Prof D Chandrasekharam

Geothermal heat pumps (GHP) are environmentally benign and represent a large potential for reduction of CO₂ emission. The CO₂ emission rates depend on the energy efficiency of the equipment as well as the fuel mix and the efficiency of electricity generation.

 The heat pump needs auxiliary power to accomplish the temperature rise needed in the system. This power, if supplied by renewable energy source like geothermal, then the amount of CO₂ emission will be near zero. On the other hand if energy supply is from fossil fuels, then there will be CO₂ emission but the amount of CO₂ emitted will be lower by several factors compared to conventional energy source used for space heating and cooling.      

The average CO₂ emission associated with generation of electricity is estimated to be 0.953 kg CO₂/kWh ( coal based power plants) while geothermal power plants emit  0.893 kg CO₂/MWhr. Electrically driven heat pump reduces the CO₂ emission by 45% compared with an oil fired boiler and 33% compared with a gas fired boiler. The total CO₂ reduction potential of heat pumps has been estimated to be 1.2 billion tonnes per year or about 6% of the global emission.

 In India, 33 % of electricity  ( coal based power) is utilized by the building sector (commercial and domestic ). A major amount is spent for space cooling, refrigeration and hot water supply. This amounts to emission of 234 x 10⁹ kg CO₂. If India utilizes  G H Ps (low enthalpy geothermal sources), so much of CO₂  emission can be reduced.