In the most simplistic definition geothermal energy is thermal energy, heat, which is generated and stored within the Earth.  Geothermal energy is considered a renewable resource for it is continuously being produced from the energy radiating out from the core of the earth.  It is relatively clean and relatively environmentally friendly when one compares it to fossil fuels.  It is one of the few renewable energy technologies that can provide a supply of continuous reliable energy.     

 In the most simplistic systems geothermal energy is collected through a system of pipes buried within the earth; the bigger the project the more complex and deeper the piping.  The pipes carry water into the earth’s crust, which warms the water turning it steam, then is pumped back to a generator.  The generator converts the steam into energy or can be used for heating and cooling.  Areas heavy within tectonic activity are more suitable for large scale operations. Geothermal energy originates primarily from the radioactive decay of minerals within the Earth.  This causes a continuous conduction of thermal energy in the form of heat from the core to the surface.  Therefore, it is renewable and naturally occurring.

The most common use for geothermal energy is in home heating and cooling.  For example, in Iceland 93% of homes are heated with geothermal energy which saves Iceland over $100 million annually in avoided oil imports. Approximately 11,400 megawatts are produced worldwide utilizing geothermal power.  New technology has allowed home heating and cooling to be more applicable within many countries.  Enhanced geothermal systems, which are the largest scale geothermal projects, can provide energy for approximately $0.054 per kW•h. Geothermal power requires no fuel (except for the pumps), and is renewable which makes it sustainable. 

The main negative of geothermal energy is the cost of setting it up.  Drilling and exploration, of deep resources, cost an extreme amount.  On average a large scale geothermal energy plant cost about $10 million to drill and there is a 20% failure rate.  There are 3 rather common methods of harnessing geothermal energy.  The first relies upon pumping water into Earth's crust, the water is heated, and then rises to the surface. The steam is used it to power an electric generator.  The other methods are extremely similar, yet use more machinery to maximize the power provided by the steam. For example a chemical, isobutene, can be used instead of water.  The chemical boils at a lower temperature, therefore the production of steam is easier.  The maintenance is rather minimal for the only maintenance is for the generator; the piping will require little to no maintenance over its lifespan. The typical time for return of investment cost varies greatly due to a multitude of factors.  Positioning, geography, and ground temperature are but a few of these factors. 

It takes approximately 3-10 years to the return of investment costs for residential use.  This estimation does include government support in the form of tax credit.  Large scale operations will take longer due the cost of drilling and exploration.   Geothermal energy uses naturally occurring energy and is relatively clean, so it does have many advantages.  The primary disadvantages is the cost of instillation, potential seismic activity, and in theory instillation requires a large amount of land (lay the pipes horizontally), yet for more money one can lay the pipes vertically.

From a social aspect it is environmentally friendly, and shouldn’t produce noise or smell. Overall, I feel that it would a socially acceptable form of energy.  It tends to be a physically demanding energy supply for it does require drilling and a lengthy set up.  It tends to be more viable in some area then others, due to the geography.  It does require professional instillation, yet if set up correctly upkeep of the system will be minimal.  

New research and technology is making geothermal energy much more viable than previously.  New techniques within mining, fracking in particular, have allowed for the well’s lifespan and overall productivity to be increased.  Geothermal wells can release greenhouse gases, but the emissions are rather minimal compared to fossil fuels.  Enhanced geothermal systems (EGS), which are the large scale geothermal operations, actively inject water into wells. The water is injected under high pressure to expand existing rock fissures to enable the water to flow freely. Hot water from geothermal sources may contain trace amounts of toxic elements such as mercury, arsenic, boron, and antimony. These form from condensation, so advances in technology should reduce this problem.  Enhanced geothermal systems can trigger earthquakes as part of the hydraulic fracturing during their setup.

The Earth's geothermal resources are theoretically more than adequate to supply humanity's current energy needs, but with current technology only a very small percent can be profitable used.  The cost of generating geothermal power has decreased by approximately 25% over the past two decades.

Questions & key points for the class to discuss

            Would you be willing to potentially experience over 10,000 seismic events during the setup of an enhanced geothermal system?  This very scenario occurred within Switzerland over the course of a week due to the initial water injection; a process resembling fracking. 

Works cited

Howard, Brian. "Estimating Geothermal Cost and Payback." the daily green. N.p.. Web. 17 Oct 2013. http://www.thedailygreen.com/green-homes/latest/geothermal-cost-payback-0911

. N.p.. Web. http://www.advantagesofsolarenergy4all.com/geothermal-energy-pros-and-cons.html

"Smart energy." . N.p.. Web. http://www.smart-nrg.com/geofaq.php

"union of concern scientists ." . N.p.. Web. http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/how-geothermal-energy-works.html

Villanueva, John. "How Does Geothermal Energy Work." . N.p.. Web. 17 Oct 2013. http://www.universetoday.com/45518/

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