Geothermal power is energy generated from the heat stored beneath our planet's surface. Currently, geothermal energy supplies less than 10% of the world's power. Geothermal energy also requires water to be harnessed, often in the form of geysers and areas where there are large magma deposits below the surface. Although not all forms of extraction require
tectonic activity, most do, so there are limitations of geothermal energy depending on your location. If you happen to live on the "Ring of Fire", a string of volcanoes that encircles the Pacific Ocean, then you're in luck. For those who don't happen to live near any active or inactive volcanoes, geothermal energy can be slightly more difficult to find--but
Is Energy From the Core Green?
Environmentally, geothermal energy is among the soundest sources out there. They
produce around 5% of the emissions created by fossil fuel power plants, and they can also be equipped with something similar to carbon capturing systems, which will inject the gases back into the earth, dropping that five percent to 0.1%. The energy is also sort of renewable, because after the very hot water is taken from the ground, and it's energy extracted, it can be re-injected back into the earth to produce more steam. However, like almost all energy sources, it does have it's drawbacks. Because these plants (in the case of hot-dry-rock plants) pump water into the dry rock below, the construction of a plant around the surface of these hotspots may negatively affect the land stability. There is also the problem of geothermal energy's
renewability. Hot spots eventually die out to a certain extent, and because there is only a certain amount of energy for every inch of land, it seems inevitable that the energy could run out. However, it is likely that spots that have already had plants built over them would replenish their heat if left alone.
So how does this geothermal power technology work? Well, there are a few methods in which our Earth's core energy can be harnessed. The first, is through flash steam power plants.
Flash Steam Power Plants
The most common type of geothermal power plant, flash steam power plants utilize hot water that is at least 180 degrees Celsius which they extract from underground geothermal reservoirs. Because the pressure is so high underground, the water surprisingly stays in liquid form, despite the fact that is at a temperature far higher than our normal boiling point. The water is pumped from underground into the power plant above, and the drop in pressure causes the geothermal water to change or "flash" into steam. This
steam then powers a turbine in the plant, and is injected back into the geothermal reservoir to be recycled.
Binary Cycle Power Plants
Binary cycle power plants use a cooler temperature of water in their processes, and the water can range from 100 to 180 degrees Celsius. The hot geothermal water, also extracted from geothermal reservoirs, is
siphoned out and passed through a heat exchanger. This heat exchanger transfers the heat from the
geothermal water to fluids that boil at a much lower temperature than water, which are then vaporized to power the plant's turbine. These plants are much more easy to set up, as they don't require the super hot reservoirs that are needed for flash steam plants. Lower temperature geothermal reservoirs are much more common, and therefore these plants have the potential to be built in areas and conditions that the flash steam plants couldn't operate.
Also known as enhanced geothermal systems (EGS) these plants pump water from our surface into the
hot rocks below and then re-extracting it to harness the heat. Unlike the other plants, this system can be set up virtually anywhere, and does not require any underwater reservoirs to operate. However, the process does require a certain amount of available water above ground, so it likely wouldn't do too well in a desert.
Why is Geothermal Energy Virtually Untapped?
Unfortunately, despite the fact that geothermal reserves are plentiful and
renewable over the long term, it is a neglected option in many countries, including the biggest energy user: the United States. Recently the Office of Management and Budget cancelled all federally funded geothermal research. This seems odd, considering oil prices are high and the fact that climate change is now the number one concern of a majority of Americans.
"There are politicians working to change this stance however, and Rep. Gerald McNerny, a democrat from California, has introduced legislation that would give $400 million to geothermal research to be overseen by the US Secretary of Energy."
If this bill passes, then one of the world's largest energy consumers can work towards a greener future. Only 3.5% of geothermal reserves are currently being used, if we can up that number it's estimated there is more than 100,000 Megawatts of power
at our fingertips.
Source(s): Blankinship, Steve. ?Geothermal Energy Barely Being Tapped.? Power Engineering; Jun2007, Vol. 111 Issue 6, pg. 16.