The slow, sure advance of the hydrogen economy
Advances in hydrogen production and the fuel’s green credentials guarantee its future in the energy industry
With hype building over the string of battery-electric cars being brought to market by big vehicle manufacturers, it may seem that earlier talk of the hydrogen economy was just hot air. But, while present cost and logistical issues are thwarting the wide-scale uptake of hydrogen in the transport and power sectors, it is set to play a crucial role in our lives – eventually.
Nissan, GM, Ford and others are rolling out rechargeable or electric-hybrid vehicles with what they hope will be mass-market appeal. Those who can afford the sizeable price tag can take advantage of the latest developments in battery and electric-motor technology simply by plugging their cars into a socket at home and charging up.
That is a simplicity that vehicles using hydrogen fuel-cell technology cannot match, for now, even if hydrogen is an equally clean means of on-board power, producing only water as a by-product.
Hydrogen remains little used as a transport fuel beyond vehicle fleets, such as vans and buses, which can return to their depots to fill up from a central hydrogen store. But the hydrogen fuel cell remains a pioneering and, so far, expensive and inefficient technology that is unlikely to win out over battery and battery-hybrid cars among mass-market consumers looking to switch to greener vehicles (PE 4/03 p22).
Meanwhile, the prospect of instant refuelling at a filling station, just like gasoline – hydrogen’s big advantage over batteries – remains distant in most parts of the world. California has invested millions of dollars developing its hydrogen highway of refuelling points in an effort to kick-start the use of fuel-cell vehicles. It is one of the few places that cars, such as the Honda FCX Clarity, can operate at something like their potential (PE 2/09 p30).
But this remains essentially a demonstration project. There are still only a few dozen fuel-cell cars on California’s roads and those are generally rented rather than owned – the Clarity is estimated to cost well over $100,000 per unit to produce. Extensive, commercially funded networks of hydrogen filling stations are unlikely to be built in the US, or anywhere else, in the near term, until the vehicle-technology costs drop and its popularity rises.
Top of the range
But this is not the end of the road. With oil supplies dwindling, gasoline prices soaring and concerns over land-competition issues for biofuels, the mass-market transport choice may narrow down to one between differing ways of supplying power to an electric motor, which is what both batteries and fuel cells do.
In that case, the need to replace the internal combustion engine with something that can also achieve long-range travel would seem to favour hydrogen, barring an unforeseen range-increasing breakthrough in battery technology.
“Battery-electric vehicles will never deliver really significant range compared with conventional cars. So, if you want a 500 mile-range electric car, you’ll need to go to hydrogen fuel cells,” says Ben Lane, director of Ecolane, a UK-based low-carbon transport consultancy.
“If that happens, many of the advances being made in battery-electric and hybrid-car technology will prove as useful for fuel-cell vehicle developments as they are for plug-ins.”
Acceptance of hydrogen transport technology may be helped by the wider future use of hydrogen in other areas. Because it provides a way of storing energy that can be unlocked later in fuel cells or industrial processes, hydrogen could become increasingly important in the power industry, as the volume of renewables in the energy mix grows.
The big problem with wind and solar is that they are intermittent – a problem that can be overcome by relying on fossil-fuelled and nuclear power for baseload electricity. But fossil fuels will grow more expensive as they become scarcer and the world is looking to reduce carbon emissions. Meanwhile, Japan’s Fukushima-Daiichi nuclear accident has done little to further nuclear power’s safety credentials (PE 4/11 p4).
If these issues mean countries become more dependent on renewables, hydrogen could help smooth the resulting intermittency in power generation. For example, a wind farm generating excess electricity on a windy night could be used to produce hydrogen through electrolysis of water. That hydrogen could then be stored, or shipped, for use in power generation, transport or industry, as and when it is needed.
“The use of hydrogen electrolysis and storage to manage the power grid means we would never have to cease renewable energy production,” said Graham Cooley, chief executive of UK hydrogen firm ITM Power, in response to a UK government call for better storage linked to renewable generation.
ITM has just sold its first small-scale hydrogen-production system to the University of Glamorgan, Wales. The proton-exchange membrane electrolyser system can supply around 4kg of hydrogen a day – the Clarity averages about 60 miles/kg.
There are already some significant precedents for hydrogen production from renewables, notably in Scandinavia, where large-scale output of hydrogen using hydropower is used in the chemicals industry. This highlights hydrogen’s already wide use in several industries worldwide, including petrochemicals.
But much of the hydrogen used is produced by steam reforming using natural gas, oil or coal – a process that creates carbon dioxide as a by-product. So, greater use of renewables in hydrogen production would also help stem carbon emissions. It may also aid the development of decentralised power production and storage – a house or village could generate renewable energy and produce its own stored hydrogen for power and transport without tapping a national grid.
There are a number of other ways to make hydrogen, the cleanest is photo-electrochemical water splitting. This uses direct sunlight to split water molecules into their constituent hydrogen and oxygen through electrolysis. A lot of work is needed to improve the efficiency of the process and make it cheaper. But, in May, a US-Danish team, including scientists at the US Department of Energy’s SLAC National Accelerator Laboratory, claimed it had gone some way towards achieving both.
A big issue so far has been the high cost and scarcity of platinum, the catalyst most effective in speeding up electrolysis to create hydrogen faster. But the scientists say they have found a cheap, abundant alternative in the form of molybdenum sulphide, discovered during studies of naturally occurring hydrogen-producing enzymes in some organisms.
The team has also improved the efficiency of the light-absorbing electrode used in electrolysis by introducing a chemical solar cell designed to capture as much solar energy as possible. This light absorber consists of silicon arranged in closely packed pillars to which the molybdenum sulphide can be added. When the pillars are exposed to light, hydrogen bubbles up from water as quickly as if platinum had been used.