Electric cars are touted as the vehicles of the future, but there are major infrastructure issues to be addressed before they could become the norm. The other option put forward by those who would like to see a replacement for the internal combustion engine is the hydrogen-powered car, using fuel cells to produce its own electricity, rather than storing it in batteries.
A decade ago, hydrogen seemed to have an equal chance of becoming the fuel of the future as did stored electricity. Not so now; despite occasional pilot projects – usually involving buses – and a handful of concept cars and filling stations, there seems to be little enthusiasm for hydrogen-powered vehicles at present. Meanwhile, plug-in hybrid cars are no longer a novelty and even pure electric cars are becoming an everyday sight in some towns and cities.
Hydrogen as a car fuel shares the same problem with electricity of lack of the necessary infrastructure for refuelling. However, there are additional difficulties that seem certain to limit its possible introduction. One is that fuel cell technology has progressed relatively slowly, meaning that it remains difficult to find space to install enough of them to power a vehicle adequately. Costs are still high as well. The other major drawback is the difficulty of keeping compressed or liquefied hydrogen properly contained. As the lightest element, it is prone to leak from almost any tank. Leaving a fuelled hydrogen car in a garage for a few days would see a noticeable loss of fuel, for example.
But although transport fuel is so much in the public eye and comprises about a quarter of total energy use, a large part of national energy consumption comes neither from transport nor electricity generation, but heating, which takes something like 30% of the total. Some of this is electric or oil-fuelled, but a high proportion of homes rely on gas. Natural gas – methane – is the lowest-carbon type of fossil fuel in use and is clean and affordable. But if the ambitious decarbonisation targets accepted by the government are ever to be realised, even this has to be changed before too long.
One major option is to convert heating to electric systems, effectively starting from scratch in most homes. This, of course, only makes sense if the electricity generated comes from low-carbon sources, otherwise emissions are simply transferred from the home to the power station, as for electric cars. Electrification of both transport and domestic heating sectors would require large investment in new nuclear power stations, unless some viable way can be found to smooth the output of solar and wind farms sufficiently to provide a secure supply. Don’t hold your breath on that one.
There is, however, another proposal, summed up in this Telegraph headline: UK homes could be heated by hydrogen under plan to tackle global warming. Northern Gas Networks, the utility responsible for the area, has published a feasibility study (H21 Leeds Citygate) in which it is estimated that converting Leeds – with a population of three quarters of a million, the third biggest city in the UK – from natural gas to hydrogen by 2030 would cost £2 billion. Other towns and cities could then follow.
The company believes that the network of plastic gas mains is perfectly capable of being used for hydrogen distribution in urban areas and that existing domestic boilers and cookers could be converted to burn hydrogen in a similar way to the way the changeover from coal gas to natural gas was carried out in the 1960s.
Problems remain, of course. One important one is the lower energy density of hydrogen means the existing distribution network has a reduced overall capacity, which would presumably have to be overcome by installing wider diameter pipes. Given that there are still existing iron gas mains being replaced by plastic ones after many years of work, this is not a small task.
In theory, at least some of the hydrogen could be produced by electrolysis of water, using the intermittent output of wind and solar installations. This is one way the output of renewable energy could perhaps be smoothed with a degree of success, but only if the system had sufficient storage capacity to cope with long periods of low output. Since storage of significant quantities of hydrogen would require it to be compressed, which greatly increases the potential for leakage, this seems unlikely to be fully successful.
The Leeds project team proposes a different solution. Natural gas would be delivered to a series of steam methane reforming plants. The first, high temperature step forms hydrogen and carbon monoxide:
CH4 + H2O → CO + 3H2
This can be supplemented by a second step using a catalyst to produce carbon dioxide and more hydrogen:
CO + H2O → CO2 + H2
So far, so good, but what to do with the carbon dioxide? To quote from the Telegraph article “The carbon would then be disposed of using carbon capture and storage technology, for example by pumping it into a disused North Sea gas field…” This almost throwaway remark highlights the highly provisional nature of this proposal. Ignoring the clear lack of understanding of the form the ‘carbon’ would be in, it assumes that Carbon Capture and Storage (CCS) would be available on a routine basis.
Although widely touted as a vital technology for a low-carbon future, it seems to have made zero progress towards becoming a commercial reality in the last decade or so. There are some relatively small demonstration projects, but offers of government funding have failed to produce a credible large-scale project in the UK.
Overall, we have to say that there are some interesting ideas floating around, but rather little evidence that any of them will be viable in the timescale demanded by the stringent carbon budgets. The UK will be struggling with the implications of Brexit for the next few years, but at some stage it will become clear that a rigorous assessment of energy and climate change targets and policies needs to be done. Perhaps this week’s announcement that energy and climate change are to become part of the overall business brief may herald a degree of realism at last.
The Scientific Alliance
St John’s Innovation Centre
Cambridge CB4 0WS