Geothermal Energy

The need for sustainable energy solutions is a concern that is brought up frequently for the United States. President Obama expressed his desire for more clean energy projects home while campaigning in Nevada. One of the options that he discussed was geothermal energy. Nevada is currently working with geothermal energy and has realized the benefits of clean energy and lower utility costs. 

Geothermal energy, like the name states, is using the heat or “thermal” from the earth, “geo.” The energy comes from water that moves through the earth’s crust that heats up as it rises to the surface. As it breaks through the crust it turns into steam.This steam is then captured to create electricity.

The areas that release the steam are known as hotspots. Most of the hotspots are located at lithospheric plate boundaries such as the Ring of Fire that circles the Pacific Ocean. Hotspots release mostly steam but can also release hot water. Determining the type of system to capture the energy depends on the type of resource that is being released from the hotspot. Geothermal power plants may even need to drill if a hotspot is not easily accessible.

There are three designs for capturing the - dry steam, flash steam, and the binary cycle. The dry steam method is the simplest and uses the geothermal hotspots that only release steam. The steam then turns a turbine, that powers a generator.  Any water condensation from the steam is returned back into the ground. The flash steam method manages reservoirs that have both hot water and steam.  The hot water is separated and returned back into the geothermal reservoir, while the separated steam goes to power a turbine generator. The binary cycle method, which is appropriate for only hot water resources, the energy from hot water to heat up a second liquid that has a lower boiling point, usually isobutane. As the isobutane heats up, it converts into vapor that turns a turbine. This third method takes advantage of sites that would otherwise not have enough steam to produce electricity.

             Dry Steam                               Flush Steam                           Binary Cycle

Enhanced Geothermal Systems (EGS) would not be limited to hotspots and are in the various stages of development in various countries.  Where the other three methods of geothermal energy extraction rely on reservoirs of steam or hot water in rock that is permeable by drilling, EGS can utilize geothermal energy trapped within inaccessible areas.  The method involves pumping high pressure water through the hot dry rock, which in turn fractures and breaks the rock.  More water is pumped through where it then resurfaces is the form of steam or hot water. From there, the one of the other three methods can be utilized to produce electricity.

While geothermal energy has many benefits, there are also several disadvantages. The need for a hotspot or hot rock reservoir limits its availability. Further, many geothermal hotspots are located below impermeable rock. Drilling is also a significant risk because if the area is not drilled correctly it could cause gas or harmful minerals to emerge on the surface, which can be a danger to both the environment and any people in the area.

On the other hand, geothermal energy does not rely on fossil fuels and has relatively low greenhouse emissions. Further, geothermal power plants may be created at a smaller scale and little maintenance is needed. As such, geothermal energy is likely to be part of a future of sustainable energy.

Notes
How Geothermal Energy Works. (2009). Union of concerned scientists. August 17, 2012. Online. Available at http://www.ucsusa.org/cleanenergy/our-energy-choices/renewable-energy/how-
geothermal-energy-works.html

Puterski, Steve. (2012). Obama addresses geothermal energy. Lahontan Valley News Online.
http://www.lahontanvalleynews.com/article/20120821/NEWS/120829985/1055&ParentProfile=1045