Concentrated Solar Works Day and Night With No Batteries Required

The massive expansion of solar panels on rooftops and solar farms across the world has captured the headlines, but the other established way of generating electricity from sunlight—concentrated solar power (CSP), or solar tower power—is also making great strides.

For a long time, using mirrors to concentrate the sun’s rays to heat molten salt and produce superheated steam to drive a generator’s turbines was thought to be a more promising technology than photovoltaic panels (PV), because it was originally cheaper.

But as the price of the panels has dropped dramatically in the last five years, CSP fell out of favor, although some countries continued to support its development.

Now the cost of CSP is also falling. But it has another major advantage: unlike the panels, it can go on producing power long after the sun has set, and can store it for up to 15 hours, for use when it’s needed.

Dubai, the largest city in the United Arab Emirates, where sunshine is almost guaranteed, is a fan of both solar technologies. It has just announced that electricity from a proposed 200 megawatt CSP project, to be completed in 2021, will be priced at 9.45 cents per kilowatt hour—40 percent below the previous world record.

The cost is well above the three cents per kilowatt hour of the cheapest solar PV, but has the advantage of running for 15 hours at full power during the night, doing away with the need for any fossil fuels for back-up generation.

CSP has many variations, all ways of concentrating solar power onto liquid to heat it and so create steam for driving turbines. The two main types use parabolic troughs or mirrors to aim the sunlight at a central tower. Troughs have been more widely used so far, but towers are gaining fast—the latest scheme, Dubai’s, uses a tower.

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