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Dual fuel locomotive concepts unveiled

G-volution (www.g-volution.co.uk) and SBL-Rail (www.sbl-rail.co.uk) present dual fuel evolution concepts of the Class 37, Class 59 and Class 66 locomotives, representative of Type 3 and Type 5 locomotives respectively and their operations.

Dual fuel engines use compression ignition and combust two fuels simultaneously. This work shows how diesel fuel can be displaced by renewable net zero carbon emission fuels.

G-volution has been developing dual fuel engines since 2008 and now shows how this technology can benefit UK freight locomotives.

The concepts presented use diesel with biomethane, diesel with biopropane and diesel with hydrogen. The Class 37’s English Electric 12CSVT and the Class 66’s EMD 12-710 engines are replaced by new dual fuel engines developed by G-volution and meeting the Stage V emission standard. A twin engine concept Class 59 and Class 66 using two smaller new dual fuel engines has also been developed as well as a dual fuel evolution of the Class 66’s original EMD 12-710 engine. Whilst the locomotives’ original engines could also be evolved to dual fuel, modern engines offer higher efficiency, the opportunity to use advanced combustion control strategies and compliance with the latest emission standards.

The original diesel tank/s of the locomotives are replaced with a smaller diesel tank and cylinders for biomethane or biopropane or hydrogen are installed in place of part of the original diesel tank. A range of fuel tank solutions were developed for each fuel, including using a number of smaller cylinders or instead using fewer larger cylinders. An example solution is shown in the figures below for each locomotive type.

Biomethane can be manufactured by anaerobic digestion of organic waste streams e.g. food, farm and sewage waste and there are currently 670 such biomethane production plants in the UK. It is a renewable fuel replacement for natural gas. Biopropane can be manufactured through a number of different routes from biomass or through biological routes and is a renewable fuel replacement for LPG (Liquefied Petroleum Gas).

The diesel component used in dual fuelling could too be replaced in due course by renewable biodiesel. Whilst biodiesel could be used alone in place of fossil fuel diesel fuel this does little to lower tailpipe emissions other than carbon dioxide – biodiesel also being a net zero carbon emission fuel. Dual fuelling lowers particulate emissions as well. If a Diesel Particulate Filter (DPF) is fitted, the engine thus spends less time working against an increased back pressure as the DPF fills, fewer DPF regenerations are then needed thus improving engine efficiency and further lowering fuel consumption.

Route simulations were completed using OTMR provided by operators of these locomotives and in combination with dual fuel engine models based on G-volution’s dual fuel combustion research to date. Results are shown in the table below. Hydrogen results assume green hydrogen is used.

Class 37 – New Dual Fuel Engine Carbon savings (%) Operating Cost Savings (%)
Diesel – Biomethane 67 58
Diesel – Biopropane 64 55
Diesel – Hydrogen 66 44
Class 66 – New Dual Fuel Engine
Diesel – Biomethane 51 29
Diesel – Biopropane 42 21
Diesel – Hydrogen 49 7
Class 66 – EMD Dual Fuel Evolution
Diesel – Biomethane 81 39
Diesel – Biopropane 71 26
Diesel – Hydrogen 79 -28

For the Class 66, the new 4 stroke dual fuel engine offers a 10% improvement in fuel consumption versus the original 2 stroke EMD engine. For the Class 37, the new dual fuel engine offers a 13% improvement in fuel consumption versus the original English Electric 12CSVT. Whilst the dual fuel evolution of the EMD engine offers higher replacement rates of diesel, this 2 stroke engine is less efficient than the new 4 stroke dual fuel engines and also doesn’t meet the latest Stage V emission standards.

On an energy equivalent basis, biomethane is 0.47 times the price of diesel, biopropane is 0.58 times the price of diesel and hydrogen is currently 1.3 times (using natural gas) to 6 times (using electrolysis) the price of diesel. Hence the negative cost savings for the EMD hydrogen dual fuel evolution. The new dual fuel hydrogen engines offer positive cost savings primarily due to these engines’ improved efficiency over the original engine thus overall lowered operating costs. Biomethane and biopropane dual fuel engines offer significant carbon and cost savings versus diesel. Hydrogen also has the potential to do this once produced from renewable sources and once it is much cheaper than it is today.

Please note that this report is based on 2020 fuel prices. Whilst diesel prices are expected to rise in the future, biomethane and biopropane are disconnected from the crude oil price and their prices are expected to fall as production volumes continue to ramp up. Green hydrogen made through electrolysis relies on renewable electricity and requires electricity prices to fall (or diesel prices to rise even further) for it to offer operating costs savings over diesel.


Figure 1 – Class 37 dual fuel concept by G-volution and SBL-Rail

Figure 2 – Class 66 dual fuel concept by G-volution and SBL-Rail