Friday, 14 February 2020

Fun with numbers - what if we all had electric cars

Qs - would we have enough electricity generating capacity if each household in the UK had one electric car? And would we have to reduce the number of miles we drive every year?

A - I don't know, but here's how I would guesstimate it.

(Feel free to pile in if you have better info, or just skip to the conclusion in my later post.)
Typical daily electricity usage per household - 9.25 kWh (from here).

Check: Total electricity generated/used in the UK per annum 335 TWh (from here), 30% of which is domestic (from here) = 100 TWh. 28 million households x 9.25 kWh x 365 days = 94 TWh.

That's (say) 16 hours a day, grid running at near full capacity.

That leaves (say) 8 hours where not much electricity is being used, in which time power stations, if they continued running at near full capacity, could generate (say) another 40% x 335 TWh = 134 TWh, = about 13 kWh per household/car per day.

A typical electric car, like a Nissan Leaf has a 40kWh battery and a 100 mile range* (from here). 40 kWh divided by 13 'spare' kWh per household per day = people can recharge their cars every three days. It would have to be staggered; if everybody plugged them in Sunday at midnight, there wouldn't be enough electricity to go round. So instead of Economy 7 electricity, which is cheaper in the night time, there would have to be a massive premium on electricity in the night from Sunday to Monday, or something.

* Check: Electric cars can do 2.9 miles/kWh (from here).

About half of all car miles are commuting, and the average journey (one way) is less than 10 miles, so most of us would be OK for commuting and a weekly shopping trip, with just one overnight charge per week (in a normal week).

Check: Total miles driven in the UK per year (car, van, taxi) = 658 billion km = 409 billion miles.(from here). 100 miles every three days (max capacity, from above) x 28 million households/cars = 340 billion miles/year, so miles driven would have to come down by about a fifth.

So ball park, yes, if we ran power stations 24 hours a day, and reduced overall miles driven (more public transport, more car sharing, work nearer home or from home, don't go on holiday by car, no driving round just for the joy of it* - a problem which solves itself), we could just about manage.

It's still a ridiculous idea, for many other reasons**, but on this narrow point***, I think the idea just about passes the feasibility test.
* Most of the miles I drive, to be honest.

** Negative impact of CO2 on climate has been exaggerated ten- or a hundred-fold; it will he hugely expensive to upgrade all the transformers and sub-stations in residential areas; there isn't enough copper for the cables or rare metals for the batteries; it will take decades to switch over; the number of people run over will increase because you don't hear them coming; and electric cars are no fun, but hey.

There's also the point that one of the many reasons why fuel duty is such an excellent tax is because it trebles the actual real cost of the fuel (a few pence per mile). Electricity only costs a few pence per mile simply because there is no tax on it (and not because it is inherently cheaper or more resource efficient), and electric cars use hardly any electricity while stationary, so the number of traffic jams might well increase.

*** Judged on its own terms, the exercise is fairly futile. Retail petrol and diesel sales are 37 bn litres/year (with another 9.5 billion litres for commercial, i.e. lorries, construction equipment, trains, tractors, who are definitely not going to go electric). So in theory we could stop burning 37 bn litres of fuel on the road.

If electricity generation goes up 40% and half of that is gas, oil or even coal, we simply use half of that 37 bn in power stations, a net saving of 19 billion litres.

We could achieve much the same reduction by simply moving to hybrid cars (as recommended by Bayard), which can achieve 80 or 90 mpg. They can do 10 - 50 miles on battery alone, so you could turn off the petrol or diesel engine while in town, thus reducing pollution where people live (Mombers' argument in favour of electric cars, about the only valid argument in favour of them IMHO). This requires absolutely no changes to our infrastructure and the shift could happen organically.

That 19 billion litres saved is only a fraction of total fossil fuel usage in the UK. 19 billion litres = 172 TWh, and current gas usage (domestic and power generation) is 869 TWh. Then there's the 9.5 billion litres of commercial diesel = 92 TWh, plus various other bits and pieces. See various charts and tables here.

I'm assuming here for simplicity that CO2 emitted per TWh is approx the same whether you are using gas, petrol, diesel or coal; whether you are using it in a car engine or in a power station to generate the electricity to run the car. On this basis, UK's CO2 emissions would come down by about one-sixth.

