Electrifiction (roads)

[Dennis]

With the launch of the Nissan Leaf, and with other manufacturers soon to follow, electric cars now seem to be entering the mainstream. One thing concerns we - do we have enough generating capacity to run these?

From the sales blurb, it takes ~1kW to cover a mile. Accepted average car mileage per year is 12 000 and there are just over 30 million cars on the road in the UK. So, if everyone was to switch to electric cars, an extra 360 000 gigawatts of electricity are going to be consumed each year (if everyone drives Nissan Leafs!).

Do we have the capacity or is the price of electricity going to rise immensely? Is this going to affect the long term economics of electrification?

 

[TGV]

Interesting line of thought actually. In reality the number of these electric cars is very small in the grand scheme of things, but it's a strong argument that shows how "plug-in" cars are not the way to go. Unless you never go more than a few miles per day and have a convenient way of recharging, I can't see them catching on any more than they already have.

Hydrogen fuel cell is the more promising technology, but it's not ready yet in terms of the supply of fuel.

 

[90019]

One thing concerns we - do we have enough generating capacity to run these?

Depends if any more power stations actually get built.

So, if everyone was to switch to electric cars, an extra 360 000 gigawatts of electricity are going to be consumed each year (if everyone drives Nissan Leafs!).

They won't though.

For a lot of people, an electric car just isn't a viable option.
They're only suitable for those making realtively short journies each day, and even there, I don't think there's that big a market, because if you then have to make a longer journey, you either have to buy a second car or rent one instead, which is probably too costly and/or time consuming for a lot of people.

 

[Dennis]

For a lot of people, an electric car just isn't a viable option.
They're only suitable for those making realtively short journies each day, and even there, I don't think there's that big a market, because if you then have to make a longer journey, you either have to buy a second car or rent one instead, which is probably too costly and/or time consuming for a lot of people.

But most journies are short and with a range of 60+ miles from one charge combined with 80% fast charge in 30 minutes means that the Leaf is reasonably capable (and no doubt battery technology will advance rapidly in the future, improving the range more).

Also, 'fuel' costs compared with petrol or diesel are allegedly about half. To my mind, if the initial purchase price comes down, which it will with mass production, the Leaf would become a viable vehicle for those doing mostly shortish trips.

 

[90019]

What does intrigue me is Renault's system of having service stations with charged batteries, so when you're running low on charge, you can just pull into one and swap batteries.
You also only lease the battery in your car, so you're not losing one you've bought for.

Unfortunately, it's only being rolled out in France atm, so isn't much use here. And I don't really think electric power is the way forward, simply because of the range limitations compared to other fuels, even with a network of charge points or battery change stations.

 

[Nick W]

I suspect there's a big problem with the sales blurb because 1KW is a measure of power (energy per second) not energy per mile.

Considering cars are roughly around 10-40kW, I suspect the worst case is that we simply burn roughly 1/4 - 1/20 of the amount of oil we do now, in a power plant instead of peoples' cars, and therefore not only do we easily have the capacity but oil prices would reduce.

 

[Dennis]

You are quite correct that kilowatt is a measure of power not energy; to simplify the calculations, I had assumed a range of 90 miles with power of 90kW being supplied. This takes out the effect of speed and time but could be an oversimplification.

The actual power pack is rated for 24kWh which gives a quoted range of between 47 and 138 miles depending on conditions. No account is being taken of inefficiencies during charging (presumably not 100% of the energy input is recoverable).

Just trying to get a feel for how the introduction of such vehicles might impact upon electricity supplies; I'm sure there is probably a degree course somewhere studying this!

 

[rail-britain]

Typical journey limit 60 miles
Why not use public transport?
If I was travelling that far regularly I would
However there would be benefits if there was no public transport (such as night work, weekends, etc)

I applied in 2005 for a Honda Hydrogen Cell Fuel car, still waiting
Cost was estimated at £45,000; with a new cell every 10K miles at a cost of about £2,000

 

[imagination]

Considering cars are roughly around 10-40kW, I suspect the worst case is that we simply burn roughly 1/4 - 1/20 of the amount of oil we do now, in a power plant instead of peoples' cars, and therefore not only do we easily have the capacity but oil prices would reduce.

Bear in mind that burning fuel in the car to make it go is a more efficient transfer of energy than burning fuel in a power station to produce electricity to then go onto the national grid where it gets converted twice before being plugged in to a battery which then in turn travels using the power of the battery. You've already lost most of the gains before you even start.

Although to be honest, burning oil is probably just about the most wasteful thing you can do anyway - what with it being arguably the most useful substance in the world for making things with.

 

[starrymarkb]

Why not have something like a Dodgem grid over the road with pole to the car.

OK the road would have to be metal to provide return, and traction might be an issue in damp conditions...

 

[Nick W]

The actual power pack is rated for 24kWh

Ah, so as a guess the actual average usage is probably about 10-15kw, so just over half that of a petrol engine. There are probably very little savings, if any, to be had supplying them with energy from a fossil fuel power plant.

Bear in mind that burning fuel in the car to make it go is a more efficient transfer of energy than burning fuel in a power station to produce electricity to then go onto the national grid where it gets converted twice before being plugged in to a battery which then in turn travels using the power of the battery. You've already lost most of the gains before you even start.

<br />
<br />
Is it really (asking because I don't know)? Based on a simple search of wikipedia, I can't find any evidence of large scale oil power plants and probably for good reason. But if one was to be built, you'd probably have an arrangement similar to a car on a large scale, except that the hot exhaust would be used to boil water and generate even more power than the large engine, as is done with natural gas after it passes through a jet-engine.<br />
<br />

<br />
Although to be honest, burning oil is probably just about the most wasteful thing you can do anyway - what with it being arguably the most useful substance in the world for making things with.

Agreed, but if all automotive use ceases, won't there be an excess of fuel oil? Of course we should probably save this in large reserves for future material use.

 

[yorkie]

Bear in mind that burning fuel in the car to make it go is a more efficient transfer of energy than burning fuel in a power station to produce electricity to then go onto the national grid where it gets converted twice before being plugged in to a battery which then in turn travels using the power of the battery. You've already lost most of the gains before you even start.

I'm not sure. I don't have any figures but you are right that the transfer is less efficient, but a power station is going to be much more efficient than a small engine, isn't it? Also there is the weight saving, by not having an engine (however if using a battery then the weight saving of the lack of engine is offset by the additional weight of the battery)

After all, electric trains are much more efficient than diesel trains, so in theory the same should apply to cars (but less so, due to the battery problem).

Ultimately though the main benefit of electricity (which, to clarify to anyone reading this, isn't a fuel itself) is the ability to use any fuel, without having to convert the end product. We are going to have to generate more electricity using sustainable methods.

Although to be honest, burning oil is probably just about the most wasteful thing you can do anyway - what with it being arguably the most useful substance in the world for making things with.

I totally agree.