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Fossil energy seems to have overtaken railways in cement, steel and other industries a few years ago. Well, that was the time. New systems for collecting and transmitting solar energy are emerging in order to produce the high heat needed for industrial processes. In the latest development, a Swiss research team is fine-tuning a solar thermal “trap” to achieve a temperature of 1,000.°C and more. It should be high enough to do the trick.
Solar Thermal Trapping for Fossil Fuels
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The new solar thermal research comes from ETH Zurich, short for the famous Swiss Federal Institute of Technology, where researchers are investigating ways to improve concentrated solar power systems.
Unlike solar cells that produce electricity directly, concentrating solar systems convert sunlight into solar thermal energy. A heat carrier – usually molten salt – can be used to provide heat energy for industrial processes. It can also provide steam to generate electricity in a power station.
That’s all well and good, but the challenge is to design a concentrating system that can efficiently transfer heat to the range above 1000.°Some industrial processes require C or higher. To overcome this obstacle, the ETH team decided to take a closer look at the thermal trap effect, which describes the ability of quartz, water and other semi-transparent substances to trap sunlight.
The heat trap effect was thought to work only at low temperatures, making it unsuitable for decarbonizing high-temperature industrial processes. Nevertheless, the ETH team gave it a crack.
Corresponding author Emiliano Casati of the research team explains: “Previous studies were only able to demonstrate the effect of heat trapping up to 170°C (338°F).
“The team developed a heat trapping device by bonding a synthetic quartz rod to an opaque silicon disc as an energy absorber,” ETH Zurich said in a press release earlier today. When exposed to 136 solar equivalents, the absorber plate reached 1050°C. The other end of the quartz rod remained relatively cool at 600°C.
“Our research has shown that solar thermal capture works not only at low temperatures, but also at temperatures well above 1000°C. This is crucial to show its potential for real-world industrial applications,” said Casati.
“Solar process heat above 1000°C can decarbonize key industrial applications such as cement production and metallurgical extraction,” the researchers emphasize in their study, “Solar heat capture at 1000°C and above,” published in the scientific journal Device. .”
New Life for Solar Thermal Energy
Don’t get too excited yet. The ETH solar thermal system is still in the proof-of-concept phase. However, it represents a breath of fresh air for the concentrating solar industry. The team simulated the new solar thermal trap under various conditions and reported results that could lead to the design of more compact, efficient concentrating solar systems.
“For example, a state-of-the-art (unshielded) receiver has an efficiency of 40% at 1200°C with a solar concentration of 500,” explains ETH Zurich. “A 300 mm quartz shielded receiver achieves 70% efficiency at the same temperature and concentration.”
“An unbiased receiver requires at least 1000 solar concentrations for comparable performance,” adds ETH Zurich.
The prospect of leaner, lower-concentration solar systems could help jump-start the industry in the US. While the technology has been rolled out in other parts of the world, the US has been slow to catch on to solar thermal heating.
It’s not for lack of trying. The US Department of Energy made a concerted effort during the Obama administration to support the next generation of concentrated solar technologies. Despite the former President’s frequent promises to save coal jobs, the agency’s concentrated solar programs have accelerated under the Trump administration.
Solar Thermal Chickens Come Home to Roost
With most of the major work done, the Department of Energy is gearing up for another concentrated solar push. In April, the agency’s Office of Solar Energy Technologies announced a new $30 million round of funding under the theme of “Concentrating Solar Energy into Heat and Power” aimed at accelerating the timeline toward large-scale commercial deployment.
“CSP technologies offer unique value as a renewable energy source that can easily deliver high-temperature heat for use in the industrial sector and incorporate energy storage for on-demand solar power,” SETO said.
The three-part funding round includes assistance for new solar collectors that help reduce costs while improving reliability.
Another portion of the funding will go to one of our new favorite topics, supercritical carbon dioxide. The use of sCO2 as a working fluid in solar thermal systems crossed the CleanTechnica radar in 2020, emerging as a compact, low-cost, energy-efficient replacement for conventional steam turbines. Last fall, we also celebrated the Department of Energy’s sCO2 showcase in Texas.
The third part is about the work of the ETH team. SETO explains that the funding will go to support “proposals for new solar collectors and solar reactors that convert concentrated sunlight into usable thermal energy at high temperatures.”
Particle receivers are considering the cut, in part because of their potential to hit the 90% efficiency mark.
Green Hydrogen, of course
Of course, no talk of new solar thermal technology is complete without bringing in green hydrogen. The Department of Energy is one of many funding agencies focusing on solar technology to lower the cost of green hydrogen.
SETO notes that its new funding round supports the goals of the Department of Energy’s Hydrogen Capture program, which aims to bring the price of “clean” hydrogen down to a level competitive with conventional hydrogen produced from natural gas or coal. The goal is to reach $1.00 per kilogram within 10 years, which is pretty ambitious considering the ballpark figure for green hydrogen is about $5.00 per kilogram.
Hydrogen Shot is casting a wide net and the field of unconventional hydrogen production continues to expand. We are following new developments that could apply new solar thermal technologies, such as the rock-based hydrogen system being explored at the University of Texas at Austin.
Another area of interest is taking place at the Princeton Plasma Physics Laboratory, where researchers are investigating the use of plasmas to replace fossil fuels in industrial processes.
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Image (cropped): A new solar thermal system uses ‘thermal capture’ to raise the temperature of concentrated solar power systems (courtesy of ETH Zurich / Emiliano Casati).
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