SOLAR ON VERGE OF SOLVING VOLUME, STORAGE, TRANSMISSION
It's not science fiction, it's Scientific American.
Sunny Outlook: Can Sunshine Provide All U.S. Electricity? Large amounts of solar-thermal electric supply may become a reality if steam storage technology works – and new transmission infrastructure is built
David Biello, September 19, 2007 (Scientific American)
French physicist Augustin Fresnel; Ausra (David Mills, CSO; John O'Donnell, VP); Mark Mehos, concentrating solar power program manager, and Nate Blair, senior analyst, National Renewable Energy Laboratory (NREL)
Schematic of a solar thermal system: oil, being heated, runs in the tube to heat water in a steam generator. (click to enlarge)
Fresnel’s reflecting and concentrating concept is being incorporated into potent concentrating solar photovoltaic and solar thermal systems which hold the promise of capturing the immense solar resource rendered daily. The light is captured by parabolic mirrors which focus its power narrowly, concentrate it on super efficient photovoltaics or heat oil which transfers its heat to water, turning it to steam to power a generator or be stored. The designers also have plans for storage and transmission of the electricity generated.
The ideas were presented September 19 in a paper for the Solar Energy Society World Congress in Beijing.
Some German versions of the concept. (click to enlarge)
- Ausra is based in Palo Alto, CA. NREL is in Golden, Colo.
- Varieties of compact linear Fresnel reflector systems (CLFRSs) are now in use in California’s Mojave Desert and in the Nevada desert south of Las Vegas.
- Ausura projects an electricity cost of 10 cents per kilowatt-hour, competitive with natural gas generating plants.
- The CLFRS develops temperatures of 750 degrees Fahrenheit (400 degrees C).
- The Ausura/Mills CLFRS design covers the ground more efficiently less wight and more durability. It works at 535 degrees F (280 degrees C) and higher pressure (50 bars, or 50 times atmospheric pressure) and the steam turns the same low-temperature turbines as ones turned by nuclear reactors. But it has not been proven on a commercial scale yet.
- Ausura also has a (still unproven) concept for storing the steam under pressure. IF AND WHEN it is proven, it could reduce the cost of electricity from solar to 8 cents/kilowatt hour. One thing that makes the storage concept seem more practical is that they plan to store heat as steam under pressure, which is widely thought to be more practical than trying to store electricity in a battery.
- If the storage concept proves out, the ability to generate enough electricity to serve large states or the entire country become within reach, even if vehicular transportation goes electric and becomes grid dependent.
- Transmission is not considered a problem. Mills/Ausra assert that transmission lines are available and grid control mechanisms to manage the intermittency of wind energy already exist so it would remain only to build out capacity.
- Mills, Ausra: "Within 18 months, with storage, we will not only reduce [the] cost of [solar-thermal] electricity but also satisfy the requirements for a modern society…Supplying [electricity] 24 hours a day and effectively replacing the function of coal or gas…We would be able to build these in Florida in the hurricane zone."
- O’Donnell, Ausra: "We're moving from 80- to 100-megawatt designs to 700 megawatts and above…"
A hypothetical solar thermal power plant with storage potential, capable of putting electricity into the grid and sending it wherever electricity can go. The clouds are emission-free steam. The only fuel needed is imported from the sky. (click to enlarge)
- Mehos, NREL: "The issue of the linear Fresnel concept is proof of performance of a large system, not just a prototype system in the field…[Ausura and other companies] are making large claims without testing in the field."
- Mills, Ausra: "The maximum you can get into the grid is about 25 percent from solar…once you have storage, it changes from this niche thing to something that could be the big gorilla on the grid equivalent to coal."
- Blair, NREL: "To do it in the East would drive up the cost because the solar resource isn't as good…Or you could build some kind of massive transmission system to try and get that power up to the East."
- O’Donnell, Ausra: "There's no new technology on the transmission side, there are megavolt transmission lines around the world today…It is the cost of building electricity transmission compared to the cost and liability of nuclear waste disposal or cost and liability of long-term carbon sequestration….We have the ability to transition to a zero-carbon electricity future without moving the electricity price around…That hasn't been part of anybody's conventional wisdom."