Hydrogen Fuel Cell Bus Technology State of the ... - NEXTHYLIGHTS

Hydrogen Fuel Cell Bus Technology State of the Art Review
5.2 CO2 emissions
Table 9, below, summarises the range of CO2 emissions per kilometre for hybrid fuel cell
buses compared with diesel and diesel hybrid buses. There is a very wide range for fuel
cell hybrids, reflecting the wide range in CO2 emissions for different hydrogen production
pathways. At the ultra-low CO2 end (production from renewable, nuclear or fossils fuels
with CCS) the CO2 emissions are over 90% lower than a conventional diesel bus.
At today‟s state of the art for hydrogen production from methane (approx. 10kgCO2/kg of
H2), there is still a CO2 advantage over both diesel and diesel hybrid buses at the
highest fuel economy for fuel cell buses (N.B.: next generation of FC buses are
expected to achieve a fuel economy up to 40% better than diesel buses over an
equivalent route at parity of calorific content). As the fuel economy drops from this point,
or less efficient methane based reformation pathways are used, the CO2 emissions tend
towards that of a conventional diesel bus and can even increase above those for hybrid
diesel buses.
This suggests that any medium term strategy for hydrogen bus rollout should target a
CO2 content below 10kgCO2/kg of hydrogen and best in class fuel economy, to ensure
that the deployment leads to real CO2 savings.
Table 9: CO2 emissions per km travelled – comparison between selected bus
technologies. The figures on the CO2 content of the hydrogen fuel reflect different
production paths.
Hybrid Fuel Cell
Bus
Hybrid Diesel
Bus
Fuel Economy
(nominal range,
current values)
Fuel CO2 content Kg CO2 per km travelled
8 – 15kg/100km 0* – 0.36 kg-CO2/kWh
(0* – 12 kg-CO2/kg-H2)
0* – 1.8
23 – 40 litres/100km 0.3 kg-CO2/kWh
(3kg-CO2/litre)
Diesel Buses 35 – 50 litres/100 km 0.3 kg-CO2/kWh
(3kg-CO2/litre)
Trolley Buses ~ 180-200kWh/100km depend on grid content
(Average EU-27: 0.6kg/kWh)
0.69 – 1.2
1.05 – 1.5
0* - 1.12 (assuming
average EU-27 grid)**
Source: Stakeholder consultation.
* For renewable hydrogen and electricity the CO2 content is assumed equal to zero.
** The average CO2 grid content in EU-27 was ~ 0.6 kg/kWh for thermal generation in 2005 (Source:
Eurostat)
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