Continuing the DOE’s push for concentrated solar, the solar technology that isn’t solar panels, the National Renewable Energy Laboratory has put out a white paper (pdf) on the value of concentrated solar power. They ran the numbers for concentrated solar projects with built-in thermal energy storage, under both estimates for California’s current renewable energy mandate (30% renewable by 2020) and under a scenario where California’s energy mix is 40% renewable. (That’s timely, since California’s mix of renewables is likely to go up beyond its current mandate, thanks to the EPA’s proposed new rule.)
The NREL found that when renewable energy is mandated, concentrated solar can result in lower energy prices than solar panels:
Compared to variable generation technologies this translates to an increase in value of 5 cents per kilowatt hour under a 33% renewable standard – the mandate for 2020 – or 6 cents per kilowatt hour under a 40% renewable standard. The added value means that at peak demands, CSP can help lower electricity bills.
The reason for that value difference: the relative ease of incorporating thermal energy storage into a concentrated solar plant. Since a concentrated solar plant uses mirrors to focus sunlight on a central spot, heating it, that heat can be transferred to a thermal storage tank which can produce energy even after the sun has gone down, and after solar panels have stopped producing. That helps alleviate one of the central challenges of using lots of solar power – the awkward way that solar energy generation and energy consumption occur at different times of day, as illustrated in the chart with the catchy name.
So does that mean that we should be building concentrated solar plants instead of solar panels? Maybe, maybe not. The NREL is careful to add this caveat to their report:
This analysis compares only the relative value of CSP-TES in various situations and configurations and does not indicate the capital cost of building a plant. Further analysis will examine the trade-off between CSP-TES capital costs and total value provided to the power system.
All this tells us is that, in some situations, concentrated solar plants can produce higher-value power that can lower electricity bills. It doesn’t tell us if putting in the money to build these concentrated solar facilities in the first place is the right move.