Every clean-tech startup these days claims to have a breakthrough that will finally make renewable and clean energy sources cheap enough to compete with fossil fuels. But are we really on the brink of a clean-energy economy?
By David Rotman
Why: Reducing the cost of constructing solar thermal plants will make them more competitive with fossil-fuel plants.
Key innovation: Software controls the mirrors that focus rays from the sun, eliminating the need to position them by hand.
The company uses arrays of tens of thousands of mirrors to focus sunlight on a central tower, producing intense heat that turns water into steam to generate electricity. The mirrors are installed on prefabricated metal frames that allow them to pivot and tilt to track the sun throughout the day and from season to season. Proprietary software ensures that all the mirrors are aimed properly.
The technology is ideal for the utility-scale solar power that could meet needs like those of California, where utilities are now required to produce 20 percent of their electricity from renewable sources. The only concentrating solar power plant in the country is a five-megawatt eSolar facility that uses two of the company’s receivers.
Last summer, eSolar received $10.8 million from the U.S. Department of Energy to develop a modified system that will use its mirrors to concentrate heat onto a receiver containing molten salt, instead of directly heating water to make steam. Molten salt can store heat for a while before it’s used to make steam, making solar more flexible as an energy source.
Challenges and Next Steps:
The declining cost of photovoltaic panels has put pressure on solar thermal companies like eSolar, which are rapidly losing their cost advantage. Last summer a planned 92-megawatt facility in New Mexico, which would have used eSolar's system, was canceled after its developers were turned down for a federal loan guarantee.