per the international reports a 1 MW Geothermal Power Plant generates about 8.3 Million Units (MU) per MW per annum compared to Solar 1.6 MU per MW, Wind 1.9 MU per MW and Hydro 3.9 MU per MW .
The worldwide average capital cost for geothermal energy power plants is around Rs. 30 - 35 crore per MW (@ power purchase tariff of around Rs. 10-12 per KWhr). This is due to high drilling cost, uncertainty of project specific exploration, etc. Interested stakeholders may look into secondary products like space cooling & heating, desalination, etc. for achieving reasonable rates.
(ii) Ground Source Heat Pumps (GSHP’s)/ Geo-exchange Pumps.
Ground Source Heat Pumps (GSHP’s) use the earth's relatively constant temperature between 16 - 240C  at a depth of 20 feet to provide heating, cooling, and hot water for homes and commercial buildings. GSHP harvests heat absorbed at the Earth's surface from solar energy. The temperature in the ground below 6 metres (20 ft) is roughly equal to the mean annual air temperature  at that latitude at the surface. It uses the earth as a heat source (in the winter) or a heat sink (in the summer). GHP’s is effective in all kind of climate zones or can be deployed anywhere in India on 24 x 7 bases. This Technology is being used worldwide from last 50 Years.
The National Building Code 2016 has included new and energy efficient options of air conditioning, heating and mechanical ventilation, such as variable refrigerant flow system, inverter technology, district cooling system, hybrid central plant using chilled beams, radiant floor components, and geo-thermal cooling and heating.  Stakeholders, like users of HVAC applications, etc., are encouraged to use geothermal heating/cooling under respective building projects as energy efficiency measures as this results in substantive reduction in costly electricity bills. This age-old proven technology has a payback period of 4-5 years and may be implemented by the interested stakeholders in market mode.
3. Technology Objectives
The objective of the technology programme is to accelerate and enhance support for the research, development, resource assessment, testing and deployment of geothermal energy in the country and to harness it for power generation and to overcome the barriers. The technology programme is open to public and private sectors to carry out projects in India. Industry lead R&D proposals are invited from stakeholders, for solving problems in Indian conditions.
- Renewable 2018 Global Status Report