Researchers have just found a way to make solar power significantly more efficient. STEG stands for Solar Thermoelectric Generator. The device works using a simple principle called the Seebeck effect, where a temperature difference between two different conductors creates a voltage.
Rochester researcher Ghunlei Guo uses artificial sunlight to test his STEG material, which is etched with thousands of laser pulses J. Adam Fenster/University of Rochester
Simply put, a STEG is a device that is cold on one end and hot on the other, with electricity flowing through a semiconductor in between. The STEG is a solid-state device with no moving parts, and while the hot end can be heated by solar energy, it can utilize virtually any type of thermal energy to maintain high temperatures.
While this all sounds like a form of passive power generation, STEGs have traditionally been able to convert less than 1% of sunlight into electricity. In comparison, perovskite/silicon solar cells have achieved energy conversion rates of over 30%, and it seems unlikely that STEG will replace perovskite/silicon solar cells as a legitimate and widespread source of clean energy in the short term.
However, a new breakthrough by researchers at the University of Rochester seems poised to change that perception. By studying the materials on both sides of the STEG, the team was able to increase its efficiency in converting solar heat into electricity to 15%. The study, published in the journal Light: Science and Applications, describes the breakthrough, which co-author Chunlei Guo said is a radical departure from previous research focuses.
"The research community has been working on improving the semiconductor materials used in STEG for decades and has made some progress in overall efficiency," he said. "In this study, we didn't even touch the semiconductor materials, but focused on the hot and cold sides of the device. By combining better solar absorption and heat trapping properties on the hot side with better heat dissipation on the cold side, we achieved amazing efficiency gains."
Team uses laser oscillator to generate light pulses to etch nanostructures onto thermoelectric generators
To achieve this improvement, Guo and his team started with a unique black metal invented by his lab in 2020. To create the metal, they first used tungsten and then sandblasted it with femtosecond laser pulses (a series of ultra-short light pulses that etch the surface of the metal). Not only does this turn the tungsten into a heat-absorbing black color, but the placement of the laser-created dimples allows it to absorb more heat from sunlight and retain it longer.
Next, the tungsten wire is covered with "a piece of plastic to create a miniature greenhouse, like the ones on a farm," Guo explains. This retains heat better.
For the cold side of the STEG, the team shined an ultrafast laser onto a sheet of aluminum to create a heat sink with excellent heat dissipation properties. In fact, the researchers say their etched aluminum dissipates heat twice as well as regular aluminum.
Close-up of etched tungsten J. Adam Fenster/University of Rochester
While it may be some time before STEG delivers grid-scale power, the researchers say their breakthrough - demonstrated by powering an array of LED lights - could be used in applications that require less power, such as working in the Internet of Things, powering wearable devices or delivering power to individual homes in rural areas.
Source: University of Rochester