A study by Ricardo and the Transport Research Laboratory (TRL) for the Department for Transport (DfT) evaluated the cross-over potential of powertrain technologies from the heavy-duty automotive, marine and power-generation sectors.
Based on detailed cost-benefit analysis, it recommend fitting the latest gas-exchange turbocharger systems to current passenger trains and stop-start technology for freight.
‘Rail is unique in how long it keeps its vehicles — there’s never been a policy of mid-life engine change or upgrade,’ Jim Buchanan, head of rail vehicle technology at Ricardo, told The Engineer.
The UK rail network is approximately 31 per cent electrified, relative to 80 per cent in mainland Europe. Further electrification will take time and be limited, and so for the foreseeable future around 69 per cent of the network will be reliant on self-powered diesel multiple units (DMUs).
‘Up until the recession there was talk about replacing anything up to half the UK diesel fleet in the UK and that just went down and down. In Derby, Bombardier has just finished a batch of Class 172s, which are state of the art, but then that’s it. We still need a sizeable fleet to deliver the service everyday and we’re running these museum pieces,’ Buchanan said.
In 2009–2010 DMUs consumed 482 million litres of fuel with a further 199 million from freight trains at a total cost of £409m. Rising fuel prices and passenger numbers could see this figure climb to at least £667m by 2022.
A compounding problem is that the majority of the trains in operation date from the 1980s — in the case of passenger trains ‘Class 150-159’ and ‘Class 66’ for freight — with their associated outdated and inefficient technologies.
Since these trains are unlikely to be replaced anytime soon, Ricardo and TRL considered retrofitting compatible components and entirely new engines to these train models.
Specifically, they evaluated transmission and driveline systems; waste heat recovery; hybrid powertrains and flywheel energy storage; alternative and biofuels; and even full fuel-cell systems with compressed hydrogen tanks.
Ed Bower, senior project engineer at Ricardo, explained these technologies have already been demonstrated to varying degrees of readiness in other sectors.
‘In essence it’s the same process applied to different applications and so the technologies you’re looking at in one sector could be applied to another sector, it’s just whether they’ll have different restrictions, usually on packaging or maximum temperature you can get to.’
The study gathered data from various inter-city and local routes because different technologies impact upon train efficiencies in different ways according to duty cycle.
From this, it identified the two most beneficial ‘technology packages’ in terms of capital, fuel savings and payback period.
For passenger trains, the solution was a new turbocharger and corresponding exhaust manifold modifications alongside new air filters to reduce inlet pressure loss. This would cost a total of £1.1m upfront for 200 DMUs, saving 5 million litres of diesel a year with an estimated payback period of three to five years.
For freight, the technology package was the addition of an idle stop-start system, a gas-exchange system upgrade and a small genset costing £50.25m (for 450 Class 66s), saving 89 million litres, with a payback period of less than a year.
‘The first thing is to recognise is that we’re running old technology here; we’re not going to get rid of it like we thought we would, we’re going to have to live with this. But the other side is that there are lots of things you can do and the report hopefully will become a catalyst to open people’s eyes to the possibilities out there,’ Buchanan said.