From: IN%"[email protected]" "Electric Vehicle Discussion List" 15-DEC-1993

12:02:21.65

To: IN%"[email protected]" "Multiple recipients of list EV"

CC:

Subj: ICEV vs. EV efficiency

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Date: Wed, 15 Dec 1993 08:48:20 -0800

From: Robert Weeks <[email protected]>

Subject: ICEV vs. EV efficiency

In-reply-to: <[email protected]>

Sender: Electric Vehicle Discussion List <[email protected]>

To: Multiple recipients of list EV <[email protected]>

Reply-to: Electric Vehicle Discussion List <[email protected]>

Message-id: <[email protected]>

X-To: Electric Vehicle Discussion List

<EV%[email protected]>

X-cc: Multiple recipients of list EV

<EV%[email protected]>

There has been quite a bit of discussion about EVs lately in the

sci.energy USENET newsgroup. For those of you that don't read this

newsgroup, I've forwarded a copy of one of the more informative postings

comparing ICEV and EV efficiencies.

--

Robert W. Weeks

[email protected]

(206) 527-1591

======================================================================

Tuomas Koskinen (of Finland) writes:

This is a real-life comparison of two ICE cars and EV-conversions that have

been converted from them. Part of this is a repost of my original post

"Electric vehicle efficiency" on 11.12.1993. I have received many questions

about this (and asks for a repost) so I decided to make an "upgraded"

version.

Both of the cars are quite small Japanese family cars (Nissan Micra). The other

is year model -83 with 215000km (133600 miles) driven before conversion and

the other -92 with 2000km (1240 miles) driven before conversion. I don`t

know if these cars are familiar in the US, but in Europe they are. Anyway,

I have data from both of them, with the original internal combustion

engine and with the electric drive in similar driving conditions.

I have personally driven both of them, both ICE and EV -versions. I use

the older one every day. This year it will be about 16000km =10000mi (it is

53km =33mi one way from my home to the university).

I have calculated some efficiency figures based on the theoretical

power requirement to drive the car under the given conditions. However, these

are not absolutely right values, because it is quite hard to estimate

losses like rest drag of brakes, bearings drag, oil viscosity friction etc.

Anyway, the relative values between the ICE and electric drive are right.

In ICE-versions Michelin MXT tires were used (rolling drag coefficient

0.011, 2.4bar). In electrics, Michelin MXN tires were used (rolling drag

coefficient 0.008, 3.0bar). This is to compensate the higher weight of

the electric versions. All other conditions were same (summer, dry road,

temperature between 5-20 C (41-68 F), wind compensated by driving the same

road both directions. It is assumed that the ICE runs at 2000rpm (4000rpm when

driving 120km/h) and the electric motor runs at 4000rpm in all of the

conditions below.

Here is the calculation method and assumptions I have used to calculate

the theoretical power demand of the vehicle:

The force needed to move the vehicle is Ftot=Fr+Fa+Fb, where

Fr=my*N is tire rolling drag, my=tire rolling drag coeff., N=m*g, mass*9.81

Fa=.5*ro*v^2*Cd*A is air drag, ro=air thickness (1.293), v=vehicle speed,

Cd=vehicle body air drag coefficient, A=frontal area of the vehicle

Fb=50N is an approximate value of bearings drag and brake rest drag, it has

been obtained empirically by pulling the Nissan -82 with a long rope at

a constant speed

The power needed at wheels at a given speed is Pw=Ftot*v. There is also

an oil friction loss in the gearbox, which depends on the speed the motor

runs. In the older Nissan it is about Po=130W /1000rpm, in the newer it is

about Po=100W /1000rpm. So the theoretical power demand is Pt=Pw+Po.

An example:

The older Nissan, ICE version, driven at 90km/h (56mph) constant speed.

