September 2018
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Fuel cell hybrid taxis: A new era for road transport

Tackling the growth of carbon emissions from road transport and meeting demanding emission standards are major challenges for the automotive industry. The concept of green motoring, however, is taking off in the UK with incentive schemes offering cash to motorists who scrap their old models in favour of cleaner alternatives like electric vehicles.

The demands of a large-scale adoption of battery electric vehicles (BEVs), however, could have serious implications for electricity grids already under increasing strain.

It would place additional burden on the electricity supply infrastructure in order to charge batteries in vehicles that currently offer very limited range and consequently few practical applications. And, we must not forget that the source of the energy required for electric vehicles is not currently low carbon in nature as the vast majority of our electricity is generated via fossil fuel-burning power stations.

Despite this, the automotive landscape of the near future is diverse and batteries will play an important role in enabling cleaner motoring. Certainly, there is an early niche market for commuter vehicles, where the requirement is only for short trips and where there is the possibility of accommodating the prolonged recharging the vehicle may require prior to a return trip. Batteries are also key components in hybrids and these are poised to be a practical and widely applicable alternative to today’s engine-based vehicles. In the near term hybrids will use a combination of batteries with internal combustion engines as with the Toyota Prius, but ultimately will be combined with hydrogen fuel cells, to provide that which many in the automotive industry see as the end-game: fuel cell battery hybrid vehicles.

The fuel cell power systems used in such hybrids are highly efficient electrochemical devices like batteries, but with some of the characteristics of engines; they combine hydrogen with oxygen from the air to make electricity and water. Unlike batteries, fuel cells do not require recharging but will generate power in a steady and continuous manner, so long as they are provided with fuel (hydrogen). This characteristic lends itself to the provision of the steady cruising power of a vehicle, while batteries provide the additional power required during acceleration. Once the acceleration is completed, the partially depleted batteries are then recharged by the fuel cell while the vehicle is in operation.

Water vapour is the only emission at the tail pipe, and carbon dioxide emissions ‘well to wheel’ can also be zero, if the hydrogen is produced renewably, or much reduced (30-50%) if the hydrogen is produced from natural gas.
Because the energy contained in the hydrogen fuel is greater than can be stored in a battery, the range of fuel cell vehicles is more akin to that of today’s conventional internal combustion engine vehicles (typically several hundred miles) than that of a BEV and refuelling time with gaseous hydrogen takes only a few minutes not several hours.

In London, Intelligent Energy (IE) is leading a programme part-funded by the Technology Strategy Board with partners Lotus Engineering, London Taxis International and TRW Conekt to develop and field zero emission fuel cell hybrid Black Cabs in London for 2012.

The fuel cell taxis will have a range of 250 miles, zero tail-pipe pollution and reduced well-to-wheel emissions but also unaltered passenger capacity, improved acceleration and will take only minutes to refuel. The first of the vehicles will be on the test track in January 2010, with the first road-legal version due in May.

Fleet applications, such as the London Taxi, often use centralised, return-to-base refuelling and Black Cabs in particular rarely stray beyond central London. Only a few hydrogen fuelling stations will be required around London to facilitate the introduction of fuel cell vehicles across the capital, a vision that the Mayor of London is already subscribed to.

A group of the world’s major automotive companies, including Toyota, Daimler, Honda and General Motors recently announced that they view 2015 as the year that will see the start the true mass market commercialisation of their fuel cell vehicles. Leading up to that time, we will see the fielding of increased numbers of fuel cell vehicles in fleet applications. By then it will be possible to have significant numbers of fuel cell taxis operational in London and to have exported the idea and the technology to other cities and other applications around the world. It represents nothing less, than a chance for the UK to gain a lead in an automotive industry going through a period of intensive repositioning and change.

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