Solar thermal has a future as low carbon, back-up power

Solar thermal power has a role alongside wind and solar PV, in a low carbon world

Pic: Bigstock

Pic: Bigstock

By Gerard Wynn

Solar thermal power could in future provide affordable and reliable electricity to cater for peak demand in sunny countries and regions, found a study published in the journal Nature Climate Change.

Wind and solar photovoltaic (PV) power are attractive as increasingly economic, low carbon technologies, but are variable according to the wind and sun.

That means they require a certain amount of back-up when they are unavailable, raising their grid integration costs.

Until now, such back-up is provided by gas and coal-fired power, which emit carbon dioxide.

A low carbon back-up technology would therefore be highly desirable, if the world is serious about slashing carbon emissions.

That is where concentrated solar power (CSP) may come in, as its costs fall.

CSP works by heating up oil which in turn is used to drive a steam turbine. As a thermal power source, it can store electricity, for example by melting salt in storage tanks which release the heat when the salt re-freezes.

Focusing on this potential to provide back-up power, the latest study found that CSP plants could provide more reliable power, faster, by increasing the number of solar mirrors per unit of generating capacity.

Their reliability could be further increased by strategically siting CSP plants to capture a wider range of weather, to counter cloudy weather at one site with full sun somewhere else.

“We show that with an optimally designed and operated system, it is possible to guarantee up to half of peak capacity before CSP plant costs substantially increase said the authors of the paper, “Potential for concentrating solar power to provide baseload and dispatchable power”.

The researchers investigated CSP deployment by region, in sunny parts of the Mediterranean, the United States, India and South Africa.

They found that CSP cannot affordably supply flat baseload, meaning constant power 24 hours a day, as a nuclear power plant does, for example.

They could provide emergency back-up power, however, at around half peak demand, and so substantially reduce the need for reserve gas and coal-fired power plants, and cut carbon emissions.

That was especially the case in the Mediterranean and South Africa, because of their meteorological characteristics where cloudy weather was less likely to affect a large area, compared with the United States and India.

“Of the four regions we examined, the Mediterranean and South Africa offer the promise of very high availability without a substantial cost penalty, whereas the United States and India do not.”

“In these latter two regions, CSP might still be able to provide a large share of reliable power, but the exact extent would be contingent on specific demand curves and the features of the other technologies in the power mix.”

The analysis assumed that CSP costs would fall as deployment increased.

The United States this year is poised to quadruple its installed CSP capacity, with five new utility-scale plants, to 1.3 gigawatts.

In addition, it assumed that the costs of battery storage of electricity would not fall substantially, thus avoiding the need for back-up of existing wind and solar PV.

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