Improving air quality in cities has long been an important issue on the political agenda. Last month’s news of record levels of air pollution in the south of the country brought the pressing problem back to the forefront of public attention. London achieved its own headline in April, recording that carcinogenic particulate matter PM2.5 – particles less than 2.5 micrometres in diameter – had hit an air quality index high of 57, six times the recommended limit.
PM2.5 particles are so small that they can penetrate into the deepest parts of the lungs. They are produced from all kinds of combustion, including power plants, agricultural burning and industrial processes, and a large amount from vehicle exhausts. So attention to reduce air pollution has unsurprisingly turned to the cars that are clogging up our cities’ arteries.
While zero-emission electric cars and hybrids have begun to be seen in greater numbers, there have been important developments with hydrogen fuel-cell vehicles. Some see them as a more viable zero-emission alternative as they deliver performance and driver experience comparable to diesel and petrol vehicles.
However, the hydrogen fuel-cell industry is still very much in its infancy. To demonstrate the technology’s viability and push it further down the road to commercialisation, there have been public transport projects running in London for the past few years.
One such trial has been conducted by Transport for London (TfL), which boasts
a fleet of eight hydrogen hybrid buses running on route RV1 between Covent Garden and Tower Gateway.
The project, announced by the Mayor of London in 2010, aimed to create the UK’s first zero-emission bus route. But as TfL engineering manager Paul Beyer recalls, it has not all been plain sailing.
The vehicles were designed using technology developed by US manufacturer of hybrid drivetrain systems ISE. This includes a Wrightbus body on a 12m SB200 chassis from Netherlands-based bus maker VDL, powered by a 75kW HD6 fuel cell from Ballard. The design also includes a modular ELFA hybrid drive system from Siemens and a hydrogen tank made by Dynetek, which stores compressed hydrogen gas at 350bar. Each bus can carry 32kg of hydrogen, with fuel consumption averaging 9kg/100km.
Beyer says: “Obviously with hybrids you have two power sources, so with the buses you have the fuel cell but also energy storage in ultra-capacitors. These store power when the vehicle brakes and quickly punch it back into the system when it accelerates.”
While TfL currently has eight buses operating, this has not always been the case. “Four out of the eight have operated over 15,000 hours of service,” says Beyer. “The others were late off the delivery line due to ISE going bankrupt in 2010. That was a bit of a disaster to say the least as they were the principal contractor.” ISE then sold its assets to rival Belgian company Bluways, which took over the project in 2010. However, by 2012 TfL had bought the contract back in-house.
Beyer says: “Mostly it is the maintenance and our supply chain that suffered. We had difficulties getting spare parts and access to technical diagnostic programs if we encountered an issue.”
Wrightbus took over the project, set it back on course and delivered the final buses to complete the fleet.
As a fledgling industry the supply chain still has its weaknesses, explains Beyer, but commercialisation projects in Europe such as 3Emotion are aiming to bring
down costs of hydrogen fuel-cell technology and increase the supply of parts with significantly reduced lead times.
Servicing the buses has also proven slightly more complex and required staff to go through additional training, mainly because of safety issues when working with high-pressured hydrogen tanks. Beyer says: “We service the vehicles as you would any other but then you’ve got the hydrogen system over the top of that. Most of it is checking to be absolutely certain that there is no leakage, as that is something you cannot afford.” Additional safety equipment and hydrogen detecting alarms have been installed in the servicing station. Despite these initial teething problems, the technology itself has proved incredibly reliable during the road trials.
Beyer says: “We have got several of these buses that will run at more than 80-85% of the time, with some approaching 94% availability. That is really good. The reason we are not at around the 99.5% mark that you’d expect with diesels is that it is an eight-bus route and the buses need to be taken out of use every month for two days to be serviced. This total comes off the operating statistics despite the fact that it won’t have broken down once in the month.”
