A group of Australian engineers has formed a company, Terrajule, to develop a novel energy storage solution.

The Terrajoule system combines concentrated solar thermal energy, steam engines and an integrated storage system using an insulated pressure vessel.

The concentrated solar thermal energy is used to produce steam. Since it is impractical to store steam for later use, the steam is condensed under pressure into water where its energy is stored. When needed, the pressure is released and the stored energy flashes the water back to steam which drives a reciprocating steam engine. The energy lost in this steam-water-steam phase change cycle is less than 2%.

According to the company, the result is storage at less than 20% of the cost of batteries, with no degradation, no cycle limits, no toxic or rare materials and a useful life of at least 25 years.

Terrajoule expects that, by 2015, it will be able to deliver power at $1.50 to $2.00 per watt which will be comparable to the price for a photovoltaic system of similar capacity. But this power could be delivered at any time – making the effective cost just a fraction of the cost of a photovoltaic system with battery storage.

Terrajoule power plants are from 100 kilowatts to 10 megawatts in capacity and are modular. Because of this and because all of the system components use well-established technologies, ramping up production requires no new factories, no new materials and no new manufacturing equipment or processes. This means that it can be quickly and massively scaled up to provide gigawatts of distributed power generation.

Terrajoule has built a demonstration plant in California and has just announced an $11.5 million round of funding, which will enable them to continue to develop and scale up their technology.