Yale University

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.

Yale University is developing a dual-junction solar cell that can operate efficiently at temperatures above 400 °C, unlike today’s solar cells, which lose efficiency rapidly above 100°C and are likely to fail at high temperatures over time. Yale’s specialized dual-junction design will allow the cell to extract significantly more energy from the sun at high temperature than today’s cells, enabling the next generation of hybrid solar converters to deliver much higher quantities of electricity and highly useful dispatchable heat. Heat rejected from the cells at high temperature can be stored and used to generate electricity with a heat engine much more effectively than cells producing heat at lower temperatures. Therefore, electricity can be produced at higher overall efficiency for use even when the sun is not shining.

If successful, Yale University’s high-temperature solar cells could be used in the next generation of hybrid solar converters, enabling more efficient utilization of the full solar spectrum than possible with either photovoltaic or concentrated solar power independently.