I’ll confess up-front: this post exists largely because I feel the need to say things about energy and environment, topics which have been a bit lacking on this page. So I feel the need for a little public communication, sharing some of the things I know – things which to me seem fairly self evident but, I recently realized, only do so because I spend so much time dealing with them . So I’m going to do a series of brain-dumps, sharing some facts about the renewable energy landscape with a dash of opinion blended in.
Hydrogen Power then.
Well that turn of phrase is wrong/misleading for a start. Hydrogen is not a power source. It is only an energy vector , a means of transporting energy generated by other means from place to place. This is because hydrogen doesn’t occur as a free gas on the earth’s surface, only in the form of compounds such as water. Energy must be used to extract it from these compounds, and since losses are inevitable in the energy chain the amount of energy that is obtainable from the hydrogen produced must be less than the amount of energy put in to obtain it. Certainly if we want to obtain hydrogen cleanly from water – the other option is to reform natural gas. Although this has a more favorable energy balance, it also produces CO2.
Now, although hydrogen isn’t an energy source, it has created a lot of interest and so it’s worth looking into why. Hydrogen is an energy rich substance by weight (although not by volume) – this should make it easier to carry a lot of energy over long distances. The primary interest was as a replacement for petrol – it seemed that it would have the energy density characteristics and ease of refueling that batteries lacked. This was also affected by the direction of fuel cell research. Fuel cells are, at their most general, devices which turn a chemical reaction into electricity. However for a long time the only successful fuel cell designs were ones which used hydrogen. Using hydrogen + fuel cells for transport therefore seemed logical.
However we are now in 2012 and hydrogen cars have gone nowhere, while battery powered ones are gradually coming onto the market and being generally well received by early adopters. The key is infrastructure – no one was prepared to make the first move to build out a hydrogen fueling infrastructure. Which is understandable given the costs and risk involved. Conversely, electricity is everywhere already, and batteries for storage have benefited massively from the synergy with mobile electronics research.
I have more recently seen efforts to introduce hydrogen as a “fuel” for other applications, such as CHP or small scale power generation, or even home heating. But I am not convinced. Producing hydrogen remains a major problem – you are not really using hydrogen as a fuel, you are just trying to transport energy generated somewhere else. If you are producing this energy anyway, why not just use it directly as electricity. It could be argued that hydrogen would allow energy to be carried much further, for instance for energy generated in the Sahara desert to be transported to Europe. But hydrogen transport is not really less challenging than long distance electricity transmission – hydrogen is not a very easy gas to handle and no infrastructure exists for shipping it, while power lines run the length and breadth of Europe (although the capacity upgrades needed are not to be taken lightly either)
If a method of producing hydrogen directly from sunlight more cost effectively than producing electricity from sunlight could be developed, the situation might change. But that’s a very big “if”.
Another less well known factor in the hydrogen debate is the emergence of other forms of fuel cells such as Solid Oxide fuel cells. These cells run on more complex molecules than the PEFCs used with hydrogen, giving them much more fuel flexibility. They can run on substances that are “real” fuels, i.e. ones which are a net source of energy rather than just an energy carrier. For example some can run on methane gas which could be produced from sewage, or on various biofuels made from waste products. They essentially target the same niche in the energy generating market as gas turbines and diesel generators do (and in fact can be made to run on the same fuels), are much more efficient making them ideal for decentralized applications and backup generators. And because they can use more classical fuels, they don’t need to wait for a hydrogen infrastructure to emerge to become commercially viable.
In the end, there just isn’t much of a niche where hydrogen provides any advantages. Possibly there will still be options in transport where the limitations of battery tech continue to bite – situations that demand very fast refueling and long ranges, and where a source of hydrogen can be guaranteed. Public transport and long haul trucks spring to mind. But outside of these niches, especially in cars which were always supposed to be at the heart of the “hydrogen economy”, hydrogen is never going to make it big.