The buses are serviced and refuelled at a depot in Leyton, London, which has a store of 350kg of hydrogen that gets delivered by tube trailer fortnightly. Beyer admits that this negates the advantage of the bus on the ground having zero emissions, but stresses that with early-stage projects it is more important to prove that the technology works.
“The ideal thing would be to see a whole bus depot running on hydrogen,” he says. “Then it would warrant having a hydrogen production plant on site, and only have the cost of the electricity which you can get from turbines.”
Beyer adds that the hydrogen fuel-cell technology has seen major advances since TfL’s demonstration project began. TfL will continue to invest in the technology, with two new Van Hool hydrogen buses due to join the fleet by 2016.
Intelligent Energy, a clean power technology business, has been conducting its own public transport demonstration trials with London’s black taxicabs. Part of a Europe-funded programme called Hytec, the project aims to assess the challenges of switching to hydrogen vehicles.
Intelligent Energy ran a fleet of five hydrogen fuel-cell taxis in the capital during the 2012 Olympic games.
James Batchelor, managing director of Intelligent Energy’s Motive division, says: “Taxis are one of the largest single sources of toxic emissions, accounting for as much as 35% of emissions from transport in the capital. Fuel-cell electric vehicles provide a much greater zero-emission range than conventional EVs and hybrids and emit only water, so are ideal for these demanding return-to-base applications.”
The company has two forms of hydrogen fuel-cell technology. The black cabs use its evaporatively cooled (EC) technology, which provides motive propulsion for relatively powerful automotive applications of 30-100kW. Compared to conventional liquid-cooled fuel-cell stacks, the EC design removes the need for individual cooling channels between each cell. Instead it uses the benefits of the heat of vaporisation in contrast to circulating coolant through the cells, reducing complexity, mass and cost.
Intelligent Energy is still successfully running the fleet of taxis, collecting data to help further develop the fuel-cell technology, which has progressed through two generations since the cabs were first put on the roads.
Batchelor says: “The work that we do with our client base, including a premium carmaker, is based on later generations of that EC technology, developing applications for use in vehicles.”
The second family of fuel-cell technology it has developed is called air-cooled (AC), which utilises low-power fans to provide cooling and the oxidant supply for operation. This has been developed over the past 20 years and has proven to be extremely cost-effective, particularly when used for power levels of between 15 and 20kW. As such it is ideal for small vehicles as shown in the Suzuki Burgman, a 4kW fuel-celled scooter.
Intelligent Energy is now using its tried-and-tested AC fuel-cell technology in a novel way – as range extenders for a new class of zero-emission battery-electric light commercial vehicles. The three-year programme is supported by £6.3 million funding from the Advanced Propulsion Centre, a government-industry partnership that aims to position the UK as a global centre of excellence for low-carbon powertrain development and production.
As part of a consortium of driveline technology and vehicle integration specialists and large fleet users, including DHL and British Gas, Intelligent Energy is set to lead the programme to develop validated systems and vehicle conversion expertise ready for volume manufacture by 2018.
Batchelor explains that the project will modify an electric vehicle that is already on the market with an AC fuel-cell system and hydrogen tank. This will help it to overcome the usual drawbacks of battery electric technology: limited range and lengthy charge-up times. He says: “We will then add to that platform this relatively modestly powered fuel-cell engine, which will act in the simplest sense as an ‘always-on’ zero-emission battery charger. It is a very simple architecture, compared to the more complex motive power vehicles where the fuel-cell engine is driving the vehicle.
“It maintains the level of charge in the vehicle’s battery and uses the hydrogen we store on board in the tank. As long as we provide the fuel cell with hydrogen from the tank it will supply electrical power which feeds into the battery system.” This will more than double the operating range of the vehicle, which usually is 80-100 miles.
Extending its focus to include light commercial vehicles is a commercially savvy move for Intelligent Energy as delivery vans and other vehicles of that size are increasingly needed to work for extended periods in cities such as London with ultra-low emission zones. Batchelor says that an added benefit is that their AC technology will be applied to vehicles described as “captive fleet”, overcoming one of the major issues facing commercial hydrogen fuel-cell vehicles: limited refuelling infrastructure. “These are vehicles that will go out on a route in the day and return to base at night to be refuelled,” he explains.
