Researchers have demonstrated a new method to harness solar power at temperatures exceeding 1,000°C that could seemingly revolutionize high-temperature industrial processes.
Considering the amount of steel, cement, and glass our modern society uses, from building football stadiums to aircraft, we need to generate a lot of heat to create those base building materials. All these industries account for approximately 25% of global energy consumption, and the power source used to heat these products to make them viable are fossil fuels.
Published earlier this week in the journal Device, a team from ETH Zurich in Switzerland utilized the thermal trapping effect in synthetic quartz, essentially capturing solar power, and achieving temperatures as high as 1,050°C. While only a proof-of-concept, these findings could reduce the reliance on fossil fuels in these industries, which are major contributors to global greenhouse gas emissions.
The thermal trapping effect leverages the unique properties of semi-transparent materials like quartz. These materials allow visible light to pass through while strongly absorbing infrared radiation emitted by hot surfaces. This phenomenon enables the material to reach higher internal temperatures than its surface, effectively trapping heat.
According to the study, the researchers attached a quartz rod to an opaque silicon carbide disk, which served as the solar absorber. When exposed to concentrated solar radiation equivalent to 135 suns, the absorber plate reached 1,050°C, while the quartz rod’s front face remained at a relatively cool 450°C.
What makes this new research compelling is the potential efficiency improvement of solar receivers using thermal trapping.
“Previous research has only managed to demonstrate the thermal-trap effect up to 170°C,” explained Emiliano Casati, one of the study’s authors. “Our research showed that solar thermal trapping works not just at low temperatures, but well above 1,000°C. This is crucial to show its potential for real-world industrial applications.”
The researchers’ 3D heat transfer model, validated against experimental data, showed that solar receivers with thermal trapping could achieve higher thermal efficiencies or require lower solar concentrations to reach the same temperatures as unshielded absorbers. For example, the study concluded that a receiver shielded with 300 mm of quartz can achieve 70% efficiency at 1,200°C with a concentration of 500 suns, compared to 40% efficiency for an unshielded receiver under the same conditions.
This efficiency improvement is the secret sauce that makes solar-powered industrial processes more viable and cost-effective. Higher efficiency means less solar input is required for a given output, reducing the size and cost of solar power collector fields.
Despite the promising results, several challenges remain before this technology can be widely adopted. One of the primary issues is minimizing reflective losses at the air-quartz interface. Approximately 4% of the incoming solar energy is lost due to reflection, which limits the maximum efficiency of the device. Future research will need to address this by exploring surface treatments like coatings or geometrical patterning to reduce reflection.
Moreover, demonstrating the economic viability of this technology at scale is a massive hurdle. While the proof-of-concept study shows significant potential, large-scale implementation will require further optimization and cost reduction. The researchers are currently investigating other semi-transparent materials and fluids that can achieve even higher temperatures, which could further improve efficiency and reduce costs.
“Solar energy is readily available, and the technology is already here,” Casati said. “To really motivate industry adoption, we need to demonstrate the economic viability and advantages of this technology at scale.”
MJ Banias covers space, security, and technology with The Debrief. You can email him at mj@thedebrief.org or follow him on Twitter @mjbanias.