How energy efficient really is railway transportation?

How energy efficient really is railway transportation?Stefan FassbinderDeutsches KupferinstitutAm Bonneshof 5D-40474 DüsseldorfTel.: +49 211 4796-323Fax: +49 211 [email protected]

[email protected]

www.kupferinstitut.de

www.leonardo-energy.org

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Does electricity boost mobility?Electric cars are• technically not feasible for long distances,• economically not viable for short distances.

To charge up a laptop PC• costs 1 cent for electricity from the socket.• The battery costs 90 € and survives 1000 duty cycles.• This means:

10 times higher energy price while battery powered!With big units for vehicles the factor still is around 3.

The »tank« of an electric car• costs 3000 €/l,• weighs 30 kg/l• and is over and done with after 1000 … 3000 fillings.

} converted to energy equivalent diesel fuel quantity (ηD = 30%, ηE = 90%)

But still the trade presswanted it yet another time:

»Market introduction of electric cars to start in 2011«

Comparison: Citroën C-Zero Citroën C1(electric) (petrol engine)

Length 3480 mm 3430 mmWidth 1475 mm 1630 mmHeight 1792 mm 1470 mmEmpty mass 1195 kg925 kgPayload 255 kg 265 kgLuggage volume 166 l 139 lTurning circle 9.0 m 9.5 mDrive back frontGears (forward) 1 5Power rating 49 kW 50 kWTop speed 130 km/h 157 km/hAcceleration 15.9 s 13.7 sCruising range 150 km 760 kmCO2 emissions 100 g/km 107 g/kmEnergy costs 2.20 €/100 km 6.90 €/100 kmPurchase price 35,165 € 13,120 €

At least one thing is certain:

These vehicles are really comparable.

This is a real electric car in its own right!

Only the payback – even without fuel tax – takes 469,000 km!

This corresponds to3,000 charging cycles – the end of the battery lifetime…

Electricity does boost mobility!If only there is a way to bring the power into the vehicle

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 miracleif railway companies prefer electric traction!

… since the energy “consumption” of an electric locomotive can be negative!

Electricity system of DB AGCharacteristic data of 16.7 Hz railways

in D-A-CH

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 railwaysin 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%Rai

lway

grid

shar

e56% of DB lines are

electrified. These 56% carry 85% of all traffic.

However …

…what about the other 15%?

e. g. the612 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?

BR 232 “Ludmila” BR 220 “Taiga Drum”

• On a series 232 diesel locomotive (6 axles, 120 t,2,200 kW, max. 120 km/h) at a constant speed of120 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 have not been any new diesel locomotives for decades.

• 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 for >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

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!

This explains it:

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of a car of a train factor(4…5 seats) (450 seats) 100

Mass 1.5 t 450 t 300Coefficient of static friction ≈1 0.28…0.35 0.3Coefficient of rolling friction≈2% <2‰! 0.1Resulting: Rolling friction force 0.3 kN9 kN 30Power demand resulting from this15 kW 450 kW 30as a share of power rating 15% 7% 0.5Air friction force 1.5 kN30 kN 20Power demand resulting from this 85 kW 1550 kW18as a share of power rating 85% 23% 0.27Total power demand 100 kW 2000 kW 20as 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 forthe energy demand are(at ≈200 km/h):

Now what are the other70% 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”, so to say).

On rails even a »Unimog« universal miniature lorry can haul 1000 t!

Though not at a particularly high speed

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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With a great deal of good willwe 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:

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But a car accelerates faster?

Well, initially yes, but the train has a lot of reserves!

Quiz question 1:

How far will an ICE2 expresstrain 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 carriagebecome 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 (after1 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!

Quiz question 3:

Why is it that in a train repairhall 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 kgRolling friction coefficient: 2%Front surface area: 2 m²cx value: 0.37

Engine power: 105 kW

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Rolling and braking:Express train (10 carriages)

versus car


Adapting the scale to the train:

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Rolling and braking:Express train (10 carriages)

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Adapting the scale to the train:

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IC fast train with DB's 101series locomotive and

9 carriages

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Power – 70% left?

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Power limit

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IC fast train with DB's 101series locomotive and 9

carriages running upan 18.5‰ incline


Not while running uphill!

When it becomes steeper than that the top speed

cannot be held any more

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ICE3 high speed railcarof DB's 403 series


At 300 km/h, however …

… the demand does increase rapidly

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The ultimate train concept

16 out of 32 axles drivenby a 500 kW motor each

provide optimal acceleration andenergy recovery

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The ultimate train concept

16 out of 32 axles drivenby a 500 kW motor each

provide optimal acceleration andenergy recovery

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 about520 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*

29

2

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

• Power density and dynamic behaviour are outstanding.

