Scientists generate heat of more than 1,000°C with solar energy instead of fossil fuels

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Thermal collection device that reaches 1050 degrees Celsius. Credit: Device/Casati et al.

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Thermal collection device that reaches 1050 degrees Celsius. Credit: Device/Casati et al.

Instead of burning fossil fuels to melt steel and cook cement, researchers in Switzerland want to use heat from the sun. The proof-of-concept study, published May 15 in the journal Deviceuses synthetic quartz to capture solar energy at temperatures above 1,000 °C (1,832 °F), demonstrating the method’s potential role in providing clean energy to carbon-intensive industries.

“To tackle climate change, we need to decarbonize energy in general,” says corresponding author Emiliano Casati of ETH Zurich, Switzerland. “People tend to think of electricity only as energy, but in fact about half of the energy is used in the form of heat.”

Glass, steel, cement and ceramics are the core of modern civilization and are essential for building everything from car engines to skyscrapers. However, the production of these materials requires temperatures of more than 1,000 °C and is highly dependent on the combustion of fossil fuels for heat.

These industries are responsible for approximately 25% of global energy consumption. Researchers have explored a clean energy alternative using solar receivers, which concentrate and build up heat with thousands of sun-tracking mirrors. However, this technology has problems in efficiently transferring solar energy above 1,000 °C.

To increase the efficiency of solar receivers, Casati turned to semi-transparent materials such as quartz, which can trap sunlight – a phenomenon called the thermal trap effect. The team created a thermal capture device by attaching a synthetic quartz rod to an opaque silicon disk as an energy absorber.

When they exposed the device to an energy flow equivalent to light coming from 136 suns, the absorber plate reached a temperature of 1,050 °C (1,922 °F), while the other end of the quartz rod reached 600 °C (1,112 ° F) stayed.

“Previous research has only been able to demonstrate the thermal effect up to 170°C (338°F),” says Casati. “Our research has shown that solar thermal energy works not only at low temperatures, but also well above 1,000°C. This is crucial to demonstrate its potential for real-world industrial applications.”

Using a heat transfer model, the team also simulated the thermal capture efficiency of quartz under different conditions. The model showed that thermal trapping achieves the target temperature at lower concentrations with the same performance, or at higher thermal efficiency for an equal concentration. For example, a state-of-the-art (unshielded) receiver has an efficiency of 40% at 1,200°C, with a concentration of 500 suns.

The receiver shielded with 300 mm quartz achieves an efficiency of 70% at the same temperature and concentration. The unshielded receiver requires a minimum of 1,000 suns concentration for comparable performance.

Casati and his colleagues are now optimizing the thermal trapping effect and investigating new applications for the method. So far, their research is promising. By investigating other materials, such as different liquids and gases, they were able to reach even higher temperatures. The team also noted that the ability of these semi-transparent materials to absorb light or radiation is not limited to solar radiation.

“Energy issue is a cornerstone for the survival of our society,” says Casati. “Solar energy is readily available and the technology is already here. To really drive industry adoption, we need to demonstrate the economic viability and benefits of this technology at scale.”

More information:
Solar thermal capture at 1000 ºC and above, Device (2024). DOI: 10.1016/j.device.2024.100399.

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