As the world focuses on decarbonizing power and transportation, reducing heat emissions from industrial processes remains a challenge. Although using solar energy is an attractive alternative, current solar converters have poor performance and are expensive when process temperatures above 1,000 degrees Celsius (1,832 degrees Fahrenheit) are required. In a new study, scientists at ETH Zurich show that the heat-trapping effect caused by exposing common translucent materials (such as quartz or water) to solar radiation absorbs sunlight by suppressing radiation losses at high temperatures. We have shown how the viability of the photoreceiver can be increased. They demonstrated this effect experimentally at industrially relevant temperatures of 1,050 degrees Celsius (1,922 degrees Fahrenheit).
Casati other. The solar capture effect was experimentally demonstrated at temperatures as high as 1,050 degrees Celsius. They performed stagnation experiments under concentrated thermal radiation and achieved a steady-state temperature difference of about 600 degrees Celsius between the absorber and the outer surface by using quartz as a volumetric absorption medium.Image credit: Casati other., doi: 10.1016/j.device.2024.100399.
“To tackle climate change, we need to decarbonize energy in general,” said Dr. Emiliano Casati, a researcher at ETH Zurich.
“Electricity can only be thought of as energy, but in reality, about half of that energy is used as heat.”
Glass, steel, cement, and ceramics are at the heart of modern civilization, essential to the construction of everything from car engines to skyscrapers.
However, manufacturing these materials requires temperatures in excess of 1,000 degrees Celsius and relies heavily on the combustion of fossil fuels for heat. These industries account for approximately 25% of global energy consumption.
Researchers have been exploring clean energy alternatives using solar receivers that concentrate and store heat with thousands of sun-tracking mirrors.
However, this technology has difficulty transmitting solar energy efficiently at temperatures above 1,000 degrees Celsius.
To increase the efficiency of solar receivers, Dr. Casati and his colleagues turned to translucent materials such as quartz that can trap sunlight. This is a phenomenon called the thermal trap effect.
The researchers created a heat-trapping device by attaching synthetic quartz rods to opaque silicon disks as energy absorbers.
When the device was exposed to an energy flux equivalent to 136 solar rays, the absorber plate reached a temperature of 1,050 degrees Celsius, while the other end of the quartz rod remained at 600 degrees Celsius (1,112 degrees Fahrenheit).
“Previous studies have only been able to demonstrate heat-trapping effects up to 170 degrees Celsius (338 degrees Fahrenheit),” Dr. Casati said.
“Our research shows that solar heat capture works not only at low temperatures, but also at temperatures well above 1,000 degrees Celsius. This is very important to demonstrate its potential in real-world industrial applications. is.”
The scientists also simulated the heat-trapping efficiency of quartz under various conditions using a heat transfer model.
The model showed that the heat trap achieves the target temperature at a lower concentration with the same performance, or the same concentration and higher thermal efficiency.
For example, a state-of-the-art (unshielded) receiver has an efficiency of 40% at 1,200 degrees Celsius (2,192 degrees Fahrenheit) and a concentration of 500 suns.
A 300 mm quartz shielded receiver achieves 70% efficiency at the same temperature and concentration.
A concentration of at least 1,000 suns is required for equivalent performance with an unshielded receiver.
The authors are currently optimizing the heat trapping effect and investigating new applications of the method. So far, their research is promising.
By studying other materials, such as various fluids and gases, even higher temperatures could be reached.
They also noted that the ability of these translucent materials to absorb light and radiation is not limited to solar radiation.
“Energy issues are fundamental to the survival of our society,” Dr. Casati said.
“Solar energy is readily available and the technology already exists.”
“To truly accelerate industry adoption, we need to demonstrate the economic viability and benefits of this technology at scale.”
The team's results were published online today. journal device.
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Emiliano Casati other. Captures solar heat over 1,000℃. device, published online on May 15, 2024. doi: 10.1016/j.device.2024.100399
Source: www.sci.news