“One of the advantages of this model is that it gives customers the opportunity to use the zero-emission hydrogen vehicles before an extensive refilling network is fully available. For instance, in the return to base model a fleet going out in the day and coming back in the evening to their depot, which can at relatively low cost have a hydrogen refuelling capability.”
The lack of refuelling infrastructure is one of the major issues holding back the commercialisation of hydrogen vehicles. Michael Dolman, principal consultant at energy consultancy Element Energy, says that this is a catch-22 situation. “Demand for hydrogen fuel-cell vehicles will be limited until there is more refuelling infrastructure in place, but there is little incentive to build refuelling stations until there are vehicles or the promise of vehicles coming,” he explains.
While there are only a handful of refuelling stations dotted around the country, Dolman maintains that the UK has made reasonable progress considering that until recently there has been no formal support for them. Demonstration projects like those in which Intelligent Energy and TfL are running fleets of fuel-cell vehicles have helped to prove that there is a viable future for the technology, he says. The lack of a formal public sector support programme for hydrogen transport has recently changed with an announcement from the government in March that it will help fund refuelling stations. The £6.6 million investment will see an initial network of 12 refuelling stations established, including new stations built in Brentford and Croydon and a mobile station that will be used across the south of England, as well as upgrades to existing demonstrator stations.
The number of hydrogen stations will in no way match the 8,500 petrol stations in the country but the move was described as a “major first step” in the right direction by the Society of Motor Manufacturers and Traders.
Dolman points out that there have already been some commercial refuelling centres opened in the UK: the first in 2011 at the Honda factory in Swindon, a station near Heathrow airport that has been operating since 2012, and a large station in Aberdeen designed to refuel buses and cars. “The most recent station that was opened in London is in Hendon,” he says. “It sits alongside a Sainsbury’s forecourt. That is quite an advance because the regulatory challenges of getting the station installed were not insignificant.”
Dolman believes this could be a regular sight once guidance and regulation catch up, with hydrogen fuelling stations due to be built on retail forecourts in Germany and California, and plans for more to be built in the UK over the next couple of years.
To speed up investment in refuelling infrastructure, Element Energy has helped to put together a project called UK H2 Mobility. Dolman explains that the project recognises the need for infrastructure and technology providers, vehicle OEMs and government to work together. He says: “We considered the issue of where you’re getting hydrogen from and how green will it be. Phase one results of the project set out a vision for hydrogen transport over the next 15 years and the central scenario includes 50% green hydrogen by 2020.”
The advantages of hydrogen fuel-cell vehicles, says Dolman, are quite well documented, including rapid refuelling times, long range, and zero emissions at point of use. “This is one of the reasons that car companies, including Hyundai and Toyota, have invested heavily in developing the technology. Many in the industry believe that fuel-cell electric vehicles will play an important role in reducing emissions from transport.”
However, Dolman stresses that projections of commercial hydrogen roll-outs are fragile, and OEMs will take a slow and steady approach. As with the initial production of hybrid cars, global production of hydrogen vehicles is expected to begin in the low hundreds.
Dolman says: “The Toyota Prius was one of the first examples of commercial hybrid car, introduced around 1997. In the first generation it only sold in the low tens of thousands. Today, despite a wider range of plug-in hybrids and electric vehicles and a plug-in car grant scheme, annual sales in the UK are still in the low thousands. Until infrastructure becomes more widespread, the OEMs will be looking to roll out their cars to targeted customers who will be suitable early adopters of the technology.”
While Dolman is keen to manage expectations of how quickly fuel-cell vehicles will move into commercialisation, Batchelor at Intelligent Energy shows a level of confidence that won’t be dampened. He says: “We will see increasing commercialisation at scale of fuel-cell technology. It is perhaps the solution to providing affordable, zero-emission, decarbonised road transport. We are at the start of a very exciting journey.”