Energy efficient-railway-transportation

1

How energy efficient really is

railway transportation? Stefan Fassbinder

Deutsches Kupferinstitut

Am Bonneshof 5

D-40474 Düsseldorf

Tel.: +49 211 4796-323

Fax: +49 211 4796-310

[email protected]

[email protected]

www.kupferinstitut.de

www.leonardo-energy.org

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Electricity boosts mobility

Electric motors

• have their highest torque at standstill:

No disengaging, no gearchange, no torque converter

required,

• provide a considerable short-term overload capability:

Higher acceleration than the power rating would let you

suppose,

• do not have any no-load consumption during standstill,

rolling or braking,

• offer the opportunity to feed back energy during braking!

Motor = Generator,

• and their primary fuel is totally flexible (fossil, nuclear,

hydro, wind – just mix as you like!).

So it is not a miracle

if railway companies prefer

electric traction!

… since the energy

“consumption” of an electric

locomotive can be negative!

Electricity system of DB AG

Type of power plantInstalled

capacity

Energy

production

Vapour 42.2% 66.0%

Hydro 11.0% 10.0%

Rotating convertor 34.3% 14.6%

Electronic convertor 11.9% 9.4%

Total 3.2GW 11.0TWh/a

Sum of all electric vehicles 22.4GW (700%)

Characteristic data of 16.7 Hz railways

in D-A-CH

DB AG ÖBB SBB

Employees 240242 42893 27822

Passengers 1919Mio. 200Mio. 332Mio.

total 33862km 11000km 3011km

electrified 19300km 8200km 3011km

of lines 57% 75% 100%

of transport

volume

85% 100%Railw

ay g

rid

share

56% of DB lines are

electrified. These 56% carry

85% of all traffic.

However …

3

…what about the other 15%?

e. g. the

612 series?

• Engine power rating: 2*560 kW = 1120 kW

• Smart and convenient:

Tilting technique, air conditioning

• Maximum permissible speed: 160 km/h

• Fuel consumption: 1.7 l/km (for one, not 100 km!)

What about diesel locomotives?

“Ludmilla” “Taiga Drum”

• On a series 232 diesel locomotive (6 axles, 120 t,

2,200 kW, max. 120 km/h) at a constant speed of

120 km/h a consumption of 3 l/km was measured.

• (for good resons railway companies reference the fuel consumptions to

one kilometre, not to 100 kilometres!)

• There are no new diesel locomotives.

• There are old diesel locomotives with new engines.

• The engine efficiency is then >40%.

• But what„s the use of this if the engine is idling over 90% of its operating

time?

• And if a DB technician explains: “Diesel locomotives hamper the traffic

when circulating on an electrified line!” …

• …and if a railway trade journal reports the electrification of a line no

longer than 22 km had already cut the circulation time by 5 minutes? „Elektrischer Betrieb bei der Deutschen Bahn im Jahre 2009“. „eb“ Elektrische Bahnen & Verkehrssysteme 1-2/2010, p.19

4

However, the 101 series electric loco

(4 axles, 84 t, 220 km/h) provides a

motor power rating of 6,600 kW!

Note: It„s electricity that wakes trains up!

of a car of a train factor

(4…5 seats) (450 seats) 100

Mass 1.5 t 450 t 300

Coefficient of static friction ≈55% 28…35% 0.6

Coefficient of rolling friction ≈2% <2‰! 0.1

Resulting: Rolling friction force 0.3 kN 9 kN 30

Power demand resulting from this 15 kW 450 kW 30

as a share of power rating 15% 7% 0.5

Air friction force 1.5 kN 30 kN 20

Power demand resulting from this 85 kW 1550 kW 18

as a share of power rating 85% 23% 0.27

Total power demand 100 kW 2000 kW 20

as a share of power rating 100% 30%! 3.3

Note: Trains are a means of mass transportation!

Note: For some good reasons railway companies give rolling

friction coefficients as per mille figures!

The parameters responsible for

the energy demand are

(at ≈200 km/h):

5

Now what are the other

70% of power good for?

Compared to a car, a train has:

- A very great mass.

- Significantly less static friction

(steel on steel rather than rubber on asphalt).

+ Significantly less rolling friction

(steel on steel rather than rubber on asphalt).

