Electric company cars

[openspaceman]

10 hours ago, Dan Maynard said:

I think the engine is only 30% efficient at converting energy from fuel to motion whereas the electric motors are more 90-95% at converting electrical energy to motion.

 

The disparity is from the hidden gap when the power station converts fuel to electricity which is only 30-40% efficient. 

It needs to be a bit more refined than that but I hope someone critiques my figures; a petrol engine at maximum torque is more efficient then a naturally aspirated diesel, except most diesels are now boosted by a turbo and the common rail injection means they burn their fuel much higher up the stroke so they become more efficient. Then cars seldom work in their most efficient range (40% with a big old diesel) . Again IC cars don't recoup energy as they slow down (even though this is actually a small amount in normal driving air and rolling resistance use most energy) and tend to use fuel when stationary.

 

For our purposes we only need to consider the energy input verses mileage.

 

My little diesel fiesta when I got it at 4 years old managed 80mpg 17.6 miles per litre on a long run. As each litre of DERV contains about 10kWh of heat energy that means I did 1.76 miles per kWh of heat. An average car is probably worse than twice that.

 

Your lower figure of 30% heat to electrical power to a consumer is about right for a steam turbine power plant but only coal, nuclear and biomass power plants use them now as far as I know. Most of our electricity comes from combined cycle gas turbines which operate at 60+% heat to electricity, a lot comes from renewables which have no heat input.

 

So even at your lowest generation to consumer figure of 30% the EV doing 4 miles per kWh is doing 1.2mile per kWh of heat and if it is charged off peak it will be having input from a combination of wind and nuclear so even less heat energy and of course much lower cost if you can get an off peak tariff.

 

And that's even before we start looking at the comparative pollution levels from centralised generation versus a diesel engined vehicle.

[openspaceman]

11 hours ago, difflock said:

So

 Therefore, a liter of gasoline has 8.76 kW/hr of energy in it, which is a much more manageable number.27 Sept 2021

 

And since we are getting 45mpg for every 40kW/hr(4.54 *8.76kW/hrs) of petrol

=bloody hell= nearer to 1 mile per kW/hr

how can this be correct?

 

Sorry missed this post but see my reply above and as you note petrol has about 90% of the calories of diesel.

[nepia]

12 hours ago, Squaredy said:

Yes.  More in summer less in winter. 

 

We use ours on max regeneration always.  It means you effectively do the majority of the braking by just easing off the accelerator,  You only really use the brake pedal in emergency or if you fail to anticipate conditions ahead,

I'm waiting for someone to pile into the back of the wife's shiny new EV as it rapidly slows with no brake lights showing: KERS is awesome!

[openspaceman]

27 minutes ago, nepia said:

I'm waiting for someone to pile into the back of the wife's shiny new EV as it rapidly slows with no brake lights showing: KERS is awesome!

Now that's wrong, brake lights should come on as soon as regeneration slows it more than traditional overrun would to be fair to other road users.

[nepia]

Ah - that may be the case.  Not my car and no such thing was mentioned to Her Maj by the dealership. I'll have to follow her one day and we'll find out (when I drive into the back of her with an overloaded Navara and 2-ton trailer 😂)

[Squaredy]

1 hour ago, nepia said:

I'm waiting for someone to pile into the back of the wife's shiny new EV as it rapidly slows with no brake lights showing: KERS is awesome!

The brake lights on my Kia are activated by regenerative braking.  I checked as this is something I was concerned about.

[nepia]

It does make perfect sense; I'm sure ours - sorry, Hers - will be the same.

 

Cheers

[Stubby]

5 hours ago, nepia said:

It does make perfect sense; I'm sure ours - sorry, Hers - will be the same.

 

Cheers

Yes but when you do pile into the back of her think of the extra regen she will get from the shove 🙂

[nepia]

😂  I'm sure she'll see it that way.  Really

 

 

 

 

 

🤥

[Squaredy]

Well I have had my EV for over three years now, and my lease expires in just under a year.  So given the long lead times on some EVs I am now hunting for my second electric car.

 

Overall I am very happy with the electric vehicle experience.  Charging away from home can still be a nightmare, but luckily I very rarely need to do this.  But for this reason I won't consider a vehicle with any less than 300 miles estimated range.

 

I have also swapped my little van for a Renault electric van - but this was an outright purchase of a second hand one.  SO far so good.