Is hydrogen the energy source of the future? Plug Power (NASDAQ:PLUG) certainly thinks so. The 27-year-old company provides green hydrogen, fuel cell systems, and other related products for its customers. It has also signed deals with two of the most recognized companies in the world: Amazon (NASDAQ:AMZN) and Walmart (NYSE:WMT).At the same time, Plug has failed to turn a profit since its inception and has generated an accumulated deficit of $4.5 billion. In its third-quarter earnings, the hydrogen company i ...