July/August 2020

A German rail operator has recently placed an order for 20 battery- powered regional trains that are due to be delivered by the end of 2023. The two-car electric trains with 120 seats will be able to operate on routes with or without overhead power lines, thanks to their battery hybrid drives, and will have a range of around 80km in battery-only operation. They are expected to cover around two million train- kilometres in the Baden-Württemburg region every year. The lithium-ion batteries can be charged either via an overhead line while operating on electrified sections on a route, or by recovering energy during braking. A big attraction of this concept is that it can be used on sections of track that have neither overhead power lines, nor electrified conductor rails. Previously, diesel propulsion would usually have been needed for such sections. Only around half of Germany’s rail routes are electrified, and electrification is not viable on many routes. To allow rail operators to decarbonise operations on these routes, Siemens has therefore developed a new generation of trains for regional and local operations that can be powered either from batteries or from fuel cells. The starting point for designing the Mireo Plus trains was to develop a scalable, modular traction system that accommodates both batteries and fuel cells. By combining a lightweight construction, high-efficiency components and intelligent energy management, the trains consume up to 25% less energy than conventional equivalents. For routes that are partially electrified, the battery-electric versions will be ideal, while for longer unelectrified routes, the hydrogen- powered versions would be more suitable. The technologies can be combined. To achieve completely emission-free transport, the trains will need supplies of electricity or hydrogen from renewable energy sources. In their battery-electric form, the trains use underfloor or roof-mounted batteries to create hybrid vehicles (called Mireo Plus B) that draw power from overhead cables when available, and from the batteries when not. A two-car train will have a range of up to 80km, while a three-car version could travel 120km – in many cases, this will be enough to bridge the gaps between electrified sections. Silicon carbide The high-performance battery system, including auxiliary systems such as battery cooling and silicon carbide converters, has been tested on a route in Austria. For routes needing longer-distance autonomous propulsion, the Mireo Plus H hydrogen trains incorporate a fuel cell system as well as batteries. In this case, the batteries act as“power banks”to compensate for high dynamic loads such as accelerating from a standstill, and to recuperate braking energy. A two-coach train of this type will have a range of up to 800km, and a three-coach train up to 1,000km – enough to cover the longest regional routes in Europe. The drive system uses two low-temperature fuel cells, created in partnership with the Canadian firm, Ballard Power Systems. They have been developed specifically for rail applications and offer twice the power density and up to four times the service lives of fuel cell systems designed for automotive applications. Because hydrogen has a lower power density than diesel, Siemens has had to develop special pressure vessels made of carbon fibre with non-metallic liners. These offer high stiffness and low dead weights, and will allow higher operating pressures than comparable steel containers. Fast refuelling will be possible, with the tanks taking about the same time to fill as it takes to refuel a diesel vehicle with a similar range. During refuelling, parameters such as temperature and pressure will be monitored continuously and communicated to the filling station to determine the amount of hydrogen required. For the past two decades, train operators (including some in the UK), have been using driver advisory systems to optimise energy consumption. The Mireo Plus trains take this a step further. By recognising their location, predictive driving is possible, with the trains able to determine performance criteria such as acceleration, as well as the likely energy returns during braking. There are also auxiliary systems, such as climate control44, to reduce energy consumption. The next-generation advisory systems will offer the driver recommendations based on algorithms of optimal and predictive control, thus helping to maximise the trains’energy efficiency. As well as the novel technologies used in the battery trains, the way that they will be financed is also unusual. Siemens is responsible for the energy consumption and energy costs over the entire contract period of 29.5 years. As well as producing and delivering the trains, Siemens will also have to ensure that they are permanently available for service. n 32 n TRANSPORTATION July/August 2020 www.drivesncontrols.com Battery and fuel-cell-powered trains charge ahead A new generation of regional trains that can be powered either by batteries or fuel cells will allow emission-free transport even on non-electrified rail routes. The developer Siemens believes that this is one of the most important achievements in more than two centuries of railway innovation. Siemens’emission-free trains use fuel cells and high-performance batteries to reduce energy consumption, and can be used on non-electrified sections of track