New research co-authored by Stefan J. Reichelstein, GSB Professor, finds that a partial solution to the cost of renewable systems may lie with hybrid energy systems that use surplus renewable electricity to make pure hydrogen. Hybrid energy plants take surplus electricity from solar or wind farms and feed it into a power-to-gas process that relies on electrolysis to split water molecules into hydrogen and oxygen. The authors looked at equipment costs, hydrogen prices and hour-by-hour wholesale electricity prices and wind generation data for a full year in Germany and California.