"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 (see Ormat signs 20-year geothermal PPA with Nevada Power Company).

Ausra itself has a manufacturing plant in Las Vegas that is expected to go online next month (see Ausra to build solar thermal factory in Las Vegas).

Supplying the nation is "an interesting theoretical possibility, but not economical," said Jack Jenkins-Stark, chief financial officer of Oakland, Calif.-based Bright Source Energy.

The main challenge is increasing the number of hours electricity generated by this technology will be available. At the moment he said, companies can add at most a couple of hours to the solar day and remain cost-effective.

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."

Deris Jeannette, president of San Diego, Calif.-based ClearDome Solar Thermal, agreed with Caputo. "Just as with the development of Solar PV, an influx of major funding will be needed to bring solar thermal electric into large scale development," he said. "The potential is there."

Keely Wachs, the environmental communication manager at California's Pacific Gas and Electric company said that one of the challenges in making solar thermal a viable energy alternative to coal and gas is building up the infrastructure to connect the solar thermal plants in the desert to the main transmission lines to deliver the electricity to customers.

PG&E has partnered with Ausra to meet its renewable energy commitmments (see PG&E, Ausra in 177MW solar thermal deal).

Wachs said many solar thermal projects are located in isolated areas because they take up to nine square miles of space. "There are very real challenges with getting renewables to fullspread use and adoption."

Despite this, he said PG&E is "very optimistic" about solar thermal's potential as a resource for future energy needs. "It's coming within striking distance of natural gas generation.