FOR IMMEDIATE RELEASE
11 July 2008

THE FUEL CELL FUTURE

Cars powered by a cheap, efficient and plentiful fuel that produces no emissions… it’s not a dream but a near reality. The key is the hydrogen-powered fuel cell vehicle. Nissan is not alone in developing the FCV, but the company has been at the forefront of the technology for more than a decade and has been leasing FCVs to customers since 2003.

For the past five years, specially modified versions of the Nissan X-TRAIL powered by hydrogen fuel cells have been in use in Japanese cities and have also been undergoing real-world trials in Canada and the United States

Nissan’s aim is to have a fuel-cell vehicle in full production and on sale in North America and Japan during the first half of the next decade, with sales in Europe following shortly afterwards.

Environmental background
The march towards series production of the zero-emission fuel cell vehicle is an integral part of the ambitious Nissan Green Program 2010. The Program aims to reduce carbon dioxide (CO₂) emissions in all of the company’s endeavours with the ultimate goal of reducing the environmental effects caused by the manufacture and use of its vehicles.

CO₂ emissions are believed to be a major cause of global warming. In the Northern Hemisphere, scientists have recorded a 15 per cent reduction of the polar ice caps since 1980, while average global sea levels increased by 0.1-0.2m during the 20th century.

If no reduction in CO₂ output is made – the so-called ‘business as usual’ (BAU) scenario – it is estimated that global temperatures will rise 2 deg C over the next century, resulting in drought and famine with a further rise in sea levels causing extensive flooding.

To prevent this happening the Intergovernmental Panel on Climate Change (IPCC) says that CO₂ emissions must be reduced and has given the car industry a 70 per cent reduction target by 2050. Nissan is treating the reduction in CO₂ emissions an as issue of high priority.

In the short term this means further development of the gasoline-powered internal combustion engine to reduce CO₂ levels to those of diesels. Nissan is also developing ‘clean diesels’ as well as cars running on bio-ethanol fuels produced from plants and other renewable sources.

And the company is accelerating development of technologies that will bring benefits in the mid term. Centred around battery power, these include plug-in hybrids, pure electric vehicles and fuel-cell vehicles. The company has already announced that its first mass produced pure EV will go on sale in 2010.

The Fuel Cell Vehicle
The principle of the fuel cell was discovered as long ago as the mid 19th century. It works by catalysis, separating the component electrons and protons of the reactant fuel, and forcing the electrons to travel though a circuit, converting them to electrical power. Another catalytic process takes the electrons back in, combining them with the protons and the oxidant to form waste products such as water.

A typical FCV is driven by motors powered by the electricity generated on board by the fuel cell stack, using hydrogen as the reactant and oxygen as the oxidant. Performance is augmented by batteries which are used as an extra power source when accelerating. Energy generated under braking is stored in the battery.

History of Nissan fuel cell development
Nissan started development towards a fuel cell future in 1996. Within three years, the company had started real world tests on its first FCV, the R’nessa model – a so-called methanol reformer FCV.

Producing hydrogen by a reaction of methanol and water, the methanol reformer stores methanol as a liquid and so doesn’t suffer the complication of having to store hydrogen under pressure. However a by-product of the chemical reaction between methanol and water is the creation of CO₂, the very gas the FCV is attempting to reduce from the environment.

In 2000, Nissan joined the California Fuel Cell Partnership (CaFCP), a collaboration between 31 different companies – including energy companies and car manufacturers – all of which believe that hydrogen-powered FCVs are the key to the future of transportation. California is among the most advanced ‘hydrogen communities’ with more than 150 passenger FCVs in use on the state’s roads and has 24 hydrogen refuelling stations currently operating with a further 14 planned.

A year later, in 2001, Nissan entered into a five-year alliance with Renault to develop FCVs and in that April started tests of an Xterra FCV in California using direct hydrogen FCV technology.

By now, development of Nissan’s FCV programme was accelerating. In December 2002, testing of a new X-TRAIL-based FCV began in Japan, followed a year later by the start of limited leasing of the vehicle. Fittingly, the first example was leased by the Cosmo Oil Co in Japan: Cosmo and Nissan had joined forces to research and develop hydrogen refuelling technology.

With more authorities in Japan joining the leasing programme during 2004 and 2005, Nissan continued development of its current FCV, also based on a thoroughly re-engineered X-TRAIL. Announced in December 2005, testing of the new model began in February 2006 in Japan, American and Canada and is still on-going. Examples are now in Europe, demonstrating the viability of the concept to journalists, environmental and governmental bodies and other interested parties.

The new Nissan FCV
Based on the Nissan X-TRAIL – a model chosen as its architecture provides ample room to house the FCV componentry under the cabin floor and in the large luggage area – the company’s latest FCV showcases a number of significant developments that combine to enhance the practicality and everyday usability of the concept.

Storing enough hydrogen on board a vehicle to provide a sufficient driving range has been one of the key problems facing engineers since serious development of the FCV began. While hydrogen is a highly efficient fuel with excellent energy density by weight, it has poor energy density by volume meaning it requires a larger tank to store the same amount of energy as petrol.

One solution has been to store the hydrogen under high pressure, with the first X-TRAIL FCV storing the fuel at a pressure of 350 bar. For the current FCV, a new storage system has been developed which compresses the hydrogen to an even higher pressure of 700 bar. This allows about 30 per cent more hydrogen to be stored in the same size tank.

