As shown in Fig. 4.13, the USA has the highest installed capacity in the world. As of March 2008, geothermal electric power generation is occurring in eight U. S. states: Alaska, California, Hawaii, Idaho, Nevada, New Mexico, Utah and Wyoming. The installed capacities of these states are given in Fig. 4.15. The highest installed capacity is in California, providing about 4.5% of California’s electric energy generation in 2007, amounting to a net-total of 13,439 GWh. Hawaii has one power plant operating in the big island of Hawaii, called the Puna Geothermal Venture (PGV). PGV delivers an average of 25-35 MW on a continuous basis, supplying approximately 20% of the total electricity needs of the Big Island.
Former USSR with total potential of 768-1,902 MW and Yugoslavia with a potential of 50-100 MW
The GEA 2007 report considered France and Guadeloupe as one entity. Also development interest identified in six countries is not identified in 2010 – Korea, Solomon Islands, St Lucia, Tanzania, Uganda and Vietnam. Guadeloupe’s 15 MW installed capacity is included in the 2010 IGA report as part of France’s total installed capacity. Mainland France has 1.5 MW installed geothermal capacity in 2010 2007 source: Installed capacity from Ruggero Bertani, “World Geothermal Generation in 2007," GHC Bulletin, September 2007, p. 9; United States from Geothermal Energy Association, Update on US Geothermal Power Production and Development (Washington, DC: 16 January 2008); capacity factor from Ingvar B. Fridleifsson et al., “The Possible Role and Contribution of Geothermal Energy to the Mitigation of Climate Change," in Hohmeyer and Trittin 
According to the U. S. Bureau of Land Management, the Western states could generate 5,500 MW of geothermal energy from 110 plants by 2015, and projected to rise by another 6,600 MW by 2025.
Geothermal resources that can be used to generate electricity may be divided into the following four categories:
• Hydrothermal fluids
• Geopressurized brines
• Enhanced (Engineered) geothermal systems or Hot dry rock systems
is the oldest type of geothermal power plant. It was first used at Lardarello in Italy in 1904, and is still in operation. The Geysers in northern California, the world’s largest single source of geothermal power, also uses the same technology to generate electricity. These plants emit excess steam and very small amounts of other gases to the atmosphere. A schematic diagram of a dry steam power plant is shown in Fig.4.16.
Flash Steam Hydrothermal Power Plants
Flash steam power plants use the hydrothermal fluid, which is primarily water, for electricity generation. Water is available at temperatures above 200°C and at a high pressure. The basic arrangement of this system is shown in Fig. 4.17. Water is sprayed into a flash-tank that operates at a lower pressure than the inlet water, causing some of the fluid to rapidly vaporize, or flash, to steam. The steam is used to drive a turbine and a generator. Depending on the temperature of the water collected in the first flash-tank, a second tank may be used to further generate steam. However, this depends on the temperature and pressure of the steam and economics of the process.