posted on 12th Jan 2018 14:04
This paved the way for exhaustive testing, both within Germany and at the VUZ Velim test centre over the coming months. At Velim Alstom made a reservation for the Coradia iLint’s testing to take place between 3 April and 19 May 2017. During these tests the train is being worked up to reach its top service speed of 140 km/h. Afterwards, in early 2018, it will be put into test commercial service with Eisenbahnen und Verkehrsbetriebe Elbe-Weser (EVB) on the latter’s Buxtehude - Bremerhaven - Cuxhaven route.
During the earlier static testing phase at Salzgitter all electrical and pneumatic functions of the train were tested and verified, while TÜV Süd certified the safety of the lithium-ion battery, the pressure tank system and the fuel cells for the forthcoming test phases. The Salzgitter dynamic tests, lasting four weeks, were used to confirm the stability of the energy supply system, and to ensure that there was a coordinated interaction between the driveline, fuel cells and battery. Braking force was also tested, to evaluate the interface between the pneumatic and the electric brake systems.
Both Coradia iLints will remain Alstom’s property, and will be used for testing purposes. To supply the train’s pressurised tanks with hydrogen gas during the tests a mobile fuelling point was installed within the Alstom works complex. This hydrogen is an industrial by-product, suitable for re-use. However in the longer term future Alstom plans to use hydrogen produced by wind power.
For the Coradia iLint project (see R 5/16, p. 52) Alstom is receiving a grant from the Bundesministerium für Verkehr und digitale Infrastruktur (BMVI - Federal Ministry of Transport and Digital Infrastructure). Considerable interest is being shown in the project, with Niedersachsen, Nordrhein-Westfalen and Baden-Württemberg Länder, together with the Rhein-Main-Verkehrsverbund, having signed Letters of Intent indicating their interest in buying 60 Coradia iLints.
The Coradia iLint prototype is fitted with two roof-mounted hydrogen tanks, one on each car, each with a maximum capacity of 94 kg. The hydrogen is contained in 24 pressurised canisters in each tank. There is one fuel cell mounted on the roof of each car. Both provide electricity for the two main traction motors, each rated at 314 kW.
Since the combustion heat of hydrogen is 33.2 kWh/kg, this means that 188 kg of hydrogen contains 6,242 kWh of thermal energy, which is equivalent to about 624 litres of diesel fuel. The fuel cell has an efficiency of around 60 %, while the compensatory Lithium battery has an efficiency of around 90 %, and the battery charger converter an efficiency of about 96 %. This means that around 3,200 kWh can be supplied to the traction circuit, the pertinent equation being:
E = m × H × ηf × ƞb × ƞc = 188 × 33.2 × 0.60 × 0.90 × 0.96 = 3,236 kWh, where:
E ... usable electrical energy,
m ... weight of hydrogen stored in the iLint,
H ... the combustion heat of hydrogen,
ηf ... the fuel cell efficiency,
ηb ... the battery efficiency,
ηc ... the converter efficiency.
In the fuel cells the hydrogen is transformed by oxidation into water. This process releases electrical energy, a harmless by-product being water vapour. However it is difficult to control the amount of energy generated by this process because the fuel cells have to operate at a continuous performance level, which is not very high. Within the traction circuit there has to be an energy storage device for surplus energy, hence the compensatory Lithium battery. This is also recharged during regenerative electrodynamic braking.
Fuel cells, unlike electro-chemical batteries, are not able to receive and store electrical energy. Thus, on services which involve repeated accelerations and decelerations, the compensatory battery will have to endure a considerably load as a result of the amount of use and charging involved. Regarding this, Alstom states that it has developed an intelligent energy management system to optimise the efficiency of the complete system and to increase the battery’s lifespan.
To ensure that a hydrogen train has a comparable performance level to a conventional DMU, the compensatory batteries must be suitably durable, and must have a relatively high nominal power. A suitable battery would weigh around 5 t to meet such requirements.