+ Significantly less air friction (since the train

travels in its own windshade!).

Worth noting:

The top speed

of a car is usually

the highest

possible speed,

limited by the

available engine

power.

of a railway vehicle

is usually the

highest

permissible

speed.

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0,0MW

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0kW

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55kW

66kW

0km/h 50km/h 100km/h 150km/h 200km/h

P(I

C t

rain

)

P(c

ar)

v

Power requirement car and IC train

P (car)

P (IC train)

With a great deal of good will

we will now let a car with a

• 66 kW engine and (very tight) space for

• 4 passengers travel at

• 200 km/h,

while a train with a drive power rating of

• 6,600 kW offers plenty of space to

• 400 passengers (including toilets, a

bistro, …). At a travelling speed of

• 200 km/h this requires:

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0km 1km 2km 3km 4km 5km 6km 7km 8km

v/v m

ax

s

Acceleration processcar and train (0 … 200 km/h)

v/vmax Car

v/vmax IC train

But a car accelerates faster?

Well, initially yes, but the

train has a lot of reserves!

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Quiz question 1:

How far will an ICE2 express

train of the 402 series continue to roll

unbraked in a flat area when suddenly

the power fails at a speed of 230 km/h?

Answer 1:

The test was not carried out all through

to the end. After 32 km the train was still

rolling at 120 km/h!

Quiz question 2:

How fast will a railway carriage

become when you let it roll down a

decline of 5‰ (just 0.5%!)?

Answer 2:

According to technical documents by

Deutsche Bahn AG it will (finally) reach

a speed of 44 m/s ≈ 160 km/h (after

1 hour of rolling)! A street car would simply just stall and not roll at all!

Note: For some good reasons railway

companies give inclines and declines as

per mille figures!

8

Quiz question 3:

Why is it that in a train repair

hall which can be opened at both ends

it is not allowed to leave both gates

open at the same time?

Answer 3:

Because the wind might blow the

locomotoves out of the hall!

So let’s just accelerate a

fully occupied street car

to 200 km/h, disengage

and see what will

happen…

Mass: 2000 kg

Rolling friction coefficient: 2%

Front surface area: 2 m²

cx value: 0.37

Engine power: 105 kW

0km/h

50km/h

100km/h

150km/h

200km/h

0km 1km 2km 3km

v

s

Car rolling out

0km/h

50km/h

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0km 1km 2km 3km

v

s

Train rolls

Car rolling out

0km/h

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s

Train rolls

Train brakes

Car rolling out

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0MW

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6MW

0kN

50kN

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Po

we

r

Ha

uli

ng

fo

rce

Speed

IC fast train with DB's 101series locomotive and

9 carriages

Required hauling force

Required power

Hauling force and power

0MW

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9 carriages


Available hauling force

Required power

Hauling force – 80% left?

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0MW

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0kN

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we

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9 carriages



Required power

Available power

Power – 70% left?

Static friction limit

Power limit

0MW

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0kN

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0km/h 100km/h 200km/h 300km/h

P

F

v

ICE3 high speed railcarof DB's 403 series



Required power

Available power

At 300 km/h, however …

… the demand does

increase rapidly

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0,00m/s²

0,15m/s²

0,30m/s²

0,45m/s²

0,60m/s²

0,75m/s²

0km/h

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0km 5km 10km 15km 20km 25km

a

v

s


Speed

Acceleration

The ultimate train concept

16 out of 32 axles driven

by a 500 kW motor each

provide optimal

acceleration and

energy recovery

0,00m/s²

0,15m/s²

0,30m/s²

0,45m/s²

0,60m/s²

0,75m/s²

0km/h

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0s 60s 120s 180s 240s 300s 360s

a

v

t


Speed

Acceleration

The ultimate train concept

16 out of 32 axles driven

by a 500 kW motor each

provide optimal

acceleration and

energy recovery

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Also you have to accelerate the train to

the desired travelling speed of 300 km/h

(83.3 m/s) first in order to run that fast

With a 4% supplement for rotating masses and an efficiency

of 87%, measured at the pantograph, this makes about

520 kWh for one single acceleration from 0 to 300 km/h.

With the DB tariff of 9 c/kWh this costs approximately 47 €!

It would be pretty sad to get nothing of this back at all.

