Geothermal--To The Ends of the Earth

Geothermal power has found an unlikely location in Chena Hot Springs, Alaska. Why unlikely? Because Chena's geothermal temperatures only reach 168 degrees F--a temperature generally considered too low for profitable power generation.

When water cooler than 350 F is released from the pressure of a geothermal reservoir, it doesn’t convert to steam efficiently enough to drive a turbine directly. Anything less than 230 F was considered too marginal for the alternative: a binary system that uses water to heat a fluid with a lower boiling point. But that threshold was a product of geography, not technical feasibility, Holdmann realized. A binary system just requires a heat source and sink: 165 F water can produce electricity if the ambient air or surface water temperature is at least 100 degrees lower. While that may be tough to find in the deserts of Nevada, in Alaska cold air and water are abundant resources.

Now all she needed was a plant, built to one important spec: “We need things that work up here,” Holdmann says. “We don’t need a bunch of things that, yeah, you can do in a lab. We need something we can take to a village and use normal people to run it. And run it every day, because we don’t need it only half the time.”...Fortunately, United Technologies Corp. was looking for a partner to collaborate on a pilot project: an air-conditioning unit that had been reverse-engineered to run off geothermal water. Instead of putting in electric power to create areas of high and low temperature, Chena provides the heat differential and the plant puts out electric power.

The technology has the added benefit of solving two remaining hurdles to low-temperature power generation. First, air-conditioning refrigerant operates more efficiently at low temperatures than isopentane and other fluids typically used in power plants. Second, the components are already mass produced, which cuts the cost of a small, modular plant in half....Chena’s two 200-kilowatt modules provide more than enough power for the entire resort and have reduced the cost of electricity from 30 cents a kwh to only 5 cents. With a capital cost of $2.2 million, including exploration and drilling, the project is expected to pay for itself in four to five years.

This fall, Chena and United Technologies received a Department of Energy grant to install a demonstration plant at an oil or gas well in the United States. The nation’s wells produce at least 40 billion barrels of wastewater per year, much of it low to moderate temperature. That’s another 6000 to 11,000 megawatts of potential electricity, according to a study by Southern Methodist University in Texas. “We feel we just need to show that it works,” Holdmann says, “and companies will pick up on it.”___PopularMechanics

The United States is the world leader in geothermal development, with plants producing more than 3,000 megawatts of electricity. California is No. 1, but resources in such other Western states as Nevada, Utah, Idaho and Oregon are being developed. Nevada has been dubbed the "Saudi Arabia of geothermal."

A recent Massachusetts Institute of Technology study found the amount of geothermal power that realistically could be recovered from deep drilling would represent almost 3,000 times the amount of energy consumed in the United States....Petty, who worked on the MIT study, said the intermountain West has emerged as ground zero for geothermal resources. ____Source
New developments in geothermal energy go far beyond geothermal hot springs to "hot dry rock" geothermal power technology. An Australian company, Geodynamics, is helping to blaze the "hot dry rock" energy trail.

Hot dry rock technology was invented to draw energy from deep underground areas where geothermal heat is abundant, but no water exists to carry the heat to the surface. To tap the energy in this hot dry rock, a well is drilled into it and water is injected at high pressure, forming fissures in the rock to create a geothermal "reservoir" consisting of water-impregnated fractured rock. At least one "production" well is then drilled into the reservoir to draw the hot water back to the surface. A completed facility would direct the hot fluid from the production well to a power plant, which would extract the heat from it to produce power, after which the cooled fluid would be injected back into the ground__Technology Newsdaily

Much of the technology for geothermal power development has already been created by the oil and gas industries. Geothermal mining engineers will develop better ways of approaching specific drilling sites as more knowledge and experience with the techniques are accumulated.

The promise of clean, sustainable electric power--which unlike other renewables can be used as baseload power--will be welcomed by most communities that are able to maintain the facilities.