How can we sustain our energy?
During the recent general election in the UK, we were bombarded with speeches and promises on the Health Service, education and taxation. However, despite its over-arching importance, very little was said by any of the main parties about future energy supplies. The mantra is that we will be moving away from a dependency on carbon fuels towards renewable ones, linked to which will be a ‘hydrogen economy’. And that’s about as much as is ever said.
While most people find the debate about future energy supplies baffling, as chemists we are in a good position to follow the discussions more closely since we understand underpinning principles like burning things and getting energy from them. And if you start doing the sums yourself, you begin to see that the future might not be so rosy as the ‘experts’ would have us believe.
The hydrogen economy
Let us consider the hydrogen economy as our example. The story goes like this. When fossil fuels run out we will still need some sort of fluid fuel since the electric aeroplane has yet to be invented. An ‘expert’ on a recent radio programme said that endless amounts of hydrogen could be produced by using electrical power generated from renewable sources. Norway could use hydro, the UK could use wind, Saudi Arabia could use solar and so on. When hydrogen burns, or reacts in a fuel cell, the only product is water, which replaces that which was used to make the hydrogen in the first place. It is a beautiful, logical solution to our energy problems until we look at the detail.
First there is the matter of production. Currently hydrogen would have to be produced by electrolysis since catalytic photolysis of water has yet to be perfected. Electrolysing sea water would be of no use because you would have to dispose of 35.5 tonnes of chlorine for every tonne of hydrogen produced. So the electrolyte would have to be based on fresh water with a non-reactive salt added, putting pressure on water supplies which are already overstretched in many countries. There would also have to be massive infrastructure installed to produce, store and distribute the hydrogen. Storing it as gas, even under pressure, would require huge facilities.
To put things into perspective, to supply just 1 per cent of the UK’s present energy needs would require the annual production of 800000 tonnes of hydrogen. Stored under moderate pressure of 1000kPa, this quantity of hydrogen would occupy a volume of one billion cubic metres. If we were importing 50 per cent of our hydrogen requirements in the gas state at a similar pressure we would witness the arrival of 240 specially converted oil tanker-sized vessels in the UK every day. Put another way, holding a two-week reserve of hydrogen fuel for the UK would require pressurised gasholders covering an area the size of Birmingham. Transporting and storing the hydrogen in liquid form would make much more sense but would require highly effective but prohibitively expensive insulation to keep H2 below its critical temperature of –240°C and all these problems exist before we even begin to consider the safety aspects of distribution and storing hydrogen in vehicles.
Next there is the question of whether the hydrogen would be so expensive to buy that the only people able to use it would be rock stars and heads of state. Most countries have little spare electricity-generating capacity so, in the UK, even more wind farms or nuclear power stations would have to be built and their cost included in the cost of the hydrogen produced over the life of the plant. To produce 10 per cent of UK energy requirements in the form of hydrogen by electrolysis would require a current-carrying capacity of 20 billion amps in the electrolysis plants and this in turn would require a massive increase in the country’s generating capacity. One experimental scheme in Germany, which uses solar energy, produced hydrogen at 30 times the cost of producing it commercially from methane. Clearly economies of scale and improving technology can bring costs down but the hydrogen economy is beginning to look like an expensive and possibly unaffordable option.
Power station © PhotoDisc |
Viable alternatives?
If we could turn the clock back, would the human race still form its dependency on fossil fuels? The answer is probably ‘yes’ because of their relative ease of extraction, convenience of use, and their ability to create great wealth. And I can foresee that we will continue depending on them until the last drop of oil and last lump of coal is extracted from the ground. Then what? It is just a guess but a more viable future than hydrogen might lie in biomass fuels which, after all, would have zero contribution to net atmospheric carbon dioxide levels. A young chemist with an eye to posterity should think about doing research into the low-energy catalytic conversion of carbohydrates into alkanes via alkanols. The hydrogen economy could provide any H2 that might be needed for the process.
Finding a replacement for fossil fuels is the tough nut to crack. On the other hand, we have any number of ways of generating electricity without burning coal or natural gas. Like it or not, there is little alternative to a much greater dependence on nuclear power if we are to have a stable and dependable electricity supply in the future. Modern reactors are much more efficient and produce much less waste than the early designs of the 1950s and the Accelerated Driven System’s sub-critical fission reactor could be the answer since it reportedly can run on waste from other reactors if necessary. Much of the fear about nuclear power stations is not backed by any hard evidence. France has been safely generating more than 75 per cent of its electricity supplies by nuclear power for decades and there is no evidence of more birth defects in France than in countries with far fewer nuclear reactors, or that the incidence of leukaemia is any higher. If asked whether I would like to live close to a nuclear power station then the answer is that I already do. It is being shut down but I think it should be replaced without delay.
Dr Wilson Flood is a chemistry education consultant. He can be contacted at wilson@flood6.fsnet.co.uk.
