A new breed of solar farm capable of delivering energy on demand even when it is dark or overcast is poised for a major breakthrough this year, according to two US firms who claim they are ready to commercialise the technology.

Molten salt technologies capable of storing heat generated from solar panels so that the energy can be harnessed at any time have been subject to widespread trials over the past decade with several facilities having already proved successful.

But now two of the leading firms in the field, US Renewables Group (USRG) and UTC-subsidiary Hamilton Sundstrand, have committed to step up commercialisation of the technology and revealed that they are likely to begin work on a major new project before the end of the year.

"With oil at $60 a barrel, the commercial case for this technology was not that strong, but with it at $100 a barrel it is very strong indeed," explained Hamilton Sundstrand's Dan Coulom.

Under the alliance, USRG will provide concentrated solar power tower technology that uses a solar farm of giant mirrors to redirect the sun's energy to the top of a tower. The concentrated energy will then be used to heat a molten salt storage system, developed by Hamilton Sundstrand subsidiary HS Rocketdyne, that is capable of storing the energy.

Larry McNamara, director of business for Hamilton Sundstrand Space Land and Sea, said that the molten salt could be heated to temperatures of around 1,000 degrees Fahrenheit and could be used to heat water and drive steam turbines on demand.

"Experience shows that the salt loses just a degree of heat a day, so even if you have a few overcast days the heat energy can be maintained," he said. "It makes solar energy more like hydro power in that you can just switch it on whe never you need it."

The technology has been tested for about 10 years at the Solar Two facility in southern California and McNamara is convinced it is now ready for commercialisation.

"There is a great deal of interest in this technology in regions such as Australia, Africa, southern Europe and the south west US," he said. "We are now ready to commercialise and we believe we'll be working on a project by the end of the year. It'll take about three years to complete but we'd expect it to be operational by around 2011."

He added that as well as being carbon free, the technology would also compete on cost with conventional fuels.

"We calculate that the technology will be cost competitive at times of peak energy demand and as we scale up we'll be able to compete with fossil fuels," he said. "And that is assuming fossil fuel prices stay stable and don't go up further."