Fr=my*N=0.011*9.81m/s^2*680kg=74N (Michelin MXT -tires)

Fa=.5*ro*v^2*Cd*A=.5*1.293kg/m^3*(25m/s)^2*0.39*1.8m^2=284N

Fb=50N

Ftot=Fr+Fa+Fb=408N

Pw=Ftot*v=408N*25m/s=10.2kW

Po=130W /1000rpm =260W /2000rpm

Pt=Pw+Po=10.2kW+260W=10.5kW, the same number that is in the table below.

Now you say that I`m favoring EV:s because lower rolling drag tires are

used with them. Actually, you can make the rolling drag coefficient better

simply by putting more air pressure in the tires. In an EV, however, the higher

weight compensates the negative effects of higher air pressure. Try 3.0bar

in your car. I`m sure you will get bumpy ride until you put 500kg more weight,

and if you do, your original springs and shock absorbers will probably do

quite bad. In the EV it works well.

Here is a comparison what happens, if you had a car body with Cd=0.19,

tires with ro=0.005 and 150kg lighter body ("simulating" the GM Impact).

I also assume here, that the bearings/brake rest drag is reduced to 30N.

Lets use the ICE / electric drive like in the Nissan -92 (90km/h):

For the ICE-version:

Fr=0.005*9.81*650=32N

Fa=0.5*1.293*25^2*0.19*1.8=138N

Fb=30N

Ftot=200N

Pt=200N*25m/s+260W=5.3kW, so the drag has reduced 47.5%

This is the same than the original power demand at 65km/h. The car used

to have a consumption of 4.5l/100km at that speed. This is 2.9l/h. Now

at 90km/h it takes 1.11 hours to drive 100km, so the consumption with the

new configuration would be 3.3l/100km. So there is 1.6l saving, which is 33%.

For the EV:

Fr=0.005*9.81*1050=52N

Fa=138N

Fb=30N

Ftot=220N

Pt=220N*25m/s+260W=5.7kW, (drag has reduced 45%)

>From the table below it can be seen that the total efficiency of the drive at

an output power like this is about 68%. So the consumption from

mains is 9.3kWh/100km. There is a 17.6-9.3=8.3kWh saving, which is 47%. The

range with the same batteries would be about 300km, which is x2 improvement!

And think: you would have an EV with a range of 300km (186mi) at 90km/h, at

50km/h it would be over 500km (311mi)!

I made this comparison to show, that

a) When the drag of the vehicle is lowered, the efficiency of an ICE gets

also lower, and the fuel economy gets only a little bit better, compare

47.5% reduction of drag leads to only 33% reduction of fuel consumpt.

b) When the drag of an EV is lowered, the efficiency of the electric drive

remains the same (actually it gets a little bit better, because battery

efficiency is better at lower power), compare 45% reduction of drag leads

to 47% reduction of consumption.

c) The range of the EV grows more than the consumption reduces (if lead-acid

batteries are used), because capasity of the battery depends on the

discharge time (capasity gets bigger when the discharge is longer).

d) You still have to have an ICE that has a peak power of about the same,

because the weight reduction is quite small, and you need an acceptable

acceleration

e) Almost everyone seem to only think that EV:s are bad because thay have so

little energy - the real fact is that CARS are bad because they have so

much drag! The EV is here to reduce waste of energy. I find it actually

a good thing that current batteries have low energy - it forces car designers

to lower the drag. The GM Impact is a great piece of work showing that

this can be done. Imagine for example the flywheel battery, it has not yet

safety approval for vehicle use, but in summer 1994 Honeywell will launch

a commercial (limited) flywheel battery that has an energy density of

220Wh/kg (whole system, it has only power inlet/outlet terminals). This is

over five times more than that of the batteries used in the Nissan -92. So

a simple calculation yieds to a range of 1500km (932mi) at 90km/h if the

batteries were replaced (which is techologically VERY easy, excluding

safety, which will be solved some day). At the same time, the efficiency

would get from 68% to 80%. My opinion is that the EV is very promising.

