Geothermal Power

Geothermal energy harnesses the heat energy stored beneath the Earth's surface. This heat originates from the original formation of the planet and from radioactive decay of minerals.

In 2006, a report from the Geothermal Energy Association concluded that Nevada was on-track to produce over 1000 MW of geothermal power over the next 3 to 5 years. This level of geothermal production would meet roughly a quarter of the state's total power needs. Author Dan Fleischmann concludes that this dramatic success is due to four major factors: the state's Renewable Portfolio Standard; the extension of the federal production tax credit to include geothermal energy; the Bureau of Land Management's efforts to reduce its leasing backlog; and the Department of Energy's support for cost-shared drilling, technical assistance, and the work of the Great Basin Center for Geothermal Energy at the University of Nevada Reno. The report identified up to twenty-nine new geothermal power projects under development in Nevada. The report found that new power plants would produce as much as 853 MW. When completed, these new plants would quadruple the existing 276.4 MW capacity from Nevada's currently operating fifteen power plants.

How Geothermal Energy Works

The process of tapping into and using geothermal energy typically involves the following steps:

1. Resource Exploration: Geologists locate geothermal resources using a variety of methods, such as ground temperature surveys, geophysical and geochemical tests. Geothermal reservoirs are typically found in regions of volcanic activity, where the Earth's crust is thinner and heat is closer to the surface.
2. Well Drilling: Once a suitable location is identified, wells are drilled into the ground to tap into the geothermal reservoir. These wells can be several kilometers deep, depending on the distance to the reservoir.
3. Steam and Hot Water Extraction: Hot water or steam from the geothermal reservoir rises up through the wells to the surface. The type of geothermal power plant depends on the state of this geothermal fluid:
   • Dry Steam Plants: The simplest type of geothermal power plant, used when the well produces mainly hot steam. The steam is piped directly from the well to drive a turbine, which powers a generator to produce electricity.
   • Flash Steam Plants: Used when the well produces high-pressure hot water. The water is allowed to "flash" into steam in a low-pressure tank, and the steam drives a turbine and generator. Any leftover water and condensed steam are injected back into the reservoir.
   • Binary Cycle Plants: Used when the well produces lower-temperature hot water. The hot water is passed through a heat exchanger, where it heats a second liquid (the "binary" fluid) that boils at a lower temperature than water. The vapor from the binary fluid drives a turbine and generator. The geothermal water is then re-injected into the ground.
4. Electricity Generation: The mechanical energy from the turbines is used to drive an electric generator, which produces electricity. This electricity can then be distributed through the grid to homes, businesses, and industries.
5. Re-injection: To sustain production over time, the fluid (water or steam) is usually re-injected into the ground after it has been used to produce electricity. This helps maintain pressure in the reservoir.

Geothermal energy has several advantages: It is renewable, environmentally friendly, and a constant (baseload) source of power, unaffected by weather or time of day. The main limitations are that suitable sites are not available everywhere, and there can be high upfront costs for drilling and plant construction. Additionally, some geothermal sites, over time, may cool down faster than they recover heat, although sustainable management and re-injection strategies can mitigate this.