What is geothermal gradient?
Future of geo thermal will be determined by natural factors.
The future of geothermal energy can pretty much be summed up with a single word: MORE.
Geothermal energy is renewable but the fluids emit gases such as CO2 , H2S, SO2 , H2 , CH4 and N2 when used for electricity generation. However, geothermal power plants are usually sited in areas of natural geothermal activity, where such emissions occur anyway.
Other potential pollutants are various ions dissolved in the geothermal fluids, but these are almost always returned to the reservoir when the spent fluids are re-injected.
As regards safety, accidents are rare, although in 1991 a well failure at a geothermal plant on the flanks of a volcano in Guatemala vented hundreds of tons of rock, mud and steam.
Protracted geothermal exploitation can induce ground subsidence, similar to that which occurs when groundwater is extracted, although this is minimized by re-injecting spent fluids. Small earthquakes sometimes result from large-scale exploitation. However, most high-enthalpy geothermal areas are naturally prone to seismicity.
The main disadvantage of geothermal power generation is that suitable high-enthalpy areas are geographically very restricted, many being in areas of low population density (or under the sea).
Conversely, the very low-enthalpy potential of normal heat flow is universal, and potentially useful for heating and even air conditioning, given the necessary investment.
In the short term, even twenty- to forty-fold growth in geothermal capacity will not result in it being a significant contributor to global energy needs by 2020. Installing capacity takes time and of course money, whatever the benefits.
Recall that geothermal power plants are generally much smaller than fossil-fuel and nuclear generators - tens of MW, rather than the tens of GW for the biggest ‘conventional’ plants. To replace a single 1 GW fossil fuel power station requires between 20 to 33 geothermal stations.
The seeming benefit of local and ‘environmentally friendly’ geothermal power generation, in the economic context of their construction, delays its adoption at national to international scales. Direct-use geothermal projects suffer from slow growth also, because of economic factors.
Even though installation of domestic ground-source heat pumps is growing at 10% per annum in a few countries, that growth rate would need to be sustained globally for a great deal longer than 20 years to make any real difference to energy use patterns. That issue characterizes all alternative energy sources.