David Strahan, New Scientist 28 Nov 08;
WHATEVER happened to the hydrogen economy? At the turn of the century it was the next big thing, promising a future of infinite clean energy and deliverance from climate change. Generate enough hydrogen, so the claim went, and we could use it to transform the entire energy infrastructure - it could supply power for cars, planes and boats, buildings and even portable gadgets, all without the need for dirty fossil fuels. Enthusiasts confidently predicted the breakthrough was just five to 10 years away. But today, despite ever-worsening news on global warming and with peak oil looming, the hydrogen economy seems as distant as ever.
Even in Iceland, whose grand ambitions for a renewable hydrogen economy once earned it the title Bahrain of the north, visible progress has been modest. After years of research, the country now boasts one hydrogen filling station, a handful of hydrogen cars, and one whale-watching boat with a fuel cell for auxiliary power. A trial of three hydrogen-powered buses ended in 2007, when two were scrapped and the third was consigned to a transport museum. More trials are planned, but that was before the meltdown of the country's banking system. In California, where governor Arnold Schwarzenegger promised a "hydrogen highway" with 200 hydrogen filling stations by 2010, there are just five open to the public. Ten hydrogen-fuelled buses are due to come into service in London by 2010, but a plan for 60 smaller hydrogen vehicles was recently scrapped.
Despite the setbacks, there is still enormous effort going into hydrogen research. "Fuel cells have been a roller coaster of hype and disillusionment," says Martin Green of Johnson Matthey, which makes fuel-cell components for the car industry, "but I am more confident now that the hydrogen economy is going to happen than ever before."
Real products are now inching closer to market (see map). Honda claims to be the first company with a fuel-cell car, the FCX Clarity, in large-scale production. The company will make just 200 of these cars over three years, leasing them to customers for $600 per month, but so far Honda has shifted only three. Meanwhile General Motors (GM) has released the first 100 of its Equinox fuel-cell cars in a free trial for potential customers around the world. The company claims to have spent more than $1.2 billion on hydrogen R&D, and its research boss, Larry Burns, believes a market for fuel-cell vehicles will have emerged by 2014. So could hydrogen finally be ready for take-off, or will the mirage continue to recede?
Enthusiasts claim the remaining hurdles are not so much technical as financial, and that mass production will bring costs down dramatically. But so far the fuel cell, which lies at the heart of the entire hydrogen project (see "Hydrogen basics"), has remained stubbornly expensive - and bringing the cost down means changing the technology.
One problem is that hydrogen fuel cells, seen as a way to provide electricity in homes as well as vehicles, rely on precious-metal catalysts like platinum. A conventional automotive fuel-cell stack contains up to 100 grams of platinum, which could cost more than $3000 at today's prices. For the hydrogen economy to happen, the amount of platinum used in fuel cells has to come down, and soon.
Green says this won't be a problem. He is convinced that car makers will be able to slash the amount of platinum needed to just 20 grams per car by the time the technology is commercialised, which he foresees in the middle of the next decade. He also points out that the platinum can be recycled. Yet the numbers still look daunting.
Global car production in 2007 was just over 71 million, and even with only 20 grams of platinum per car a wholesale shift to hydrogen fuel cells would need 1420 tonnes of platinum per year, six times current production. At that rate the world's resources of platinum-group metals would be gone in 70 years, with output peaking long before reserves are exhausted. And that calculation makes no allowance for any growth in car production, or for the use of fuel cells in homes.
"Platinum is really scarce, and only produced in five mines around the world", says Armin Reller of the University of Augsburg in Germany, a former adviser on hydrogen to the Swiss government. Reller has studied the resource constraints on a range of new technologies (New Scientist, 23 May 2007, p 34) and is convinced that hydrogen can only be a partial solution at best, because it won't be possible to get platinum out of the ground quickly enough. "When you introduce new technologies the dynamics are such that even if you have the reserves, you can't produce them in time." It looks as if finding an alternative to platinum is a key challenge.
