Low-Emission Bus Trial Final Report Phase Two

Minister Eamon Ryan has welcomed the completion of the Department of Transport’s Low-Emission Bus trials and publication of the final Phase Two report on the trials.

The publication of the Phase Two report marks the conclusion of the Department’s low-emission bus trials which have been running since 2018 and which have tested a range of low-carbon fuels and alternative fuel bus technologies.

The trial results concluded that electric bus technologies remain the most favourable investment option in terms of energy efficiency and real-world emissions.

Minister for Transport, Eamon Ryan T.D., said: “I welcome the publication and conclusion of this important study. This analysis helps provide us with confidence that the purchasing decisions we are making to help transition the public transport fleets in our cities and towns to electric or hybrid models will deliver real impact in terms of emissions abatement. I would like to thank all the Department’s partners who were involved in these trials and look forward to seeing the transition to a cleaner, more sustainable public transport fleet continue to be rolled out over the coming months."

An earlier Phase One report was published in February 2020 and this final Phase 2 report updates the analysis to include findings from testing of two hydrogen fuel-cell buses between November 2020 and August 2021. The buses were tested on a modified Dublin Bus route and analysed the emissions and energy performance in real-world driving conditions.

Over the course of these trials, the Department collaborated with the NTA, Bus Éireann, Dublin Bus, BOC, Byrne Ó Cléirigh, and Go-Ahead Ireland.

The Phase 2 findings will be used to inform future procurement decisions for Ireland’s urban bus fleets and help to support the development of a sustainable transport system across Ireland.

Notes

The Department’s low-emission bus trials have been running since 2018 and the final report is now being published. Findings from the trials allow us to assess the feasibility of a range of low-carbon fuels and technologies for Ireland’s urban PSO bus services in real-world conditions. An initial Phase 1 report was published in 2020 Low-Emission Bus Trials Report

The final Phase 2 report provides findings relating to testing of two hydrogen fuel-cell buses (a single-deck Caetano H2. City Gold and a double-deck Wrightbus Streetdeck). The report also updates the original cost-benefit analysis to account for six additional fleet investment options and compare them to the investment options set out in the original report.

The low-emission bus trials were set up in response to the commitment in the National Development Plan to stop purchasing diesel-only buses for the urban PSO fleet by July 2019. In response to this commitment, the Department needed to understand the viability of alternative technologies and the emissions generated under real-world conditions in each alternative.

Of note amongst the buses tested, the report finds that hydrogen fuel-cell technology is comparable to diesel-hybrid for energy efficiency. On a primary energy basis, which accounts for consumption, distribution, and conversion losses in transforming energy from one form to another, hydrogen ranks below diesel-hybrid technology. Electric buses remain the most energy efficient technology for urban bus fleets.

The first phase of the trials was carried out on fifteen buses over a five-month period (December 2018 to April 2019) in Dublin and Cork, and included trials of diesel, hybrid, compressed natural gas, and electric buses. The second phase of the trials was carried out with two hydrogen fuel-cell buses between November 2020 and August 2021.

The following are the key findings from the Phase 2 hydrogen fuel-cell bus trials:

• The average energy consumption of the hydrogen fuel-cell buses, on a final energy basis, was 8.3 MJ/km, which is marginally higher than the average energy consumption of the electric buses (7.5 MJ/km).
• The single-deck fuel-cell bus was more efficient than the double-deck (7.6 MJ/km compared to 9.0 MJ/km).
• When compared on a primary energy basis, the average energy consumption of the fuel-cell buses is comparable to the Euro IV and Euro V diesel buses.

The two hydrogen buses were tested according to the standardised methodology established in the initial phase of the trial. This allows direct comparison to other fuels and technologies test as part of the trial on a range of key metrics: final energy and primary energy efficiency, contribution to renewable energy and emissions reductions targets, and cost-benefit analysis.

While the initial range of buses were tested in both Dublin and Cork, the hydrogen buses were tested in Dublin only due to current limited availability of hydrogen refuelling points on the island. To support the testing of hydrogen fuel-cell buses, the Department collaborated with the NTA, Bus Éireann, Dublin Bus, BOC, Byrne Ó Cléirigh, and Go-Ahead Ireland.

The report sets out the following information:

• Outlines hydrogen production methods and describes the methodology for testing the buses and reports on energy efficiency findings
• Reviews four international fuel-cell bus evaluations and compares findings;
• Calculates the contribution alternative fuels and technologies could make to renewable energy targets and emissions reductions under several scenarios.
• Describes the approach to the cost-benefit analysis and sets out the findings for several fuel-cell fleet adoption scenarios.
• Provides conclusions on the trials and make recommendations on actions that could be taken in the coming years to comply with policy requirements and improve the performance of the national bus fleet.

The analysis suggests that the following priority should be given to the technologies assessed:

• Electric
• HVO diesel-hybrid
• BioCNG
• Diesel-hybrid
• Hydrogen produced from 100% renewable electricity
• Hydrogen produced from grid electricity
• CNG