Certified for use by the High Pressure Gas Safety Institute of Japan, the new tank has an inner aluminium liner and an outer layer of carbon fibre reinforced plastic (C-FRP). The C-FRP layer uses a high-strength, high elasticity carbon fibre weave with a special winding pattern designed to withstand high pressure.

While the new high pressure tank helps to improve the FCV’s range, the biggest boost to its performance comes from a new fuel cell stack, developed in-house by Nissan.

A highly compact design with a high power output, the stack features a newly developed thin separator – the component which separates the hydrogen and oxygen gases supplied to the individual cells and transfers the electricity produced to the next cell.

It has a cell pitch – the space between adjacent cells connected in series – that is 40 per cent narrower than before. Typically a stack used in a vehicle uses several hundred cells connected in series to obtain the necessary voltage.

These features, together with integrated parts in the air intake and exhaust systems and a built-in cell monitor, contribute to its smaller size.

The stack itself uses a polymer electrolyte membrane (PEM) and gas diffusion layer (GDL) for quicker start up and shut down responses. The PEM is an ion-exchange membrane which allows hydrogen ions (protons) produced in the cells to pass through the membrane while the porous GDL diffuses the hydrogen and air to provide consistent delivery to the electrode layer. Improvements to the electrode materials have more than doubled their service life compared to previous fuel cell stacks used by Nissan.

Tests have shown that the new stack improves its volume to power ratio by a factor of 1.7 and the weight to power ratio twofold. It is some 40 per cent smaller than the one used previously and weighs half as much.

This is coupled to a significantly improved coaxial electric motor which produces 90kW, a 50 per cent increase over the motor used previously. This is regulated by a highly efficient and compact inverter.

The efficiency of the electric motor is matched by that of Nissan’s latest compact lithium-ion (Li-Ion) battery. With research into high output Li-Ion cells starting as long ago as 1992, development on the concept is today carried out by The Automotive Energy Supply Corporation (AESC), a joint venture company set up by Nissan, the NEC Corporation and NEC Tokin.

Unlike a conventional lithium-ion battery with its bulky cylindrical cells, Nissan’s latest Li-Ion battery has thin laminated cells and has fewer components overall. This boosts its power by a factor of 1.5 at the same time as halving its physical size. It also remains twice as efficient as a conventional cylindrical Li-Ion battery even after five years or 100,000 kms of continuous usage.

Another bonus of the thin modular design delivers a commensurate improvement in battery cooling efficiency. Higher power outputs are achieved through material improvements made to its lithium manganate positive electrode and carbon negative electrode. The use of chemically stable spinal-structured manganese for the positive electrode also helps ensure safe operation. Its compact dimensions also provide packaging benefits within the vehicle architecture.

In the Nissan FCV, the battery is used as an auxiliary power source under acceleration and also provides storage for energy generated during deceleration.

The results give the latest FCV – particularly when equipped with the high-pressure hydrogen storage tank – performance that’s moving close to that of a conventional petrol-powered car. It has a top speed of 150km/h (93mph) and an operating range of more than 500kms (310 miles). Maximum power is 90kW (120PS) and maximum torque is 280Nm. The weight of the vehicle has reduced by a considerable 100kg over the previous version and has room for five adults and their luggage.

As well as undergoing laboratory tests and real world usage in the hands of genuine customers – in Japan, one customer uses an FCV as a chauffeur drive taxi – the Nissan FCV is being used to demonstrate the practicality of the system to the public.

At Nissan’s headquarters in Tokyo, interested customers are given twice monthly opportunities to drive the FCV themselves. Typical impressions after the test praise the quietness of the car, its brisk acceleration and its ease of use. Examples are also taken to schools and colleges to give the next generation of drivers an early introduction to the cars they will be driving in the years to come.

And with the cars being used on public roads, the Nissan FCV has undergone rigorous crash testing for front, rear and side impacts, passing Japanese safety standards for passenger protection as well as crash stability of the hydrogen and high-voltage electricity systems.

The future
So what is the future for the FCV? If the technology works, why aren’t we all driving one today? The simple answer is that there is a great deal of development work still to be done before we can all be driving around in near silence producing no emissions other than water.

Although the lifecycle of the system componentry has improved dramatically since Nissan started work on the FCV, there is still some way to go before operational degradation – particularly in a typical stop/start urban environment – reaches acceptable levels.

The cost of the system, too, is currently too high for series production. Further simplification of the system and cost reductions through the use of new innovative materials are key factors. According to Nissan’s calculations, solutions to the technical issues, including durability, should become clear by 2010 while drastic cost reductions and a further breakthrough in hydrogen storage systems by 2015 will secure the viability of technology.

But that’s on the vehicle side. There are other huge issues that need to be solved at the same time if we are to see a decline in our reliance on fossil fuels and a drastic reduction in worldwide CO₂ emissions.

The generation of hydrogen itself is an issue. The cheapest and easiest way to create hydrogen is from natural gas, but this process creates CO₂ as a by-product. Alternative renewable methods include generation of the gas via solar energy but this, currently, is costly and relatively inefficient.

And there needs to be a comprehensive infrastructure of hydrogen refuelling stations available to all if we are to be weaned away from the internal combustion engine. This is beyond the remit of the car manufacturers and needs joint action from energy companies and local and national governments.

One thing is for certain, however, the fuel cell vehicle is on its way.

ends…

FOR FURTHER INFORMATION CONTACT:

All news releases and pictures can be downloaded from www.nissanpress.co.uk

55594/110708