Hydrogen Cars

There has been a lot of hype about hydrogen cars over the past few years.  Every so often there's a news story about an auto maker developing a hydrogen fuel cell car, but some large question marks remain around this technology.

Hydrogen Fuel Source

Fossil Fuels

Currently most of the hydrogen we produce comes from fossil fuels.  48% comes from natural gas, 30% from oil, 18% from coal, and just 4% from electrolysis.  When extracting hydrogen from fossil fuels, it negates much of the potential environmental benefit of using hydrogen as a fuel.

Aluminum Alloys

New research has shown that hydrogen can be obtained by combining aluminum alloys and water.  However, this is a new discovery which will first be tested in small engines, such as lawn mowers.  There are concerns with the amount heat produced by the reaction, but it may one day provide an environmentally friendly and abundant source of hydrogen, because aluminum is an extremely common element.  This process is probably the most promising development for hydrogen technologies because it both provides a environmentally friendly source of hydrogen fuel and potentially solves the transportation and storage problems discussed below.

Electrolysis

The reason hydrogen has been hyped so strongly is that theoretically it can be extremely environmentally friendly, through eletrolysis.  This is when the atomic bonds in a water molecule are broken by passing an electric current through the water, separating the hydrogen and oxygen atoms.  However, it requires large amounts of energy to break these strong atomic bonds, and the process is only 50-70% efficient.

Efficiency

Either obtaining hydrogen from fossil fuels or electrolysis, the process is no higher than 70% efficient.  In other words, 30% of the energy involved is wasted.  The other efficiency problem is with hydrogen fuel cells, which are only approximately 40% efficient.  In comparison to electric vehicles, which use extremely efficient processes (chargers, batteries, and electric motors are all on the order of 90% efficient), this is a poor efficiency.  Electric cars are 3-4 times more energy efficient than hydrogen fuel cell cars.

 [Image source: MovGPO, Battery EV vs. Hydrogen EV.png, 2007-07-26]

Infrastructure

Another serious downside to using hydrogen as a fuel source is the lack of a transportation and storage infrastructure.  If hydrogen is to be used as fuel, people need to have a way to access it at refueling stations.  So first you would need some sort of hydrogen storage stations - which is not an easy proposition for a highly flammable and explosive gas - and you also need a way to transport large quantities of hydrogen to these fueling stations.  Building this infrastructure from scratch is an incredibly expensive proposition, and one which will not be undertaken unless there is a demand from hydrogen fuel cars.  But people won't purchase hydrogen cars unless there is a fuel source available, and thus there is a chicken-and-egg challenge.

In comparision, electric cars already have this infrastructure in place - the power grid.

Cost

Currently hydrogen fuel cells require platinum - anything but a cheap metal.  The Honda FCX Clarity

hydrogen fuel cell car is going to lease for $600/month over a 3 year period.  Leasing the Clarity over those 3 years will cost as much as outright purchasing a Toyota Prius, and will do more environmental damage because of the source of its hydrogen (as discussed above, mainly from fossil fuels).  Until there is a technological breakthrough, hydrogen fuel cars will not be economically viable.

On top of that, hydrogen fueling stations appear to cost 1,000 times more than electric car recharging stations.

Are hydrogen cars worth the hype?

Considering that electric cars have the same benefits of hydrogen cars, plus the technology is equally or more advanced, the fuel is readily available, and the infrastructure is already in place, electric vehicles are a far more promising technology.  It's possible that a technological breakthrough - such as the hydrogen from aluminum alloy process - could make hydrogen cars competetive with electric vehicles, but EVs are currently the more promising technology.