Scientists looking for ways to increase the capacity of solar generators have discovered ways that can be 15 times more efficient.
The breakthrough is located in the unique laser etched “black metal” developed by researchers over the past five years and is currently hoping to use it in solar thermal generators (STEGs).
Steg is a type of solid-state electronic device that converts thermal energy into electricity through the Siebeck effect, a phenomenon that occurs when temperature differences between materials displace charged particles and create electromagnetic forces (EMFs).
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The STEG contains semiconductor material sandwiched between the “hot” and “cold” sides. When the hot side is heated by either the sun or another thermal energy source, the movement of electrons through the semiconductor material creates an electric current.
The challenge with existing dyeing is that they are very inefficient, converting less than 1% of the sunlight into electricity. This converts about 20% of the light they receive into electricity, as opposed to solar panels that are usually installed in people’s homes.
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However, in a new study published in Journal Light: Science and Applications on August 12, researchers used laser-treated metal, also known as “black metal,” for its deep, in-black appearance, to increase the energy efficiency of solar thermal generators by 15 times.
Laser treatment
This method blew tungsten with extremely fast and accurate laser pulses to etch microscopic grooves onto the surface. These “nanoscale etchings allowed tungsten to absorb more thermal radiation and hold it for longer.
Laser pulses also blacken the pure white surface of metal, increasing the ability to absorb heat. The researchers then created a “mini greenhouse” that covered black tungsten with plastic and trapped heat.
For the cold side of Steg, the scientists took the regular aluminum and blow it up with a laser pulse again. The small etching in the metal created “ultra-high capacity microstructured thermal dissipators,” which the team claimed to be twice as efficient as typical aluminum heat sinks.
To test the system, researchers used it to run the LEDs in simulated sunlight. A typical STEG could not illuminate the LED even when exposed to light 10 times stronger than normal sunlight. However, because both sides were treated using black metal, the device was illuminated by the LED under five times stronger light than normal sunlight. This corresponds to a 15x increase in the output.
Although they won’t be replacing solar farms any time soon, researchers say they could ultimately use technology on low-power wireless Internet of Things (IoT) sensors or wearable devices, or act as a rural off-grid renewable energy system.
“For decades, the research community has focused on improving the semiconductor materials used in Fates, resulting in a small benefit on overall efficiency,” said Chunlei Guo, research co-author at the University of Rochester Institute at Raser Energetics, in a statement.
“In this study, we don’t even touch the semiconductor material. Instead, we focused on the hot and cold sides of the device. By combining better thermal dissipation on the cold side and better thermal dissipation with better solar energy absorption and thermal trapping, we have a surprising improvement in efficiency.”
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