Hybrid system designed to harvest ‘full spectrum’ of solar energy

Hybrid system designed to harvest ‘full spectrum’ of solar energy
September 14, 2016 SNH Editorial Team
Full Spectrum Solar Energy

Tech Xplore revealed some new concepts around solar energy that could result in higher levels of efficiency by combining three types of solar technologies into one combined system. The combined system would leverage the full light spectrum and also store energy for use after the sun goes down.

“Harvesting the full spectrum of sunlight using a hybrid approach offers the potential for higher efficiencies, lower power production costs, and increased power grid compatibility than any single technology by itself,” said Peter Bermel, an assistant professor in Purdue University’s School of Electrical and Computer Engineering. “The idea is to use technologies that, for the most part exist now, but to combine them in a creative way that allows us to get higher efficiencies than we normally would.”

The new concept combines standard photovoltaic cells, which convert visible and ultraviolet light into electricity, thermoelectric devices that convert heat into electricity, and steam turbines to generate electricity. It’s the pairing of the thermoelectric devices to convert heat into electricity and steam turbines to generate electricity that makes the new concept interesting.

The thermoelectric devices and steam turbines would be driven by heat collected and stored using mirrors to focus sunlight onto a newly designed “selective solar absorber and reflector.”

“This is a spectrally selective system, so it is able to efficiently make use of as much of the spectrum as possible,” he said. “The thermal storage allows for significant flexibility in the time of power generation, so the system can produce power for hours after sunset, providing a consistent source of power throughout the day.”

The full findings of the research will be available in a future print issue of the journal of Energy & Environmental Science.

The new concept system could potentially meet varying electric demands at different times of the day.

“Typically for U.S. households, you have low usage overnight, then the demand goes up substantially in the morning, drops off a little during the day and then spikes upward around 5 p.m.,” Bermel said. “Photovoltaics match very well with the load during the day, but not when it spikes. So the idea is to store energy just for a few hours, and that helps you address times of spiking demand.”

According to Tech Xplore, the system ideally could achieve efficiencies of more than 50 percent using realistic materials, compared to 31 percent for photovoltaic cells alone.

The new selective solar absorber and reflector is the key for this new concept by increasing efficiency by reflecting visible light but also absorbing near-infrared photons, and increase the temperature of stored heat. Then the energy is harnessed as electricity when it is needed throughout the course of the day.

“I think that this hybrid approach is doable,” Bermel said. “In principle, we understand what needs to be done, but we need to do the experiments to validate the components and the whole system together.”