Enhanced geothermal energyNew approach would boost use of geothermal energy
Existing U.S. geothermal power plants generate up to 3.4 gigawatts of energy, making up about 0.4 percent of the nation’s energy supply. Geothermal power is generated by tapping the heat that exists under the Earth’s surface to extract steam and turn power plant turbines. Conventional geothermal power plants rely on the natural presence of three things: underground water, porous rock, and heat. A new approach to geothermal power, called enhanced geothermal systems, pumps fluids underground, a step which is called “reservoir stimulation,” to enable power production where conventional geothermal doesn’t work. It is estimated that enhanced geothermal systems could boost U.S. geothermal energy output 30-fold to more than 100 gigawatts, or enough to power 100 million typical American homes.
More American homes could be powered by the earth’s natural underground heat with a new, nontoxic, and potentially recyclable liquid which is expected to use half as much water as other fluids used to tap into otherwise unreachable geothermal hot spots.
The fluid might be a boon to a new approach to geothermal power called enhanced geothermal systems. These systems pump fluids underground, a step which is called “reservoir stimulation,” to enable power production where conventional geothermal doesn’t work.
The new reservoir stimulation fluid features an environmentally friendly polymer which greatly expands the fluid’s volume, which creates tiny cracks in deep underground rocks to improve power production. This fluid could also substantially reduce the water footprint and cost of enhanced geothermal systems. A PNNL release reports that a paper describing the fluid has been published by the Royal Society of Chemistry in an advance online version of the journal Green Chemistry.
“Our new fluid can make enhanced geothermal power production more viable,” said lead fluid developer Carlos Fernandez, a chemist at the Department of Energy’s Pacific Northwest National Laboratory. “And, though we initially designed the fluid for geothermal energy, it could also make unconventional oil and gas recovery more environmentally friendly.”
Natural power beneath us
Geothermal power is generated by tapping the heat that exists under the Earth’s surface to extract steam and turn power plant turbines. Conventional geothermal power plants rely on the natural presence of three things: underground water, porous rock, and heat. Existing U.S. geothermal power plants generate up to 3.4 gigawatts of energy, making up about 0.4 percent of the nation’s energy supply.
Enhanced geothermal power can be generated at sites where heat exists, but is not easily accessible because of impermeable rock or insufficient water. A 2006 report, led by the Massachusetts Institute of Technology, estimates enhanced geothermal systems could boost the nation’s geothermal energy output 30-fold to more than 100 gigawatts, or enough to power 100 million typical American homes.
Interested in this potential, DOE has funded five enhanced geothermal system demonstration projects across the country. At one demonstration project in Nevada, enhanced geothermal methods increased a conventional geothermal plant’s productivity by 38 percent. The use of enhanced geothermal systems, however, has been limited due to technical challenges and concerns over their cost and heavy use of water.
