GREEN MEANS GO
LOTUS BUILDS HYDROGEN FUEL CELL TAXI FOR LONDON 2012 The sound of squeak-
ing plastic parts is a minor irritant as the black cab surges into a sharp corner,
its
body leaning heavily. Normally, at high speed, the rattling would have been drowned out by a rumbling, whining diesel engine.
But this taxi is differ- ent. It is a hydrogen-powered London cab, devel- oped to showcase zero exhaust emission vehicles during the 2012 London Olympics.
The taxi has been put together by Lotus, a UK company more famous for its Formu- la 1 team and for making sports cars such as the Elise.
Long-range electric motoring
From the outside, the taxi looks like any other black cab and it weighs as much too - a whopping 2.6 tonnes.
But driving it at the Lotus test track in Norfolk feels com- pletely different as it accelerates from 0- 60mph (0-100km/h) in 15.5 seconds - slow compared with most cars, but a full seven seconds quicker than an ordinary black cab. Under the taxi’s famil- iar exterior - within its generous bulk - the truly special bits are hidden.
The back wheels of the taxi are powered by two electric motors - though it is not an electric car in the con-
ventional sense of the term. Yes, the taxi has a lithium polymer bat- tery that delivers electricity to the elec- tric motors, but this is not its main source of power.
The cab also has a stack of fuel cells that convert energy from hydrogen, which is stored in a tank under the car’s bonnet, into electricity.
The electric motors can be powered by either the fuel cell system, or by the bat- tery, or by a combination of the two.
During braking the battery, which is located in the middle of the taxi under the floor of the cabin, is recharged by two sources: surplus elec- tricity created by the fuel cells is sent to the battery; kinetic ener- gy captured during braking is sent to the battery from the back wheels, via the elec- tric motor.
With two different power sources - fuel cell system and bat- tery - the taxi could be described as a hybrid vehicle, but again, not in the conventional sense of the term, which usually refers to petrol-electric hybrids.
Technology showcase
The point of all this is to create a car with zero emissions; or rather, the taxi does not have an exhaust pipe as it only emits water vapours.
Now, whether that
makes it green is another matter.
Hydrogen is made by splitting water into hydrogen and oxy- gen, but this process is energy intensive. If it is done with the help of renewable energy sources such as wind turbines, the car will be green, though in practice the hydrogen is more likely to be produced using fossil fuels such as gas.
So rather than being seen as a green car, it is perhaps more apt to see the taxi as a marketing vehicle. “The black cab is a good tool for us to demonstrate the tech- nology,” Dr Ashley Kells, programme manager at Intelligent Energy, the company that developed the cab’s fuel cell system, told BBC Business News.
A fuel cell is “very much like a battery” in that it delivers elec- tricity, according to Dr Kells, though there is one major difference: recharging a battery is a slow process, whereas refuelling a hydrogen tank is not. “And as long as you keep on providing fuel for the cell, it will keep on providing power,” he explains.
Five-minute fill
For London’s cabbies, the fuel comes in the form of gaseous hydrogen that is pumped into a tank under the taxi’s bon- net.
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“The fuelling is very quick,” says Dr Kells as he demonstrates how the fuel connec- tor is fixed to the taxi whilst fuelling to make sure the hydrogen gas does not leak. There is another cru- cial difference bet- ween fuel cells and batteries, he adds, namely “the energy density of a fuel cell system, which is a lot greater than current battery technology”. In other words, elec- tric cars powered by fuel cells carry much less weight and deliv- er much greater range.
One tank of gaseous hydrogen gives the taxi a range of at least 160 miles, or up to 240 miles if driven carefully, so the cab- bies should be able to do what they do in conventional taxis, namely fill up in the morning then drive all day.
“They go to the filling station and five min- utes later they’ve got a tank full of fuel and a copy of the national daily from the garage,” says Dr Kells.
As a marketing vehi- cle, the taxi has a role to play in the enor- mous PR machine that has grown up around the 2012 Lon- don Olympics.
By then, there will be a handful of hydrogen fuel cell taxis in Lon- don, served by six hydrogen filling sta- tions that they will share with at least five hydrogen fuel cell buses.
“We’re not just doing this as a one-off,” says Dr Kells, insist- ing the project offers “a real, tangible solu- tion for 2020”.
By then, London Mayor Boris Johnson wants every taxi oper- ating in London to deliver zero exhaust emissions. However, for engi- neers at Lotus, who are more accustomed to working with ultra- light cars such as the 1.1 tonne Lotus Elise, this is just the begin- ning.
They hope to push
the project further and develop lighter, more efficient taxis in the future.
“I would really have liked to do it with a new chassis to make it an optimal system,” says Steve Doyle, chief engineer, hybrid and electric vehicle integration, Lotus Engineering.
Dr Jon Moore, com- munications director and one of the founders of Intelligent Energy, agrees. “If we can do it with this, we can do it with anything,” he says.
HOW THE TAXI WORKS
1. Hydrogen tank
2. Fuel cell 3. Battery 4 Motor Source: Lotus
•The taxi is powered by a stack of fuel cells that get their fuel from a hydrogen gas tank under the bonnet.
•The fuel cells convert the energy stored in the hydrogen into electricity, which drives two electric motors that drive the two back wheels.
•The electricity stored in the battery is then used to supplement the electricity from the fuel cells to propel the car forward.
•During braking, the energy from the fuel cells is not needed so it is instead channelled into a battery. The battery also gets energy from the wheels during braking.
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