Power play

5 min read

Alternative energy innovator ITM Power is to market a Green Box domestic electrolyser that can produce affordable hydrogen for powering homes and cars. Berenice Baker reports.

As the cost of petrol and domestic energy bills hit the roof, a system that produces and stores hydrogen that can fuel your car and heat your home — and remains affordable and green — sounds like a gift from the technology gods.

Sadly for motorists and householders, the much-vaunted hydrogen economy has remained an elusive dream, dogged by high costs and a lack of infrastructure.

Alternative energy innovator ITM Power, based in Saffron Walden, believes part of the solution may lie in its fridge-freezer-sized domestic electrolyser, the Green Box. The device, soon to enter production, produces affordable hydrogen using water and solar or wind energy, which can fuel vehicles and power homes.

Jim Heathcote, ITM’s chief executive, says the system overcomes one of the fundamental problems of renewable energy, whether for domestic or commercial use.

He claims renewable energy is not a substitute for a reliable grid system and is impracticable without storage. ITM’s vision is to store hydrogen produced by wind or solar energy, or off-peak electricity. ‘You can’t run a factory just when the wind blows, and countries with a large wind penetration have to run fossil-fuel plants in parallel in case the wind drops. So renewable energy systems don’t do the job without storage,’ said Heathcote.

‘What we have to do is take this intermittent renewable energy and make a useful fuel. The battle for energy security is based on whether we can make hydrogen cost-competitive with the competing fuels, and that is what we are attempting to do.’

The heart of ITM’s technology is a polymer membrane that it claims is superior to existing alternatives.

Heathcote says electrolysis technology can be difficult because of the aggressive chemical environment it entails, which has so far made a low-cost endurable electrolyser impossible. Alkaline electrolysers use a liquid electrolyte that can absorb some of the gases produced, making it potentially explosive and requiring the extra cost of degasification plant. Acid chemistry electrolysers use a fluorinated polymer membrane to keep the hydrogen and oxygen separate, but the polymer and the platinum catalyst used in the process are too expensive.

Standard membrane materials cost about £250/m2, but ITM Power’s membrane could be produced for about £2.50/m2, the company claims.

ITM has developed a new class of material called an ionically conducting hydrophilic cross-linked polymer, which it claims costs one per cent of the price of current polymers and its high ionic conductivity gives increased gas output.

The materials start as liquids, which are poured into a mould and made to cross-link using gamma or ultraviolet radiation. The molecules join together in 3D so there are no ends that would be susceptible to end-chain degradation and no need for fluorine. ‘We have made a low-cost, endurable polymer,’ said Heathcote, ‘and after years of testing, we have not been able to identify a failure mode for it.

‘Because our materials start as liquids, we are able to add an alkaline component or an acid component before we polymerise it, so we got rid of the degasification of the traditional alkaline electrolysers and the platinum from the acid electrolysis.’

The electrolyser could have a significant impact in transportation. ITM is collaborating with Roush Technologies to build a system incorporating the Green Box to refuel a car so it can go 25 miles (40km) — the average US commute — on hydrogen before switching to petrol in the same engine. Roush is adapting internal combustion engines to run on hydrogen.

Heathcote claims this approach means there would be little cost in converting a petrol engine car to run on hydrogen. The most expensive part would be the fuel tank, costing £3,000, which could get cheaper with volume production. ‘It is unlikely fuel cells will be able to compete with the internal combustion engine in the near future,’ said Heathcote. ‘The first step is evolution, not revolution. If you could travel 25 miles on hydrogen, you would have a remarkable impact on our energy dependency for petrol, and a dramatic impact on emissions.’

He also claims the battery alternative is unsustainable. ‘One of our scientists calculated that if you tried to move cars to nickel cadmium batteries, you would need more than twice the known cadmium inside the planet. Within one major car programme, you would run into resource problems with cadmium.’

The eventual aim of the deal with Roush is to produce dual-fuel commercial vehicles that go further on hydrogen than cars because they can carry bigger tanks. ITM has developed a hydrogen-fuelled Ford Focus with PhD researchers at Hertfordshire University, which it plans to launch with a refueller soon.

As well as vehicles, the Green Box could also be used to enable zero- carbon housing, which Heathcote also describes as energy independence or grid independence. Electricity from renewable sources would be used to produce hydrogen and fill a propane-style tank. A single unit could produce enough for direct cooking and heating, to use in a generator for grid- independent electricity and to fill a car.

The first systems will be commercially available this year after 10 or 15 years of development. The launch model will be able to produce hydrogen with a pressure of about 75 bar, enough to fill the car tanks Heathcote envisages. ‘The higher the pressure, the more expensive it becomes,’ he said. ‘Commercial companies may want a lower-pressure system, but a with hydrogen compressor to take it up to 300 bar.’

ITM had a low-pressure stack using its technology independently costed and claims the unit would cost £82/kW. ‘If it were 50 per cent efficient and it lasted an hour, it would cost £164 for a kilowatt-hour’s worth of hydrogen,’ said Heathcote. ‘But the economy comes through the cost-of-life calculation — at 10,000 hours, it comes down to 3.28 cents [less that two pence] per kilowatt-hour.’ Domestic electricity bills range from two to 10 pence/kWh.

ITM’s initial target market will be large units to fuel vehicles for local authorities and commercial companies interested in reducing their energy dependence and to power forklift trucks that cannot use fossil fuels in an enclosed warehouse.

The company also plans to go into production in the second half of 2009 with a 1W-2W domestic electrolyser that would be used to refuel a metal hydride cylinder. This could be used with a fuel cell to give backup electricity for essential appliances, or users could buy several to use with solar panels to power a hydrogen home.

Although other manufacturers are making electrolysers, ITM claims its model is more affordable and more environmentally friendly, because the polymer is made from common hydrocarbons with no fluorine, which would cause disposal problems.

ITM has been testing its electrolyser technology for more than 10 years. Durability and chemistry testing has already been completed, and pressure testing is under way.

The first fuel-cell stacks are achieving power densities of about 1W/cm2, says ITM, which claims its internal tests are giving power densities in excess of published figures for other systems. It has not revealed specific efficiency figures, but believes its technology will be at least as efficient as existing PEM (proton exchange membrane) alternatives.

Turning wind or solar energy into a fuel that that can be stored and is cheaper than fossil fuels is more important than overall efficiency, says Heathcote. ‘The primary driver will be economics, not thermodynamics. The only issue for a viable hydrogen economy is that the cheapest pump has to be the hydrogen pump. To quote one of the US speakers at a conference I attended, thermodynamics is for sissies.’

Hydrogen power may hold the key to practical renewables, with applications for the home and car, according to ITM