Geothermal energy is literally the heat of the earth. This heat is abnormally high where hot and molten rocks exist at shallow depths below the earth’s surface. Water, brines, and steam circulating within these hot rocks are collectively referred to as geothermal resources. Geothermal resources often rise naturally to the surface along fractures to form hot springs, geysers, and fumaroles. For centuries, people have used naturally occurring hot springs as places to bathe, swim, and relax. More recently, some individuals have constructed buildings over these springs, transforming them into elaborate spas and resorts, thereby establishing the first direct use of geothermal resources for business purposes. Businesses have also established other direct uses of geothermal resources by drilling wells into the earth to tap the hot water for heating buildings, drying food, raising fish, and growing plants. Where the earth’s temperature is not high enough to supply businesses with geothermal resources for direct use, people have made use of the ground’s heat by installing geothermal heat pumps. Geothermal heat pumps consist of a heat exchanger and a loop of pipe extending into the ground to draw on the relatively constant temperature there for heat in the winter and air conditioning in the summer. Geothermal resources can also generate electricity, and this is their most economically valuable use today. Only the highest temperature geothermal resources, generally above 200 degrees Fahrenheit, are suitable for electricity generation. When companies are satisfied that sufficient quantities of geothermal resources are present below the surface at a specific location, they will drill wells to bring the geothermal fluids and steam to the surface. Upon reaching the surface, steam separates from the fluids as their pressure drops, and the steam is used to spin the blades of a turbine that generates electricity. The electricity is then sold to utilities in a manner similar to sales of electricity generated by hydroelectric, coal- fired, and gas-fired power plants. In the United States, geothermal resources are concentrated in Alaska, Hawaii, and the western half of the country, primarily on public lands managed by the Bureau of Land Management (BLM). The Congress set forth procedures in the Geothermal Steam Act of 1970 for leasing these public lands, developing the geothermal resources, and collecting federal royalties. Today, BLM leases these lands and sets the royalty rate, and the Minerals Management Service (MMS)—another agency within the Department of the Interior (DOI)—collects the federal geothermal royalties and disburses to the state governments its share of these royalties as required by law. In 2005, MMS collected $12.3 million in geothermal royalties, almost all of which was derived from the production of electricity. Geothermal resources currently account for about 0.3 percent of the annual electricity produced in the United States, or 2,534 megawatts— enough electricity to supply 2.5 million homes. Even though the percentage of electricity generated from geothermal resources is small nationwide, it is locally important. For example, geothermal resources provide about 25 percent of Hawaii’s electricity, 5 percent of California’s electricity, and 9 percent of northern Nevada’s electricity. As of January 2006, 54 geothermal power plants were producing electricity, and companies were constructing 6 additional geothermal power plants in California, Nevada, and Idaho that collectively will produce another 390 megawatts of electricity. Over half of the nation’s electricity generated from geothermal resources comes from geothermal resources located on federal lands in The Geysers Geothermal Field of northern California; in and near the Sierra Nevada Mountains of eastern California; near the Salton Sea in the southern California desert; in southwestern Utah; and scattered throughout Nevada. Industry and government estimates of the potential for electricity generation from geothermal resources vary widely, due to differences in the date by which forecasters believe the electricity will be generated, the methodology used to make the forecast, assumptions about electricity prices, and the emphasis placed on different factors that can affect electricity generation. Estimates published since 1999 by the Department of Energy, the California Energy Commission, the Geothermal Energy Association, the Western Governor’s Association, and the Geo-Heat Center at the Oregon Institute of Technology indicate that the potential for electrical generation from known geothermal resources over the next 9 to 11 years is from about 3,100 to almost 12,000 megawatts. A more comprehensive and detailed study of electricity generation from all geothermal resources in the United States was published in 1978 by the U.S. Geological Survey (USGS). This assessment estimated that known geothermal resources could generate 23,000 megawatts if all of them were developed. The USGS estimate is greater because it did not consider how much electricity could be economically produced, given competing commercial sources of electricity. In addition, the USGS estimated that undiscovered resources could generate an additional 72,000 to 127,000 megawatts. In short, geothermal resources that could generate electricity are potentially significant