European Research: Air and water
Date published : 16/01/2002
By 2010, 7% of road transport fuel should be clean. By 2020, this should be 20%. Apart from the 'traditional' solutions - electricity, natural gas, biofuels, etc. - hydrogen fuel cells offer the 'purest' alternative, but it is perhaps not the easiest to manage.
In a fuel cell, the energy is produced by the combination of oxygen and hydrogen atoms. The only emission is steam, hence there is zero pollution. Manufacturers seem to be increasingly placing their faith in this solution, with DaimlerChrysler (DE) set to invest 1 billion euros in developing this alternative energy source between now and 2004. The group - which has formed a partnership with Canadian company Ballard and Xcellsis to develop a fuel cell-powered vehicle that has already received financial interest - unveiled its Necar 4 prototype, modelled on a Mercedes-Benz Classe A, in 1999. The fuel cell runs on liquid hydrogen contained in a tank placed at the rear of the vehicle. This experimental vehicle, which requires 6 litres of hydrogen to produce 1 kW of power, has a top speed of 145 km/hr. The tank gives the 55 kW electric engine an autonomy of 450 kms, after which the driver has to fill up with more liquid hydrogen.
The race to production
For the past year, PSA, Peugeot-Citroën and Renault have been engaged in a joint research programme on the fuel cell which should make it possible to acquire the know-how and determine the feasibility for such a vehicle to go into production by 2010 at the latest. PSA is also involved in a European project which, in 2001, should produce a prototype fitted with a battery fuelled with gaseous hydrogen at high pressure. With an autonomy of 350 kms, the vehicle's performance will match that of a diesel vehicle of the same range.
Although BMW has opted for an internal combustion engine using hydrogen directly. It is also teaming up with Renault and Delphi in developing a small SOFC-type cell. With this technology, a small fuel cell supplies all the electrical energy necessary for the on-board network. Lastly, Opel - a subsidiary of General Motors - has also unveiled a prototype operating on the same principle.
The race to the production line is on. Honda has announced mass production of its first models in 2003, and DaimlerChrysler in 2004, while other constructors have their sights on around 2010.
Where to store the hydrogen?
These clean and autonomous engines which emit only steam do, however, pose one major problem: how to store the compressed or liquid hydrogen, which must be handled with the greatest care. To obtain an autonomy close to that of a vehicle powered by hydrocarbons, the tank must provide almost perfect insulation to ensure the hydrogen remains in the liquid state at a temperature of under 253 degrees. This type of storage can cause explosions during a collision and also presents certain risks when refueling. It is possible to fill the car with traditional fuels (petrol, methanol or GPL) using a 'reformer' fitted to the car to extract the hydrogen. But in such a case CO2 emissions would be between 85 (methanol) and 100 grams (petrol) per kilometre, which is almost half the emissions of a combustion engine. Producing hydrogen from methanol also consumes a lot of energy. Also, methanol attacks engine coating and seals and is also more toxic than petrol. The use of a reformer should in fact be a non-starter.
Researchers are therefore trying to come up with alternatives, such as carbon nanotubes. Some laboratories have managed to store up to 6 grams of hydrogen in 100 grams of nanotubes, but it is likely to be another 12 to 15 years before such technology is applied to an automobile.
europa.eu.int ... original report
SAE Tech Briefs April 2002
Delphi fuel-cell APU for BMW
<http://www.sae.org/automag/techbriefs/04-2002/04.jpg>
Delphi and BMW have joined forces to demonstrate the viability of a solid-oxide fuel-cell system as an auxiliary power unit.
Delphi Automotive Systems announced at the SAE 2002 World Congress that it and BMW are jointly developing a solid-oxide fuel-cell auxiliary power unit (APU). Applying the fuel-cell APU for transportation is part of a significant trend for the electrification of vehicle accessories. Many automotive systems are being converted to electric power to support cost, weight, and packaging objectives. Intermittent accessories, such as power steering and brakes, have already been adopted.
High-power accessories, such as air-conditioning and valvetrain systems, have been developed more slowly due to the limited onboard electrical capacity and their low efficiency. Now, high-power, high-efficiency electrical machines are being introduced for 42-V operation. These high-voltage systems will provide capacity to continue the electrification of new features. Fuel-cell systems have over a 50% fuel-to-electric conversion efficiency because of the direct chemical-to-electrical conversion. This efficiency allows for the continued transition to electric accessories that operate independent of the engine. Such capability is an important step for the introduction of mild hybrid vehicles.
Engineers from Delphi discussed at Congress the advantages of applying a fuel-cell power unit to the dual-voltage 42-/14-V automotive electrical system using the evolving 42-V PowerNet specifications. These vehicles require the APU to operate on fuels other than gasoline, such as diesel or jet fuel, and the applications are expected to play an important role in the introduction of this technology to the marketplace.
<http://www.sae.org/automag/techbriefs/04-2002/05.jpg>
Delphi used a fuel-cell reformer supplied by Global Thermoelectric.
The solid-oxide fuel-cell-based APU is a major shift in the supply of electric power for transportation. Its applications can include premium class automobiles, work trucks, recreational vehicles, fire-rescue vehicles, military vehicles, ships, and aircraft. The separation of onboard electricity production from the vehicle's internal-combustion engine is consistent with providing increased comfort to the customer in an efficient, clean way. Solid-oxide fuel-cell technology also is easily applicable to stationary power. Residential primary and back-up power, distributed power, and co-generation are achievable with any liquid or gaseous hydrocarbon fuel.
Current development is focused on reducing cost; improving cycle durability, startup characteristics, and power density; and developing reformation technology for a broad range of hydrocarbon fuels. With solutions to these challenges, this technology offers the potential for high market penetration in the next decade.
- John Fobian
sae.org ... original report with pictures
globalte.com ... more information about Solid Oxide Fuel Cell development |
