| H2Go: are we nearly there yet? | ||
| Remember the hydrogen economy? A few years back, you couldn’t move for stories of how pollution-free fuel cells were going to keep us all powering ahead into a low-carbon future. Now it’s all gone rather quiet. So has hydrogen been oversold? Simon Hadlington sorts hope from hype. | ||
|
For a world
panicked by peak oil and rising temperatures, hydrogen has a simple,
seductive appeal. We don’t have to abandon our cars or dim the lights: we
just switch from hydrocarbons to hydrogen. After all, cars, buses, trucks,
not to mention domestic generators and who knows what else, could be powered
not by fossil-fuels but electricity produced in onboard fuel cells. They’d
take in hydrogen – plus oxygen from the air – and all that would come out of
the exhaust pipe would be water clean enough to drink.
The concept is compelling. The prototypes work. There are fuel cell motors in operation out there – even in experimental commercial service, notably on London’s RV1 bus route [see right]. Enterprising initiatives are out there demonstrating the technology in other ‘real life’ applications, from the latest in road signs to lighthouse lamps. Surely all we have to do now is scale up into the bright new tomorrow. So what are we still waiting for? Four things...
To take the last first: fuel cells are already available commercially, and the technology is advancing rapidly, but price is still a big barrier. They currently cost about £2,000 per kilowatt – about ten times too expensive to be commercially viable in cars. The other main problems are durability and weight. Kevin Kendall, chemistry professor at the University of Birmingham and one of the UK’s leading experts on fuel cells, sums up the challenge: “We need to develop cheaper, simpler and longer-lasting membranes, to improve the catalysts at the electrodes to be able to use something less expensive than platinum and less sensitive to impurities in the hydrogen, and to improve the design of the cells to make them lighter and more compact.” When it comes to storing hydrogen onboard a vehicle, the key issues are space, compression and safety. Together they add up to a significant set of technological hurdles. The simplest solution is to compress the hydrogen and store it in tanks, probably made of reinforced carbon composite. But the compression itself needs a large input of energy. Another promising technology involves storing the hydrogen as a ‘metal hydride’ within the structure of various metallic alloys. Absorbed into the structure of the metal, it can then be released by gentle warming. The system is capable of storing relatively large quantities of hydrogen, but is susceptible to contamination. Other, more exotic, methods are being researched, including the use of carbon ‘nanotubes’ and tiny hollow glass spheres. Then there’s the infrastructure needed to get the hydrogen from the point of production to the point of use. The most likely approach would be to pipe it to bulk storage facilities, and then on to fuelling stations. A new pipeline system, then? Some people think that lines currently used to transport natural gas might be useable, but it will take more research to determine the best materials for carrying hydrogen, and how best to avoid the risk of pipes becoming brittle and breaking. Similar questions apply to safe bulk storage. For fuelling stations, new dispensers akin to petrol pumps need to be developed. And finally – how to produce hydrogen in sufficient quantities to fuel a genuine hydrogen economy? This is the real crux of the matter. Much has been made of the fact that hydrogen is such a hugely abundant element – after all, each molecule of water is two-thirds hydrogen. However, it’s not just there on tap – on the contrary, it requires energy to extract it from water in its useful, molecular form, as hydrogen gas. The process itself isn’t complicated. The simplest way is to pass an electric current through water – the process of electrolysis. But it is rather chicken and egg: where does the electricity come from in the first place? Burning fossil fuels to make it rather defeats the object of the whole exercise – you are just shifting your CO2 emissions from the point of use (your old car’s petrol engine) to the point of production of the (hydrogen) fuel. So much for so-called ‘zero emission’ vehicles.
So what are the other options? Well, there’s nuclear power. Uncomfortable as it may be for some hydrogen evangelists, there’s plenty of enthusiasm for that in the nuclear lobby. The wind, wave and solar power brigade might make more appealing bedfellows – but will we be getting enough?
“Five thousand offshore wind
turbines could produce enough hydrogen to run 4.32 million cars.”
