Ammonia avenue to hydrogen highway

Two US engineering firms claim to have made the most significant step yet towards the mass production of fuel cell-powered cars following the modification of an alkaline propulsion technology.

Two US engineering firms claim to have made the most significant step yet towards the mass production of fuel cell-powered cars following the modification of an alkaline propulsion technology widely used in the space industry.

Voltage Vehicles, a subsidiary of Californian transportation specialists ZAP, has announced it is to buy $100m (£55m) worth of fuel cell engines from Apollo Energy Systems, which has refined the alkaline fuel cell (AFC) for automotive applications.

According to Apollo, the system has a higher voltage, higher efficiency and greater reliability than other types of fuel cell. The AFC is ready for production, years before similar propulsion fuel cell systems are expected to be available, said chief executive Robert Aronsson.

ZAP will initially fit the fuel cell, plus a tri-polar lead-cobalt battery, also developed by Apollo, to the Smart car which it will import to the US especially for the purpose – one of the first appearances of the tiny car on US roads.

Both firms propose to demonstrate the vehicles on a ‘hydrogen expressway’, a coast-to-coast route from Florida to California serviced by dedicated filling stations.

The key to the AFC’s viability, said Aronsson, is that it can be fuelled with liquid ammonia, which is cracked onboard the vehicle to produce hydrogen. Ammonia is much more readily available in large quantities than hydrogen, and is much easier to transport and store.

‘The immediate use of ammonia can jump-start the country into a hydrogen economy,’ said Aronsson. ‘Ammonia is widely produced and can be competitive in price to petrol. Ammonia fuelling stations could be set up at very little cost, as the infrastructure already exists.

Distributors could begin making weekly deliveries of ammonia to gas stations in the 100 largest metropolitan areas of the US. ‘Former plans, proposed by others, of equipping gas stations with mini-factories for producing hydrogen by electrolysis at $1m (£560,000) per gas station, could be replaced by this low-cost system.’

He said that the concept of a hydrogen expressway could be realised in less than a year.

Dr Karl Kordesch, Apollo’s director, said ammonia has a high storage density at low pressure, and is also easy and efficient to reform into hydrogen. ‘A medium temperature cracker made from stainless steel produces 75 per cent hydrogen and 25 per cent N2, without any noble metal catalysts.’

Ammonia, which is cheaper and generally safer to use than hydrogen, can only be used in the alkaline fuel cell, said Kordesch.

‘The more common proton exchange membrane (PEM) fuel cell intended for transportation cannot tolerate even the small traces of ammonia. Alkaline fuel cells, however, require no further cleaning of the hydrogen gas after it has been produced from the ammonia fuel,’ said Kordesch.

The AFC, he said, is cheaper and less complex than a PEM cell. It uses low-cost electrodes, which are carbon based and plastic bonded, in mono polar stacks. There is no need for a humidifier, compressor or membrane. The AFC is capable of simple shutdown and starts, and in the hybrid system the rechargeable battery supplies the peak power.

Apollo has also patented a tri-polar lead-cobalt rechargeable battery for use with the AFC. It is made with lead-foam electrodes making it lighter than lead-acid batteries with a higher voltage as well as greater energy and power density, said Kordesch. Three patents are pending on the battery, which Apollo says would replace nickel-metal-hydride and lithium-ion for around 20 per cent of the cost.

‘The most expensive component in a lead-cobalt battery is lead which is one-tenth the cost of nickel. The price of a lead-cobalt battery will be around US$75 per kWh against US$400 per kWh for nickel-metal-hydride batteries,’ said Kordesch.

In combination with the fuel cell, he said the system is expected to give performance ‘equivalent to that of petrol or diesel-powered vehicles, but with zero pollution’.