Ok, back to the original comparison.

The electric versions have commercial lead-acid batteries, microprocessor

based controllers and ac-induction motors directly coupled to the original

gearbox. The older one (-83) takes advantage of all gears, the newer (-92)

has an automatic electric sifting and uses only gears 1 and 3. Both of them

have regenerative braking.

NISSAN -83 NISSAN -92

ICE Electric ICE Electric

Weight 680kg 1100kg 800kg 1200kg

Top speed 140km/h (87mph) 125km/h (78mph) 145km/h (90mph) 145km/h

Acc. 0-100km/h 15s 29s 15s 22s

Motor type 1 liter ac, 80kg 1 liter ac, 55kg

Motor max.power 37kW/50hp 26kW/35hp 40kW/55hp 40kW/55hp

50km/h (31mph) constant speed

Theoretical 3.2kW 3.6kW 3.3kW 3.5kW

power demand =0.23MJ/km =0.26MJ/km =0.24MJ/km =0.25MJ/km

Real consumpt. 5.0l/100km 8.2kWh/100km B 4.2l/100km 7.5kWh B

B=from battery =46mpg 11kWh/100km M =55mpg 10kWh M

M=from mains =1.8MJ/km =0.39MJ/km =1.5MJ/km =0.36MJ/km

Efficiency 12.8% 66.7% 16% 69.4%

Range 750km/466mi 135km/84mi 1000km/622mi 300km/186mi

90km/h (56mph) constant speed

Theoretical 10.5kW 11kW 10.1kW 10.4kW

power demand =0.42MJ/km =0.44MJ/km =0.40MJ/km =0.42MJ/km

Real 6.5l/100km 14.4kWh/100km B 4.9l/100km 13.4kWh B

consumption =36mpg 19kWh/100km M =47.5mpg 17.6kWh M

=2.34MJ/km =0.68MJ/km =1.76MJ/km =0.63MJ/km

Efficiency 17.9% 64.7% 22.7% 66.7%

Range 570km/354mi 65km/40mi 850km/528mi 150km/93mi

120km/h (75mph) constant speed

Theoretical 21.2kW 21.9kW 19.9kW 20.3kW

power demand =0.64MJ/km =0.66MJ/km =0.60MJ/km =0.61MJ/km

Real 8.5l/100km 20.5kWh/100km B 6.7l/100km 19.4kWh B

consumption =27mpg 28.4kWh/100km M =35mpg 25.8kWh M

=3.1MJ/km =1.02MJ/km =2.4MJ/km =0.92MJ/km

Efficiency 20.6% 64.7% 25% 66.3%

City driving (avg. speed 38km/h, 24mph)

Theoretical 2.1kW 2.5kW 2.2kW 2.4kW

power demand =0.20MJ/km =0.24MJ/km =0.21MJ/km =0.23MJ/km

Real 7.0l/100km 10.5kWh/100km B 6.6l/100km 9.4kWh B

consumption =33mpg 13.6kWh/100km M =35mpg 12.4kWh M

=2.52MJ/km =0.49MJ/km =2.38MJ/km =0.45MJ/km

Efficiency 7.9% 49% 8.8% 51.1%

With the electric drive, there are two different values for "Real consumption".

The value marked with a `B` means consumption from the batteries of the

vehicle. The `M` -value means total consumption of the vehicle from mains

power (this includes battery and charger losses). A single phase 230V/16A

charger with power factor correction is used.

Now it is easy to see that the total efficiency of an EV is

2.7 - 6 times better than that of an ICE car with the same body. These

EV:s have ordinary commercial lead-acid batteries and ordinary ac-motors

you can find almost everywhere. Also the controller is no more complicated

than your VCR and PC together. There is nothing special.

