With the inexorable rise to $100-a-barrel pricing, alternative-fueled transportation once again will rise up the agenda. The recently completed trials of hydrogen-based buses across Europe provided some salutary information on how transportation based upon this energy carrier could survive as a viable transportation fuel. The data are in and the conclusions are far from convincing. While most of the European trials—the CUTE project—were extended beyond their two-year lifespan (two of the nine city fleets were not renewed) the Australian trials—the STEP project—was completely scrapped. A fleet introduction in China has just concluded, although the results are not yet available.
In terms of public perception of the safety of hydrogen-fueled buses, of those surveyed in Europe, people were generally well-disposed to the technology and felt safe with it. It was the over-40s demographic group that was interested in knowing more about the technology. The drivers themselves were more positive (than the public as a whole) to the technology, and although the environment was rated as a big factor in influencing purchasing decisions, 64 percent of the passengers surveyed were not willing to pay more for a journey taken on a fuel-cell bus compared to a regular diesel-powered vehicle.
System Infrastructure Failures
The CUTE project, like any major technology introduction, experienced its share of technical problems. Analysis of the data for all the cities included within the CUTE initiative (and the complementary ECTOS program in Iceland and STEP program in Australia) supports the idea of most reported system failures being due to the refueling infrastructure rather than the buses themselves. Despite some rigorous documentation, the majority of failures were attributable to ‘unspecified incidents.’ The hydrogen dispensing system (and the unavailability of hydrogen) and compressor failure collectively accounted for more than 70 percent of all reported failures. By comparison, there were only 10 bus-related failures across the entire fleet of more than 30 vehicles throughout the trial period.
Of the nine European Union (EU) cities included within the trial, only two—Porto and Barcelona—significantly came in below the average of 100,000 kilometers of travel. In the case of Porto there were above-average problems with the bus itself due to modifications to the hydrogen supply. In Barcelona’s case, there was a serious case of graphite contamination within the hydrogen line that affected purity of the supply. At the other end of the success scale, the three buses operating in Luxembourg totaled more than 140,000 kilometers of travel.
Averaged out for all cities, the monthly totals of distances covered increased from under 3,000 to more than 5,000 kilometers over the trial period. Likewise, hydrogen consumption increased from around 700 kg per city to almost 1,200 kg as the trials reached their conclusion. For the project as an entirety, the on-site production of hydrogen in general remained steady, in terms of volume, throughout the project lifetime. Whereas the consumption of electricity for electrolysis of water to produce hydrogen was steady, the other source of on-site hydrogen generation (steam reforming from natural gas) was highly variable, reflecting the difficulties in adapting the reformation technology to the required volumes of hydrogen production.
Throughout the trials, unexpected vehicle stops were mostly attributed to compressor failure at the station, with failure of the electrolyser and the filling nozzles accounting for the bulk of other vehicle stops. The filling nozzles had to be retrofitted in all the filling stations. Failures in the hose and breakaway were recorded in three of the cities (London, Stockholm and Perth).
Compressor problems were the main cause of downtime for the refueling stations. They also caused consequential damage, such as contamination of the gas and the fuel tanks with oil (in Hamburg) and with graphite (in Barcelona and Perth). The risk of hydrogen embrittlement to the nozzle was considered serious enough to trigger a redesign. There was a serious enough disagreement on the root cause of the nozzle issue as to cause a complete shutdown for several weeks early in the project.
The electrolysers in Reykjavik and Hamburg experienced stress corrosion caused by a combination of high temperatures and high pressures. The natural gas reformer in Madrid experienced leakage, pipework failure and gas quality problems to the extent that it was operating at only 11 percent capacity for the year of 2004. Redesigns of the fueling hose in Perth was undertaken resulting in a capability to refuel at pressures up to 1,000 bar(g).
Emergency shutdown data for the refilling stations are revealing. The major contributor to shutdowns was a failure in the filling nozzle. Low pressure into the compressor was a factor on two occasions. Gas leakages that were detected were mostly also attributable to the dispenser. Only one reported leakage at the connection to the bus was recorded for the entire fleet across Europe. Ninety percent of ‘incidents and abnormal situations’ that were recorded were attributable to technical failure—the rest to human activities.
The use of regenerative braking (in which the energy generated in the braking process is redistributed into the transmission for moving off again) was put forward as a major factor in fuel economy computations. Relative to conventional diesel engines, the hybrid design (through the use of battery power) and this braking capability returns a greater fuel economy than diesel. In California bus fleets with this fuel cell capability operated by SunLine and AC Transit, fuel efficiency gains of 149 percent and 67 percent more than conventional diesel were returned for trials in 2005-2006. A fuel cell fleet operated by VTA that had neither regenerative braking nor a hybrid design returned 12 percent inferior fuel efficiency.
