The US Department of Energy (DOE) predicts that renewables will be the fastest-growing US energy source for the next thirty years. Additionally, concentrated solar power (CSP), which has remained on the back burner for at least a decade, could become an important part of the energy mix. Despite the forecasts, there are formidable challenges to this promising energy technology.
While there are a variety of designs in use, CSP plants generally work by using mirrors to focus and direct solar radiation onto thermal receivers. This concentrated thermal energy can be used immediately, channeled into turbines to produce electricity, or stored (as molten salt, for example) for later use, such as when the sun is down.
Key Challenges to Building CSP Plants
However, while the CSP operating principle is relatively straightforward, engineering full-scale commercial plants needs to take several factors into consideration. For starters, size is an issue. CSP systems tend to require a significant amount of land to concentrate enough sunlight. Because of their scale, they are more suited to providing power to the grid and industries than to residential homes. In addition, they require direct access to sunlight. This means they are best suited to regions with strong radiation such as Southern Europe, Northern Africa, the Middle East, South Africa, parts of India, China, Southern US, and Australia. Another limiting factor is cost. CSP technology is more expensive than solar photovoltaics, both in terms of the cost of installation and the Levelized Cost of Energy (LCOE), or the cost over time to produce energy.
New Technologies Promise Cost Reduction
However, work is underway to develop technologies that can reduce the costs of CSP. There are several pathways to achieving higher temperatures for CSP plants using either liquid, solid particle, or gaseous materials. The key is to increase the temperature at which the receiver material is heated to enable more efficient electricity production. Ideally, this would require the development of new salts or other materials that can withstand temperatures of up to 1,300°F (705°C).
In 2018, the DOE announced a $72 million budget for new projects to advance high-temperature CSP technologies. Three teams—Brayton Energy, National Renewable Energy Laboratory, and Sandia National Laboratories—were selected to compete using three different pathways: alternative liquid, gas, and solid media. Each competitor’s task was to design a next-generation CSP system that could economically and reliably deliver temperatures above 1,300°F for advanced power cycles. Another goal of the project was to lower the cost of a CSP system by approximately $0.02 per kilowatt-hour. This is forty percent of the way to the DOE’s 2030 cost goals of $0.05 per kilowatt-hour (kWh) for baseload CSP plants.
DOE Awards Sandia $25M for CSP Research
After three years of evaluating the work of the three competing teams, the DOE announced in March 2021 that it was going to back the solid particles pathway over the other two alternatives. Solid particles, it said, “provided the most promising pathway to achieving higher temperatures in CSP plants to meet 2030 cost targets.” The following month, it awarded $25 million to the New Mexico-based Sandia to build, test, and demonstrate a next-generation concentrating solar thermal power plant at their National Solar Thermal Test Facility (NSTTF).
Cliff Ho, project leader of the Sandia team, told The Earth & I: “The new third generation Particle Pilot Plant (G3P3) is designed to tackle some of the engineering challenges of providing carbon-free reliable electricity with long-duration energy storage. We’re planning to break ground on the pilot plant this fall and expect it to be completed in late 2023.”
Next-generation concentrated solar power plants could store large quantities of energy overnight less expensively than large photovoltaic arrays with lithium-ion batteries, according to Sandia’s project leader.
Regarding what makes Sandia’s CSP system unique, Ho shared that it “stores energy from the sun in the form of heated sand-like ceramic particles rather than in the form of molten salts. This allows the system to get much hotter—more than 1,300°F (700°C)—compared to conventional molten-nitrate-based systems which can only reach approximately 1100°F (600°C).”
Higher temperatures improve the conversion of solar energy into electricity which, in turn, can benefit heavy industries. “Particle-based concentrated solar power technologies could also be applied to a wide range of industrial heat processes such as drying, chemical and materials synthesis, and petroleum refining,” according to Ho.
Consistent, high-energy production even overnight is another significant benefit. “Particle-based concentrated solar power also allows for storage of these hot particles to produce electricity overnight. In fact, particle-based concentrated solar power plants could store large quantities of energy (approximately 1GWh) overnight—for over ten hours—less expensively than, say, a photovoltaic array with lithium-ion batteries,” Ho continues.
CSP Growth Could Exceed Expectations
An increase in government support for the adoption of renewable technologies, coupled with a rise in energy demand and the capability to supply power without CO2 emission, is expected to drive the growth of the CSP market in the coming years. GE Power's forecast, which predicts a 10.8% growth rate for CSP over the next seven years, is just one of a number of forecasts that predict a positive outlook for CSP.
A new report from Rethink Technology Research, entitled “Last Chance Saloon for Gen 3 CSP,” suggests CSP will also benefit from new technologies developed in the West that could provide temperatures of “1,800°F (1,000°C) and even higher.” This is way more than the 1300°F (705°C) temperature goal that is currently being proposed and will enable CSP technology to play a role in the decarbonization of the cement, steelmaking, and mining industries
By the end of this decade, the Rethink Technology report expects annual CSP development to be an over $10 billion global industry. And although the DOE favors the development of solid material technology, CSP is advancing across a broad front, taking in all three technologies that utilize traditional thermal oil and molten salt as well as ceramics and other materials. Chinese developers, for instance, have chosen to move ahead with molten-salt plants, which are providing cost-effective, overnight energy storage to the grid in locations ranging from Greek islands to Thailand.
CSP Offers a Stable Energy Future
CSP technology has a promising future as a cost-effective option for the supply of renewable energy. Cost reduction is already well underway with recent figures showing a 16% decline in the price of electricity from utility-scale CSP plants in 2020. As GE Energy points out, the use of thermal energy storage tanks, which enables CSP to be dispatched even when the sun isn't shining, is much easier than storing electricity using batteries.
Further, with growing concern around battery supply chains, CSP may prove to be even more essential going forward. Kerry Rippy, a researcher at the US NREL, recently said that one of the biggest obstacles to the development of high-capacity battery storage is the limited supply of lithium and cobalt. According to some estimates, about 10% of the world’s lithium and “nearly all of the world’s cobalt reserves will be depleted by 2050,” she said. The forecasted shortfall in the global supply of lithium and cobalt should help put CSP technology in the driver’s seat of renewable energy and enable it to deliver on its promise of clean and affordable electricity.
*Nnamdi Anyadike is an industry journalist specializing in metals, oil, gas, and renewable energy for over thirty-five years.