If you make the electricity from oil (which is the worst case, coal being

about equal), you can have a typical diesel motor (size > 1MW) with an

efficiency of 53%. When you combine this with a synchronous generator

(eff. 96%) you have electricity-from-oil -efficiency of 51%. Now add

distribution (eff. >90%) losses and you have a total efficiency from

oil to electricity in the wall outlet where the EV is charging of 46%. This

is 1/2.2. The electric drive is still 1.2 times more efficient even in

motorway driving (120km/h, 75mph) which is the best case for an ICE car and

the worst case for an EV. In city driving, the electric drive is 2.6-2.8

times more energy efficient, based on oil consumption. The emissions

of a large power plant are much lower than if the same amount of fuel

were burned in car-size motors. Conclusion: An EV causes many times less

pollution than an ICE-car.

OK, but what about the batteries? For example the lead-acid batteries in

the Nissan -83 last about 30000km (18600mi). The efficiency of the batteries

does not get remarkably lower during their life, it lowers a few % to the

end of the lifespan. The capasity remains constant the first 85% of the

lifespan and then reduces to 75%-80% of nominal at the point they have to

be replaced. The batteries used in this particular EV (Nissan -83) are

already recycled. Unfortunately I don`t have exact numbers about how much

energy it consumes to recycle them, but I have heard estimates in the

magnitude of 20-30 times battery energy which in this case means 200-300kWh.

This is about 4-6% of the total used energy during the 30000km.

I don`t have a written document of the recycling energy requirement.

That is because there are none. These numbers are from the local battery

dealer (TUDOR Group) that has supplied batteries for these EV:s. Even

they don`t have exact data, because the energy required depends very much on

how large series are handled. If these batteries were used widely like say

in 50000 vehicles, these numbers should apply.

-- --

Tuomas Koskinen

[email protected]

ICEV vs. EV efficiency RAD

12:02:21.65

To: IN%"[email protected]" "Multiple recipients of list EV"

CC:

Subj: ICEV vs. EV efficiency

Return-path: <[email protected]>

Return-path: EV <@PSUVM.PSU.EDU:[email protected]>

Received: from Jnet-DAEMON by ARCH.PSU.EDU (PMDF #12866) id

<[email protected]>; Wed, 15 Dec 1993 12:02 EDT

Received: From PSUVM(MAILER) by PSUARCH with Jnet id 5262 for [email protected]; Wed,

15 Dec 1993 12:02 EST

Received: from PSUVM.PSU.EDU (NJE origin [email protected]) by PSUVM.PSU.EDU

(LMail V1.1d/1.7f) with BSMTP id 5676; Wed, 15 Dec 1993 12:02:27 -0500

Date: Wed, 15 Dec 1993 08:48:20 -0800

From: Robert Weeks <[email protected]>

Subject: ICEV vs. EV efficiency

In-reply-to: <[email protected]>

Sender: Electric Vehicle Discussion List <[email protected]>

To: Multiple recipients of list EV <[email protected]>

Reply-to: Electric Vehicle Discussion List <[email protected]>

Message-id: <[email protected]>

X-To: Electric Vehicle Discussion List

<EV%[email protected]>

X-cc: Multiple recipients of list EV

<EV%[email protected]>

There has been quite a bit of discussion about EVs lately in the

sci.energy USENET newsgroup. For those of you that don't read this

newsgroup, I've forwarded a copy of one of the more informative postings

comparing ICEV and EV efficiencies.

--

Robert W. Weeks

[email protected]

(206) 527-1591

======================================================================

Tuomas Koskinen (of Finland) writes:

This is a real-life comparison of two ICE cars and EV-conversions that have

been converted from them. Part of this is a repost of my original post

"Electric vehicle efficiency" on 11.12.1993. I have received many questions

about this (and asks for a repost) so I decided to make an "upgraded"

version.

Both of the cars are quite small Japanese family cars (Nissan Micra). The other

is year model -83 with 215000km (133600 miles) driven before conversion and

the other -92 with 2000km (1240 miles) driven before conversion. I don`t

know if these cars are familiar in the US, but in Europe they are. Anyway,

I have data from both of them, with the original internal combustion

engine and with the electric drive in similar driving conditions.

