The heat in the upper six miles of Earth's crust contains many times the energy found in all the world's oil and gas reserves combined, experts say.
Despite the abundance, researchers say, only 10,700 megawatts of geothermal electricity generating capacity have been harnessed worldwide, Inter Press Service reported.
The oil, gas, and coal industries have been providing cheap fuel by omitting the costs of climate change and air pollution from fuel prices, environmentalists charge, so little investment is being made in geothermal energy, which has been growing at scarcely 3 percent a year, the report said.
About half the world's existing generating capacity is in the United States and the Philippines, with Indonesia, Mexico, Italy, and Japan accounting for most of the remainder. About two dozen countries convert geothermal energy into electricity.
El Salvador, Iceland, and the Philippines get 26 percent, 25 percent, and 18 percent, respectively, of their electricity from geothermal power plants.
In 2006, a team of scientists and engineers assembled by the Massachusetts Institute of Technology assessed U.S. geothermal electrical generating potential.
Geothermal electricity technology involves drilling down to the hot rock layer, fracturing the rock and pumping water into it, and then extracting the superheated water to drive a steam turbine.
The MIT team said the technology would provide enough geothermal energy to meet U.S. needs 2,000 times over.
About 152 power plants are under development in 13 U.S. states and are expected to nearly triple U.S. geothermal generating capacity, now at about 3,000 megawatts.
