This is how heat from a volcano can be used to power an entire town

Active volcanoes are proving to be a hot commodity in the global race to transform to renewable energy as regions all over the world that reside near these natural wonders work to harness their heat.

Geothermal energy, the process of using the heat from the inner cores of the earth to create power, is one of the most sustainable forms of energy, experts told ABC News. The technology works by pushing hot water from the reservoirs of volcanoes and geysers toward the surface, which then turns to steam due to the reduced pressure.

The steam then gets pushed toward a turbine, which then generates electricity.

There are virtually no carbon emissions from this process once the infrastructure is in place, other than the diesel-powered pump required to bring the water and steam to the surface, Pete Stelling, a retired geology professor formerly at Western Washington University, told ABC News.

Geothermal energy is considered one of the most sustainable energy sources, Amanda Kolker, program manager for geothermal energy at the National Renewable Energy Laboratory, told ABC News. "

It's also a relatively invisible renewable source, both figuratively and, you know, metaphorically, because it's literally underground," Kolker said.

If there are any leaks in the pipes, the substance leaking out is simply water or steam, and there is no hazardous waste, Jackie Caplan-Auerbach, a professor of geology at Western Washington University, told ABC News.

Other than the land use and the environmental damage done by the initial construction, there are no other hazards, Caplan-Auerbach.

"There are no refineries that need to be built or shipped to," she said. "There's no gas station on the corner that you need to develop to sell the product."

The caveats to geothermal energy, however, are cumbersome, Stelling said.

The technology is only available in select places around the world. What makes a region ideal for harnessing geothermal energy is the availability of something "really hot" near the surface.

The vast majority are near active volcanoes, where an underground magma chamber heats the water around it, simply because they are the easiest locations to find, Stelling said. Geysers and inactive volcanoes can also be options, he added.

The residents and businesses who can benefit from geothermal energy need to reside near the plant, as it is not possible to transport the energy, Stelling said. Instead, the energy is placed directly into the power grid.

In addition to determining whether the fractures in the ground are big enough to allow water to flow through them, geologists also have to consider the inherent risk of constructing an energy plant near an active volcano and whether a possible eruption can damage the plant, Caplan-Auerbach said.

The biggest roadblock to installing geothermal production plants is the cost, Stelling said. Construction crews must drill several kilometers into the earth and pull the hot water out of open fractures in the ground. The turbine will then run off of the steam and produce electricity.

A construction project aimed at bringing geothermal energy to Unalaska, a city in the Aleutian Islands in Alaska, is expected to cost about $235 million to build a plant powered by the Makushin Volcano.

"The initial upfront investment is pretty high," Stelling said. "But once you get the equipment in place, and you establish that geothermal field, it works really well. And it's really cheap."

The introduction of geothermal energy into a community has the ability to decrease energy costs for residents and businesses, especially in Alaska, which is so dependent on importing oil for heat and electricity, Stelling said. The wind in the Aleutian Islands is so heavy that it "just blows the turbines apart," making wind production impossible, he added.

Geothermal energy currently generates about 3.7 gigawatts of electricity in the United States, according to the Department of Energy. A new analysis showed that geothermal energy could provide 90 gigawatts of "firm, flexible power" to the U.S. grid by 2050.

Many who live near geothermal energy plants may not know that their cities are powered by the heat of the earth, Kolker said. For example, San Francisco at one point obtained a third of its power from the Geysers, which is the world's largest geothermal complex. The Geysers, located in the Mayacamas Mountains 72 miles north of the city, contain 18 geothermal power plants that draw steam from more than 350 wells.

The U.S. Department of Energy is currently researching the extent of geographical constraints that geothermal energy presents, Kolker said.

"There are efforts to try to expand the geographic possibilities for geothermal using more unconventional approaches," she said.

The Department of Energy announced funding of up to $74 million on Wednesday for up to seven pilot projects that will test the efficacy and scalability of enhanced geothermal systems.

"Advances in enhanced geothermal systems will help introduce geothermal energy in regions where, until recently, the use of this renewable power source was thought to be impossible," said U.S. Secretary of Energy Jennifer M. Granholm in a statement. "These pilot demonstrations will help us realize the enormous potential of the heat beneath our feet to deliver clean, renewable energy to millions of Americans."