Geothermal Energy http://www.calenergy.com/aboutus4.aspx http://www.clean-energy-ideas.com/articles/disadvantages_of_geothermal_energy.html http://www1.eere.energy.gov/geothermal/resources.html http://www.geothermal.org/GeoEnergy.pdf http://geothermal.marin.org/index.html http://smu.edu/geothermal/ http://www.geo-energy.org/pressReleases/Geothermal_Energy_On_Launch_Trajectory_in_2009_-_December_14_2009.pdf http://smu.edu/geothermal/GPW_TX/SMU%20_Teachers_Geothermal_Resource_projects.pdf

Overview Geothermal energy, as the word implies is heat from deep in the earth. It is a clean, renewable energy source because it relies on a practically unlimited source of heat from the earth. It is used in 3 main ways: Directly - Since mankind first found the places where hot water seeped to the earth’s surface, we have used it for pleasure and believed in its medicinal powers. Resorts around the world use it. Hot water near the earth’s surface is used directly for residential, industrial, and commercial uses to heat homes and offices, commercial greenhouses, fish farms, food processing facilities, gold mining operations, and a variety of other applications. Dehydration, or the drying of vegetable and fruit products, is the most common industrial use of geothermal energy.

Overview Continued Geothermal heat pumps can be used all over the country to pump liquid into the ground to bring heat to buildings in the winter and reversed to cool buildings in the summer. Hotter liquid from deep in the earth is also used to generate electricity. There are three geothermal power plant technologies being used to convert hydrothermal fluids to electricity. The conversion technologies are dry steam, flash, and binary cycle. Most geothermal electricity generation is in the western states .

Advantages A geothermal electricity plant produces continuous, reliable “baseload” power. Geothermal energy produces very little pollution. Geothermal electricity generation plants release less than 1% of the carbon dioxide emissions and 97% less acid rain-causing sulfur compounds than are emitted by fossil fuel plants. After the steam and water from a geothermal reservoir have been used, they are injected back into the earth so there are not disposal problems. The land needed for a geothermal power plant is less than for an oil, gas, coal, or nuclear power plant.

Advantages Continued The running costs for geothermal plants are very low because: no fuel is used to generate the power. there are no costs for purchasing, transporting, or cleaning up of fuels to generate the power. It is resistant to interruptions of power generation due to weather, natural disasters or political rifts that can interrupt transportation of fuels. You only need to provide power to the water pumps, which can be generated by the power plant itself. Oil & gas wells can be converted to geothermal production if the temperature is high enough deep in the well.

Disadvantages Geothermal energy for electricity generation is often found in areas where it is not practical to build a plant such as near volcanoes or fault lines. It is possible for a geothermal site to just stop producing steam with no warning or indication as to how long it will not be producing. An environmental disadvantage is that gases can escape through the holes which must be contained and disposed of properly.

Technical Considerations Heat is continuously produced deep in the earth by the decay of radioactive particles. This heated magma comes near the earth’s surface along the lines of the continental plates and can be observed in the form of volcanoes, geysers and hot springs. Geothermal energy is located by land surveys which often take many years to complete. The survey looks for sufficient heat deep in the earth with heat that will be sustainable for a significant amount of time, rock that is soft enough to drill through, and an environment that is fit for a power plant. The vast majority of geothermal energy within drilling reach is in dry and non-porous rock called hot dry rock,(HDR) Enhanced geothermal system

Technical Considerations Continued (EGS) technologies create geothermal resources in this HDR through hydraulic stimulation. Geothermal electrical energy is generated by pumping water through holes drilled deep into the earth’s crust where the heated magma heats it to hundreds of degrees Celsius. This heated water is used to create steam to drive a turbine in a power generator. The water can be reused or pumped back into the earth.

Technical Considerations Continued There are different types of geothermal power plants. Most small geothermal power plants are binary power plants. If the water available is less than 300 degrees F, it is not hot enough to produce steam so the hot water is fed into a heat exchanger. The heat from the water is absorbed by a liquid which boils at a lower temperature, such as isopentane. The steam then is used to turn turbines to produce electricity. The isopentane condenses back into a liquid state and can be used again.

The United States generates more geothermal electricity than any other country, but the amount of electricity it produces is less than 0.5% of all electricity produced in United States. Four States have geothermal power plants: California has 34 geothermal power plants which produce almost 90% of U.S. geothermal electricity. Nevada has 15 geothermal power plants. Hawaii, Montana, and Utah each have one geothermal plant. Texas has great potential for geothermal generation when the technology is developed to use the heat deeper in the earth.

The U.S. map below shows estimated subterranean temperatures at a depth of 6 kilometers as determined by synthesized data from thermal conductivity, thickness of sedimentary rock, geothermal gradient, heat flow, and surface temperature. Texas is estimated to have 910,000 EJ of Thermal Energy … enough to power the state of Texas for the next 100 years.

http://www1.eere.energy.gov/geothermal/geomap.html

Economic Considerations Although there is no cost for the fuel, the cost to construct a geothermal plant is higher than fossil fuel plants. Also geothermal well drilling is more expensive than oil and gas wells accounting for 30-50% of a geothermal project’s total outlay. A typical geothermal plant capable of generating 50 megawatts, enough to meet the needs of 50,000 people would cost about $40 million to design and build. Exploration and field development of wells and pipelines would cost about $70 million. Operating and maintenance costs range from $0.01 to $0.03 per kWh. Most geothermal power plants can run at greater than 90% of the time.

Economic Considerations Continued In the American Recovery and Reinvestment Act of 2009, Congress appropriated $400 million for the DOE Geothermal Technologies Program. In October 2009, the U.S. Department of Energy awarded an additional $338 million for the development of geothermal energy. These grants will support 123 projects in 39 states, with recipients including private industry, academic institutions, tribal entities, local governments, and DOE’s National Laboratories.  The new geothermal plant projects underway in 2009 will have the potential to produce 140 MW of new geothermal power in fourteen states. These projects will be completed in 3-5 years.

Legal Regulatory Considerations Progress in geothermal energy has expanded greatly in the past 5 years due to changes in state and federal policies. Legal considerations affecting geothermal energy include: state renewable energy standards federal tax credits and incentives which attract investors federal and state land becoming more available research and development support from the DOE.

Anticipated Status An exciting future for geothermal energy has already begun and promises to be very useful for relieving our energy needs. Research is developing more cost effective methods for exploration , drilling, and transmission of geothermal energy. One area that holds great promise is the use of oil field co-production. Since water is heavier than oil and gas, it is at the bottom of many of those wells. Technology is being developed to utilize that fluid where it is over 200°F instead of abandoning the well. Researchers at Southern Methodist University believe that oil field co-production can become an important source of power. They have identified potential areas for similar development that could bring thousands of megawatts of new power on line.

Anticipated Status Continued Another important possibility for the use of oil and gas wells is that CO2 is being researched to be used as a fluid for heat extraction. Its reduced surface friction and increased heat capacity over water would create a geothermal power plant that is carbon negative. This research is enticing to hydrocarbon companies who see geothermal as a carbon offset mechanism.

Summary Geothermal energy holds great potential to relieve our dependence on petroleum resources for electricity generation. Research and development is needed in the areas of exploration, drilling, and power plant costs in order to make geothermal more immediately profitable.