WP3: Rail Passenger Transport - TOSCA Project

3.3 Technology descriptions
The potential for reducing energy use or GHG emissions is presented in percent per unit load
(passenger-km), assuming the same average speed, in comparison with the reference system of
2009. Change of speed is taken into consideration in Sections 3.4 and 3.5. In most technology
descriptions below (except FH, FI. FJ) energy savings is the immediate target, but these
savings directly translate into GHG reductions proportionally.
At this stage technologies are mainly described independently of cost effectiveness. In Sections
4 and 5 economic, social and user considerations are also taken into account.
PA. Low-drag train
Technologies are basically available for reducing air drag by 15–30 %, compared with the
reference trains in Table 2-1. Some of them will need further maturity and acceptance (UIC,
2010) (Diedrichs, 2010). Low air drag is most important for high-speed long-distance trains,
but has a significant impact also on fast regional trains and local trains as the two latter trains
have today usually a modest aerodynamic performance. The low-drag train is estimated to have
a long-term energy-savings potential of around 15 % – with an intermediate step at about 10 %
– compared with the reference ‘High-speed’ as well as for the ‘Intercity and regional’ segment.
PB. Low-mass train
Lower mass will reduce energy consumption and related GHG emissions per pkm, in particular
on stopping trains (local trains and metros), although re-generation of braking energy in
electric operations to some extent will reduce the positive impact of low mass. Technologies
are today not available for a major reduction of train mass (around 20 %), but may become
available as a result of massive R&D. New materials and/or designs are needed and likely also
economic incentives. The potential of energy savings is estimated to 10 % in local or metro
trains - ‘City trains’- less in other train types, all compared with reference trains in Table 2-1.
PC. Energy recovery
Today’s modern electric passenger trains use the (electric) motors as generators when braking,
thus feeding back electric energy to other trains on the line, or (sometimes) to the public
electric grid. Alternatively, electric energy can be stored onboard in batteries or supercapacitors,
for storage of braking energy until the next acceleration; the latter is of special
interest for non-electric trains (diesel fuel and similar) with no external electric connection. All
this is called energy recovery or regeneration. Energy recovery braking will also reduce the
maintenance of the mechanical brakes.
This technology is partly introduced already today. The feed-back ability is however usually
smaller than optimum due to the limited power (in kW) of the propulsion equipment of the
train and/or by the limited number of powered axles, as well as of the limited recovery capacity
of the electric supply chain. With the rapid development of electric power equipment it is
increasingly technically and economically feasible to install more power in trains and in the
supply network, and also to improve possibilities of feeding electricity back to the general grid.
Energy recovery has been subject to extensive simulations in this study and is estimated to be
able to save energy use and related GHG emissions by up to 20 % over the long-term, in
relation to today’s ‘Local city trains’. This potential is smaller in high-speed operations with
only few stops, although also downhill gradients contribute to energy recovery. In some cases
the electric supply system must be modified or rebuilt. A continuous improvement of
regeneration and energy recovery is anticipated over the years.
Energy recovery interacts with other technologies, such as ‘Eco driving’, ‘Low drag’ and ‘Low
mass’. To fully understand and evaluate the impact of Energy recovery combination scenarios
are needed; see further Section 3.5.
Deliverable D4 – WP3 passenger 8