As the global demand for energy increases, the alternatives to meet demand must reflect an expanding portfolio of clean energy options.From 2000 to 2013, cumulative global renewable electricity installed capacity grew by 108% (from 748 GW to 1,560 GW)and renewable sources accounted for 23% of all electricity generation worldwide (5,095 TWh) in 2013.Wind and solar electricity have been the fastest growing renewable electricity technologies globally.Wind electricity generation grew by a factor of 18 and solar electricity generation grew by a factor of 68 between 2000 and 2013.