The Promise of Particles: A Solid Bet for Concentrating Solar-Thermal Power

While black sand is most famous for coating pristine beaches, it also plays a role in powering the clean energy transition. Heating small, sand-like ceramic particles to 1000°C or more may be the key to making concentrating solar-thermal power (CSP) plants more efficient and unlocking cheap, long-duration energy storage.

To visualize the process, picture grains of sand falling through an hourglass. An elevator lifts ceramic particles up to a storage bin, known as a hopper. The particles fall from the hopper, absorbing beams of concentrated sunlight until they exit the bottom of the solar receiver. While this is new technology, falling particle receivers can also be incorporated into existing CSP power tower technology.

The U.S. Department of Energy has been funding innovative research in particles for more than a decade, investigating particle properties and developing models for particle-based components such as receivers, heat exchangers, and storage vessels.

In 2021, DOE determined that solid particle-based CSP systems have the most potential to work cost effectively at higher temperatures and enable advanced (highly efficient) power cycles. Particles can withstand heat up over 1000°C, compared to commercially deployed molten nitrate salts that have a maximum temperature of 565°C. Particle-based systems also require fewer components, are less complex to operate compared with liquid- and gas-based systems, and need relatively few expensive materials to collect and transport thermal energy.

DOE has a growing portfolio of particle system-based research and development, including a megawatt-scale test facility at Sandia National Laboratories, to prove the promise of particles as a cost-effective heat transfer “fluid.” Research in particle-based systems focuses on three primary applications.

Dispatchable Electricity with Long-Term Energy Storage

Energy storage is critical for power grid managers to match incoming electricity supply to demand. Particle-based thermal energy storage is literally dirt cheap, and therefore more affordable than traditional systems. Low-cost materials are critical to making storage windows last beyond the four-hour time limit of lithium ion batteries. The particles have flexible configurations, meaning they can support applications of nearly any temperature or size. Unlike high temperature liquids, particles can also resist corrosion.

Direct Solar Fuel Production

Solar energy can be used to convert basic chemical feedstocks such as carbon dioxide and water into clean alternative fuels that offer greater grid stability, energy security, and environmental benefits.

Solar fuels, like hydrogen, can be created and burned without producing greenhouse gases. A particle-based CSP system can enable temperatures over 1000° C that are needed for a solar thermal reactor to produce hydrogen or other transportable fuels.

Industrial Decarbonization

Decarbonizing the energy sector by 2050 will require innovation in American manufacturing to reduce emissions in industries like chemicals, iron and steel, and cement. The ability to withstand very high temperatures makes particles uniquely practical for delivering heat to a variety of industrial sectors. In September 2022, DOE announced the selection of five projects that will focus on advancing industrial uses for this technology, specifically in the cement, hydrogen, and chemicals sectors, and help advance the goals laid out in DOE's Industrial Decarbonization Roadmap.

Opportunities for Researchers 

For scientists and engineers, there are many opportunities to get involved in the growing field of particle research to meet decarbonization and climate goals. Future areas of exploration include achieving even lower cost particles that can last for 30 years and developing innovative materials that can hold the particles at the most extreme temperatures in the receiver and the storage vessel.

Learn more about SETO’s research in CSP.