“You want water? Wait, let me get you some from the hydrogen fuel tank, and let me charge your cell phone while I’m at it,” might sound dramatic, but it is science. We know from high school chemistry that 2 atoms of hydrogen and 1 atom of oxygen are in 1 molecule of water (H2O). And, it is also science that hydrogen when mixed with oxygen not only produces water but energy as well. And, this energy is as clean as any energy can get, as the by-product is only water, and that too, in its purest form. This is the fundamental of the fuel cell that uses hydrogen as its fuel, and either pure oxygen or atmospheric air for its combustion and thereby the extraction of heat energy.
All roads lead to Rome
There are many ways hydrogen could be used to produce energy, only one such being the fuel cell. Hydrogen could be mixed with diesel in regular internal combustion engines, they could charge electric batteries with the energy extracted from their combustion, they could power heavy moving objects from trucks, to trains, to rockets, they could generate stationary energy as in power plants, and they could be used as an alternative to natural gas for heating applications. (Link)
Making cheese from pasta
Hydrogen is not naturally occurring in nature in large quantities. Hence, it has to be produced only by synthetic means and using external intervention or energy. However, it could be produced in a multitude of ways, a few of them being extraction by oxidation of natural gas, or any hydrocarbon for that matter, from water through electrolysis, by biomass gasification, or by solar thermochemistry. There are color codes to categorize how hydrogen gas has been produced, such as, ‘grey’ hydrogen indicating it was a by-product of an industrial process, ‘blue’ hydrogen indicating it was produced through a process that produced CO2 as well, and finally ‘green’ hydrogen indicating it was produced entirely through renewable sources. So, yes, it is possible to not only use hydrogen in an environmentally-friendly way but also use it so. In fact, hydrogen could also be produced by a photobiological process using the photosynthetic activity of bacteria and green algae, making the hydrogen as green as the greenest algae you could find. (Link)
Where we stand today
Research on using a mix of diesel and hydrogen in heavy commercial vehicles has yielded a result that boasts a 40% reduction of CO2 emissions. Trials are also underway to adapt engines to use 100% hydrogen as fuel, which could provide a range of 300 km/17 kg of hydrogen. For comparison, one could consider 1 kg of hydrogen to have the same energy as 1 gallon of diesel. Hence, this indeed points to the superior overall efficiency of the hydrogen fuel system, as a typical diesel engine consumes 105 – 150 liters of diesel for a 300 km range, on average (Link).
Got to pull our socks up
The problem with hydrogen is that under normal pressure, it has low energy content, that is, enormous space would be required to store enough hydrogen to power a reasonably-sized vehicle for a small distance. For this reason, hydrogen is usually stored under high pressure, and low temperature to minimize volume. Unfortunately, this introduces high cost and weight to the vehicle. For example, a full tank on the Toyota Mirai contains only 5.7% hydrogen by weight, with the rest of the weight being that of the tank itself, which is also one of the reasons that hydrogen fuel is more suited for heavy vehicles, while batteries are more efficient for cars. Also, because hydrogen could produce heat on exposure to atmospheric air (since it contains oxygen), leakage of hydrogen tanks could be hazardous, as it needs very little energy to combust and produce heat/fire. Explosions of hydrogen filling stations have been reported in the past as well. (Link)
Although hydrogen as an energy source has its limitations, the present political drive towards clean and green energy is bound to push research to evolve the production/storage/usage of hydrogen, as it is a versatile fuel and energy source. And, this has already resulted in the research and development of alternative storage media, such as complex metal hydrides. With the advancement of technology as it is, hydrogen is so much the in-thing of tomorrow’s fuel that it won’t be surprising to find it in every heavy vehicle in the coming decades. Also, we are not far from a day when we could cook using fire from a stove powered by hydrogen fuel, extracted from a small tank of water, through electrolysis driven by electricity from a small wind turbine. “Camping out, are we? No problem!”