Partially Transmitting Mirror
There are two primary methods for capturing and using sunlight today: direct conversion of sunlight to electricity using photovoltaic (PV) solar panels, or focusing sunlight onto a fluid that is used to drive a steam turbine in concentrated solar power (CSP) systems. Storing hot fluid in CSP systems is a less expensive way to generate electricity when the sun is not shining compared to storing electrical energy from PV in batteries. However, PV uses just part of the solar spectrum at high efficiency, while CSP systems use the entire solar spectrum but at low efficiency. Combining the best elements of these two technologies could provide a means to get the most out of the full solar spectrum, generating both electricity and storable heat (for later use) within the same system. Developing hybrid solar energy systems that perform both functions at the same time could provide electricity at cost comparable to traditional sources, whether the sun is shining or not.
Project Innovation + Advantages:
University of Arizona is developing a hybrid solar converter that splits the light spectrum, sending a band of the solar spectrum to solar cells to generate electricity and the rest to a thermal fluid to be stored as heat. The team's converter builds off the CSP trough concentrator design, integrating a partially transmitting mirror near the focus to reflect visible wavelengths of light onto high-efficiency solar cells while passing ultraviolet and most infrared light to heat a thermal fluid. The visible light is concentrated further before reaching the solar cells to maximize their power output. A thermal management system built into the solar cells allows them to be maintained at an optimal operating temperature and could be used to recover useful waste heat. Hot thermal fluid generated by the converter can be stored and used when needed to drive a turbine to produce electricity. The converter leverages the advantages of both PV and CSP to use each portion of the solar spectrum most effectively. This could enable utilities to provide dispatchable, on-demand, solar electricity at low cost even when the sun does not shine.
If successful, University of Arizona's hybrid solar converter will utilize sunlight to provide both on-demand electricity and dispatchable heat, providing sustained solar power even when the sun is not shining.
Developing new hybrid solar systems that generate heat and electricity at the same time could provide domestically-sourced solar power at cost comparable to traditional sources for use at all times of the day.
Replacing energy systems powered by fossil fuels would provide an immediate decrease in greenhouse gas emissions, 40% of which come from electricity generation today.
Cost-effective, dispatchable solar energy alternatives would stabilize electricity rates for consumers as the penetration of renewable energy increases in the coming years.