Interestingly, UK CO2 emissions have been dropping by a compound average of 1.5% a year since the peak in 1975 and we're already back at the level of 130 years ago (from here), so we'd achieve that one-sixth saving in ten or fifteen years anyway if this trend continues.


View from the Solent said...

I'd approach it differently.
Take the energy density of the fuel -
petrol ~8.8 kWh/litre
diesel ~9.7 kWh/litre

(values vary depending on the data source0

Find out how much diesel & petrol is sold in UK per annum.
Convert that into MWh.
That will give you a straight comparison against the installed UK generating capacity.

Then you can play with the numbers.

DAD said...

Another thing to consider. Assume each and every household can take (say) 10kw of load, If all the households that were connected to the local transformer did take 10kw, the current/power taken would be more than the cable and transformer can supply.

The result - explosion! Plus it would take quite some time to replace and upgrade the cable and transformer.

The result - no electricity for all the households on that transformer. Every other transformer and connecting cables would also become overloaded. Electricity grid overloaded

The result - chaos! large pockets of electricity deprived houses and businesses. No light, heating or infrastructure.

The results - riots.

Bayard said...


Electric motors are damn near 100% efficient. IC engines are much less so.

Mark Wadsworth said...

Vfts, I'll give it a go.

Dad, yes, we'd need a major upgrade to national grid, transformers, fuses etc.

B, sure, but electricity generation is not 100% efficient, so you lose at one end or the other.

Mark Wadsworth said...

VFTS, I battled for a few hours with the various sources and tried your approach as well as a cross reference. I have updated the post accordingly, it appears that the number of miles driven would only have to come down by about a fifth, not by half. Still a Quixotic idea though.

Blissex2 said...

«the number of miles driven would only have to come down by about a fifth, not by half. Still a Quixotic idea though»

This is assuming "other things being equal", that is markets don't work, and buyers never adapt their requirements to new market conditions. That is that people will continue to buy large comfortable cars for transport regardless of cost. But in a few decades some countries have moved from mopeds and tuktuks to cars and vans, so actually large swings are possible.

As to electricity a little remarked and colossal swing that I may have mentioned on this blog previously is that since 2003-2004 electricity per head consumption in the UK (and for example also in Spain, Greece, Italy) has collapsed, falling by 15-30%, after rising at a fairly steady rate ("Jevon's Effect") for the hundred years previous (except wars of course). In richer countries, or richer parts of those countries, it has merely stalled, and in "offshore" countries (most obviously China) it has risen phenomenally.

Consider this graph and the big loud message it sends (and add USA, south Korea, etc. for further comparison):

Mark Wadsworth said...

B2, yes, agreed to all that on the facts.

My conclusion was that going all electric is actually feasible in terms of our current generating capacity. It might lead to a one-fifth reduction in miles driven, which is also perfectly feasible.

It's everything else about it that is Quixotic.

Nick Drew said...

Mark, as requested I am attending upon your post w. comments - in several sections

Part 1

preliminary: there are quite a few folk trying to "prove" that EV policy is infeasible. Most of them decided that "infeasile" was the answer before commencing their arithmetic (ideological reasons, I suppose); and are barking up the wrong tree because some very smart businessmen employing some very smart engineeers are working ingeniously and productively to solve the (very many) practical problems involved. With several caveats below, I strongly advise that nobody should bet large sums against them succeeding: these are only technical problems

I am glad you have not fallen into this trap!

1) you are as good at www-research + arithmetic as anyone, and without duplicating your efforts they all ring true

Nick Drew said...

Part 2

2) the situation is not, however, static and you might like to stew in the following factors

2a) there is going to be at least some electrification of space heating, and thus the generating fleet (on a de-rated basis) and the grid as a whole, and the distribution systems will also need expanding: so your 'existing grid / existing fleet' baseline is overly "pessemistic" as regards the feasibility of the EV policy

[BTW/1, there is quite a bit of slack in the Grid & distrib system right now because demand has fallen noticeably in recent years and they were sized for those higher, previous levels of demand. So the capacity upgrades aren't needed in a rush. But the fleet capacity needs additions all the time, as coal and then nukes retire]

[BTW/2, there is a distinct limitation on how much domestic space heating demand can conceivably be electrified: because peak winter domestic space heating requirement on an energy basis is SEVERAL TIMES GREATER THAN THE ENTIRE NATION'S ELECTRICTY DEMAND, FOR ALL PURPOSES, DOMESTIC AND INDUSTRIAL AND EVERYTHING ELSE. And although capacity in the Grid etc can be increased, it can't be MULTIPLIED BY SEVERAL TIMES. There's your real "zero-carbon" challenge. It'll be met, if at all, by switching to hydrogen, incidentally. Plus a bit of electrification, as above.]

