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Researchers make game-changing breakthrough that could change how we heat our homes: 'Has great potential'
While photovoltaics convert the sun's rays into electricity, solar thermal collectors absorb its heat energy for home and industrial purposes.
A researcher at Umeå University in Sweden recently developed new sustainable coatings for these collectors that can improve their efficiency and durability, according to a report from the school.
"Solar thermal has great potential to contribute to the green transition, especially as a source of industrial process heat. But the technology needs to become even more competitive to gain broader traction," said Erik Zäll, a doctoral student in experimental physics at Umeå University.
By leveraging more sustainable methods of heat or electricity generation, companies can reduce their carbon footprints, decrease their operating costs, and even pass on those savings to consumers.
Zäll explained in his doctoral thesis how optical coatings could be tailored for two key components of solar thermal collectors: the cover glass, where light enters the system, and the receiver that absorbs the light and converts it into heat.
An anti-reflective silica coating with small, hexagonally ordered pores helped improve light transmission through the cover glass while boosting the coating's resistance to environmental factors such as scratches, dirt, and moisture.
For the receiver, two solutions were presented that helped absorb most of the sunlight while emitting little thermal radiation. Both can be manufactured using low-cost, environmentally friendly methods that can be scaled up for production.
One option uses an electroplated cobalt-chromium coating that absorbs light and is more environmentally friendly than other types of chromium previously used.
The second is a composite film made up of carbon nanotubes and silica, which the report said can be spray-coated onto annealed stainless steel using ultrasonic technology. The thermal treatment of the steel helps create a thin oxide layer that boosts optical properties and heat resistance.
According to the World Economic Forum, heat accounts for half the world's energy consumption, from home space heaters to industrial applications. The processes used in creating this heat contribute more than 40% of global energy-related carbon dioxide emissions.
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Solar energy systems can use the sun's rays to heat water or air in buildings, with flat-plate collectors being the most common type for applications where temperatures of 200 degrees Fahrenheit are sufficient.
Some industrial-scale solar thermal power plants use vast arrays of concentrating collectors that focus the sun's rays on a smaller absorber for heat generation.
Zäll's research was done in collaboration with Absolicon Solar Collector and is specifically adapted to the Swedish solar energy company's designs, which have led to two patent applications for more efficient solar collectors.
Absolicon's website details how its sustainable heat collector systems can work alongside solar photovoltaics to lighten the load on the electricity grid and boiler systems that use dirty fuels.
Those systems include thermal energy storage in the form of heat batteries, which allow them to operate around the clock, even when the sun isn't shining, increasing the sustainability factor for the technology.
"Our work shows that it's possible to combine sustainability, cost-effectiveness and high performance in optical coatings – a key to making solar heat a viable alternative to fossil fuels on a larger scale," Zäll concluded.
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