The energy source developed by Northeast professor Yi Zheng will use waste heat generated by space equipment and sunlight that does not reach Earth.
A Northeastern University researcher is developing a device for the U.S. Air Force that can absorb waste heat from space equipment, reflect sunlight and turn it into a power source for spacecraft and Mars rovers.
„Even if you can only provide 10% to 15% backup power to the electronics, you can extend the life of the electronics and a spacecraft,” he says. Yi ZhengAssociate Professor of Mechanical and Industrial Engineering and Director of the Nanoenergy Laboratory at Northeastern.
Zheng will work on the thermal device with Ohio-based Faraday Technology Inc., which specializes in developing applied electrochemical engineering technology for the US government and commercial customers.
„Our goal is to design a high-performance thermal absorber and thermal emitter that can absorb, convert, and emit energy at the desired wavelength,” Zheng says.
He says the technology would be suitable for both short- and long-duration space travel, including satellites launched from the Moon, Mars or our own galaxy.
In the past few years, Zeng has been developing materials for harvesting and storing energy, waste energy, and nanoengineered materials.
The primary source of energy in space, he says, is usually the sun — high-efficiency solar panels are energy space equipment that converts sunlight into energy.
Zeng’s power source will use waste heat generated by space equipment.
Spacecraft and space equipment, Zeng says, must operate in extreme conditions — really low temperatures (typically minus 454 Fahrenheit; or minus 270 Celsius) and near-total vacuum. Additionally, propulsion of space vehicles requires energy resources.
“We cannot simply launch another oxygen tank [for example] for travel equipment,” Zeng says.
Electronics operating on spacecraft or high-temperature surfaces can produce thermal radiation, or infrared light, which is invisible to the eye but can detect the sensation of heat on the skin, Zeng says. This heat is dissipated and lost to space.
Waste heat is everywhere, including Earth, Zeng says. For example, if a hot engine or furnace is heated to a high temperature, it will dissipate some of that temperature.
Recovering that energy has been studied for the past few decades, Zeng says, and his team uses recently developed technologies in designing their heating system.
First, they use a variety of man-made materials and surfaces – called metamaterials and metasurfaces, respectively – for their proposed heat sink. Metamaterials have certain properties not found in natural materials. They don’t occur naturally on Earth and, therefore, must be synthesized or nano-manufactured in the lab, Zheng says.
The problem with common materials, he says, is that they don’t have much absorption or emission properties at the desired wavelengths of infrared energy. Zheng says the wavelength of infrared light is about 1.5 to 2.5 micrometers, which is 12-24 times smaller than the diameter of a human hair.
„So some theoretical and experimental work is needed from our group,” he says. „In fact, my research interests focus on active and dynamic tuning of thermal, radiative and optical properties [of materials].”
„Also, weight and cost must be balanced,” Zheng says. „We have to balance a lot of things. So, given the limited choice of materials for space applications, it pushed us to think and adopt nanotechnology to design functional materials as a heating device.
Although nanotechnologies or nanomaterials are expensive, they perform remarkably well, he says. Without nanotechnology, absorbing specific wavelengths under extreme conditions would be impossible.
To make nanomaterials, scientists use inert or heat-resistant materials that are stable and have high melting points above 2,700 degrees (or 1,500 Celsius) and long lifetimes.
A good candidate is tungsten, Zeng says, a rare metal with the highest melting and boiling points of any known element on Earth. He believes that not only this material, but in combination with other materials will be useful in the extreme conditions of space.
Zheng is spending this summer as a NASA faculty fellow at the Glenn Research Center in Cleveland. He is conducting research on thermal management for the Artemis campaign, which aims to return Americans to the Moon in preparation for the first manned mission to Mars.
„I believe that what I’m doing for both the Air Force and NASA can actually contribute to future programs for long-duration spaceflight,” Zheng says.
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