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Une pile à combustible à hydrazine, sans platine

15.11.2007

Le constructeur automobile Daihatsu a développé une pile à combustible fonctionnant à l'hydrazine (N2H4) et ne nécessitant pas de métaux nobles comme le platine. Ce nouveau modèle peut fournir une puissance équivalente aux piles à combustibles classiques. Le développement a été réalisé en collaboration avec l'AIST (Advanced Industrial Science and Technology) au Japon.
Comparaison pile à hydrogène / pile à hydrazine

Le combustible utilisé est l'hydrate d'hydrazine (N2H4,H2O) en solution aqueuse à 5%. La réaction à l'anode produit du N2 et de l'eau uniquement (pas d'émission de CO2). La puissance maximale fournie est de 500 mW/cm2 selon Daihatsu, équivalent des valeurs des PEMFC classiques. Théoriquement, cette puissance peut augmenter puisque la force électromotrice de la pile à l'hydrazine est plus de 25% supérieure à celles au H2: 1,56V pour la première contre 1,23V pour la deuxième.
Après analyse, il s'est avéré que les métaux qui conviennent le mieux comme catalyseurs sont le nickel à l'anode (face combustible) et le cobalt à la cathode (face oxygène). L'utilisation de ces métaux revient à 500 yens environ par véhicule, contre 400.000 à 500.000 yens pour le platine (3 euros contre 2700 euros).

Dans les piles à combustibles à membrane d'échange de cations (PEMFC ) classiques, la réaction qui a lieu entre le H2 et le O2 se fait en milieu très acide et c'est pourquoi le platine, qui a une très grande résistance à la corrosion, est utilisé. Ici, la membrane d'échange est de type anionique, faisant circuler les ions OH- en milieu alcalin et permettant ainsi l'utilisation de métaux non nobles comme le cobalt ou le nickel.

Le constructeur avait déjà présenté en 2005 les potentialités d'une pile à combustible à l'hydrazine mais un des problèmes majeurs qui avait alors été soulevé se rapportait à la sécurité du système. En effet, les dérivés d'hydrazine sont considérés comme des substances délétères au-delà d'une concentration massique de 30% au Japon ainsi que comme des matières inflammables quand la concentration massique excède 80%. Le groupe a donc développé un système permettant de fixer l'hydrate d'hydrazine afin de le stocker, et de libérer uniquement la quantité nécessaire sous forme liquide. L'hydrazine est fixée à un groupe carbonyle (C=O) et donne l'hydrazone, qui hydrolysée se transforme facilement de l'hydrazine. En pratique, le véhicule posséde un réservoir contenant le polymère avec le groupe carbonyle où est stocké le combustible, ainsi qu'une sortie d'eau chaude permettant l'hydrolyse de l'hydrazone en hydrate d'hydrazine.

Actuellement, l'hydrazine est produite industriellement à partir de NH3 pour un prix au litre de 200 yens (1,25 euros) mais le coût de production pourrait être réduit de moitié en le synthétisant à partir de N2 et de H2.

Ce nouveau modèle de pile é combustible est doublement écologique car en plus d'assurer l'autonomie face aux hydrocarbures, il contribue é la réduction des émissions de CO2. Daihatsu considàre cependant que la quantité de CO2 réduite grâce aux piles é l'hydrazine équivaut à celle des piles à l'hydrogène. C'est principalement le coût du matériel qui change. Le constructeur envisage d'utiliser ce modèle de pile à combustible dans ses futurs petits véhicules low-cost et cherche à lier des partenariats pour le développement de cette technologie, avec Toyota par exemple.

Source: BE Japon numéro 457 (21/09/2007) - Ambassade de France au Japon / ADIT
Illustration: SST – Ambassade de France au Japon
http://www.bulletins-electroniques.com/actualites/51102.htm

Honda Debuts All-New FCX Clarity Advanced Fuel Cell Vehicle; limited marketing to begin in summer 2008

25.11.2007

LOS ANGELES, U.S.A., November 14, 2007 Honda unveiled the FCX Clarity fuel cell vehicle at the Los Angeles Auto Show, announcing plans to begin limited retail marketing of the vehicle in the US, starting summer 2008.

Honda FCX Clarity introduced at LA Auto Show

The FCX Clarity is a next-generation, zero-emissions, hydrogen-powered fuel cell vehicle based on the entirely-new Honda V Flow fuel cell platform, and powered by the highly compact, efficient and powerful Honda V Flow fuel cell stack. Featuring tremendous improvements to driving range, power, weight and efficiency - and boasting a low-slung, dynamic and sophisticated appearance, previously unachievable in a fuel cell vehicle - the FCX Clarity marks the significant progress Honda continues to make in advancing the real-world performance and appeal of the hydrogen-powered fuel cell car.

American Honda plans to lease the FCX Clarity to a limited number of retail consumers in Southern California with the first deliveries taking place in summer 2008.

