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In a groundbreaking effort to reduce reliance on fossil fuels in heavy industries, researchers from Switzerland have pioneered a method to generate extreme heat using solar power instead. Published in the journal Device on May 15, 2024, their study introduces a novel approach using synthetic quartz to harness solar energy, achieving temperatures exceeding 1,000 degrees Celsius (1,832 degrees Fahrenheit). This innovation holds significant promise for revolutionizing carbon-intensive sectors like steel manufacturing and cement production by offering a clean and sustainable alternative to traditional fuel-based heating methods.

The manufacturing of essential materials such as glass, steel, cement, and ceramics is fundamental to modern civilization but requires temperatures well above 1,000°C, typically supplied by burning fossil fuels. These industries collectively account for approximately 25% of global energy consumption, contributing significantly to greenhouse gas emissions. Recognizing the urgent need to decarbonize energy systems, Emiliano Casati and his team from ETH Zurich have focused on leveraging solar energy as a viable solution.

The Challenge of Solar Thermal Energy

Solar thermal energy, which involves concentrating sunlight to generate heat, has long been explored as an alternative to fossil fuels. However, existing technologies face challenges in efficiently transferring solar energy above 1,000°C. Traditional solar receivers, composed of sun-tracking mirrors, struggle to achieve the necessary temperatures with optimal efficiency.

Introducing Synthetic Quartz for Thermal-Trapping

To address these limitations, Casati and his colleagues turned to semitransparent materials like synthetic quartz, known for their ability to trap and retain solar energy through a phenomenon called the thermal-trap effect. Their experimental setup involved a thermal-trapping device comprising a quartz rod attached to an opaque silicon disk, designed to absorb solar energy effectively. When exposed to intense solar radiation equivalent to 136 suns, the absorber plate reached temperatures as high as 1,050°C, while maintaining lower temperatures at the other end of the quartz rod, showcasing the effectiveness of thermal trapping even under extreme conditions.

Advancements in Thermal-Trapping Efficiency

Previous research had demonstrated the thermal-trap effect at significantly lower temperatures, up to 170°C. Casati's team's breakthrough extends this capability well beyond 1,000°C, demonstrating its potential for practical applications in heavy industries. Through advanced modeling and simulations, they verified that the use of quartz significantly enhances thermal efficiency compared to conventional unshielded receivers. For instance, while a standard receiver achieves 40% efficiency at 1,200°C with a concentration of 500 suns, a quartz-shielded receiver can achieve 70% efficiency under similar conditions, or maintain comparable efficiency with lower concentrations, thereby reducing the infrastructure requirements for solar thermal systems.

Future Prospects and Applications

Looking ahead, Casati and his team are focused on optimizing the thermal-trapping effect further and exploring new applications for the technology. Initial experiments with different materials, fluids, and gases have shown promising results, hinting at the potential to achieve even higher temperatures and efficiencies. Their ultimate goal is to demonstrate the economic viability and scalability of solar thermal technologies, encouraging widespread adoption across industrial sectors.