Also having to endure a considerable load during acceleration and electrodynamic braking of the iLint will be the two traction motors, which have a combined rating of 628 kW. To achieve
a comparable performance to that of a Lint 54 DMU, which has a specific output of 8 kW/t, they would each have to be rated at 480 kW, giving a combined rating of 960 kW. Nevertheless Alstom states that the Coradia iLint has an acceleration and braking performance similar to that of a conventional Coradia Lint 54, which is usually powered by three 390 kW diesel engines.
With full tanks the Coradia iLint has a range of between 600 and 800 km, depending on passenger loading, the number of stops, gradient and other route characteristics which govern fuel consumption. Alstom reckons that its operating costs will be similar to those of a Lint 54 DMU. But Alstom is talking only about operating costs, and not purchase costs. So far the market price tag of the train has not been revealed. It is bound to be higher than that of a Lint 54 DMU, and other factors, such as operational safety and the need to build a network of hydrogen fuelling points, are bound to add to the overall final cost.
The Coradia iLint offers certain advantages over a standard DMU design. It is quieter, and the only exhaust emissions are steam and condensed water. The big questionable aspects are the environmental footprint of hydrogen production and its distribution to fuelling locations. At present in Germany hydrogen is produced either using electrolysis or as a chemical industry by-product. However, the size of the environmental footprint depends not only on the mix of types of electricity production used for the creation of hydrogen, but also on the source of hydrogen. By 2020 it is expected that the means of production of hydrogen will have changed, and become more environmentally-friendly
That will not alter the fact that hydrogen is not a sustainable replacement for hydrocarbon-based fossil sources of energy. It is not a naturally occurring fuel, and has to be produced either from fossil fuels (coal, oil or natural gas), or from electricity. As far as the use of fossil fuels for hydrogen production is concerned, it is not possible to develop a project for the future of a large fleet of hydrogen trains, quite simply because the whole objective behind looking for alternative sources of energy for trains used on non-electrified lines is to liberate them from their dependency on fossil fuels.
Hydrogen can also be produced using electricity. This might look more positive, since the global tendency is to produce electricity using emission-free means. Using electrolysis to produce hydrogen is around 65 % efficient, while fuel cells themselves have an efficiency level of about 60 %. The resulting efficiency level of energy storage thus is barely 40 %, which is less than half the efficiency of a straightforward Lithium battery (around 90 %). The pertinent equation is:
Ee = Ef/(ηe × ƞf) = Ef/ηef = Ef/(0.65 × 0,60) = Ef/0.39 = 2.56 x Ef, where:
Ee ... electrical power consumed by electrolysis,
Ef ... electrical energy supplied by the fuel cell,
ηe ... the efficiency of electrolysis,
ηf ... fuel cell efficiency,
ηef ... the efficiency of the electrolysis - fuel cell chain.
It is thus evident that compared with a Lithium battery-powered train, a hydrogen fuel cell train has more than double the amount of electricity consumption. Moreover, the latter type of train has to be fitted with heavy compensatory batteries in the same manner as a battery-powered train, and it is not possible to avoid the extra weight, size, and cost of these.
EU energy strategies are designed not only to reduce fossil fuel dependency, but also to increase energy usage efficiency. On both these counts hydrogen trains would appear to be deficient. Regarding this issue Alstom states: „A full battery-powered train needs a much heavier set of batteries than does the Coradia iLint. Given the weight of this energy storage element a train powered entirely by batteries consumes much more electric energy than does the Coradia iLint. Moreover it is difficult to integrate such large batteries into a low floor regional train. The Coradia iLint was designed with a view to use on lines which will in the future in any case remain non-electrified. It is necessary to compare the Coradia iLint with trains equipped with combustion engines, instead of with an EMU used on electrified lines.“
We consider the above observations to be a misunderstanding of the facts which we are considering here, these being that:
Therefore, at the present level of technological development it is not possible for hydrogen to be considered as a substitute for existing energy sources. Instead, it is a product of the latter. For details see our analysis in R 5/16, pp. 76 - 78. Therefore, basically, in terms of environment and efficiency hydrogen fuel cell trains can hardly be perceived as a sustainable replacement for DMUs, as we explain below.