but largely untapped. In 2005, over 2,300 businesses and heating districts in 21 states used geothermal resources directly for heat and hot water. Nearly all of these are on private lands. About 85 percent of these users are employing geothermal resources to heat homes, businesses, and government buildings. While most users heat one or several buildings, some users have formally organized heating districts that pipe hot water from geothermal wells to a central facility that then distributes it to heat many buildings. The next most plentiful direct use application is for use by resorts and spas, accounting for over 10 percent of sites. About 244 geothermally heated resorts and spas offer relaxation and therapeutic treatments to customers in 19 states. Two percent of geothermal direct use applications consist of heated greenhouses in which flowers, bedding plants, and trees are grown. Another two percent of geothermal direct use applications are for aquaculture operations that heat water for raising aquarium fishes for pet shops; catfish, tilapia, freshwater shrimp and crayfish for human consumption; and alligators for leather products and food. Other direct use geothermal applications include dehydrating vegetables, like onions and garlic, and melting snow on city streets and sidewalks. The potential for additional direct use of geothermal resources in the United States is uncertain due to the geographically widespread nature of low-temperature geothermal resources and the many different types of applications. USGS preformed the first national study of low-temperature geothermal sites in 1982, but this study was not specific enough to identify individual sites for development. In 2005, the Geo-Heat Center at the Oregon Institute of Technology identified 404 wells and springs that might be commercially developed for direct use applications—sites that had the appropriate temperatures and are within 5 miles of communities. Geothermal heat pumps have become a major growth segment of the geothermal industry. They make use of the earth’s warmer temperature in the winter to heat buildings and use the earth’s cooler temperature in the summer for air conditioning. The Geothermal Heat Pump Consortium estimated that 1 million units were in operation in all 50 states as of January 2006. Because geothermal heat pumps are effective where ground temperatures are between 40 and 70 degrees F, they can be installed in almost any location in the United States and, therefore, constitute the most widespread geothermal application and represent the greatest potential for future development. The development of geothermal resources for electricity production faces major challenges, including high risk and financial uncertainty, insufficient transmission capacity, and inadequate technology. Geothermal groups reported that most attempts to develop geothermal resources for electricity generation are unsuccessful, that costs to develop geothermal power plants can surpass $100 million, and that it can take 3 to 5 years for plants to first produce and sell electricity. Although some geothermal resources are easy to find because they produce tell-tale signs such as hot springs, most resources are buried deep within the earth—at depths sometimes exceeding 10,000 feet—and finding them often requires an in- depth knowledge of the area’s geology, geophysical surveys, remote sensing techniques, and at least one test well. The risks and high initial costs associated with exploring for and developing geothermal resources limit financing. Moreover, few lenders will finance a geothermal project until a contract has been signed by a utility or energy marketer to purchase the anticipated electricity. Geothermal industry officials describe the process of securing a contract to sell electricity as complicated and costly. In addition, lack of available transmission creates a significant impediment to developing geothermal resources for electricity production. In the West where most geothermal resources are located, many geothermal resources are far from existing transmission lines, making the construction of additional lines economically prohibitive, according to federal, state, and industry officials. Finally, inadequate technology adds to the high costs and risky nature of geothermal development. For example, geothermal resources are hot and corrosive and often located in very hard and fractured rocks that wear out and corrode drilling equipment and production casing. Developing geothermal resources for direct use also faces a variety of business challenges, including obtaining capital, overcoming specific challenges unique to their industry, securing a competitive advantage, distant locations, and obtaining water rights. While the amount of capital to start a direct-use business that relies on geothermal resources is small compared to the amount of capital necessary to build a geothermal power plant, this capital can be substantial relative to the financial assets of the small business owner or individual, and commercial banks are often reluctant to loan them money. Challenges that are unique to certain industries include avoiding diseases in fish farms; combating corrosive waters used in space heating; and controlling temperature, humidity, and light according to the specifications of the various plant species grown in greenhouses.