Honing power of Honda's fuel-cell FCX

The FCX uses California's hydrogen highway refuelling stations.

Honda says its hydrogen-powered FCX concept car "is about showing fuel cells in something that doesn't look like a milk float".

The low and lean FCX - a pared-down, sedan development of the people-mover Odyssey - is the carmaker's latest fuel-cell study.

It introduces to future-fuel scenarios the Home Energy Station, a system that uses home-heating natural gas to power a hydrogen fuel-cell car.

Waste heat from the process can provide about 5kW of electricity, enough to warm the domestic water tank or power the beer fridge.

Ultimately, says Honda, the system could lower the cost of household electricity, natural gas and vehicle fuel by 50 per cent.

The FCX concept was shown at the Tokyo Motor Show and is a world away from the road-going FCX, a hatchback fuel-cell car that Honda is leasing on three-year agreements in California.

The hatchbacks use California's Hydrogen Highway refuelling stations, a state-wide infrastructure expected to be finished by 2010.

The hatchback FCX is certified by the United States Environmental Protection Agency (EPA) and California's Air Resources Board (Carb) as a Zero Emission Vehicle (Zev).

Honda says the FCX hatchback was the first fuel-cell vehicle to be listed in the EPA's fuel economy guide. It carries a fuel economy rating of around 3.7 litres/100km, or around 60mpg, and a range of 300km. It remains efficient at temperatures as low as minus 4C.

The FCX concept comes when about 65 per cent of Americans believe the US Government should make a major funding commitment to transform the automotive industry from a petrol- and diesel-based system to a hydrogen-based system.

Fifty-nine per cent identified hydrogen-powered vehicles as those with the best chance for long-term success, compared with 23 per cent for hybrids and 18 per cent for traditional petrol-powered engines.

The poll revealed that there was a major gap between public perceptions of the efforts of America's big three carmakers to develop energy-efficient vehicles and their record and accomplishments in this area.

GM and Ford were named most often as the carmakers doing the worst job developing energy-efficient vehicles, while Honda and Toyota were seen as doing the best job.

Honda and Toyota have been selling fuel-saving petrol-electric hybrids in the US for about five years, while Detroit's carmakers began only last year, when Ford sold its first Escape hybrid SUV.

For the FCX Tokyo show car, Honda halved the size of the fuel-cell stack and doubled the hydrogen stored in on-board tanks, which gives the FCX a range of 560km on 5kg of hydrogen. The hydrogen is stored at pressures of around 5000psi.

Honda says the smaller fuel-cell stack is easier and cheaper to make and reduces the number of necessary components by 50 per cent. It also provides improved cold weather performance, vital to the success of the fuel-cell.

Fuel cells are seen as a green alternative to the internal combustion engine.

They create electricity by passing hydrogen through a membrane, a thin sheet of special plastic.

When hydrogen passes through it, electrons are stripped off, generating electricity.

A separator divides the serially connected membranes, acting as a pathway for the electrons.

Water is the only emission if pure hydrogen is the fuel. But cold temperatures make fuel cells difficult to start. Cold reduces efficiency and may freeze a fuel cell.

The Jazz-based FCX fuel cell car operates below the freezing temperature of water (minus 20C).

Honda says the fuel-cell in the FCX concept operates at much colder temperatures, although it declines to be specific.

The aim is to produce a fuel-cell car that works at minus 30C, or comparable to one powered by an internal combustion engine.

"Without an improvement to run at minus 30C, we can't expand the use of fuel cell cars all over the world," says Yozo Kami, executive chief engineer of Honda's research division.

The FCX concept uses three electric motors for the drive train: one producing 50kW in the front and two delivering 25kW each in the rear, driving all four wheels.

Says Honda: "The efficient delivery of this power and the low centre of gravity platform combine to deliver torque performance and agile handling."

"The space-efficient layout also contributes to the interior efficiency of the low-floor design, eliminating the need to use floor space for motors."

Honda calls its low-floor design the "3V" system: vertical gas flow, vertebral layout, and volume-efficient packaging.

"In the 3V scheme, oxygen and hydrogen flow from the top to the bottom of the fuel cell stack (vertical gas flow) and the fuel cells are arranged vertically in the centre tunnel (vertebral layout) for new, high-efficiency fuel-cell packaging (volume efficiency)," it says.

"Compact enough to fit neatly into the centre tunnel but robust enough to deliver 100kW (135bhp) of power, the V flow fuel-cell stack offers both space efficiency and high energy output.

"The key to fuel-cell performance is water management. With vertical gas flow, an innovative process in which oxygen and hydrogen flow downward through the stack, the new fuel-cell stack takes full advantage of gravity to efficiently discharge water formed during electricity generation."

Both 25kW rear motors are housed in the car's wheels. This frees up space between the wheels for the hydrogen storage tanks.