Many experts tout fuel cells as one of the cleanest forms of green energy, because the devices reduce CO2 emissions and provide greater energy efficiency than combustion engines. The only exhaust products are water, heat and oxygen-depleted air. The technology has huge potential, but several big hurdles continue to challenge engineers.
Hydrogen has always been considered too expensive for widespread commercial use. However, prices to manufacture fuel cells have dropped dramatically in recent years, allowing more affordable applications.