Solar power harnessed to generate 1,000°C heat in bid to clean up manufacturing

Process currently relies on energy-intensive process of burning fossil fuels

Sun-tracking mirrors reflect sunlight on to boilers within towers at the Ivanpah Solar Electric Generating System in the Mojave desert near the California-Nevada border. Reuters

Researchers aim to harness heat generated by the sun to manufacture building materials such as glass, steel, ceramics and cement.

Tests have shown that generating 1,000°C heat, which is required for the manufacturing process, is possible without using fossil fuels.

Manufacturing industries account for about 25 per cent of all global energy consumption.

“To tackle climate change, we need to decarbonise energy in general,” says corresponding author Dr Emiliano Casati of ETH Zurich, Switzerland.

“People tend to only think about electricity as energy but, in fact, about half of the energy is used in the form of heat.”

Renewable energy sources such as solar receivers, which concentrate and build heat with thousands of sun-tracking mirrors, have been identified as a possible replacement.

But the technology struggles to reach the temperatures needed in an efficient way.

To optimise that, researchers led by a team in Switzerland explored the idea of using quartz to trap sunlight, in a process known as the thermal-trap effect.

They attached a synthetic quartz rod to a silicon disc to act as an energy absorber, exposing it to light equivalent to 136 suns. The absorber plate reached 1,050°C while the quartz rod remained at 600°C.

“Previous research has only managed to demonstrate the thermal-trap effect up to 170°C (338°F),” said Dr Casati.

“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 team was also able to show that thermal-trapping effect achieves the target temperature at lower light concentrations.

Fields of sun-tracking heliostat mirrors reflect sunlight at the Ivanpah Solar Electric Generating System, the world’s largest solar thermal power station, in the Mojave desert. Reuters

For example, a receiver with a normal efficiency of 40 per cent at 1,200°C that uses a concentration of light from 500 suns can hit 70 per cent efficiency when shielded with 300mm of quartz. To obtain that performance would normally require the light from 1,000 suns.

Dr Casati and his team are now working on optimising the thermal-trapping effect and investigating new uses for the method.

So far, the research has been promising, using other materials such as different fluids and gases to reach even higher temperatures.

“Energy issue is a cornerstone to the survival of our society,” said Dr Casati.

“Solar energy is readily available, and the technology is already here. To really motivate industry adoption, we need to demonstrate the economic viability and advantages of this technology at scale.”

Last month, Zap Energy said it had “joined the rarefied ranks” to make a plasma that replicates the core of the Sun.

The extreme heat is needed to make parts of atoms fuse together – unleashing massive amounts of carbon-free energy, as the Sun does.

Funded by oil and gas company Chevron and the Bill Gates-founded Breakthrough Energy, scientists at US company Zap are among many trying to make this work on Earth.