Muscle to CSP

The storage capacity of concentrating solar power (CSP) can add significant value to a utility company's optimal mix of energy sources, a new report by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) suggests.

The report found that CSP with a six-hour storage capacity can lower peak net loads when the sun isn't shining, enough to add $35.80 per megawatt hour to the capacity and operational value of the utility, compared to photovoltaic (PV) solar power alone, and even higher extra value when compared to CSP without storage.

The net load is the normal load minus variable renewables such as photovoltaic and wind. The additional value comes because thermal storage allows CSP to displace more expensive gas-fired generation during peak loads, rather than displacing lower-priced coal; and because it can continue to flatten the peak load in the evenings when PV isn't contributing to the mix because the sun has set.

The report, "Simulating the Value of Concentrating Solar Power with Thermal Energy Storage (TES) in a Production Cost Model,"  noted that the $35.80 per megawatt extra value would come in a scenario in which there is relatively high penetration of renewables into the utility's mix, about 34 percent. If the penetration was lower, the extra value would be lessened.

CSP with TES, with an ability to store thermal energy in, say, molten salt, can use its heat-energy to drive turbines at power plants over much longer stretches of the day. Compared to other renewable options, at high penetration levels CSP with TES can be dispatched to displace natural gas rather than coal. This is important because electricity produced from natural gas fired generators is typically more costly than that produced from coal.