The Clean Energy Educational Trust’s website (www.hydrogen.co.uk) carries a cogent argument for the use of wind power to provide the electricity to make hydrogen for transport. The Trust calculates that 5,000 offshore wind turbines, each generating 2 megawatts of electricity and dedicated purely to the production of hydrogen, could produce enough to run 4.32 million small- or medium-sized cars. Which sounds a lot (of cars, as well as turbines). But we’ve already got more than five times that many cars in the UK, and the motor industry is reckoning on 30 million by 2020. Even by the Trust’s calculations, it would need something in the region of 35,000 wind turbines to run that lot on hydrogen fuel cells. Energy consultant Jim Oswald is concerned that “the enormity of the green challenge is not understood.” He and Andrew Oswald, an economist at the University of Warwick [see ‘ Taxing Tomorrow’, GF51] , say that there are many good reasons to consider switching vehicles from oil to hydrogen, to reduce both emissions and the country’s reliance on importing oil. But their estimate is that providing enough hydrogen to run all the UK’s road vehicles would require around 100,000 wind turbines. If these were sited offshore, there would be a 10-kilometre-deep strip of turbines encircling the entire coastline of the British Isles. Evolution not revolution Reach for the sun? Mike Koefman, secretary of the Campaign for a Hydrogen Economy, believes that photovoltaic technology has the long-term potential to deliver hydrogen across the globe. Hot, sunny regions such as North Africa would export energy to northern Europe. Such a scenario, however, would require big advances in so-called organic photovoltaic systems. These are prospectively much cheaper and easier to mass-produce than current solar cells, but most experts accept that they are only at an embryonic stage of development. So a hydrogen revolution seems less likely than some of those sunnier forecasts a few years back. We’re not poised to see a wholesale switch from hydrocarbon fuels to hydrogen. But a hydrogen evolution is less fanciful. Dr Graham Hillier, director of fuel cell applications at the Centre for Process Innovation, puts this in context. “A hydrogen economy would go hand in hand with other strategies such as combined heat-and-power plants and district heating. I am not entirely convinced we will ever escape from fossil fuels, but we can go a long way towards improving energy efficiency and recycling existing sources of energy such as methane from landfill. Personally I envisage more integrated energy systems, with smaller, self-sufficient communities in which hydrogen plays an important role.” There’s a lot of useful infrastructure already in place, as a legacy of the chemical industry, to give a flying start to hydrogen micro-economies in various parts of the country. By ‘joining up the dots’ to link up with facilities in other regions, a nationwide shift could become a practical prospect – even if, initially, a patchy one. Northern lights If the hydrogen economy’s going to happen anywhere in Britain, the Tees Valley is the best bet. The long-established chemical industry on Teesside already produces 75,000 tonnes of hydrogen a year and has an extensive storage and distribution infrastructure. These are the building blocks of the Tees Valley Hydrogen Project, part of Renew Tees Valley Ltd, a publicly funded company charged with generating green jobs, mainly in energy and recycling. “The generators and consumers are linked together by some 30km of pipelines, which means 700,000 people are never very far away from a hydrogen main available on tap, at a hundredth of the cost of hydrogen in cylinders,” says chief exec Dermot Roddy.
“If the hydrogen economy’s going
to happen anywhere in Britain, the Tees Valley is the best bet.”
The hydrogen is produced mainly from methane, but there are plans to develop a coal gasification plant, producing hydrogen and carbon dioxide. The latter will be piped out to North Sea oil wells and forced into the seabed where it will enhance recovery of oil while itself remaining trapped – part of the much-hyped carbon sequestration approach to tackling climate change. “While this is not a completely green solution – we are burning coal – we are recovering more oil than we would otherwise and we are manufacturing hydrogen [in the process],” says Roddy. Construction of the plant is due to start this year, and it should be in production in 2009. The company is also looking to generate hydrogen from biomass, notably willow coppice, through a process of gasification. The hydrogen is produced through incomplete combustion of the biomass in an oxygen-depleted atmosphere. It should be a carbon neutral process, as the CO2 emitted is effectively captured by the newly growing crop. Simon Hadlington is a freelance science journalist. Additional material by Hannah Bullock. To subscribe or visit go to: http://www.greenfutures.org.uk/ |
||