Utilization of Abandoned Coal Mines as a Low Enthalpy Geothermal Resource and Subsequent Energy Exploitation

摘要

Renewable Energy Investment triggering a debate on clean energy Vs conventional energy. The house of conventional energy i.e. Coal Mines which are abandoned can be serve as a green and clean energy option for the world. Abandoned and flooded coal mines have good potential as low enthalpy geothermal resources, which could be used for small to medium scale power generation and for heating and cooling purposes. The paper describes the exploitation strategies of geothermal energy from abandoned coal mines. In India, the average depth of coal mines is varying from 100 meter to 1500 meter. At this depth, there is an intense heat exchange between the rocks of the caved rock mass and the mine water. This arrangement forms an eco-system similar to that of a geothermal system. The surface temperature of the abandoned coal mines varies from 35 °C to 95°C for thermal springs and 20 °C to 25 °C for cold springs. The reservoir temperature is in the range of 120 °C to 260 °C, which favors low to medium enthalpy geothermal reservoirs. Both thermal spring and cold spring can be utilized for direct and indirect applications of geothermal energy. The paper also describes the utilization of thermal source using Organic Rankine Cycle (ORC) for production of electricity. A simulation program has been developed in EES for the calculation total power through the ORC system. The results have been calculated by changing evaporator temperature & pressure ratio and observing the effects on other parameters. A trade-off is done to select the working fluid among turbine outlet volume flow rate, volume flow ratio, network output, first law efficiency, total irreversibility and second law efficiency of the system. This paper critically reviews implementation of this low to medium enthalpy geothermal energy recovery strategy from the abandoned coal mines of the central parts of India Son-Narmada-Tapti belt.