I have personally driven both of them, both ICE and EV -versions. I use

the older one every day. This year it will be about 16000km =10000mi (it is

53km =33mi one way from my home to the university).

I have calculated some efficiency figures based on the theoretical

power requirement to drive the car under the given conditions. However, these

are not absolutely right values, because it is quite hard to estimate

losses like rest drag of brakes, bearings drag, oil viscosity friction etc.

Anyway, the relative values between the ICE and electric drive are right.

In ICE-versions Michelin MXT tires were used (rolling drag coefficient

0.011, 2.4bar). In electrics, Michelin MXN tires were used (rolling drag

coefficient 0.008, 3.0bar). This is to compensate the higher weight of

the electric versions. All other conditions were same (summer, dry road,

temperature between 5-20 C (41-68 F), wind compensated by driving the same

road both directions. It is assumed that the ICE runs at 2000rpm (4000rpm when

driving 120km/h) and the electric motor runs at 4000rpm in all of the

conditions below.

Here is the calculation method and assumptions I have used to calculate

the theoretical power demand of the vehicle:

The force needed to move the vehicle is Ftot=Fr+Fa+Fb, where

Fr=my*N is tire rolling drag, my=tire rolling drag coeff., N=m*g, mass*9.81

Fa=.5*ro*v^2*Cd*A is air drag, ro=air thickness (1.293), v=vehicle speed,

Cd=vehicle body air drag coefficient, A=frontal area of the vehicle

Fb=50N is an approximate value of bearings drag and brake rest drag, it has

been obtained empirically by pulling the Nissan -82 with a long rope at

a constant speed

The power needed at wheels at a given speed is Pw=Ftot*v. There is also

an oil friction loss in the gearbox, which depends on the speed the motor

runs. In the older Nissan it is about Po=130W /1000rpm, in the newer it is

about Po=100W /1000rpm. So the theoretical power demand is Pt=Pw+Po.

An example:

The older Nissan, ICE version, driven at 90km/h (56mph) constant speed.

Fr=my*N=0.011*9.81m/s^2*680kg=74N (Michelin MXT -tires)

Fa=.5*ro*v^2*Cd*A=.5*1.293kg/m^3*(25m/s)^2*0.39*1.8m^2=284N

Fb=50N

Ftot=Fr+Fa+Fb=408N

Pw=Ftot*v=408N*25m/s=10.2kW

Po=130W /1000rpm =260W /2000rpm

Pt=Pw+Po=10.2kW+260W=10.5kW, the same number that is in the table below.

Now you say that I`m favoring EV:s because lower rolling drag tires are

used with them. Actually, you can make the rolling drag coefficient better

simply by putting more air pressure in the tires. In an EV, however, the higher

weight compensates the negative effects of higher air pressure. Try 3.0bar

in your car. I`m sure you will get bumpy ride until you put 500kg more weight,

and if you do, your original springs and shock absorbers will probably do

quite bad. In the EV it works well.

Here is a comparison what happens, if you had a car body with Cd=0.19,

tires with ro=0.005 and 150kg lighter body ("simulating" the GM Impact).

I also assume here, that the bearings/brake rest drag is reduced to 30N.

Lets use the ICE / electric drive like in the Nissan -92 (90km/h):

For the ICE-version:

Fr=0.005*9.81*650=32N

Fa=0.5*1.293*25^2*0.19*1.8=138N

Fb=30N

Ftot=200N

Pt=200N*25m/s+260W=5.3kW, so the drag has reduced 47.5%

This is the same than the original power demand at 65km/h. The car used

to have a consumption of 4.5l/100km at that speed. This is 2.9l/h. Now

at 90km/h it takes 1.11 hours to drive 100km, so the consumption with the

new configuration would be 3.3l/100km. So there is 1.6l saving, which is 33%.

