Action stations

European car manufacturers BMW, Fiat and DaimlerChrysler have joined forces with petroleum giants BP, Agip and Linde to develop the roadside infrastructure needed for a future hydrogen economy. The Zero Emission Region, or Zero Regio, project involves the construction of hydrogen refuelling stations in Germany and Italy.

The scheme is one in a series of hydrogen partnerships Linde has been involved with. Last year Linde worked with nine other companies, including DaimlerChrysler, on the Clean Energy Partnership (CEP) project to build a liquid and gas hydrogen refuelling station in Berlin.

Peter Winkler, project manager on Zero Regio, said the scheme was one evolving process rather than just a series of projects. ‘The number of cars involved are so small that it’s quite a tight-knit hydrogen family working together on all of these,’ he said.

As part of Zerio Regio, Linde will use its expertise in storing and transporting liquid hydrogen to install a pump, dispenser, and station in Frankfurt by next summer. The equipment is undergoing final testing at Linde’s facilities.

The difficulties in dealing with liquid hydrogen arise from the fact that it must be kept at –253ºC so it does not evaporate. To do this, Linde developed a number of new insulating technologies, including a coupling that allows transfer of liquid hydrogen from a cryogenic pump to the tank of a hydrogen car. This coupling is being tested in collaboration with BMW.

‘We think that within the next three to six months the coupling will go into serious production in all new liquid hydrogen cars, especially BMWs,’ said Winkler.

The insulating technology forms a crucial means of keeping the hydrogen sufficiently cold. Linde has developed a patented system to protect the cryogenic liquid from the outside temperature. As well as being kept in a vacuum, the hydrogen is carried from the storage tank to the dispenser in pipes made from more than 40 layers of aluminium and glass fibre.

‘We must be very careful not to make mistakes in this,’ said Winkler. ‘Every line and every coupling that carries the hydrogen must be isolated to keep it as cold as possible.’

An additional cryogenic pump is needed to pressurise the liquid from 1.6 bar in the storage tank to 5.5 bar to allow the car to be refuelled quickly and easily. ‘People need to be able to refuel with hydrogen just as easily as they would do with conventional fuel,’ said Winkler.

According to Winkler, a hydrogen infrastructure has been developing for the past 15 years, but he believes the involvement of companies such as BP will take it to a new level. One change has been in the safety standards that companies such as BP insist upon.

‘In new technologies such as hydrogen, where the level of experience is still low, safety standards are higher than in the conventional fuel industry,’ said Winkler.

‘The safety standards at a hydrogen station are maybe three times as rigorous as that of a conventional fuel station, because every possible scenario has to be take in to consideration.’

The other factor that must be considered in hydrogen station design is whether to sell liquid or gas hydrogen. Winkler believes that in future there will be room for both. The final choice will come down to user preference and driving habits more than anything else, he said.

Liquid hydrogen has a higher energy content and more can be stored in the vehicle. However, it has the disadvantage that if the car is not driven regularly, the hydrogen in the tank will gradually evaporate over a few days.