How It Works

The FCX Clarity utilizes Honda's V Flow stack in combination with a new compact and efficient lithium ion battery pack and a single hydrogen storage tank to power the vehicle's electric drive motor. The fuel cell stack operates as the vehicle's main power source. Hydrogen combines with atmospheric oxygen in the fuel cell stack, where chemical energy from the reaction is converted into electric power used to propel the vehicle. Additional energy captured through regenerative braking and deceleration is stored in the lithium ion battery pack, and used to supplement power from the fuel cell, when needed. The vehicle's only emission is water.

Honda V Flow Fuel Cell Platform

The FCX Clarity's revolutionary new V Flow platform packages the ultra-compact, lightweight and powerful Honda V Flow fuel cell stack (65 percent smaller than the previous Honda FC stack) in the vehicle's center tunnel, between the two front seats. Taking advantage of a completely new cell configuration, the vertically-oriented stack achieves an output of 100 kilowatts (kW) (versus 86kW in the current Honda FC stack) with a 50 percent increase in output density by volume (67 percent by mass). Its compact size allows for a more spacious interior and more efficient packaging of other powertrain components, which would otherwise be unattainable in a sleek, low-slung sedan.

The FCX Clarity boasts numerous other significant advances in the performance and packaging of Honda fuel cell technology, compared to the current-generation FCX. These include1:

	·	a 20-percent increase in fuel economy - to the approximate equivalent of 68 mpg2 combined fuel economy (about 2-3 times the fuel economy of a gasoline-powered car, and 1.5 times that of a gasoline-electric hybrid vehicle, of comparable size and performance);
	·	a 30-percent increase in vehicle range - to 270 miles;
	·	a 25-percent improvement in power-to-weight ratio, in part from an approximate 400-pound reduction in the fuel cell powertrain weight, for superior performance and efficiency despite a substantial increase in overall vehicle size;
	·	a 45-percent reduction in the size of the fuel cell powertrain - nearly equivalent, in terms of volume, to a modern gas-electric hybrid powertrain;
	·	an advanced new lithium-ion battery pack that is 40 percent lighter and 50 percent smaller than the current-generation FCX's ultra-capacitor; and
	·	a single 5,000-psi hydrogen storage tank with 10 percent additional hydrogen capacity than the previous model.

CO₂ Emissions

The FCX Clarity's only emission is water. Carbon Dioxide (CO₂) emissions come only from the production of hydrogen, which varies by source; however, well-to-wheel CO2 emissions using hydrogen reformed from natural gas - the most widely used method of production today - are less than half that of a conventional gasoline vehicle. With the production of hydrogen from water by electrolysis, CO₂ emissions can be further reduced and ultimately approach zero if the electricity used for electrolysis is generated using solar, wind, water or nuclear power.
Honda has developed its own solar cells, with half of the CO₂ emissions in the production stage compared to conventional crystalline silicon cells; and has begun mass-production and retail sales of this technology in Japan for both commercial and residential use.

Fuel Cell Leadership

Honda's pioneering achievements in this area include the first EPA and CARB certification of a fuel cell vehicle (2002); the first lease of a fuel cell vehicle (2002); the first fuel cell vehicle to receive an EPA fuel economy rating (2002); the first cold-weather customer (2004); the first and still only individual retail customers (2005, 2007); and the first and still only fuel cell vehicle to be eligible for a federal tax credit.

Source: Honda

Swatch founder launches Fuel cell car energy project

30.08.2007

Billionaire Nicolas Hayek, the Swiss entrepreneur famous for reviving the country's watch industry, has launched a project to develop renewable energy systems for affordable green cars. Hayek's Swatch group, the world's largest watch company, has joined a consortium including the electricity group E and the Ecole Polytechnique Fédérale de Lausanne, in a bid to develop alternative energy to that used by the internal combustion engine.

Hayek and Philippe Virdis, of Group E, announced the project on Wednesday. Under the plan, a high-tech holding company will be created, which in turn could spin off companies with partners in such sectors as automobile manufacturing. The aim is to provide non-polluting energy from hydrogen fuel cells for household uses as well as for mobility. Hayek, 79, believes that Switzerland has an opportunity to develop alternative energy sources because the country does not have car manufacturing or petroleum production industries with a vested interest in supporting existing technologies. "I want to do everything within my powers to accelerate the development of alternative and renewable energy," Hebdo magazine reported Hayek saying. "In Switzerland, like elsewhere in the world, we are going far too slowly."

Born in Lebanon, Hayek has a fortune estimated at more than SFr3.2 billion. He is credited with turning around the ailing Swiss watch industry in the 1980s when he merged two companies and began producing the low-cost but arty Swatch line of watches. The Swatch group, headquartered in Bienne, now has more than 150 factories worldwide. Hayek was also involved in the development of the Smart car, the micro vehicle built by Mercedes Benz. He pulled out of a partnership with the car manufacturer when the final design for the car fell short of his expectations.

Source: Tribune de Genève