For the EV:

Fr=0.005*9.81*1050=52N

Fa=138N

Fb=30N

Ftot=220N

Pt=220N*25m/s+260W=5.7kW, (drag has reduced 45%)

>From the table below it can be seen that the total efficiency of the drive at

an output power like this is about 68%. So the consumption from

mains is 9.3kWh/100km. There is a 17.6-9.3=8.3kWh saving, which is 47%. The

range with the same batteries would be about 300km, which is x2 improvement!

And think: you would have an EV with a range of 300km (186mi) at 90km/h, at

50km/h it would be over 500km (311mi)!

I made this comparison to show, that

a) When the drag of the vehicle is lowered, the efficiency of an ICE gets

also lower, and the fuel economy gets only a little bit better, compare

47.5% reduction of drag leads to only 33% reduction of fuel consumpt.

b) When the drag of an EV is lowered, the efficiency of the electric drive

remains the same (actually it gets a little bit better, because battery

efficiency is better at lower power), compare 45% reduction of drag leads

to 47% reduction of consumption.

c) The range of the EV grows more than the consumption reduces (if lead-acid

batteries are used), because capasity of the battery depends on the

discharge time (capasity gets bigger when the discharge is longer).

d) You still have to have an ICE that has a peak power of about the same,

because the weight reduction is quite small, and you need an acceptable

acceleration

e) Almost everyone seem to only think that EV:s are bad because thay have so

little energy - the real fact is that CARS are bad because they have so

much drag! The EV is here to reduce waste of energy. I find it actually

a good thing that current batteries have low energy - it forces car designers

to lower the drag. The GM Impact is a great piece of work showing that

this can be done. Imagine for example the flywheel battery, it has not yet

safety approval for vehicle use, but in summer 1994 Honeywell will launch

a commercial (limited) flywheel battery that has an energy density of

220Wh/kg (whole system, it has only power inlet/outlet terminals). This is

over five times more than that of the batteries used in the Nissan -92. So

a simple calculation yieds to a range of 1500km (932mi) at 90km/h if the

batteries were replaced (which is techologically VERY easy, excluding

safety, which will be solved some day). At the same time, the efficiency

would get from 68% to 80%. My opinion is that the EV is very promising.

Ok, back to the original comparison.

The electric versions have commercial lead-acid batteries, microprocessor

based controllers and ac-induction motors directly coupled to the original

gearbox. The older one (-83) takes advantage of all gears, the newer (-92)

has an automatic electric sifting and uses only gears 1 and 3. Both of them

have regenerative braking.

