Solar energy installation at the Weizmann Institute in Rehovot, Israel. Photo by Alla Leitus. |
Arizona Electric Power Cooperative (AEPCO), which provides electricity to six distribution co-ops serving more than 120,000 consumer-members, is part of a multi-state consortium of utilities looking at a solar-thermal facility in Arizona or Nevada.
The technology, often described as concentrating solar, uses concave troughs to heat a liquid to about 700 degrees Fahrenheit to create steam that spins turbines used to generate power.
“This technology can be supplemented with natural gas backup, using the same equipment,” explained Dennis Criswell, vice president of marketing and strategic ventures at AEPCO.
“Instead of a boiler producing the steam, you use the concentrated solar panels to create it,” Criswell added. “Once you get to the steam portion of the process, it is the same technology we’ve used to produce electricity for 150 years.”
The Benson-based G&T is pursuing the 250-megawatt project with Arizona Public Service, Salt River Project, Tucson Electric Power, Xcel Energy and the Southern California Public Power Authority. The projected output could supply power to about 75,000 homes.
Working as The Joint Development Group, the participants are seeking a qualified developer to finance, build and operate the project in return for long-term purchase agreements ensuring a market for the power it would produce.
The technology is particularly suited to desert regions where large swaths of undeveloped land, with limited agricultural or recreational potential, could meet the project’s relatively large acreage requirements. One site under consideration is south of Las Vegas, while another is west of Phoenix.
“It takes between 4.5 and 5 acres of solar panel troughs for each megawatt of generating capacity,” said Criswell. That means the troughs will cover a minimum of 1,200 acres, with additional land needed for the plant, support structures and other essential requirements.
“It has to be reasonably flat, with a slight slope for drainage,” he added. Sites under consideration would ideally be located near existing power transmission corridors.
Concave mirrors would be mounted on automated pedestals that would follow the arc of the sun from dawn until dusk. The heat would be conducted through a small tube, connected to a heat exchanger used to produce steam from water or a liquid such as pentane, which has a lower boiling point.
The plant could have excess conductive capacity to allow storage of heated oil to produce electricity overnight or on overcast days.
Officials at the G&T consider the technology among the most cost-effective options for meeting the mandate to produce 15 percent of the state’s electricity from renewable sources by 2025.
Potential bidders are expected to submit proposals in March, with a decision expected in June, said Criswell. “The goal is to have power flowing from the project by 2012.”
This article by Derrill Holly was reprinted with permission from Electric Co-op Today.