A unitized regenerative fuel cell (URFC) is a fuel cell based on the proton exchange membrane which can do the electrolysis of water in regenerative mode and function in the other mode as a fuel cell recombining oxygen and hydrogen gas to produce electricity.
Livermore physicist Fred Mitlitsky studied the possibilities of reversible technology.
In the mid-1990s Mitlitsky received some funding from NASA for development of Helios and from the Department of Energy for leveling peak and intermittent power usage with sources such as solar cells or wind turbines.
By 1996 he produced a 50-watt prototype single proton-exchange membrane cell which operated for 1,700 ten-minute charge-discharge cycles, and degradation was less than a few percent at the highest current densities.
The aircraft unfortunately crashed on its second URFC test flight June 26, 2003.