Northrop Grumman Aerospace Systems

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.

Northrop Grumman Aerospace Systems is developing a dish-shaped sunlight-concentrating hybrid solar converter that integrates high-efficiency solar cells and a thermo-acoustic engine that generates electricity directly from heat. Current solar cells lose significant amounts of energy as heat, because they do not have heat storage capability. By integrating a high-temperature solar cell and thermo-acoustic engine into a single system, thermal energy losses are minimized. The thermo-acoustic unit, which was originally designed for space missions, converts waste heat from the solar cell into sound waves to generate electricity using as few moving parts as possible. The engine and solar cell are connected to a molten salt thermal storage unit to store heat when the sun shines and to release the heat and make electricity when the sun is not shining. Northrop Grumman’s system could efficiently generate electricity more cheaply than existing solar power plants and lead to inexpensive, on-demand electricity from solar energy.

If successful, Northrop Grumman’s hybrid solar converter could generate heat and electricity efficiently and inexpensively from renewable solar energy.