ETH Researcher Drives Solar Heat Industry Breakthrough

Many industrial processes, such as pasteurising, dyeing and drying, need one thing above all: heat. Currently, factories often burn natural gas to reach the necessary temperatures. This reliance on fossil fuels remains a challenge in the energy transition. ETH engineer and Pioneer Fellow Luca Thommen is developing a solar thermal collector that converts sunlight into usable process heat more cost-effectively than before. His goal is to develop a straightforward, efficient technology that can be adopted by industry to replace fossil fuels.

From mechanical engineering to the energy question

Thommen started out as a classical mechanical engineer. His studies focussed on combustion engines and robotics until the climate debate raised new questions. "I started wondering how I could use my skills to make a contribution," he says. The answer led him to renewable energies.

The idea arose while he was working on his Master's thesis under Aldo Steinfeld, who is now Professor Emeritus of Renewable Energy Carriers. What began as a research project soon developed further, thanks in part to the early interest shown by industry.

Heat rather than electricity

While photovoltaics generates electricity from sunlight, Thommen focuses on heat extraction. That is why he has developed a collector that concentrates sunlight to heat air or water. Reflective elements direct the light to an absorber panel, which traps the solar energy and transfers it as heat to a medium such as air or water. Insulation minimises heat loss. This heat can be used directly in industrial processes, such as those in the food, chemical and pharmaceutical industries. Many industrial applications require temperatures of up to 150°C. At this threshold, renewable energy solutions have historically been prohibitively expensive, resulting in ongoing reliance on fossil-based heat sources. Examples include pasteurisation and sterilisation of milk products, cooking and cleaning in the food industry and distillation in the chemical and pharmaceutical industries.

Thommen explains: "The technology I have further developed already exists in principle, but it is not yet cost-effective." His project aims to change this by adopting a straightforward approach: using minimal, inexpensive materials in the collector's construction and avoiding complex designs.

A large part of the collector is made from lightweight, readily available and inexpensive insulation material, with metal used only where absolutely necessary. "My goal is to deliver the same performance at a significantly lower cost than earlier collectors," he says. Industry will consider switching only if the overall costs are justified.

From design to prototype

The initial prototype demonstrated that the approach worked. Once installed on the roof, the collector reached the target temperatures. "That was a key moment," says Thommen. "It was then clear that the idea worked."

There was also positive feedback from industry. Talks with companies such as Climeworks confirmed that demand exists. The ETH spin-off currently uses heat of around 100°C for its absorption and desorption processes to extract CO₂ from the atmosphere, which is within the temperature range that Thommen's technology can handle.

The Pioneer Fellowship is providing Thommen with the time and resources to advance his technology. He plans to develop a market-ready product within a year and conduct testing at a pilot facility. He is also engaging with potential customers and investors. "The technology is the start," he notes, "but it's the market that ultimately decides."

A technology with potential

The potential is significant: as electricity generation increasingly shifts to renewable sources, supplying heat to industry remains a challenge. Thommen offers a solution. His technology could help companies lower their CO2 emissions and become less dependent on volatile energy prices. Whether a spin-off will arise from this remains to be seen. One thing matters to him above all: "It is important that the technology is actually used and that it makes a difference out there."