NISSAN -83 NISSAN -92

ICE Electric ICE Electric

Weight 680kg 1100kg 800kg 1200kg

Top speed 140km/h (87mph) 125km/h (78mph) 145km/h (90mph) 145km/h

Acc. 0-100km/h 15s 29s 15s 22s

Motor type 1 liter ac, 80kg 1 liter ac, 55kg

Motor max.power 37kW/50hp 26kW/35hp 40kW/55hp 40kW/55hp

50km/h (31mph) constant speed

Theoretical 3.2kW 3.6kW 3.3kW 3.5kW

power demand =0.23MJ/km =0.26MJ/km =0.24MJ/km =0.25MJ/km

Real consumpt. 5.0l/100km 8.2kWh/100km B 4.2l/100km 7.5kWh B

B=from battery =46mpg 11kWh/100km M =55mpg 10kWh M

M=from mains =1.8MJ/km =0.39MJ/km =1.5MJ/km =0.36MJ/km

Efficiency 12.8% 66.7% 16% 69.4%

Range 750km/466mi 135km/84mi 1000km/622mi 300km/186mi

90km/h (56mph) constant speed

Theoretical 10.5kW 11kW 10.1kW 10.4kW

power demand =0.42MJ/km =0.44MJ/km =0.40MJ/km =0.42MJ/km

Real 6.5l/100km 14.4kWh/100km B 4.9l/100km 13.4kWh B

consumption =36mpg 19kWh/100km M =47.5mpg 17.6kWh M

=2.34MJ/km =0.68MJ/km =1.76MJ/km =0.63MJ/km

Efficiency 17.9% 64.7% 22.7% 66.7%

Range 570km/354mi 65km/40mi 850km/528mi 150km/93mi

120km/h (75mph) constant speed

Theoretical 21.2kW 21.9kW 19.9kW 20.3kW

power demand =0.64MJ/km =0.66MJ/km =0.60MJ/km =0.61MJ/km

Real 8.5l/100km 20.5kWh/100km B 6.7l/100km 19.4kWh B

consumption =27mpg 28.4kWh/100km M =35mpg 25.8kWh M

=3.1MJ/km =1.02MJ/km =2.4MJ/km =0.92MJ/km

Efficiency 20.6% 64.7% 25% 66.3%

City driving (avg. speed 38km/h, 24mph)

Theoretical 2.1kW 2.5kW 2.2kW 2.4kW

power demand =0.20MJ/km =0.24MJ/km =0.21MJ/km =0.23MJ/km

Real 7.0l/100km 10.5kWh/100km B 6.6l/100km 9.4kWh B

consumption =33mpg 13.6kWh/100km M =35mpg 12.4kWh M

=2.52MJ/km =0.49MJ/km =2.38MJ/km =0.45MJ/km

Efficiency 7.9% 49% 8.8% 51.1%

With the electric drive, there are two different values for "Real consumption".

The value marked with a `B` means consumption from the batteries of the

vehicle. The `M` -value means total consumption of the vehicle from mains

power (this includes battery and charger losses). A single phase 230V/16A

charger with power factor correction is used.

Now it is easy to see that the total efficiency of an EV is

2.7 - 6 times better than that of an ICE car with the same body. These

EV:s have ordinary commercial lead-acid batteries and ordinary ac-motors

you can find almost everywhere. Also the controller is no more complicated

than your VCR and PC together. There is nothing special.

If you make the electricity from oil (which is the worst case, coal being

about equal), you can have a typical diesel motor (size > 1MW) with an

efficiency of 53%. When you combine this with a synchronous generator

(eff. 96%) you have electricity-from-oil -efficiency of 51%. Now add

distribution (eff. >90%) losses and you have a total efficiency from

oil to electricity in the wall outlet where the EV is charging of 46%. This

is 1/2.2. The electric drive is still 1.2 times more efficient even in

motorway driving (120km/h, 75mph) which is the best case for an ICE car and

the worst case for an EV. In city driving, the electric drive is 2.6-2.8

times more energy efficient, based on oil consumption. The emissions

of a large power plant are much lower than if the same amount of fuel

were burned in car-size motors. Conclusion: An EV causes many times less

pollution than an ICE-car.

OK, but what about the batteries? For example the lead-acid batteries in

the Nissan -83 last about 30000km (18600mi). The efficiency of the batteries

does not get remarkably lower during their life, it lowers a few % to the

end of the lifespan. The capasity remains constant the first 85% of the

lifespan and then reduces to 75%-80% of nominal at the point they have to

be replaced. The batteries used in this particular EV (Nissan -83) are

already recycled. Unfortunately I don`t have exact numbers about how much

energy it consumes to recycle them, but I have heard estimates in the

magnitude of 20-30 times battery energy which in this case means 200-300kWh.

This is about 4-6% of the total used energy during the 30000km.

I don`t have a written document of the recycling energy requirement.

That is because there are none. These numbers are from the local battery

dealer (TUDOR Group) that has supplied batteries for these EV:s. Even

they don`t have exact data, because the energy required depends very much on

how large series are handled. If these batteries were used widely like say

in 50000 vehicles, these numbers should apply.

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Tuomas Koskinen

[email protected]

ICEV vs. EV efficiency RAD