A question of delivery

Availability of hydrogen supplies is one of the key issues facing developers of fuel cell vehicles, with the big question being: which comes first, filling stations or the vehicles to use them?

Without refuelling facilities in sufficient numbers, fuel cell vehicles will only function in limited areas, but without demand, why build filling stations at all?

Hydrogen filling stations have opened around the world, including in California, Iceland, Singapore, and Germany, but in general they have been designed to serve captive markets. One example of this is the global programme of fuel cell bus trials that are underway in major cities like London, Reykjavik, Barcelona, Hamburg, Perth (Australia), and now Beijing, or delivery van fleets in the US and Germany.

Scheduled for an opening in April 2005, the UK’s first hydrogen filling station in Hornchurch, Essex, will serve the three prototype hydrogen powered buses operated by Transport for London as part of the two-year European Union financed Clean Urban Transport for Europe (CUTE) project. The filling station built by BP Amoco incorporates liquid hydrogen tanks provided by the industrial gases concern, BOC, and is complemented by renewable energy from solar cells and wind turbines. The facility also incorporates a natural waste water management system. Construction has been delayed by local concerns initially regarding the installation of the turbines, which led to concerns regarding the storage of hydrogen.

Delivery, or generation For the designers of filling facilities, an early decision must be whether to cater for the delivery of hydrogen as a liquid, mimicking conventional gasoline, or to produce hydrogen on-site on-demand. The filling station at the headquarters of the California Fuel Cell Partnership in Sacramento has liquid hydrogen delivered by road tanker. The facility was opened in November 2000 and demonstrates that existing logistics can be applied to hydrogen fuel. On-site, apart from a double-wall stainless steel storage tank designed to contain liquid hydrogen at –253°C and a pressure of 10 bar, there is a ‘vapouriser’; a compressor to increase the gas pressure to 438 bar; and storage tubes with a design pressure of over 500 bar.

In April 2004 Governor Arnold Schwarzenegger signed an executive order to create a partnership for a network of hydrogen filling stations across the state, and in October, he dedicated the station at Los Angeles Airport (LAX). The facility is one of 13 to be built by the South Coast Air Quality Management District (SCAQMD) in Southern California in support of the California Fuel Cell Partnership and the Governor’s Hydrogen Highway Network initiative.

Unlike the Sacramento filling station, the LAX site is the first in the USA to demonstrate hydrogen generation, storage and dispensing in a facility that looks like a conventional gasoline filling station. Although initially only being used by hydrogen-fuelled vehicles operating within the airport, the filling station has been constructed to look like a gas station to overcome consumer concerns, and will be open to the public at a future date.

The station, a joint project between BP, Praxair, Los Angeles Airports, SCAQMD, the California Energy Commission and the US Department of Energy, uses a hydrogen-generation module supplied by Stuart Energy, based in Ontario, Canada, to produce 24 kg/day of pure hydrogen. The Stuart Energy Station (SES) is claimed to be the world’s first multipurpose scalable hydrogen infrastructure product range, transforming electricity into stored hydrogen that can be made available on demand. Hydrogen is generated using the company’s proprietary Vandenborre Inorganic Membrane Electrolysis Technology (IMET), which features a pressurised alkaline electrolyser generating highpurity hydrogen at up to 25 bar. For fuelling purposes, higher pressures are required and the Energy Station therefore incorporates a diaphragm compressor.

To facilitate refuelling, hydrogen is stored in a cascade system of storage tanks arranged in a series of ‘banks’ with a control system that determines which bank is able to deliver or receive hydrogen. During refuelling, the first bank delivers hydrogen until the pressure is equalised in the bank and the receiving tank. This pressure equalisation triggers the delivery of hydrogen from the next storage bank. This ensures that some hydrogen is always kept at a higher pressure, so that more complete vehicle tank fills can be obtained at different pressures from the same volume of hydrogen storage.

Stuart Energy has also supplied the hydrogen fuel dispensers that enable the driver to select the correct fill pressure, either 250 or 350 bar, after connecting the filling hose. The built-in computer control in the dispenser then manages the remainder of the filling process automatically shutting off the hydrogen supply when the tank is full. Designing hydrogen filling stations to look like gasoline filling stations was also the approach adopted for an Aral filling station opened in Berlin in 2004. A vehicle service facility has also been included together with an automatic carwash, conventional gasoline filling facilities and shop, making it probably the first integrated hydrogen filling station in the world. The station also uses on-site electrolytic production of hydrogen linked to pump demand.

The project cost E22 million, and was financed partly by the companies in the Clean Energy Partnership (CEP), a consortium formed by in June 2002 by Aral, part of the BP Group; the vehicle manufacturers BMW, DaimlerChrysler, Ford, GM/Opel, the Berlin Public Transport authority; the process engineering concerns Hydro/GHW and Linde; and energy provider, Vattenfall Europe, and partly by the German federal government.

The Berlin installation is based around an electrolyser produced by Hydro/GHW, the Norwegian energy and aluminium concern. It comprises a series of cells, each containing an anode, a gasket, a diaphragm, a gasket, and the cathode. The cells are circular in shape and are pressed together between two rigid end frames using tie bolts fixed by nuts and disc springs for controlled tension. The cell frames are made from nickel-plated carbon steel to resist corrosion, while the electrodes are 100% nickel. DC voltage is applied between the first and last electrode, producing a current flow through the cells which generates the gas. The gas formation takes place on the electrodes and a woven non-asbestos diaphragm separates the oxygen and hydrogen sides of the cell. The cell gaskets are also made from an asbestos-free material. The gas from each cell is collected in flow ducts that run in parallel along the top of the cell package and fed into the gas/lye separators above the electrolyser.

The lye from the electrolyte system is recycled back into the lye distribution channels in the bottom of the cell package. Linde also supplied the pumps at the station together with the compressor plant for gaseous hydrogen in line with Linde’s High Booster System, which compresses 15 bar gaseous hydrogen to 350 bar. The pumps will initially operate to 350 bar but are capable of being upgraded to 700 bar. The liquid hydrogen pump is equipped with a decanter pump and a cold-drawn coupling for rapid filling.

In addition, Linde supplies liquid hydrogen directly by tanker from its Ingolstadt plant, the only industrial hydrogen liquefaction plant in Germany. At the filling station, liquid hydrogen is stored in a super-insulated 10 000 litre cryogenic tank.

Linde is also looking even further ahead by sponsoring a group researching the biological production of hydrogen at the Christian-Albrechts-Universität in Kiel. The group is studying the ability of cyanobacteria and single-cell green algae to produce hydrogen through photosynthesis, and have succeeded in genetically modifying these microorganisms to multiply the amount of hydrogen released, which is usually too small for industrial use Wolfgang Reitzle, President of the Executive Board and Chief Executive of Linde, believes the research complements Linde’s own hydrogen know-how.

‘With this project, we are demonstrating our long-term, sustained commitment to the furtherance of a hydrogen economy: it is essential that we begin actively thinking today about life after oil.’

Neil Whitwell is a freelance science and technology writer based in London.