In contrast to road infrastructure (with the exception of trolleybus networks), the network electrification of railways has now been possible for well over a century, and in many countries, such as Germany, Austria and Norway, has reached an advanced stage. In all three of the latter countries, much of this electricity is derived from emission-free sources. Indeed, in Norway only 2 % of all electricity generated comes from fossil fuels. The railway electrification strategy thus needs to be pursued further.
Instead of trying to develop trains which, superficially, appear environmentally friendly and are capable of operating autonomously without direct reliance on fossil fuels, it makes more sense
to pursue intensive electrification strategies covering all lines with heavy passenger and freight traffic. The energy supply from the catenary can then be used to charge the batteries of trains designed for short stretches of operation on non-electrified lines.
Such a strategy would mean that for rail purposes it would not be necessary to develop a range of autonomously-powered trains for long journeys with a working radius of several hundred kilometres. An operating range of around 100 km would be the most suitable for an EMU fitted with batteries of size and weight comparable to the compensatory batteries requiered for a fuel cell-powered train. Alstom comments as follows on this observation: „It all depends on the structure and the length of the remaining non-electrified lines and networks. Battery-powered trains with a range of 100 km are not efficient for a lot of operations on non-electrified lines and will remain a niche product.“
Again, this is a debatable argument. For example, the Coradia iLint is considered for the non-electrified Hermann-Hesse-Bahn (HHB) between Calw and Weil der Stadt, which has a length of only 23 km (see R 2/15, p. 16). The reopening campaign for this stretch of line was encouraged by the fact that the 5 km between Weil der Stadt and Renningen became part of the S-Bahn Stuttgart network in late 1970s and were electrified at 15 kV AC. Therefore the HHB would be quite suitable for operation using battery-powered trains.
Moreover, in general it must be borne in mind that in most countries railway electrification programmes are still on-going. As a result the length of the stretches of non-electrified lines is shrinking year by year, while the length of overhead wire, which can be used for vehicle battery charging (either while the trains are in motion, or at a standstill), is steadily increasing. This reduces the requirements for the operational range of vehicles equipped with energy storage facilities. Therefore, logically, are required vehicles with an autonomous range considerably lower than the 600 to 800 km proposed for hydrogen fuel cell trains.
This same development has taken place in the market for urban buses. It was not long ago that e-buses were being built for full day operation, with a range of around 300 km, with battery recharging taking place overnight. Nowadays it is quite possible to realise a full day of operation using an e-bus, but with battery recharging taking place at intervals throughout the day, while the speed of battery charging has increased substantially over recent years. Similarly, trolleybus networks are being extended without the need for overhead wires, with trolleybuses being fitted with batteries, which are then recharged via the overhead wire.
This issue is even more pertinent to rail-based transport. Here vehicles are designed for service lives of 30 years or more. Over the coming years it can be expected that the length of electrified networks will increase to the extent that it will be possible to operate the remaining short stretches of non-electrified line using conventional electric vehicles fitted with lithium batteries. From the point of view of investment and operation such trains are cheaper and more energy-efficient to use than vehicles powered using with fuel cells.
Let us return to examine an earlier quote from Alstom: „It is necessary to compare the Coradia iLint with trains equipped with combustion engines, instead of with an EMU used on electrified lines.“ However, it is illogical to compare a hydrogen-fuelled rail vehicle with one powered by an internal combustion engine (which in the long term does not have any perspective) or with a conventional EMU powered using electricity (which can not run on non-electrified lines). The real equivalent to a hydrogen-fuelled vehicle is a vehicle equipped with batteries.