The battery performance is being targeted for future designs. Prof. Herbert Kohler, vice president, Body and Powertrain Research at DaimlerChrysler, announced at the conclusion of the trials, “We intend to use a high-performance battery into which we can feed energy recovered from the braking process. ... The fuel cells will only have to meet the normal level of energy requirements. Peak demand will be met by the battery. This will save both volume and weight.”
The consensus view is that the buses themselves have performed better than expectations. The onsite technicians from DaimlerChrysler were thought to have provided adequate support. (This was not the experience of the Perth project, however.) Spare part supply for the buses was found to be lacking. Of the infrastructure partners, the fuel retailers (BP and Shell), it turns out, had ‘other expectations’ than those not normally in the fuel business. The gas and energy sector partners collectively expressed that the performance of the hydrogen refueling stations was “lower than expected.” Despite the documented failures throughout the trials, the troubleshooting, reporting and corrective actions procedures “have improved over time in the project.” Post-trial surveys designed to establish any sense of “regret” over the use of hydrogen refueling stations identified only two cities stating this—Luxembourg, due to the high cost of trucking in natural gas for reformation, and Madrid, because of an unreliable reformer.
78 Million Euro Investment
Perhaps, understandably, there is very little credible data on the true cost of the program. Seventy-eight million euros was invested in the overall project, of which 18.5 million euros was provided through European Commission public sector funding. The remainder was provided through the project participants, including cities, public transport operators, infrastructure partners and vehicle manufacturers. A similar public-private contribution has characterized the U.S. fuel-cell bus program.
The fuel-cell buses are heavier than existing bus technologies. The Citaro buses weighed in at 14 tons unladen; this is 2 tons heavier than an equivalent capacity CNG vehicle and 3 tons more than a diesel. The buses were also approximately 2 feet taller than regular buses—this required some adjustments to infrastructure, such as the washing facilities which had to be upgraded to accommodate the taller buses.
Some of the drivers apparently reported an unusual sensation requiring adjustment of speed on tight corners. Generally, drivers were very positive about the driving experience with comfortable stop-start cycles and smooth acceleration. Public surveys noted that the silent operation of the buses, relative to regular buses, was a favorable driving experience. So much so, in fact, comments were received about the noise levels of the air conditioning systems.
The failure of the Perth trials is rather perplexing. The demands placed upon the buses were not significantly greater than any of the European trials in terms of the distances covered or the gradients over which the vehicles had to operate. The fuel cell repair time (the most prone component responsible for 41 percent of all failures) did increase over the duration of the trial. Despite a real-time troubleshooting link to the Australian suppliers, the refueling station, however, was unavailable on 39 percent of days in 2005 and the averaged fuel costs (in terms of Australian dollars per kilometer of travel) did work out at between five and six times that of diesels and between six and seven times that of CNG buses, dependent upon the route selected. The criticism that the average inter-stop distances in Perth were too great to optimize fuel-cell buses stop-start cycle performance, and that the emissions gains from cleaner idling periods did not really cut much ice with the true detractors of the project. The Australian trials were characterized by modest successes, however. The occurrence of call-outs decreased over the first 12 months of the trials and the general maintenance reliability data were considered comparable with diesels.
One of the biggest hurdles with the fleet introduction in Australia has been in gaining approval for gas-powered buses from all the involved authorities. According to Simon Whitehouse of the Western Australia Dept. of Planning and Infrastructure, “Codes and standards for hydrogen and fuel cells for transport just do not exist in Australia yet.” The same department stated that, despite winning a prestigious national environmental award in 2005, it was “not economically viable to retain the prototype” which was officially decommissioned in October 2007. A figure in excess of 1 million AU$ per vehicle per year was cited as the maintenance cost. Technical issues are still far more significant for the Australian investing parties it would seem.
The high summer temperatures in Perth were blamed for much of the failure associated with the nozzle/hose connection. Madrid, however, experienced higher average summer temperatures without the same failure rates. Informed opinion supports the theory that there was insufficient political will to continue subsidizing the program—all the more surprising in a state heavily in surplus. (As of December 2007, Australia is now a signatory to the Kyoto Protocol.)
Across the entire CUTE fleets, the other principal conclusions drawn from the investing parties were that the actual refueling process was too lengthy, that the concept of self-service refueling by the public was still remote and that the cost element was still a problem. Gunter Elste, CEO of Hamburger Hochbahn, commented, “Mrs. Benz bought the first petrol she needed for the first car at great expense from her pharmacy.”
