Jul 17 2009

Whatever Happened to Hydrogen Fuel Cells?

I wonder if in 20 years comedians will joke about the coming of the hydrogen economy the way they now joke (in the US) about the coming of the metric system. For about the last decade I have been reading about hydrogen fuel cell cars as if they were just around the corner. General Motors fatefully decided to pursue hydrogen fuel cell cars rather than developing hybrid or battery technology. In 2003 G.W. Bush announced a 1.2 billion dollar initiative to develop the technology. In California Governor Schwarzenegger decided to build a hydrogen infrastructure in anticipation of the coming fuel cell car.

I was reminded of all this by yet another breathless article, this time on BBC news, talking up the hydrogen fuel cell car.  This one links development of hydrogen technology to the Apollo missions – a timely connection, given the upcoming 40th anniversary of Apollo 11. This article could have been written 10 years ago (minus a couple of anachronisms).

To be clear, I am not down on the hydrogen fuel cell. It is a nice technology with many advantages. The technology itself is about 150 years old – combine hydrogen and oxygen and you get energy + water. Water is a better byproduct than carbon dioxide. Hydrogen is a reasonably energy dense material. There are already hydrogen fuel cell cars on the road – the technology can work.

However, there are major roadblocks to filling our highways with such cars, and it is frustrating when the media or politicians gloss over these problems.  The BBC article does address one of them – where are we going to get all the hydrogen? They point out that currently hydrogen is stripped off of natural gas – a fossil fuel, and doing so releases carbon dioxide, although only about half as much as burning the gas directly. Therefore burning hydrogen from this source is not 100% green but it is still better than burning fossil fuels directly.

But then the article says this:

The ultimate goal is to produce an efficient way of extracting hydrogen from water. Imagine that? Cars powered by water.

Ugh!  Such cars would not be “powered by water” – they would be powered (ultimately) by whatever energy source was used to “extract” the hydrogen from water. This is a common mistake, often exploited by cranks and cons – water is not a source of energy. It takes energy to separate the hydrogen from the oxygen in water, and you get some (but not all – darn thermodynamics) of that energy back when you recombine hydrogen with oxygen back into water.

The bigger issue here is that there is no significant source of free hydrogen on the earth. If we lived in the upper atmosphere of Jupiter, maybe we could use hydrogen as an actual energy source. But on earth, hydrogen is not a source of energy – it is only a reservoir for storing energy, but that energy must come from somewhere else. Today most energy stored as hydrogen comes from natural gas (the real source of the energy), which is not a renewable source. In the future we may obtain most of our hydrogen by hydrolyzing water, using solar, wind, nuclear, or some other power source.  This all has to be calculated in when we contemplate a hydrogen economy.

The BBC article, however, did not even mention the biggest roadblock to fuel cell cars at present – how to store significant amounts of hydrogen on board a car.  Free hydrogen gas must be stored under pressure, and in order to get a decent range would require high pressures – 5,000-10,000 psi. This would still require a large tank to hold 4kg of hydrogen, which would get a range of 200-320 miles. Doable – but not easy.

Also, compressing the hydrogen to that pressure requires a lot of energy – and that energy has to be calculated into the efficiency of using hydrogen fuel.

There are possible solutions in the works. One method is to use metal hydride to absorb the hydrogen, allowing hydrogen to be stored without the need for high pressures.  However, this process creates heat, requiring cooling, or else the refueling process may take up to 40 minutes, which is not practical.

Another approach is to use a stack of a material that holds the hydrogen tightly packed together.

These approaches are all promising, and one or more of them may pan out. But so far there is no workable solution that can go into production now and produce a hydrogen fuel cell car that is practical enough (in terms of energy efficiency, range, safety, cost, and refueling time) to be widely used today. Further, no one can predict when the technology will be ready. And of course these issues are all separate from the need for a massive hydrogen infrastructure, which has its own technical limitations.

Further, the potential of the hydrogen fuel cell needs to be compared to the potential for battery powered electric cars. A battery powered car has the major advantage of not necessarily requiring a new infrastructure to be practical. This technology is also not ready for prime time, but advances in battery capacity and efficiency are also in the works.

This is, actually, an exciting competition between these two major approaches to replacing the fossil fuel engine. I honestly don’t know which one will win – both still require significant breakthroughs in order to cross that line where everyone will want one.

For this reason I think it is folly for politicians to bet on one technology over the other. In 2003 President Bush bet on hydrogen fuel cells. Now, President Obama is cutting funding for hydrogen research for cars and shifting into developing electric vehicles. I know the government has to decide what to fund, but it seems they should be hedging their bets a bit more rather than banking on one winner, and they certainly shouldn’t be trying to rig the game.

The auto industry also needs to decide where to spend their research dollars. Honda, Toyota and GM are continuing to invest in hydrogen, but are also developing electric car technology. These decisions may very well determine industry winners and losers in the next decade. We may be heading for a VHS vs Betmax war.

Let the better technology emerge victorious.

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