January 4, 2006
The Myth of the Hydrogen Economy
By: Rowan Wolf
BY: DALE ALLEN PFEIFFER also see his blog
There is a lot of talk about the hydrogen economy. It is at best naïve, and at worst it is dishonest. A hydrogen economy would be a pitiful, impoverished thing indeed.
There are a number of problems with hydrogen fuel cells. Many of these are engineering problems which could probably be worked out in time. But there is one basic flaw which will never be overcome. Free hydrogen is not an energy source; it is rather an energy carrier. Free hydrogen does not exist on this planet, so to derive free hydrogen we must break the hydrogen bond in molecules. Basic chemistry tells us that it requires more energy to break a hydrogen bond than to form one. This is due to the Second Law of Thermodynamics, and there is no getting around it. We are working on catalysts which will help to lower the energy necessary to generate free hydrogen, but there will always be an energy loss, and the catalysts themselves will become terribly expensive if manufactured on a scale to match current transportation energy requirements.
All free hydrogen generated today is derived from natural gas. So right off the bat we have not managed to escape our dependency on nonrenewable hydrocarbons. This feedstock is steam-treated to strip the hydrogen from the methane molecules. And the steam is produced by boiling water with natural gas. Overall, there is about a 60% energy loss in this process. And, as it is dependent on the availability of natural gas, the price of hydrogen generated in this method will always be a multiple of the price of natural gas.
Ah, but there is an inexhaustible supply of water from which we could derive our hydrogen. However, splitting hydrogen from water requires an even higher energy investment per unit of water (286kJ per mole). All processes of splitting water molecules, including foremost electrolysis and thermal decomposition, require major energy investments, rendering them unprofitable.
Hydrogen advocates like to point out that the development of solar cells or wind farms would provide renewable energy that could be used to derive hydrogen. The energy required to produce 1 billion kWh (kilowatt hours) of hydrogen is 1.3 billion kWh of electricity. Even with recent advances in photovoltaic technology, the solar cell arrays would be enormous, and would have to be placed in areas with adequate sunlight.
We must also consider the water from which we derive this hydrogen. To meet our present transportation needs, we would have to divert 5% of the flow of the Mississippi River. This would require yet more energy, further reducing the profits of hydrogen. This water would then have to be delivered to a photovoltaic array the size of the Great Plains. So much for agriculture.
The only way that hydrogen production even approaches practicality is through the use of nuclear plants. To generate the amount of energy used presently by the United States, we would require an additional 900 nuclear reactors, at a cost of roughly $1 billion per reactor. Currently, there are only 440 nuclear reactors operating worldwide. Unless we perfect fast breeder reactors very quickly, we will have a shortage of uranium long before we have finished our reactor building program.
Even hydrogen fuel derived from nuclear power would be expensive. To fill a car up with enough hydrogen to be equivalent to a 15 gallon gas tank could cost as much as $400. If the hydrogen was in gaseous form, this tank would have to be big enough to accommodate 178,500 liters. Compressed hydrogen would reduce the storage tank to one tenth of this size. And liquefied hydrogen would require a fuel tank of only four times the size of a gasoline tank. In other words, a 15 gallon tank of gasoline would be equivalent to a 60 gallon tank of hydrogen. And, oh yes, to transport an equivalent energy amount of hydrogen to the fueling station would require 21 times more trucks than for gasoline.
Compressed and liquefied hydrogen present problems of their own. Both techniques require energy and so further reduce the net energy ratio of the hydrogen. Liquid hydrogen is cold enough to freeze air, leading to problems with pressure build-ups due to clogged valves. Both forms of hydrogen storage are prone to leaks. In fact, all forms of pure hydrogen are difficult to store.
Hydrogen is the smallest element and, as such, it can leak from any container, no matter how well sealed it is. Hydrogen in storage will evaporate at a rate of at least 1.7% per day. We will not be able to store hydrogen vehicles in buildings. Nor can we allow them to sit in the sun. And as hydrogen passes through metal, it causes a chemical reaction that makes the metal brittle. Leaking hydrogen could also have an adverse effect on both global warming and the ozone layer.
Free hydrogen is extremely reactive. It is ten times more flammable than gasoline, and twenty times more explosive. And the flame of a hydrogen fire is invisible. This makes it very dangerous to work with, particularly in fueling stations and transportation vehicles. Traffic accidents would have a tendency to be catastrophic. And there is the possibility that aging vehicles could explode even without a collision.
On top of this, we must consider the terrific expense of converting from gasoline to hydrogen. The infrastructure would have to be built virtually from scratch, at a cost of billions. Our oil and natural gas based infrastructure evolved over the course of the past century, but this transition must be pulled off in twenty years or less.
Automobile engineers and others within the industry do not believe we will ever have a hydrogen economy. Daimler-Chrysler has admitted as much. Rather than developing a hydrogen economy, it makes more sense - and will always make more sense - to buy a more efficient car, ride public transport, bicycle or walk.
Posted by Rowan at January 4, 2006 9:25 AM Category: Peak Oil