2b) the ability to optimise EV charging times, and indeed all load on the system, is going to improve in leaps and bounds. That's not to predict how much optimisation can squeeze out of a given system - sometimes it can be disappoitingly little - but the capabilities are getting better and better.

[Some people hate this because they consider it will involve wicked Big Brother interventions on their private electricity usage. That, IMHO, is bollocks. (i) it will be done via carrot, not stick - and what's more, the early adopters (domestic and industrial) will make good money from it so that it will rapidly become a matter of Fashion - always the best way for things to spread fast.]

Nick Drew said...

Part 3

2c) Mr "Little Git" Tesla will eventually agree to make his car batteries so that they can export power back into the distribution system, which at present he refuses to do. This will be very useful for boosting the scope of the above optimisation

2d) several of the dozen or so firms that own UK distribution systems have tolerated really dumb management regimes (you'd be amazed) in said affiliates (on the basis it's a business based on digging holes in roads, I suppose). This will change, Darwin-wise: because the better distribution companies will show what can be done and everyone will scrable to catch up. (By contrast there are plenty of smart people at National Grid, albeit not always at the forefront of dynamic innovation)

2e) the current non-duty regime for EV electricity will, of course, change! Or, a £30bn revenue shortfall will occur.

2x) and many other scenery-changing developments besides

3) No fun? Have you seen the acceleration potential of EVs?? That's why they will become POPULAR

Nick Drew said...

Part 4

4) But just to add to the list of difficulties: it ain't just coppper / rare earth shortages that will ensure developments will be slow and steady rather than earth-shatteringly fast. There are some big H&S / modern slavery scandals in the battery industry supply chain, that will break at some point in the next few years causing big headaches for the Corporate Social Responsibility wallahs. I've indicated above that there's loads of business activity in every part of the EV / charging / battery industry, with private money pouring in. At the same time there are several pension funds of my acquaintance that are very nervous about these CSR aspects

Nick Drew said...

Apologies for the several typos in the above ...

Mark Wadsworth said...

ND, many thanks, I'll read and digest properly. My short summary is, you reckon it's do-able, which of course it is. Question is, how long will it take and how much will it cost, or whether it's worth the hassle (which nobody can know).

Nick Drew said...

my pleasure: & here's another couple of factors

- it may dish the German auto industry, with extraordiary consequences (tho' they have lots of good engineers, too: but the vehemence with which they are resisting EVs may be more than a smokescreen)

- I'm increasingly coming to the view that a lot of this is pure Keynsianism, barely one level up from digging holes & filling them in at public expense. Now I'm no macro-economist, but I do recall that Keynsianism Works In Some Circumstances (but definitely not in others)

so a lot of this probably hinges on whether the circumstances are propitious for a massive burst of Keynes. Anyone have views?

See C@W passim for discussion on The Only Game In Town, which is the mega-expansion, nay, the giga-expansion of what officially counts as "green" that occurred last year (early 2019); so that it now embraces "adaptation" to climate change. This is so big, it's amazing - a once-in-a-generation, state-backed bonanza (think US economy in WW2). Steel-and-concrete mega-projects! Flood defences. Sea walls. Irrigation schemes. Desalination projects ... Every industrialist and bank is all over it.

(of course, so are the sophisticated "green" NGOs; and the Left - everyone has their own plan of how it's to be done; everyone wants to take charge of the world's pension funds (and take their cut) as the money becomes earmarked for these schemes; lots of them plan to smuggle in other policies wholesale under the "green" flag ("world governance" for the NGOs; workerism and nationalisation for the Left - see the Labour 2019 manifesto. Makes you feel kinda sorry for the old hippy-greens, who are being left in the dust ...)

Mark Wadsworth said...

ND "I'm increasingly coming to the view that a lot of this is pure Keynsianism"

Crikey, of course. The government gives it mates loads of taxpayers money, that's the Tory way. And indeed the Labour way.

Robin Smith said...

Fiscal policy is all there is left:

More monetary policy will mean killing more starving people.