London Hydrogen Partnership
The future of hydrogen in public transport is being taken very seriously in London. Mayor Ken Livingstone has recently announced the establishment of the London Hydrogen Partnership, a public-private partnership initiative aimed at addressing air quality, climate change and ambient noise issues in England’s capital city. Integral to this is a public auction process for the supply of a hydrogen transit fleet for use on the city’s roads by 2010. The award criteria are revealing; the heaviest weighting (25 to 35 percent) is reserved for the whole life cost of the hydrogen vehicle purchase and subsequent operation, all other six criteria, including maintenance capabilities, previous design experience, medium-term commercial viability, operational fit with existing roads, etc., rank lower in importance. Cost is still the paramount issue with hydrogen-based design.
There are currently three London buses running on hydrogen fuel cells served by H2 refueling station. Transport for London is in the process of acquiring another 10 vehicles with 60 more to follow by 2010 that will provide some transportation support to the 2012 Olympic Games. This will still only represent 1 percent of the current fleet serving 7 million Londoners daily.
Worldwide Fuel Cell Use
So, is there a future for fuel cells in mass transport outside Europe? The Perth experience should not be seen as the death-knell for fuel-cell buses.
Canada may be a Kyoto signatory, but it has performed worse than any other G8 nation, including the United States, in terms of meeting its emissions obligations. As part of its hydrogen infrastructure plans for the Vancouver-Whistler 2010 Olympic Games, BC Transit announced recently that it has signed a contract to take receipt of no less than 20 newly built fuel-cell buses for use in the Greater Vancouver area.
This will be the largest fleet of hybrid fuel-cell buses in operation, and second only to Germany in terms of a national total. Hamburg and Berlin together will have 23 buses running.
The first pre-production bus will arrive in Victoria in 2009 and is expected to be seen transferring spectators around the Olympic venues during the games. The fuel cells will be provided by Ballard, the drive train from San Diego-based ISE Corp., and the buses themselves assembled by New Flyer. The initial specifications for this fleet are in line with previous designs, 130 kW fuel cells, 350 bar hydrogen storage, ISE’s ThunderVolt electric drive system and nickel-metal hydride battery storage systems.
The total outlay on the British Columbia project is forecast to be 89 million CAN$, 10 million from the Province, 34 million from BC Transit and the remaining 45 million from the federal Public Transit Capital Fund. The 46 million CAN$ that is to be apportioned to the manufacture of the buses will be approximately equal to the amount ring-fenced for infrastructure projects. This creates a target figure of close to 2.32 million CAN$ for each vehicle—close to a 30 percent reduction on current fuel-cell bus manufacturing costs; a step in the right direction on the all-important cost factor. A figure of 60 percent was cited by the organizers of the CUTE evaluation conference as the target reduction on FCB cost.
Despite the disappointments of the Perth trials (as of November 2007, Porto in Portugal has also put its three buses into storage), the CUTE program has generally been viewed as a worthwhile venture. Proof of this is evident in the continuation of the trials under the description HyFleet. The cities of Stockholm and Stuttgart did not extend their projects but their buses are being redeployed to Hamburg to augment their existing fleet to a total of nine. Hamburg currently boasts the largest fleet in Europe, at least until the 14 fuel-cell buses planned for Berlin become operational under HyFleet. These vehicles will be hybrid hydrogen-ICE designs; four will be naturally aspirated and 10 will be powered by a new turbocharger-based engine design, designed by Neoman of Germany. HyFleet will be a consortium comprising eight transport companies, two bus manufacturers and one car manufacturer, 10 oil and utility companies, nine university consultants and two governmental organizations. In total, 13 nations are represented within HyFleet, more than that for the original CUTE program.
The H2-ICE hybrid design is likely to be the fuel-cell bus design of the future. Trials by Ford, under the Freedom Car initiative, on the specific technical gains that are achievable using fuel cells in hybrid designs have confirmed that fuel economy increases with fuel cell peak power whereas the efficiency of the regenerative energy capability decreases markedly at lower battery power. They claim that adding a 10 kW fuel cell system increases the range of the vehicle, relative to a vehicle without fuel cell power, by more than 20 percent. The figure rises to 30 percent for a 20 kW fuel cell addition.
Similar fuel economy gains have been recorded for 20 kW fuel cells when deployed in an H2-ICE design relative to an equivalent specification hybrid electric vehicle. Ford’s new H2-ICE shuttle bus, the E-450 is scheduled for delivery in 2007, first in Florida and then elsewhere across the United States.
As passengers cannot be expected to bear the additional burden of cost, nor are they willing to, perhaps oil has to hit $150 and gasoline has to reach $5 a gallon before hydrogen makes a serious contribution to public transportation. For the time being, initiatives such as these need support. Sometimes the cost of progress cannot be measured in dollars and cents.
Peter Ion, MSc, MBA, is a Vancouver-based technical author specializing in science and technology issues. He set up a fuel cell R&D company in the UK with European Commission funding before transferring out to Canada to consult with the organizations active in PEM fuel cell applications in Vancouver. He is published widely in transport-based technology introductions.