Electrified freight with Class 99s

As we reported in the last issue, the Innotrans rail trade fair in Berlin offers a great insight into railway operations outside the UK. At this fair, the only diesel-only freight locomotives on display were shunters as almost all freight trains are electrically hauled in Europe where it is recognised that electric freight trains offer many advantages. This includes them being more powerful and offering net-zero carbon traction.

In contrast, in Britain a mere 2.8% of rail freight traction energy consumption is from electricity. ORR figures show that in 2023/24 rail freight’s traction electricity consumption was 46 million kilowatt hours and its diesel consumption was 156 million litres of diesel (energy in a litre of diesel is 10.7 kWh).

Although a large amount of the main rail freight network is electrified, lines to the ports, freight terminals, and other key infill routes are not. For some time, the Rail Freight Group and others have lobbied for the electrification of such lines. In March 2023 the Chartered Institute of Logistics and Transport published a report calling for such infill electrification. Rail Partners has estimated that electrification of the 6km London Gateway has a cost benefit ratio of 4.7:1.

With no sign of such electrification being authorised, the rail freight business took it upon itself to find ways of increasing electrified rail freight by the introduction of bi-mode electric locomotives with diesel engines that can haul freight trains on unelectrified routes, albeit at low speeds.

The first to do so was Direct Rail Services which ordered 10 Class 88 Bo-Bo locomotives from Stadler which were introduced in 2017. Under the wires, these electric locomotives have a 4MW power output, off the wire, their diesel engines have 750kW of power. 

Rail Operations UK then ordered 30 Class 93 tri-mode locomotives from Stadler. As described in issue 185 (July-August 2020), these are based on the Class 88 but have a 900kW engine. When in diesel mode, their power output can be boosted by 400kW for short periods when accelerating by a Lithium Titanate Oxide battery. These locomotives are currently under test in the UK.

Enter the Class 99

One of the highlights of last years’ Innotrans was the unveiling of the next UK electric bi-mode locomotive number 99002. Unlike its predecessors, this Class 99 Co-Co locomotive is a heavy machine that weighs 113 tonnes. This compares with the 86 tonnes for a Class 93. Yet, the Class 99 is not as heavy as the 130-tonne Class 66 diesel locomotive.

During the Class 99’s unveiling speeches, GB Railfreight (GBRF) CEO John Smith said that “the Class 99s are a game-changing moment for the UK rail freight industry. These locomotives offer our customers the chance to run faster, wholly sustainable, heavy-haul services across length and breadth of the country.”

He considered that these locomotives were “the new Class 66” as they are envisioned as the replacement for diesel traction for many freight flows.

Speaking to Rail Engineer at Innotrans, Smith advised that typical freight haul using the West Coast Main Line (WCML) involves around 30 miles of non-electrified routes. As it is not operationally feasible to change locomotives, these freight trains are currently diesel hauled despite almost all their haul being under the wires.

In April 2022 Stadler, leasing company Beacon Rail and GBRF signed an agreement for the supply of 30 Class 99 bi-mode Co-Co locomotives that have a maximum speed of 120km/hr. This order includes spare parts and an option for a further 20 locomotives.

The Class 99 locomotives are being built at Stadler’s Valencia factory in Spain and are essentially a UK loading gauge version of the company’s EURODUAL locomotives, of which about 100 are in service in Europe. 

In January, locomotive number 99001 left Spain for testing at the Velim test centre in the Czech Republic. No 99002 will join it there in February. After extensive testing the first Class 99 locomotives should arrive in the UK later this year and it is hoped they will be in service by the end of the year when, GBRF advises, its diesel engine will be fuelled solely by renewable fuels such as Hydrotreated Vegetable Oil (HVO).

Under the bonnet

Innotrans provided an opportunity to go inside the Class 99 locomotive to see how its engine and other equipment fits inside as shown by the photographs.

Other than the ABB-labelled casing, there was little to see of the electric traction equipment that can deliver up to 6.17MW to provide a continuous tractive effort of 430kN. The traction system has one IGBT inverter per axle.

The diesel engine, its alternator and cooler group, which delivers 1.79 MW, took up much of the locomotive interior. The engine is a Cummins QSK50, 50 litre 16- cylinder 60° Vee engine which is turbocharged and aftercooled. It is EC26/2004 Stage V compliant. The alternator is provided by VEM Sachenwerk GmbH model DREBZ 4516-6. This can deliver up to 2,204kVA, 1,404V at 1,860 rpm.

Also visible inside were the traction motor cooling fans and the brake panel which has two pneumatic distributors which blend with the electrical brake which can either be rheostatic or regenerative.

The driving cab has a central desk with good visibility.

 It has a screen which will provide an ETCS display. The Class 99 also has Stadler’s latest generation of vehicle control system and advanced remote diagnostics. It has front view, pantograph, and shunting cameras.

Outside could be seen the three-axle bogies with primary coil springs and rubber metal secondary suspension that provide high adhesion with low track forces. The underframe equipment includes a 3,000-litre diesel tank.

Electric freight potential

Throughout Europe, rail freight operators benefit from the high-powered electric freight trains. As an example of such benefits, our feature on the Class 93 locomotive in issue 185 (Mar-Apr 2022) showed that the running time of a 1,500-tonne freight train between Felixstowe and Mossend, outside Glasgow, is 11 hours 9 minutes with a Class 66 locomotive and modelling shows that a Class 93 locomotive would reduce this to 8 hours 32 minutes.

A further example is that a Class 93 would enable a train to make two return trips each day between Thames Gateway and Corby. The Class 99 will offer similar benefits, albeit with heavier trains.

As shown below, on the core WCML route to Glasgow, freight trains have twice to climb around 1,000 feet up the steep banks of Shap and Beattock summits. GBRF CEO John Smith advised Rail Engineer that a typical diesel-hauled freight train will climb up to these summits at around 55km/h whereas the Class 99 is expected do this climb at 100km/h.

As these freight trains have to be timetabled around passenger trains that climb these summits at speeds over 160km/h, fully electrified freight services would also increase line capacity and so would also benefit passenger services. 

Despite the benefits of electric traction, it has to be acknowledged that the cost of electricity has doubled in the last 10 years, while fuel duty has been frozen at 58p a litre since 2011, with a further cut to 53p a litre in 2022 which has yet to be lifted. However, GBRF’s substantial investment in its Class 99 fleet indicates it considers that, despite such fuel prices, electric traction still offers significant business benefits as well as a reduction in carbon emissions.

It is to be hoped that the introduction of the Class 99 fleet will significantly increase the percentage of electrically-hauled freight trains. However, if there are to be increasing numbers of electric freight locomotives under the wires, the OLE power supply will need to be able to provide sufficient power for them.

Image credit: Stadler