It comes up straight from the heart of mother earth, is clean, and to top it all, free. Geothermal energy is green and the energy of the future and comes from the sub-surface of the earth. It’s contained in the fluids and rocks beneath the crust of the earth and can be found right down t the hot molten core of the earth, the magma.
And unlike biofuel, it is limitless as the core of our planet holds enough energy to last forever. And even as we extract and use this geothermal power, we leave our planet just the way it is.
Even as we realize the mess we have made over the last 100 years by sifting to fossil fuel, we make a desperate attempt to shift from oil and coal to solar, water, and geothermal power. While the economy has relied on energy derived from burning something, be it coal, oil, or natural gas, it has led to huge amounts of carbon emission that has brought about global warming.
Geothermal energy has been used for over a hundred years, albeit in an elementary form. Electricity from geothermal power is derived by harnessing it from the core of the Earth. We leverage this thermal energy which in turn power steam turbines.
The core of the earth has multiple layers. It comprises an innermost core made of dense iron. The outer core is magma, above which is the mantle which contains both rock and magma. Above it are solid and partially melted layers ending with the rigid crust which is anywhere between 5 and 70 kilometers thick.
Geothermal power is derived by boring down several kilometers deep inside and constructing wells that let the steam rise from geothermal layers. The energy at time rises on its own through natural vents in the ground.
The infrastructure and the process change with the type of geothermal power plant used. There are 3 basic types of plants to generate geothermal power according to the National Renewable Energy Laboratory (NERL).
The oldest process in use is the dry steam geothermal power plant. In this process, the steam is directly piped from the underground wells right to the plant. This process takes advantage of the natural source of the steam as it spews out of the core with minimal intervention.
But this system of extracting geothermal power is rare, according to geothermal energy authority, Maurice Dusseault. The north San Francisco facility, Geysers Geothermal Complex, that hoses this type of geothermal power generation also is the largest plant that generates geothermal power.
The second system is the flash steam plants.it is deemed the most followed form that generates geothermal power. Geothermal fluids get pumped up through a pressurized tunnel into a chamber above the ground. Here the fluids evaporate and are transformed into steam.
The binary cycle system of geothermal power production is the third form. Here multiple chambers are used, and the geothermal fluids are kept separately from the secondary fluid. The secondary fluid is heated to a predetermined temperature using a heat exchanger. The geothermal liquid is used to increase the temperature as it transforms into vapor and rotates the turbine.
The enhanced geothermal system (EGS) is used to extract the heat out of low porosity and low permeability rocks that lack fluids in a significant amount. This is done in Maine, Massachusetts, and New Hamshire.
Geothermal energy has uses other than the production of electricity. It is used to heat homes directly from on-site pumps. The buildings of Reykjavík, the capital of Denmark, are heated using geothermal energy. Pools formed out of geothermal energy also creates hot pools and springs.
Finding A Site That Is Suitable For Geothermal Power
Hot water and steam, the geothermal fluids, are vital for the rotation of a turbine generator. They are siphoned so that the thermal energy can be transformed into electricity.
The second requisite is that the reservoir should have sufficiently high temperatures to justify the project. The rock also has to be sufficiently permeable to permit the fluids to flow. The temperature increases the deeper you go into the earth’s crust.
But Dusseault says that in places such as Maine, the absence of hotspots and sediments makes it necessary to bore down 6 to 7 kilometers through rock to finally access sufficiently high temperatures. This at times makes the project financially unviable.
The preferred temperature for hotspots varies with the requirements. For geothermal power, extremely high temperatures are needed, and also it has to be readily accessible to make it economically viable.
But if the energy is to be used merely to heat, it would be prudent for a developer to go for areas with comparatively lesser temperatures in a rock formation that are hard to penetrate.
Major Geothermal Power Plants
Most geothermal power projects are situated on the western coast of the US as most hotspots are located there, especially in Nevada, Utah, Hawaii, and California. Though the US leads the world in geothermal power generation, it accounts for a mere 0.4% of the total utility-scale generation of electricity in the country. But it has the potential of developing at 2% a year and is expected to increase from 16B kWh to 52.2 kWh by the year 2050, a 226.25% rise in 31 years.
The generation of geothermal power is concentrated within 6 countries other than the US, Indonesia, Turkey, New Zealand, Philippines, and Mexico. They together have an installed generation capacity of 72% of the total. But Indonesia, Turkey, the Philippines, and Kenya, are set to do better in generating new capacity.
The downsides of geothermal power generation are few. It is cheap, is stable in the long run, and has few emission issues. But the cost of accessing the energy, and the highly technical nature of the work pose problems. There is also the use of the controversial method of hydraulic fracking used for extracting oil from underground reservoirs.