In the beginning of this century you could not open your news paper or switch on your television, or you were confronted with the term hydrogen economy. Now ten years later the hydrogen economy has become less prominent in public discourse. The question of this article is whether the hydrogen economy was nothing but a hype? But first what is the hydrogen economy?
One could classify modern society as a petroleum or more accurately a fossil-fuel economy (since besides petroleum, coal and natural gas are still important). This because our society and its economy heavily depends on burning fossil fuel to meet our energy demands. Though fossil fuel are often referred to as energy sources, they are actually a form of energy storage as they are the products of photosynthesis accumulated over millions of years. That we call fossil fuels energy sources nevertheless, is mostly because they have been formed without human involvement and are available in nature.
A hydrogen economy is a hypothetical society where hydrogen is the primary energy carrier. Unlike fossil fuels pure hydrogen cannot be found in nature on Earth. Due to its low density free hydrogen will escape into outer-space once released, consequently free hydrogen will not accumulate naturally on this planet. Therefore hydrogen has to be produced artificially, but this process takes energy and only a portion will be regained once hydrogen is burned.
There are several methods to produce hydrogen, the most common are electrolysis of water and steam reforming of natural gas. The latter process is cheaper and is currently the most important source of commercial hydrogen gas. But since it is depends on fossil fuel, it is generally rejected by proponents of the hydrogen economy. Hence we are left with electrolysis, though some scientists are investigating biological production of hydrogen.
Since we need electricity to make hydrogen, the question is now how to generate electricity? Assuming that fossil fuels are out of the picture, we have basically two sides: one at the “green” side which promotes primarily wind and solar power to generate electricity, and on the other side which primarily promotes nuclear power.
But why should we use electricity to make hydrogen? First electricity not be stored, which is a problem because production and consumption often do not match. Nuclear power station works most efficient if they have a constant out put and windmills produce electricity whenever there is wind. Consequently there might be periods of over and under production, this could be mitigated if we could store the surplus electricity for use during periods of peak consumption.
The idea is to use surplus electricity to make hydrogen, to store this and to use fuel cells during peak demand. A fuel cell is a kind of battery which use the reaction between hydrogen and oxygen to produce electricity and water. Fuel cells are more efficient than internal combustion engines. Because fuel cells are relative small, they are championed for use in mobile application like cars.
One could ask why hydrogen for energy storage? Initially the prime reason was that “classical” batteries had several disadvantages. These are mainly that batteries took hours to be charged and then only limited energy capacity. Of all chemical fuels hydrogen has the highest energy content per unit mass, but because hydrogen is a gas with an extremely low density it has a low energy density per unit volume.
For stationary applications, such as a peak power plant, this not a very big concern as one could just build big tanks. But for mobile applications such as cars, this is very inconvenient. So the bottleneck for the hydrogen economy is hydrogen storage, not the production of it. Various methods have been proposed to story hydrogen, but none has been yet proven to be practical.
The lack of progress in hydrogen storage, combined with the fast development in “conventional” batteries, have led that around 2008 the hydrogen economy has faded into the background. Electric cars are hot, all self-respecting cities are busy with installing charging points, while no-one ever talks about hydrogen cars in public anymore.
Another issue which has forestalled the transition towards a hydrogen-economy, is a variant of the chicken-egg dilemma. Should people first buy hydrogen cars or should there be first hydrogen gas stations? The introduction of plug-in hybrid cars has eliminated this dilemma for electric cars, since they could use gasoline where no charging points are available, while creating enough incentives to install charging points.
Motivated by the problem of storing hydrogen, some scientists have proposed to use hydrogen gas created through electrolysis to produce synthetic hydrocarbons. This process, also called Fischer-Trops fuels, require a source carbon dioxide. This could be CO2 from air, but currently mostly CO2 from burning coal or biomass is used. A major advantage of these synthetic fuels is that they could be used in conventional internal combustion engines without modifications.
My conclusion would that the “hydrogen economy” was nothing more than a hype. Developments in conventional battery technology has made the hydrogen car obsolete even before it had become common. Given problems with hydrogen storage, synthetic fuels seem to be a more promising alternative.
The Oil Drum – site on post-peak oil energy
Space-based solar power? – On Republic of Lagrangia
Solar Islands and Seasteading – On Republic of Lagrangia
The New Girl in Town – A story written by me set in a post-peak oil future