Given the fact that most main lines in Europe are now electrified, it is no longer necessary to design battery-powered rail vehicles for autonomous operation with once-daily recharging, because they can be recharged several times a day, either at rest between services, or even while in motion. The required battery size can be calculated from the energy balance. The pertinent equation for energy consumption of such a train is:
E = w x m x L, where:
E ... the energy required for the run,
w ... the specific energy consumption,
m ... the vehicle weight,
L ... the distance travelled.
The energy delivered by the accumulator is:
Ea = k x ma, where
Ea ... the energy of the battery,
k ... the specific energy of the battery,
ma ... the battery weight.
From the equality of the two types of energy required (E = Ea) a relationship can be derived to determine the weight ratio of the battery (this is a Kummler relationship), found by:
ma / m = L x w / k
For the typical values (the specific energy consumption of a regional stopping passenger train w = 0.040 kWh/ tkm, and the usable energy density of a Lithium battery with a nominal specific energy of 100 kWh/t with a 30 % reserve k = 70 kWh/t or 0.070 kWh/kg) the following applies:
ma / m = L x W / k = L x 0.040 / 0.070 = L x 0.57 (kg/tkm)
For a journey of 1 km a battery weight of 0.57 kg per 1 t of the vehicle weight is required. For a vehicle weighing 120 t a battery weighing 120 x 0.57 = 69 kg is required for this 1 km journey. Therefore, for a 100 km journey with a vehicle weighing 120 t a battery weighing 100 x 0.69 = 6,900 kg is required. Analogously, for a 50 km journey, it is enough to have a battery weighing only 3,450 kg. The foregoing demonstrates that the weight of batteries in a purely battery-operated vehicle is acceptable.
To date Alstom has not released data showing how heavy the iLint is, or how much its batteries weigh. Moreover, Alstom’s argument that it is difficult to install batteries in low floor regional trains is not wholly valid. There are numerous rail networks where low platforms do not exist, and variations exist within countries - for example Russia, Britain, Spain and the USA.
As stated earlier, hydrogen-fuelled vehicles must be equipped with batteries to ensure that the fuel cells and traction drive have a correct power balance. Essentially, a fuel cell system is a hybrid system, the concept being that of a battery-powered vehicle equipped with a hydrogen fuel source, to extend operating autonomy range.
Given the drawbacks of the hydrogen cycle (increasing power consumption to 225 % compared with that of
a battery-powered vehicle, not available hydrogen infrastructure at present), and simultaneously taking in mind that most of electrified rail networks are being expanded (the length of operating autonomy range of battery-equipped EMUs is decreasing), it is questionable whether hydrogen should be introduced as yet another fuel type for rail vehicles. Even Alstom’s argument stating that the disadvantages of applying hydrogen as a fuel for trains are reduced if wind turbines are used for electricity generation for the electrolysis necessary to produce the fuel does not carry substantial weight.
At present worldwide research is being conducted into the development of lithium batteries. This research is mainly being directed at the need to find lightweight batteries for road vehicles. For example, in case of a successful development of lithium-sulfur batteries with a specific energy of between 200 and 300 kWh/t, the end result is that the weight of a battery will be reduced by around half, or possibly to one third, compared with present-day ones, offering the same amount of specific energy. The successful development of such batteries will again reduce the need for projects to create vehicles with a hydrogen fuel source to extend their operating autonomy range.
Sadly, the exhibition of a train making use of hydrogen as a fuel, rather than the exhibition of a standard EMU fitted with a conventional pantograph, has an amazingly dynamic effect on trade fair visitors as well as on those politicians and civil servants who are the decision-makers when it comes to allocating the (often generous) subsidisation made available for railways.
In spite of this „blindness“ shown by the latter, who dictate the future strategies for railways, it is encouraging to note that at InnoTrans 2016 there were fewer exhibits powered using fossil fuels than in previous years and more exhibits demonstrating ways of replacing internal combustion prime movers with emission-free drivelines. But as with all human activities, it will probably be necessary for many cul-de-sacs to be explored, fruitlessly, before a rational and sustainable strategy is adopted.