The University of Delaware is testing the use of electric vehicles as energy storage devices, long the dream of the wind, solar, and battery industries. There are both opportunities and challenges with such a system. 

Owners of a Tesla (NASDAQ:TSLA) Model S or a Ford (NYSE:F) Focus Electric could generate income from their vehicles just for use of the battery. In turn, the grid could become more efficient and cost-effective, with EVs to balance out load. 

But would car owners like burning their batteries more quickly? And right now Ford and General Motors (NYSE:GM) don't make vehicles that could store much energy and still have enough to drive any reasonable distance. 

For more discussion, check out the following video with Fool contributor Travis Hoium.