Ballard Power Systems makes emission-free proton exchange membrane (PEM) fuel cells and systems used in electric buses, forklifts, and as backup power for telecom networks. The stacked thin cells generate electricity by combining hydrogen fuel with oxygen, leaving only water and heat as by-products. Ballard's fuel cell stacks are incorporated into batteries from FirstEnergy, IdaTech, Palcan Fuel Cells, and Plug Power. The company generates 35% of its sales from the US; it operates through a handful of facilities in Canada, Mexico, and the US.