Ancillary consumption of railways - heating 2

Diesel fuel and heating oil are chemically identical. »Only« the tax rate the final consumer has to pay is (very much) different. But obviously the difference looks a lot different for railway fuel, i. e. the difference makes no difference there. This smart, modern German railcar of the Baureihe 612 series (google for »BR 612« for photos), which comes as a twin carriage (4 bogies / 8 axles) with 2 diesel engines (of 560 kW each!), has 2 separate tanks for engine fuel and for heating oil. But obviously it doesn’t matter what you fill in where.

If you have had the opportunity to join a locomotive driver on the predecessor, BR 610, then you may have seen that this series still used to have an engine power indicator, which was omitted later in the 611 and 612 series, and that the full power (»only« 2*525 kW on the 610 version and 2*540 kW on the 611 version) is only used for accelerating the weighty vehicle and for travelling uphill. To sustain its constant maximum permissible speed of 160 km/h in the plains an engine power output level of ≈35% is enough. Several kilometres before the next stop the locomotive driver disengages the engines, and the railcar rolls and rolls and rolls, you just don’t realize any drop in speed. Then the brake is operated, the train brakes and brakes and brakes, while the engines keep on running with their (though low – but technically at least during these stages totally avoidable) stand-by loss. But the »waste« heat is needed for the passengers inside – while simultaneously the brake disks need cooling.

What do we conclude from all of this for our areas of interest, electric railway traction and ancillaries? First of all that railway traction requires high peak powers but in total fairly little energy, and that the energy consumption can be substantially reduced by recuperation of braking energy. Unfortunately a diesel engine that can be driven by a decelerating vehicle and converts exhaust fumes into fuel and fresh air has not yet been invented, but fortunately today’s electric drives do allow for something equivalent!

Next, we learn that when the train is constantly running at full speed the diesel engines will produce sufficient heat to heat the interior even with Siberian outdoor temperatures. When running uphill they even produce several times more heat than needed. But when idling in the railway station there is too little heat »loss« available, and a supplementary oil heater has to help out!

So when considering monovalent battery operated electric railcars, although they have existed (see BR 515), heating may become even more a problem than the drive energy! The old BR 515 / 815 series (whereas BR 815 stands for an optional supplementary carriage without a drive but with a driver’s cabinet) already managed 300 km with one battery charge – with commonplace lead accumulators, I suppose, and I even doubt whether that vehicle already had the recuperation feature. This highlights that railway drive by principle uses little energy with respect to the vehicles’ volume and mass but provides more scope for hybrid electric drives (trolley wire plus battery) and for hybrid diesel-electric drives (diesel engine plus generator plus battery or super-capacitors). In the former case one should consider heat pump heating. In the latter case the diesel engine and the generator could be downsized to a fraction, about the size of a car engine, constantly running at full power and optimum speed. The battery could be of limited energy capacity, only the output power rating would need to be high. The overall heat production would then be approximately constant, and the extra oil heater could be omitted.

But oil is still way too cheap. It is just so cheap! When strolling the platforms on a cold winter’s day you may have heard one of our ancient diesel locomotives still standing but with e. g. the 16 cylinder 2000 kW engine of the BR 218 series roaring as if it were hauling a heavy goods train uphill – evidently not idling in neutral. No new models have been released for decades because of a decrease in goods traffic and an increase of electrification of principal lines. On the other hand, all new passenger trains are designed as railcar units. Diesel locos are out. Just fancy, the roots of the 216 / 217 / 218 series date back to 1954, but nowadays the BR 218 has a website of its own: www.br218.de!

Now you may meet a railway employee on the train and ask him about said noise, and he explains to you that, indeed, the engine is running under load because the locomotive is heating the train. You say, ‘It is what?’ Well, there is a generator in the loco generating the power for the electric train heating. Of course, he says, the heating is switched off during the train’s acceleration, for otherwise it would hardly accelerate at all.

On the 219 series, as an alternative, they had installed a separate gas turbine to drive the generator. Incredible: A power plant inside a diesel locomotive only for the electric heating!

And of course this approach is much cheaper than sending out an employee to connect the train to the »ZVH« units described here under railway heating #1 and disconnect it again before departure. And installing electric heating as a replacement of the old steam heating in the passenger carriage was much cheaper than installing a water heating system that could use waste heat from a diesel locomotive – although both the steam and electric systems have existed in parallel in most carriages for decades. Why not replace the steam with a water system?

Because oil is just too cheap.

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