Technology Collaboration Programme


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Task 16

Alternatives for Buses

Objective of Task

The objective of the project is to bring together the expertise of IEA’s transport related TCPs to produce information on the overall energy efficiency, emissions, and costs of various technology options for buses. Here technology options cover variations in engine technology, powertrain technology (including hybridisation), and fuels.

The various TCPs have expertise and knowledge in the following areas:

  • Advanced Fuel Cells (AFC): automotive fuel cells,
  • Advanced Motor Fuels (AMF): alternative fuels in general and fuel end-use,
  • Advanced Materials for Transport (AMT): lightweight materials,
  • Bioenergy (specifically Task 39): production of biofuels,
  • Combustion: new combustion systems,
  • Hybrid and Electric Vehicles (HEV): hybrid and electric powertrains,
  • Hydrogen: the use of hydrogen as an energy carrier.

The outcome of the task will be the production of unbiased and solid IEA-sanctioned data for policy- and decision-makers responsible for public transport using buses.

Three of the TCPs –Advanced Motor Fuels, Bioenergy and Hybrid and Electric Vehicles – contribute with actual funding to the project. All transport-related Implementing Agreements are expected to contribute with condensed technology outlooks for their respective technologies.

working method

The project encompasses a combination of desk studies and actual measurements on new types of buses. The financing model is a combination of task and cost sharing. The overall budget of the project is €1.2 million.

The project is divided into two main parts, WTT (well-to-tank) fuel pathway analysis and TTW (tank-to-wheel) vehicle performance. For the well-to-tank studies, experts at institutes like Argonne National Laboratory (ANL), Natural Resources Canada (NRCan), and VTT Technical Research Centre of Finland are co-operating to evaluate and filter data for the chosen fuel alternatives. Well-to-tank energy efficiency and GHG emissions are expected to show a range of values depending on feedstock and process technology for the various fuel alternatives.

Environment Canada (EC) and VTT are carrying out chassis dynamometer emission testing on buses to establish tank-to-wheel performance (see figure 1). EC will cover North American vehicle technology and VTT will test European vehicle technology. In addition, Swedish powertrain developer and consultant AVL is conducting on-board emission measurements on buses in conjunction with VTT’s chassis dynamometer emissions tests. This will enable a comparison of chassis dynamometer and on-board measurements, with the expectation that the comparison will show the influence of ambient conditions and real traffic situations on tank-to-wheel performance. Alternatively, on-board measurements may also be used on vehicles which are not available for chassis dynamometer measurements. The first set of on-board emission measurements took place in November 2009. 

Task 16 figure


City bus tests (tank-to-wheel) were run in vehicle laboratories at both EC and VTT.

In 2009, EC performed preliminary tests with several fuels on a model year 2008 40-foot bus powered with an 8.9-liter Cummins ISM (with EGR, or exhaust gas recirculation) engine and hybrid transmission. Next in line, a 2008 6.7-liter Cummins ISB (with EGR) engine with hybrid transmission is being tested.

VTT started its bus measurements with a comprehensive fuel matrix in vehicles with conventional drivelines. Two older buses representing Euro II and Euro III emission certification have been measured for reference. Three new buses with EEV certification (enhanced environmentally friendly vehicle) have also been measured: one diesel vehicle representing SCR technology (selective catalytic reduction), one diesel vehicle representing EGR technology (exhaust gas recirculation), and one natural gas bus with a stoichiometric engine. The diesel buses were tested with several types of fuels.

The well-to-tank analysis has also commenced at Argonne National Laboratory, Natural Resources Canada, and VTT. A review of 25 LCA (Life Cycle Assessment) studies for biofuels has been done. The results of the various LCA studies vary remarkably and are currently being analysed and documented.

Different calculation models (US GREET, Canadian GHGenious, EU Directive (2009/28/EC) were evaluated and a number of fuels were selected as references for comparison. Biofuels analysed were: FAME (fatty acid methyl ester) from rapeseed, FAME from soybeans, FAME from palm oil, HVO (hydrotreated vegetable oil) from palm oil, HVO from rapeseed, HVO from soybeans, HVO from jatropha, HVO from animal fats, BTL (biomass to liquid) from wood residues, BTL from energy crops, ethanol from grain, ethanol from sugarcane, ethanol from cellulosic feedstock, and ethanol from waste.