Solar thermal power could supply most of US Demand  

Ausra's David Mills has been promoting solar thermal power as the answer to all our energy needs (when coupled with large scale energy storage). While this is theoretically true, I suspect once we've completed the transition to 100% clean energy solar thermal will supply maybe half the required energy - with PV (especially thin film) and a range of other renewables making up the rest.

"I took it as a theoretical presentation – what in theory could one do if you were starting from scratch," said Tom Fair from Nevada Power's renewable energy program. Fair was discussing the presentation David Mills, CEO of Palo Alto, Calif.-based Ausra, gave at the International Energy Agency's SolarPACES solar research conference in Las Vegas, Nev.

Mills said that over 90 percent of the nation's electricity, and most of the transportation sector's energy needs, could be supplied by solar thermal technology within the next 50 years. The study is available here. It's possible from a technology standpoint, Fair told Cleantech.com. "Deploying everything in that timepoint is obviously a challenge," he said. "There's still a lot of infrastructure in electricity and transportation that would need to be replaced."

One of the key improvements that would need to be made is in storage. Mills said the solar thermal plants would need just 16 hours of storage to continuously generate electricity. Fair said Mills' idea was "a really great target to shoot for. We'd like to see it become commercially viable."

Nevada Power is getting some of its energy from renewable sources, including a 64 megawatt solar thermal plant and a 12 MW photovoltaic plant. A geothermal power plant is expected to supply another 18 to 30 MW to the company's customers. Ausra itself has a manufacturing plant in Las Vegas that is expected to go online next month. ...

One of the storage technologies currently being used is molten salts, which must maintain a temperature above 200 degrees Celsius to continuously provide energy. Keeping the molten salts from freezing without taking energy from the grid is a hurdle, said Jenkins-Stark.

The solar day is now 24 hours long, according to John O'Donnell, Ausra's executive vice president. He said Spanish solar thermal power station Andasol is currently running 24-7 and has a 16-hour storage reservoir.

One of the factors in Mills' paper that makes the storage viable is using an oversized solar field – this allows some of the energy collected during the day to keep the electricity generation process running all night long as well, at no extra storage cost. The biggest thing about Mills' work, O'Donnell said, is that it proposes a path forward "where there's no cost increase."

The correlations Mills found between electricity load and seasonal changes suggest that the notion of using solar thermal power for the whole nation within a few decades is viable.

"We can move to an all-renewable future with the technologies commercially available right now," O'Donnell added. "It's more a matter of mobilization and deployment."

Richard Caputo, a director on the board of the San Diego Renewable Energy Society, said making Mills' proposal a reality would require more high voltage DC lines to carry the electricity from the southwestern U.S. to the rest of the country. It's an investment that would have to be made, he said, but not necessarily now.

"When you think the future and you think renewables, you start building it within two decades so it'll be ready in four decades," he said. "After World War II, the country decided it needed a national road system. Now's the time to decide we need a national electric system."