Counted with an efficiency of 87% again, you can retrieve

75% during brakage – if all goes well.

kWhGJNms

mkgv

mWkin 43456.110*56.13.83*

2

000,450²*

2

9

2

Bad outlook for the diesel Electric traction turns out to be far superior:

• Power density and dynamic behaviour are outstanding.

• 8% of all electricity consumed by locomotives in Germany

has been used once before by another locomotive and fed

back again into the supply system.

• Usually this works only with water (or e. g. copper!) but

never ever with coal, gas and oil.

• The share will continue to grow, since by and large more

and more old electric locos without feedback capability are

being replaced with modern power electronic ones.

• But we will still have to wait for a long time to see a diesel

engine coming around that, when braking, sucks up fumes

and converts them back into fresh air and fuel.

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Electric power speeds us up! • For 2009, DB„s department for Energy Cost Management

gives an average circulation of 347,620 km for each of their

145 locomotives of the 101 series.

• The average consumption is ≈17 kWh/km (including

electricity the locomotive has fed into the train for heating

the carriages and for ancillary supplies).

• This yields an electricity cost of half a million Euros per

year.

• The purchase price of the 101 series is around 3 million

Euros.

• So for the power consumption of a locomotive„s 30-year-

long life you could buy in 5 complete locomotives!

• 8% of energy fed back saves 1.2 million Euros per loco

during 30 years!

Or let’s have a look at

suburban transportation

The regional train from Aachen to Dortmund

travels about 160 km far, calling 22 times.

Its top speed is 140 km/h.

If it went all through non-stop, it would consume

only 800 kWh for overcoming the friction.

But accelerating 22 times costs 1600 kWh!

So this is 2/3 of the overall energy consumption!

Hence, in theory about 3/4 out of 2/3, say half of the

energy, could be recovered, but unfortunately …

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Or let’s have a look at

suburban transportation

… according to DB Regio the real rate of recovery

is only 10% in this business unit!

And now what to do? What’s the deficiency?

Hence DB’s plans for the

coming decades are:

• Increase the share of inverter

locos from 47% (2009) to 100%

• Improve control infrastructure –

no more odour of hot brakes

• Replace all Loco-and-carriage

trains with railcars, since:

10% → 20%

20% → 50%

50% → 60%

• Railcars are lighter and hence use less energy

• The dispersed drive expands the opportunities

for energy recuperation

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Now what„s up with

the 44% of lines

without a trolley wire? • There is a diesel railcar standing at the railway station. There are 2

engines mumbling under no-load conditions inside it – and are being

cooled, while an oil heater fuelled with diesel fuel at the price of diesel

fuel is heating the passenger cabin.

• The railcar starts. The engines raise their voices a little bit.

• Only above some 30 km/h … 60 km/h the full power can be transmitted

to the rails: Now the engines hum a bit more vigorously – for about one

minute. Then the top speed has been reached. About 30% of the

engine rating suffice to sustain a constant speed of 160 km/h.

• But very soon we are approaching the next station. The railcar is kept

rolling for several minutes, the engines disengage, mumbling calmly.

• Then the railcar brakes. The engines rev up – just to dissipate the

heat from the hydraulic braking system via the engine radiators!

Is this a concept for the future? – Or rather a makeshift solution?

But wasn‘t there something else?

Oh, right: The 515 series! • Accumulator-operated railcars

have been in use since 1907!

• for 40 years, from 1955 to 1995, well over 220

motor vehicles of the 515 series have been in use:

• Power rating 2*150 kW

• Maximum speed 100 km/h

• 10 t … 16 t of lead accumulators

• Capacity 352 kWh … 602 kWh

• Cruising range 300 km

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Mental experiment:

A modern re-issue

• Today„s Li ion accumulators provide 4 times the

energy density of the old lead acid batteries, so:

• you can double the capacity while halving the

mass.

• Doubling the capacity doubles the cruising range

to about 600 km.

• halving the weight along with the use of modern

inverter technique with generative brakage im-

prove the performance (min. 140 km/h) and the

comfort (e. g. air conditioning).