For the hydrogen economy to happen, industry must also come up with clean ways of producing it. Most hydrogen is currently made in refineries by heating natural gas with steam in the presence of a catalyst, but this usually relies on energy from fossil fuels and can generate carbon dioxide as a by-product. Because of this, the climate benefits of fuel-cell vehicles are scarcely better than those of petrol hybrids, according to a 2003 study led by Malcolm Weiss at the Massachusetts Institute of Technology. To make hydrogen cleanly and in bulk will almost certainly mean using renewable energy to electrolyse water, though this process is costly and energy-intensive.
Here too an enormous research effort is under way. A small British company, ITM Power, says it has found a way to slash the costs of electrolysis, allowing it to produce a small-scale electrolyser that will eventually be so cheap that every home could have one. This would also solve the hydrogen distribution problem. Instead of a system of pipelines, production could be decentralised, with fuel produced close to where it will be consumed. All this because the company has invented a new material which it says solves a long-standing conundrum of electrolysis.
Industrial electrolysis uses huge cells containing a liquid electrolyte like potassium hydroxide solution. This is alkaline, and so requires a nickel catalyst, much more plentiful and far cheaper than platinum. However, the hydrogen and oxygen gas must be kept separate within the cell - they are explosive when combined - and the equipment needed to do this with a liquid electrolyte would make the cell too bulky and costly for home use.
In the 1960s, NASA developed fuel cells that replaced liquid electrolytes with proton exchange membranes (PEMs), and the technology was applied to electrolysers too. However, the membranes were acidic, and an acidic membrane needs a platinum catalyst. What's more, the membranes themselves remain hugely expensive.
Now ITM Power claims to have found the holy grail of both electrolysis and fuel cell technologies: a membrane that can be made alkaline so nickel can replace platinum. Using half a dozen commonly available hydrocarbons, it has developed a solid but flexible polymer gel that is three times as conductive as existing PEMs. Thanks to its simplicity and the fact that it is made from readily available materials, it should also be massively cheaper.
The company claims that with mass production its membrane would cost just $5 per square metre, compared to $500 for existing PEMs. As a result, ITM Power says the electrolyser would cost $164 per kilowatt of capacity, against a current average of $2000 per kilowatt.
To start with, the company is building 10 of its "green box" electrolysers, each about the size of a large refrigerator. Jim Heathcote, chief executive of ITM Power, won't say what they will cost - certainly tens of thousands of pounds each - though he claims that mass production will bring the price tag down to less than £10,000 each.
These home electrolysers will be connected to mains water, the company says, and at least partially driven by solar panels or a wind turbine. The hydrogen produced could be used to drive a generator or fuel cell to produce electricity. It could also drive a car powered either by a fuel cell or an internal combustion engine converted to run on hydrogen. Heathcote argues this set-up would not only be low carbon but also reduce reliance on power grids, which he believes will become increasingly unreliable.
But do the sums add up? Take Heathcote's own home, where he has installed 60 square metres of solar panels - more than twice the average on UK properties with solar installations. Heathcote's array, costing £50,000, generates about 10,000 kilowatt-hours (kWh) per year. Connected to ITM's electrolyser, which is about 60 per cent efficient, the solar cells would produce enough hydrogen annually to yield 6000 kWh if used to power fuel cells. However, the average house in the UK uses almost four times as much energy as that each year.
If that same hydrogen were used to power ITM's converted Ford Focus, the results would be scarcely better. Using the output of Heathcote's home, the car could travel about 7200 kilometres a year, about half the average annual mileage of a British car. "It sounds absurd," Heathcote admits, "but that's how every technology starts. There are early adopters and then mass production brings costs down hugely." He accepts that many homes will never go completely off-grid, but he believes that with extra insulation many could use ITM Power's approach to obtain most of their household energy. And while he also admits that hydrogen cars will probably never be powered solely from the roof of the house, he maintains the fuel could still be produced by a home electrolyser using other energy sources, such as off-peak nuclear power.
The problems don't end there, though. ITM Power might have found a way to slash the costs of electrolysis, but nobody has solved a more fundamental problem: the inefficiency of the whole hydrogen fuel chain.
