Resource Details

In the U.S., the higher quality geothermal resources (both hydrothermal and HDR) are predominately located in th e western states, including Alaska and Hawaii, as shown in the map below. Development of hydrothermal resources for electric power generation has been limited to California, Nevada, Utah, and Hawaii. Most of the western U.S. contains HDR resources, with the highest grade resources probably located in California and Nevada.

Scientists have made various estimates of the geothermal resource in the U.S. The U.S. Geologic Survey (USGS) completed the nation's most comprehensive assessment of geothermal resources, documented in USGS Circular 790 , published in 1978 [2]. Circular 790 estimated the known, accessible hydrothermal resource to be about 23,000 M W

Figure 1. Geothermal resource quality in the United States.

>100 mWm-2

80-100 mWm-2

60-80 mWm-2

40-60 mWm-2

<40 mWm-2

Figure 1. Geothermal resource quality in the United States.

of electric capacity for 30 years, and the as yet undiscovered accessible hydrothermal resource to be 95,000 to 150,000 MW of electric capacity for 30 years. It should be noted that the accessible resource is that which is accessible wit h current technology, but not necessarily economic. Considerable geothermal exploration and development in the U.S . since the mid 1950s has identified and characterized (moderately well) about 3,000 to 5,000 MW of hot water hydrothermal resources. Exploration work in the Cascade Mountains of Oregon in the 1990s seems to preclude the existence of the significant hydrothermal resource once estimated for that area.

An unpublished study by the University of Utah Research Institute in 1991 estimated about 5,000 MW of electri c capacity for 30 years would be available at a cost of 5.50/kWh [4]. Recent preliminary analyses by the authors of the geothermal TCs suggest that for Hydrothermal electricity in 1997, no capacity would be available at <20/kWh, about 5,000 MW would be available at <30/kWh, and about 10,000 MW available at <50/kWh. If the predicted technology improvements for 2020 hold true, then 6,000 MW would be available at <20/kWh, about 10,000 MW available at <30/kWh, and about 19,000 MW available at <50/kWh. (These prices are levelized in constant dollars, using th e "GenCo" financing assumptions described in Chapter 7.) Also note that the lowest prices given here are lower tha n the price calculated for the characterized geothermal flash power plant because the characterized plant is for a "typical" rather than "least expensive" geothermal high-temperature reservoir.

Although the potential of the nation's HDR resource has been studied less and is less well understood, it is believe d to be very much larger than that of the hydrothermal resource. Tester and Herzog estimated the U.S. high grade HDR resource to have the potential of generating 2,800,000 MW at a cost <8.70/kWh (1996$) using 1990 technology [5]. For the year 2020 technology projected in the Hot Dry Rock TC, the current authors estimate that about 2,000,000 MW would be available from very high quality resource regions at <50/kWh, and that as much as 17,000,000 MW (about

24 times the current installed electric capacity in the U.S.) of HDR would be available at <60/kWh. (The economic assumptions here are the same as stated in the paragraph above.)

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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