World's largest solar installation to use Stirling engine technology

ROSEMEAD, CA, USA -- A Stirling engine is commonly referred to as an "external combustion engine" in contrast to the "internal combustion engines" found in most vehicles. Combine a Stirling engine with solar as the source of heat, and you have a highly efficient means of converting solar power into usable energy.

On Aug. 8, 2005, President Bush toured the DOE's National Solar Thermal Test Facility at the Sandia National Laboratories complex, situated on Kirtland Air Force Base in Albuquerque, N.M., where he signed the energy bill.

Now they are ready to go big-time, with an agreement signed Tuesday with Edison International (NYSE:EIX) a subsidiary of Southern California Edison (SCE), the nation's leading purchaser of renewable energy.

On Tuesday they announced an agreement that could result in construction of a massive, 4,500-acre solar generating station in Southern California. This comes to around seven square miles, with a perimeter of nearly 30 miles. The completed power station would be the world's largest solar facility, capable of producing more electricity than all other currently-operating U.S. solar projects combined.

This signing was a day after President George W. Bush visited their Sandia National Laboratories installation where they have six prototypes in operation, having chosen this location as his backdrop for the signing of the Energy bill.

Signed Tuesday, the 20-year power purchase agreement, which is subject to California Public Utilities Commission approval, calls for development of a 500-megawatt (MW) solar project 70 miles northeast of Los Angeles using innovative Stirling-engine/solar-dish technology. This is enough power to run approximately half a million homes.

According to the California Energy Commission, there are 966 power plants in California that generate more than 0.1 MW. Of those, a 500 MW plant would be in the top 3% for size.

Initially, Stirling would build a one-MW test facility using 40 of the company’s 37-foot-diameter dish assemblies. (Each dish generates 25 kilowatts.) This phase is slated to be completed in the first quarter of 2007. One of the 40-unit arrays capable of a 1 MW output, will be dubbed a "solar power group" and will be the basis of modular calculations for future installations.

Subsequently, the 20,000-dish array is to be constructed near Victorville, California, during a four-year period, starting in early 2008. If Edison opts for the additional 350 MW installation, that will take two more years, and will bring the total number of panels to 34,000.

“At a time of rising fossil-fuel costs and increased concern about greenhouse-gas emissions, the Stirling project would provide enough clean power to serve 278,000 homes for an entire year,” said SCE Chairman John Bryson. “Edison is committed to facilitating development of new, environmentally sensitive, renewable energy technologies to meet the growing demand for electricity here and throughout the U.S.”

“We are especially pleased about the financial benefits of this agreement for our customers and the state,” said Alan Fohrer, SCE chief executive officer. “The contract requires no state subsidy and provides favorable pricing for ratepayers because tests have shown the Stirling dish technology can produce electricity at significantly lower costs than other solar technologies.”

Gil Alexander, spokesperson for Southern California Edison said, "We operate in a competitive marketplace. While [for confidentiality reasons] we cannot give out precise dollar amounts for how much these installations will cost, we believe the final agreement is very beneficial to our customers. We do not need any subsidies to make this work."

Although Stirling dish technology has been successfully tested for 20 years, the SCE-Stirling project represents its first major application in the commercial electricity-generation field. Experimental models of the Stirling dish technology have undergone more than 26,000 hours of successful solar operation. A six-dish model Stirling power project is currently operating at the Sandia National Laboratories in Albuquerque, New Mexico.

However, this isn't the first commercial application of Stirling engine technology. For instance, Swedish submarines use Stirling engines for propulsion. (ref)

The Stirling dish technology converts thermal energy to electricity by using a mirror array to focus the sun’s rays on the receiver end of a Stirling engine. Each panel tracks azimuth and elevation to keep the sun’s rays focused at greatest intensity possible.

The internal side of the receiver then heats hydrogen gas which expands. The pressure created by the expanding gas drives a piston, crankshaft, and drive-shaft assembly much like those found in internal combustion engines but without igniting the gas. The drive shaft turns a small electricity generator. The entire energy-conversion process takes place within a canister the size of an oil barrel. The process requires no water and the engine is emission-free.

Tests conducted by SCE and the Sandia National Laboratories have shown that the Stirling dish technology is almost twice as efficient as other solar technologies. These include parabolic troughs which use the sun’s heat to create steam that drives turbines similar to those found in conventional power plants, and photovoltaic cells which convert sunlight directly into electricity by means of semiconducting materials like those found in computer chips.

While the number of potential applications for this technology is huge, in the near term Stirling Energy Systems will be keeping their focus on these utility installations.

It was in a news item I saw about a month ago. Can't find it now. I am tremendously skeptical about their claims for 80% efficiency. Probably a hobbyist trying to raise big bucks from investors so he can build bigger toys, I'm afraid.

Current small Stirlings I can find run about 20% and are sold as "low polution" stationary power sources in California. This one is fairly compact. Notice that what you can see looks like an aero engine, and is sure to be very expensive. Pretty, though. Maybe 30 kw, about 45 - 50 horse power. Obviously hand made.

These machines are obviously not ready for prime time.

Approaches certainty as a limit that this project is a net resource loss. Tremendously so on the human labor, that is for sure. Placates the Greens.

Trivial calculation shows the approach is hopeless. "Renewable energy" cannot be done with agriculturally produced fuels or any other solar.

Possible that satellite solar power is the exception. Possible, only.

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