Hydrogen-fueled Internal Combustion Engine Buses in Europe
As noted in GreenCarCongress nearly two years, ago, the hydrogen economy is not emerging as rapidly as some had anticipated or hoped. The pace of progress is starting to increase, but the question is how to foster transitional technologies that deliver near-term benefit to users and support a business case, while still advancing solutions regarding barriers to the longer-term use of hydrogen and fuel-cells.
In North America, hydrogen-fueled internal combustion engines (HICE) are gaining ground, in both direct drive and hybrid applications, using both hydrogen and hydrogen-CNG blends. Fiscal concerns and energy security are big factors in the U.S. Coincidentally, HICE - which like diesel - originated in Europe, seems to be getting solid traction there, where the driving factors are partly related to Kyoto concerns, partly to long-term economics. In either case, HICE deserves a look as a transitional step in some deployments, and as a solution in others.
Excluding the issue of greenhouse gas production during the fuel cycle, the primary operational emissions issue with HICE is NOx, as all other criteria emissions are practically at zero with careful designs. Engine designers have two basic approaches to take with HICE for NOx:
A lean-burn design that minimizes NOx emissions but has an effect on power; or
A richer fuel mixture, which ups the power, but also increases NOx requiring aftertreatment.
HICE systems theoretically can deliver greater efficiencies than their gasoline counterparts. The Department of Energy has set a target of 45 percent BTE (brake thermal efficiency) with 0.07 g/mile of NOx. BMW reported 37 percent with its hydrogen-fueled 750h prototype in 2006, with an internal target of 50 percent. With other technology enhancements, optimized HICE power plants can achieve terrific efficiency and deliver excellent performance.
Augmenting HICE systems with hybrid technology can deliver even more efficiency. Also, direct injection HICE with hydrogen fuel has been successfully tested, and is theoretically capable of delivering well in excess of 100 percent of the power density provided by port-injection gasoline systems, according to Sandeep Munshi at Westport Innovations.
Previously, it's been difficult to discuss engine durability for HICE or CNG blends because they have been on the road in insufficient numbers and miles driven, that situation is changing, and the growing story is positive. For example, MAN Hydrogen Internal Combustion Engine (ICE) buses were put into operation in Berlin during the 2006 Football World Cup. Since that time, they've established a record in excess of 60,000 km (as of mid-2007) with good fuel economy and no major breakdowns. The company has continued intense development efforts on a lean-burn, turbocharged engine with low pressure direct injection and spark ignition capable of efficiency greater than 40 percent. As a result, MAN has recently opted to go with a smaller, lighter engine in their HICE buses.
Another testing bed offering great promise is in London, where a new fleet of hydrogen-fueled Wrightbus vehicle is being deployed. Between now and 2010, London Buses, part of Transport for London, wants to have 10 of the buses in service. Five will be hydrogen fuel cell buses powered by fuel cell stacks manufactured by Ballard of Canada, and five will be hydrogen internal combustion engine buses utilizing propulsion systems provided by ISE Corp. of the U.S. There are options to up the hydrogen fleet to 20 total, split equally.
While there are positive signs of interest in HICE technologies by European regulators and transit systems, their North American counterparts could benefit from continued encouragement via policy initiatives, incentives and R&D funding.