Converting sunlight directly into electricity, the photovoltaic (PV) solar panel industry has dominated the solar generation market recently because of its astounding price drops. Prices have fallen 99 percent in the past quarter century and over 80 percent since 2008 alone. This has also helped to slow the growth of the “other” form of solar, concentrating solar thermal power (CSP), which uses sunlight to heat water and uses the steam to drive a turbine and generator.
Fortunately, one country appears to be making a major bet on CSP — China. SolarReserve, the company that built the Crescent Dunes plant (pictured above) recently announced a deal with the Shenhua Group, the world’s largest coal provider, to build 1,000 megawatts of CSP with storage in China. And the country as a whole has plans to build some 10,000 megawatts of CSP in the next five years.
I say “fortunately” because CSP has one huge potential advantage compared to PV. The heat it generates can be stored over 20 times more cheaply than electricity — and with far greater efficiency. So CSP’s “killer app” is that it can provide power long after the sun has set — and it doesn’t disrupt the grid when a cloud passes overhead.
CSP has several possible designs, including a power tower such as the Crescent Dunes plant (top picture), which uses movable mirrors to focus sunlight on a central tower that holds the engine, and the parabolic trough, which uses mirrors to focus sunlight on a long tube filled with a heat-storing fluid (right).
Because of its built-in cheap, efficient storage, CSP — aka Solar Thermal Electric (STE) — has the ability to directly address the “variability” or “intermittency” problem that PV has when the sun isn’t shining. As a result, the 2014 STE Technology Roadmap from the International Energy Agency (IEA) concludes that while PV could generate 16 percent of the world’s electricity by 2050, as much as 11 percent could be generated by STE at the same time.
In this scenario: “Combined, these solar technologies could prevent the emission of more than 6 billion tonnes of carbon dioxide per year by 2050 — that is more than all current energy-related CO2 emissions from the United States or almost all of the direct emissions from the transport sector worldwide today.”
But this isn’t a forecast or projection by the IEA, it is a roadmap or scenario of what could happen with the right policies and continued technology improvement. In the past decade, though, solar PV has leap-frogged the competition because of aggressive pro-PV policies by governments around the world, most especially in Germany and China.
Both of those countries embraced massive deployment programs that turned PV from an expensive renewable source with limited deployment into one of the cheapest and most rapidly expanding sources of new power in the world:
One technology’s miracle is, however, another technology’s competitive nightmare. And so the question has been, will any country try to do for CSP which Germany and China (and others) did for PV — make major investments to bring CSP down the learning curve?
Both the IEA and the U.S. National Renewable Energy Lab have said that after solar PV makes a deep penetration into the electricity market, CSP will likely become more valuable. A 2014 NREL study found a CSP project with thermal storage “would add additional value of 5 or 6 cents per kilowatt hour to utility-scale solar energy in California where 33 percent renewables will be mandated in six years.”
Right now, solar PV produces power at the most valuable time — the daytime peak in electricity consumption, especially during the summer, when air conditioning use creates a huge power draw. But once solar PV hits 10 percent to 15 percent of annual electric generation in a region, it can become less valuable. The IEA projects that when that occurs, perhaps around 2030, “Massive-scale STE deployment takes off at this stage thanks to CSP plants’ built-in thermal storage, which allows for generation of electricity when demand peaks in late afternoon and in the evening, thus complementing PV generation.”
But, again, that assumes the world sees continued investments in CSP so that its price and performance steadily improve, and it can scale up quickly to become a large-scale contributor to a zero-carbon power grid.
For a while it seemed as if the United States would be that big driver, but CSP was stalled by the collapsing price of PV. Also, the reputation of CSP as “green” was harmed in this country by a shocking estimate of 28,000 birds burned a year by one CSP facility — an estimate that turned out to be no more than pure speculation. The actual number of birds burned in one year appears to be 700 — and that was before any abatement actions were taken. It turns out that just using standard strategies to ward off birds can cut that number by two thirds. And the Crescent Dunes facility built by SolarReserve (see top picture) was able to virtually eliminate bird burning entirely by changing how the mirrors were operated when in standby mode.
But the public relations damage had already been done to U.S. CSP plants. And so this May, SolarReserve announced a partnership with China’s Shenhua Group, the world’s largest coal provider, to build 1,000 megawatts of CSP with storage. The two companies explain:
The unique power dispatch capabilities of these utility scale projects will facilitate the deployment of additional wind and PV generation, while ensuring the reliability and security of the new ultra-high voltage transmission lines being constructed to bring clean, renewable power from the north and west regions of China to load centers in the east.
This is important because China had been forcing wind plants “to shut down at times to let coal power plants meet their generation quotas,” as the American Wind Energy Association explained last year. As a result, some 17 percent of potential wind generation was lost due to curtailment in 2012. The figure may be even higher today.
China has committed to prioritize the dispatch of renewable power first as part of its overall “war on coal,” as we have reported. A big increase in CSP — together with a big planned increase in pumped storage at hydropower plants — could go a very long way to enabling further reductions in coal use in China.
And, indeed, China aims to build 10,000 megawatts of CSP over the next five years (and they have over a dozen plants planned or under construction right now). If China is able to achieve even half that target, they would likely become the world’s largest deployer of CSP. Here’s a chart of current CSP from the recent “Renewables 2016 Global Status Report” by REN21, the Renewable Energy Policy Network for the 21st Century:
The continued expansion of CSP worldwide is crucial to reducing its costs, just as it was for wind and solar PV. Obviously, CSP has a very long way to go to catch up to PV, which hit 227 gigawatts of capacity in 2015 and continues to rise rapidly.
That said, SolarReserve CEO Kevin Smith believes that by around 2020, with the help of its Shenua deal, it can reduced the cost of the electricity it provides up to 40 percent, “well into the single digits per kilowatt-hour.” And that’s pretty good for a carbon-free source of dispatchable power — cheaper than new nuclear.
Lastly, the biggest threat to CSP in a carbon-constrained world probably may turn out to be battery technology. If batteries continue their miraculous price drops, then the need for the kind of low-cost, built in storage that CSP delivers may be reduced, especially if electric vehicles also continue their recent exponential growth leading to widespread vehicle-to-grid systems.
May the best technology win!