Phoenicians, your air conditioners will now run partly on geothermal energy from Utah.
Some 350 miles to the north of the Valley of the Sun, Enel Green Power’s Cove Fort geothermal power plant has begun operations. The 25-megawatt binary cycle plant is expected to produce about 160 gigawatt-hours of energy per year, which will go to the Salt River Project – a public utility serving parts of central Arizona, including much of Phoenix – under a 20-year agreement.
Geothermal resources are classified as low, medium or high enthalpy, a measure of the heat content in the fluids. Cove Fort is medium enthalpy, Enel said, and as is now common for such resources, it uses binary cycle technology to turn that heat into electricity. What that means is that unlike dry steam and flash steam systems, the water or steam from the geothermal reservoir never comes in contact with the turbine/generator units. As the U.S. Department of Energy explains:
Low to moderately heated (below 400°F) geothermal fluid and a secondary (hence, “binary”) fluid with a much lower boiling point than water pass through a heat exchanger. Heat from the geothermal fluid causes the secondary fluid to flash to vapor, which then drives the turbines and subsequently, the generators.
Binary cycle power plants are closed-loop systems, so except for water vapor, they have no emissions.
Salt River Project relies on a lot of coal generation, from power stations in Arizona, Colorado and New Mexico, but is aiming to get 20 percent of its retail electricity requirements through sustainable resources by 2020. Solar has been an obvious go-to source, but geothermal is coming on: In September, the utility contracted to purchase 50 MW of geothermal energy from the Salton Sea area in California. SRP also has agreements to purchase geothermal energy from the Hudson Ranch plant in Southern California which opened last year.
For Utah, this project boosts its operating installed geothermal capacity from 48 MW to 73 MW. That’s the third most in the nation, though it’s far behind No. 2 Nevada (518 MW) and top dog California (2,732 MW). But geothermal boosters think Utah can do a lot better, particularly in light of recent research revealing a potentially well-placed resource in the Black Rock Desert.