• 9% 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.

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!

• 9% of energy fed back saves 1.2 million Euros per loco during 30 years!

Or let’s have a look at suburban transportationThe 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 …

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:

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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Stock of drive vehicles with DB AG

Drive vehicles with feedback capability

Tap changer regulated drive vehicles

Not fragile …

Tap changer operated vehicles have no longer been commissioned

already since 1985, but still…

If you see a tap-changer controlled locomotive today

then it is most likely to be 36 years old.

In case of the 110 series, for instance, this vehicle must be between 42 and 54 years old!

And it still keeps on running …

Stock BR supplied 2007 2009 2010 2011 Age

103 1972 to 1974 3 3 3 37a to 39a

113 1962 to 1963 2 3 3 48a to 49a

115 1962 to 1964 28 19 17 47a to 49a

110 1957 to 1969 109 88 64 42a to 54a

111 1975 to 1984 225 225 224 27a to 36a

112 1992 to 1993 89 89 89 18a to 19a

114 1990 to 1992 40 39 38 19a to 21a

143 1984 to 1990 556 520 487 21a to 27a

420 1969 to 1994 189 167 163 17a to 42a

450 4 4 4

140 1957 to 1973 172 74 81 38a to 54a

151 1973 to 1975 163 140 133 36a to 38a

155 1974 to 1984 219 195 185 27a to 37a

Locomotives 1877 1606 1395 1324 33a 36a 40a

Railcars / integr. trains 205 193 171 167 17a 30a 42a

Total 2082 1799 1566 1491 25a 33a 41a

LocomotivesDB Regio

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RailcarsDB Regio

Sumsresp.

mean values

115

1115

205

LocomotivesDB Schenker Rail (freight)

648

Stock BR supplied 2007 2009 2010 2011 Age

103 1972 to 1974 3 3 3 37a to 39a

113 1962 to 1963 2 3 3 48a to 49a

115 1962 to 1964 28 19 17 47a to 49a

110 1957 to 1969 109 88 64 42a to 54a

111 1975 to 1984 225 225 224 27a to 36a

112 1992 to 1993 89 89 89 18a to 19a

114 1990 to 1992 40 39 38 19a to 21a

143 1984 to 1990 556 520 487 21a to 27a

420 1969 to 1994 189 167 163 17a to 42a

450 4 4 4

140 1957 to 1973 172 74 81 38a to 54a

151 1973 to 1975 163 140 133 36a to 38a

155 1974 to 1984 219 195 185 27a to 37a

Locomotives 1877 1606 1395 1324 33a 36a 40a

Railcars / integr. trains 205 193 171 167 17a 30a 42a

Total 2082 1799 1566 1491 25a 33a 41a

LocomotivesDB Regio

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ha

ng

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ted

dri

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LocomotivesDB Long Distance

RailcarsDB Regio

Sumsresp.

mean values

115

1115

205

LocomotivesDB Schenker Rail (freight)

648

Old tap-changer vehicles still on duty with DB AG

Legacy from the GDR railways

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

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

TeslaElectricRoadster railcar

Energy capacity 55 kWh 1100 kWh

Energy demand 200 Wh/km2000 Wh/km

Energy demand per seat 100 Wh/km10 Wh/km

cruising range 350 km 600 km

Battery mass 0.45 t9 t

as share of the vehicle 36% 12%

Battery price 45.000 € 900.000 €

as share of conv. vehicle 50% 25%

How much really is theelectricity 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 €/kWhEnergy price from the battery – – – 0.36 €/kWh

Net energy cost 1.80 €/km 0.18 €/kmEnergy cost incl. battery – – – 0.72 €/km

At 250,000 km/a 450,000 €/a 180,000 €/aDuring a 30 years‘ life 13,500,000 € 5,400,000 €

Comparison to the existing series 612 diesel railcar

The comparison is biased?It is, but towards which side?Note:• The battery railcar will need at least 2 new

batteries during its 30-year service lifeBut:• Diesel driven trains require 3 times as much

maintenance costs as electric trains doSo there is scope enough for 2 new batteries!

Local trains often leavethe city centres onelectrified lines and turnoff onto the secondaylines 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 railcarsDo 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.

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 abroad 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 pantographJust 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?

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.

How energy efficient really is railway transportation?

Technology

Transcript of How energy efficient really is railway transportation?