Nanotechnology could reduce the cost of the most expensive part of a solar thermal power plant by roughly 75 percent. The Department of Energy gave a team of researchers at the University of Illinois, the University of Michigan and the National Renewable Energy Laboratory $1.4 million to develop new solar concentrators.
The grant is one of 16 that DoE announced today in an $11 million program to advance innovative, early-stage solutions in solar cells and solar concentrator systems.
The improved devices, in combination with a new coating from a U-M engineering lab, could make concentrated solar power cheaper and more efficient.
Rather than turning sunlight directly into electricity, solar thermal plants concentrate the sunlight on a pipe to heat the fluid inside. The fluid then evaporates and drives a turbine, much like conventional power plants operate. Typical installations involve big mirrors arranged in a sort of half-pipe shape that focuses the sun’s energy onto the actual pipe.
The researchers plan to concentrate sunlight with a flat, nanostructured surface. By patterning this “metasurface” with features on the scale of the light waves themselves, the team will be able to control the light in a way that isn’t possible with natural crystals or reflective surfaces.
The development of such a metasurface would be a game-changing contribution to solar power and to this type of nanotechnology, said project leader Kimani Toussaint, an associate professor in the mechanical science and engineering at the University of Illinois Urbana-Champagne.
The flat light concentrator will be significantly lighter and more wind resistant than the current mirrors. The team intends to prove that they can be mass-produced with a printing-press-like manufacturing technique, pioneered by Jay Guo, a professor of electrical engineering and computer science at the University of Michigan.
"Our manufacturing process has gained much attention in recent years as it promises fast, low-cost production of nano-structured surfaces,” said Guo. “It is 10 to 100 times faster than conventional nano-patterning methods, yet it has an equally high resolution. If we print metasurfaces over large areas, we can produce very inexpensive solar concentrators."
The team expects to concentrate sunlight by a factor of 50, with the device costing less than $50 per square meter.
“We have a really exciting opportunity to harness the best of nanotechnology to truly impact the world’s energy portfolio,” Toussaint said.
Guo anticipates that these solar concentrators could be combined with another new technology developed in his lab, boosting the efficiency of the system. The receiver pipe, which contains the heated fluid, gets extremely hot – over 1,800 degrees Fahrenheit. A significant portion of the energy is lost when the hot pipe releases heat in the form of infrared radiation.
Earlier this year, Guo’s team reported a new coating that could allow sunlight to pass into the pipe and heat it while also preventing infrared radiation from escaping. It could reduce the amount of heat leaving the tube by 80 percent while maintaining 65 percent solar power absorption.
The study, titled “Efficient Thermal–Light Interconversions Based on Optical Topological Transition in the Metal-Dielectric Multilayered Metamaterials” was published in the journal Advanced Materials.
Toussaint and Guo are joined on the solar concentrator project by Placid Ferreira, a professor of mechanical science and engineering at the University of Illinois Urbana-Champagne; and Tim Wendelin, Guangdong Zhu and Robert Tirawat, members of the Concentrating Solar Power Group at the National Renewable Energy Laboratory.
The U.S. Department of Energy (DOE) Solar Energy Technologies Office focuses on achieving the goals of the SunShot Initiative, which seeks to make solar energy cost-competitive with other forms of electricity by the end of the decade.
by Katherine McAlpine
July 28, 2016