Engineers at euro engineering AG’s Commercial Vehicles business line in Neu-Ulm, Germany, began development in 2007 of a new hybrid technology that could allow vehicles to be driven using multiple power sources—and enable a potential fuel savings of up to 30%.
The result is a “more flexible” series-hybrid drive module, for urban buses initially, that combines a diesel (or CNG-fueled) engine and an electrical or fuel-cell drive packaged in a steel-cage-like structure. Its design enables different power sources for the engine to be built into different models, with the module simply taken out and replaced during the vehicle’s day-to-day operation in “much less time” than a normal fueling operation.
It takes less than one minute for experienced handlers to change out the module, according to project leader Andreas Reuter, “whereas the charging of the same amount of batteries (NiMH) takes about 8 hours. Fueling a diesel tank of the same size of our changing hybrid module takes about 10 minutes.”
Once the module is removed, it is recharged/refueled and then reused in another bus. “There should be no bus that cannot be equipped with it,” he noted.
A concept model of the changing hybrid module was debuted at the IAA Commercial Vehicles Show in September. The next step is construction of a driven prototype in 2011; a realistic target for a production application is in 2013, Reuter told AEI at the exhibition in Hanover, Germany.
“Innovations such as the changing hybrid module can help the emission-free urban bus to quickly achieve general acceptance. It’s ideal for the inner city stop-and-go operation,” Reuter said. “It offers maximum leeway for the vehicle package, i.e., for the positioning of the installation spaces for components and cable routes, and also means a low-floor construction can be used throughout the bus.”
The euro engineering team—including plastics, chassis, and interior specialists—relied on CAD data of a series-hybrid bus to selectively test and adjust aspects of the vehicle and then to modify them for the project.
To construct a diesel-electric changing hybrid module, the engineers calculated the size of the individual drive components, such as the diesel engine (about 6.0 to 6.5 L), generator (about 440 to 480 kW), and exhaust unit, and then reproduced them inside a 2.5-m³ (88-ft³) body structure constructed in-house. Changes to the shell and to the taillight area provided additional space, Reuter explained, making it possible to install a busbar system in the vehicle’s body. Spring-loaded pins prevent leakages from the compressed air circuit.
Test drive data for the hybrid urban bus have confirmed that these changes carried out in CAD do not conflict with the original construction design for the bus, Reuter added.
“The diesel engine is only used 35% of the time now,” he said, noting that, in city traffic, a hybrid bus can already undertake an average journey of 70 km (43 mi) using just its electrical power source. This figure rises to 100 km (62 mi) if fuel cells are used, too.
“We are already in a position to construct and test it and to modify the individual components in line with customers’ wishes and the vehicle’s demands,” Reuter said, but added that a few significant steps still need to be taken before series production can begin. For example, the forces occurring during operation and in a potential crash need to be analyzed, the thermal characteristics in the vehicle’s body and module must be researched, and detailed stress calculations need to be made.
“I hope that in 10 years’ time in this country [Germany], at least one-third of the public transport vehicles running on short-distance routes will be using electric power at least 50% of the time or even 100% of the time,” he said.
The technology is suitable for global markets but will likely gain traction in European markets before spreading elsewhere, according to Reuter. In the future, there may be application for certain types of trucks as well.
“I do not think it is a ‘bridge technology,’” Reuter replied when asked if the module is just intended to fill the space until full-electric and/or fuel-cell powered buses are developed that have longer range and shorter charging times, and the infrastructure to support such vehicles is established. “It can be used for a long time and is a fairly unique selling proposition for the user. We think it will also be used to introduce new technology.”