<P> A hydrogen vehicle is a vehicle that uses hydrogen as its onboard fuel for motive power . Hydrogen vehicles include hydrogen - fueled space rockets, as well as automobiles and other transportation vehicles . The power plants of such vehicles convert the chemical energy of hydrogen to mechanical energy either by burning hydrogen in an internal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to run electric motors . Widespread use of hydrogen for fueling transportation is a key element of a proposed hydrogen economy . </P> <P> As of 2016, there are 3 hydrogen cars publicly available in select markets: the Toyota Mirai, the Hyundai ix35 FCEV, and the Honda Clarity . Several other companies are working to develop hydrogen cars . As of 2014, 95% of hydrogen is made from natural gas . It can be produced using renewable sources, but that is an expensive process . Integrated wind - to - hydrogen (power - to - gas) plants, using electrolysis of water, are exploring technologies to deliver costs low enough, and quantities great enough, to compete with hydrogen production using natural gas . The drawbacks of hydrogen use are high carbon emissions intensity when produced from natural gas, capital cost burden, low energy content per unit volume, production and compression of hydrogen, and the large investment in infrastructure that would be required to fuel vehicles . </P> <P> Automobiles, buses, forklifts, trains, PHB bicycles, canal boats, cargo bikes, golf carts, motorcycles, wheelchairs, ships, airplanes, submarines, and rockets can already run on hydrogen, in various forms . NASA used hydrogen to launch Space Shuttles into space . A working toy model car runs on solar power, using a regenerative fuel cell to store energy in the form of hydrogen and oxygen gas . It can then convert the fuel back into water to release the solar energy . Since the advent of hydraulic fracturing the key concern for hydrogen fuel cell vehicles is consumer and public policy confusion concerning the adoption of natural gas powered hydrogen vehicles with heavy hidden emissions to the detriment of environmentally friendly transportation . </P>

Where do scientists hope to get hydrogen to use in cars
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