Concentrating solar needs molten salt energy storage to survive


Concentrating solar power creates electricity by using the heat of the sun. The heat generally is focused to a central tower or stored in tubes next to parabolic troughs, then used to power turbines, creating electricity. Solar PV is way cheaper than CSP. However CSP has a huge advantage that makes it competitive. Excess heat can be stored in molten salt, then used to generate power when the sun isn’t shining or at night. Specifically, CSP can be used as backup power for solar PV when the sun is setting and demand is generally at its highest.

A ginormous CSP plant in Tunisia will generate 2.5 GW, equal to that big coal and nuclear power plants, when built and send the power to Britain via high-voltage DC cable. The builders say the cost will be competitive although Bloomberg New Energy disagrees.

Contrary to Nur Energie’s estimations, Bloomberg New Energy Finance calculates that most solar thermal plants would need a power-purchase agreement in excess of $200 per megawatt-hour to be commercially viable.

This compares to just under $100 per megawatt-hour for PV “in a similar sunny location,” Chase said. “The only reason anyone would give you that premium is if you were supplying power that matched the demand of the grid you were feeding into better than PV does.”

And that is exactly what CSP does, it provides large amounts of power precisely at the time when solar PV can no longer do so. And this is the only reason it remains viable competition.

This is particularly the case in markets such as South Africa, where there is a need to meet evening demand peaks that PV cannot handle. South African regulators have approved at least half a dozen CSP plants with storage.

BLS explains how CSP works.

Although there are several different CSP technologies, they all involve reflecting sunlight onto a focal point that contains a heat-transfer material. The heat-transfer material, usually synthetic oil or molten salt, is collected in a heat storage unit and eventually used to create steam that powers conventional generators. One advantage of CSP is that at night or on extremely cloudy days, the conventional generators can be run on natural gas or petroleum, allowing the plant to continue to generate power when the sun is not shining.

That’s right. CSP is not completely renewable. The turbines can run off carbon fuel too. However, they are still way greener that say, a coal plant.

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