The Ivanpah solar plant in the Mojave Desert marches ever closer to its official opening this summer. That plant, a huge concentrating solar power (CSP) facility using mirrors aimed at central towers, will join others in Spain, Abu Dhabi, and elsewhere. So there's a sizeable capacity potential for CSP, but is the technology worth it? When Ivanpah and a number of other plants were designed or suggested, photovoltaic prices hadn't dropped off the map just yet, so the economics of building plants that concentrated light seemed reasonable. That has since changed and PV is incredibly cheap, and the actual value CSP provides has yet to really be quantified. A recent analysis from the National Renewable Energy Laboratory (NREL) tries to do that—specifically in California, though the methodology can certainly be used elsewhere.
The basic answer is that CSP is very valuable to the grid, especially when it is capable of providing "operating reserves," or short-term extra capacity in times of high demand or failures in other parts of the grid. The value is essentially based on how much fossil fuel-based generation can be avoided through the use of CSP; the NREL researchers compared a baseline scenario to photovoltaics, CSP alone, and CSP with operating reserves. CSP beats out the baseline scenario by about US $6 per megawatt-hour, and by $12 per MWh over PV.
By using operating reserves, though, those differences increase fairly dramatically: CSP wins in that case by $22 per MWh over baseload and $29 per MWh over PV. Interestingly, running CSP plants with operating reserves would mean a shift in standard practice: generally, these plants are run at full capacity whenever the sun shines, but to provide operating reserves would mean running at only partial capacity some of the time and then ramping up when needed.
This analysis was conducted solely for the California grid, and was based on the state's renewable energy portfolio standard calling for 33 percent of electricity from renewables by 2020. The same method, though, could be extended to other regions as well. And quantifying CSP's value may help it continue to grow, given some recent struggles; BrightSource Energy, the Ivanpah plant's developer, has shelved a full gigawatt of further CSP plans this year alone thanks to cost and other issues. PV is cheap these days, but can't incorporate storage using molten salts or other ideas the way CSP can, and clearly doesn't add value to the overall grid the way CSP does. To really scale up renewables we will need both in huge amounts, but understanding CSP's value is an important step toward its expansion.
Photo: BrightSource Energy