Comparing a hypothetical electric

battery railcar to a street car Tesla Electric

Roadster railcar

Energy capacity 55 kWh 1100 kWh

Energy demand 200 Wh/km 2000 Wh/km

Energy demand per seat 100 Wh/km 10 Wh/km

cruising range 350 km 600 km

Battery mass 0.45 t 9 t

as share of the vehicle 36% 12%

Battery price 45.000 € 900.000 €

as share of conv. vehicle 50% 25%

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How much really is the

electricity from the battery?

Battery price: 900.000 €

Life time: 3000 cycles

Energy capacity: 1100 kWh

So in effect the power from the battery costs:

Electricity taken from trolley wire 90 €/MWh

Charge cycle / conversion losses +10 €/MWh

Night tariff rebate -10 €/MWh

Wear of the accumulator battery +270 €/MWh

Electricity cost from the battery 360 €/MWh

Comparison to the existing

series 612 diesel railcar

Diesel railcar Batt. railcar

Primary energy demand 20 kWh/km <6 kWh/km

Secondary energy demand 17 kWh/km 2 kWh/km

(1.7 l/km)

Net energy price 1.03 €/l 0.09 €/kWh

Energy price from the battery – – – 0.36 €/kWh

Net energy cost 1.80 €/km 0.18 €/km

Energy cost incl. battery – – – 0.72 €/km

At 250,000 km/a 450,000 €/a 180,000 €/a

During a 30 years„ life 13,500,000 € 5,400,000 €

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Local trains often leave

the city centres on

electrified lines and turn

off onto the seconday

lines only a bit later on.

Here the vehicles could

• be charged up during ride

• in part be driven as conventional electric railcars

with pantograph (»pop-up hybrid«)

• and thus require only a fraction of the (expensive)

battery capacity.

Alternative 1: Accumulator

railcar with pantograph

Alternative 2:

Hybrid diesel railcars Do not confuse with the principle of the diesel-

electric locomotive! Since this is an electric locomotive lugging around

its own power plant

• With the hybrid railcar, however, the diesel engine has only some 10%

of the electric power (e. g. a 66 kW car engine instead of 2*315 kW

railway engines).

• For the diesel engine is always running at the optimal point of operation

(rated speed and power) instead of idling ≈90% of its time.

• Also the generator rating is only 10% that of the electrical traction

power.

• The battery provides 90% or bears 110%, respectively, of the electrical

traction power during acceleration and brakage, respectively.

• Continuous heat generation. Combined heat and power generation

replaces the oil heater.

• Facilitates combination with alternative 1.

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Hybrid diesel railcars – also

for long-distance fast trains?

Just take a trip from Berlin to Copenhagen!

There they are using up the unfortunate series 605 now.

• These railcars are equipped with diesel-electric drives, so

these already avail of electric drive motors and inverters.

• These trains arose on the platform of the 415 series 5-

carriage electric railcar!

• They had been withdrawn from service for several years.

• They were offered for sale, but nobody wanted them.

• One of the reasons given for the latter two points are high

fuel costs.

So why not convert these trains first?

Series 605 – ICE without pantograph Just consider:

• Here the train does not run very fast and rarely stops.

• Still the fuel consumption lies around 3 l/km!

• This costs around 1800 € per single trip

• For this alone 7 full-charge or 45 low-cost ticket passengers

will have to be sitting on the total of 195 seats

• Whereas the major share of the easement is electrified!

• And for one hour the train is not travelling at all but is

standing on a ship.

So why not

• remove 3 of the 4 diesel engines and generators,

• replace them with accumulator batteries,

• possibly add a pantograph and a transformer

• but in any case reduce the fuel consumption by 1 l/km

• and save about 600 € of fuel cost on one trip?

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Summary and conclusions • Electric railway drives clearly outperform diesel

engines.

• At the same time electric railway drives are way more energy efficient

than diesel traction is.

• SBB operate 100% electrically – nothing left to do.

• E. g. DSB are 27% electrified – need for action!

• DB AG operate 85% electrically – this is fine so far.

• For the remaining 15% a re-introduction of battery operated railcars

based on modern lithium ion cells should be considered. 40 years of

good experinece even with lead acid accumulators support this idea.

• The economic viability of electric cars lies about 10 times further

away from reality than that of the battery operated railway vehicle!

The German Department of Technology and the EU Commission

should urgently take this into consideration with their energy efficiency

support programmes.

Energy efficient-railway-transportation

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