Energy losses
The point was made forcefully by Gary Kendall of the conservation group WWF in a recent report called Plugged In. Kendall, a chemist who previously spent almost a decade working for ExxonMobil, highlights how the energy losses in the fuel chain - from electrolysis to compression of the hydrogen for use to inefficiencies in the fuel cell itself - mean that only 24 per cent of the energy used to make the fuel does any useful work on the road.
By contrast, battery-powered electric vehicles and plug-in hybrids, with no electrolysis or compression to worry about, use 69 per cent of the original energy. "Cars running on hydrogen would need three times the energy of those running directly on electricity, and that would force us to build many more wind turbines," says Kendall. "The developed world needs to completely decarbonise electricity generation by 2050, so we can't afford to just throw away three-quarters of the primary energy turning it into hydrogen." Another study, conducted by the consultancy E4Tech for the UK's Department of Transport, found that if the UK were to switch to battery electric vehicles, electricity demand would rise by 16 per cent, whereas switching to hydrogen fuel cell cars would need a jump more than double that.
Of course, battery electric vehicles also have their drawbacks, including the fact that no country as yet has a recharging infrastructure of any sort. But this kind of challenge is solvable, and money is now pouring into the sector.
Since September, around $1 billion of new investment in vehicle battery technology has been announced by companies such as Toshiba, Bosch, Samsung and ExxonMobil. Battery electric vehicles have also attracted the interest of renowned investor Warren Buffett, whose MidAmerican Energy subsidiary recently bought a $230 million stake in the Chinese battery electric car maker BYD. MidAmerican's chairman, David Sokol, says that while he is not opposed to hydrogen in principle, only battery electric transport can deliver the necessary emissions cuts in time and cheaply enough. "Battery electric technology is critical to achieving the major CO2 reductions that the world is looking for," says Sokol. "As the economics pencil out today, hydrogen still has a way to go."
Many companies, including car makers, continue to invest millions in hydrogen R&D but some, like GM, are hedging their bets by developing battery electric technology too. Lars Peter Thiesen, GM's director of hydrogen strategy, acknowledges the greater efficiency of batteries, though he insists that hydrogen, with its higher energy density and thus superior range, will eventually win. "If there's enough money, if the technical development continues as it has for the past few years, and if the stakeholders - not just car companies, but in politics and energy - are all on the same page, then it really could happen in the middle of the next decade," Thiesen says. In other words, the hydrogen economy is still five to 10 years away, which has a familiar ring.
Other industry observers are far more equivocal. "The jury is out on battery versus fuel cell," says Richard Wenham of car industry consultancy Ricardo. "That's why everybody is researching everything."
But for all the research into hydrogen, fuel cells remain dependent on platinum, and hydrogen generation is still punitively inefficient. Meanwhile battery technologies are developing rapidly and continue to attract huge investment. The jury may not be out for very much longer. According to Kendall: "Hydrogen has always been the fuel of the future, and it looks like it always will be."
Hydrogen basics
Since hydrogen burns to give just energy and water, using it as fuel could eliminate the carbon dioxide released by burning fossil fuels. But there are a number of problems to solve, including finding the best way to generate it in the first place.One solution is electrolysis. A typical hydrogen production plant might use platinum electrodes dipped in a tank of water or brine. Passing electricity through the fluid generates hydrogen at one electrode and oxygen at the other. If the electricity is generated from renewable sources, the process produces no greenhouse gases.Hydrogen can either be burned to generate heat or used in a fuel cell to make electricity. A fuel cell essentially consists of two electrodes separated by an electrolyte - a material, sometimes a membrane, that conducts electricity. Hydrogen fuel enters at one electrode and oxygen at the other. These undergo a redox reaction - the electrochemical equivalent of combustion - across the electrolyte, releasing energy and pushing electrons around an external circuit. The only by-product is water.
David Strahan is the author of The Last Oil Shock: A survival guide to the imminent extinction of petroleum man (www.lastoilshock.com)
