Is the 'Decarbonisation' of UK cars secure, reliable and affordable?

Is the 'Decarbonisation' of UK cars secure, reliable and affordable?

by Jack Ponton
article from Monday 7, May, 2018

IN JULY 2017 Michael Gove announced the UK would ban the sale of new diesel and petrol cars from 2040. It is odd that the Secretary of State for Environment, Food and Rural Affairs should initiate a policy with such a far-reaching impact on transport and infrastructure, but the announcement seems to have been triggered by the finding that at a number of UK sites, EU environmental limits for particulates and nitrogen oxides were being exceeded. 

At the same time various figures, between 35,000 and 50,000, for 'premature deaths' per year caused by vehicle emissions were being reported in the press. These figures, from a study submitted to the House of Commons in 2010, actually referred to all air pollution sources. More nuanced figures however, appear in other studies, e.g. Europe wide deaths 'associated' with diesel vehicle emissions are put at 10,000 per year by a Norwegian group. Precisely how premature these are is hard to establish but seems to be of the order of months rather than years.

The problem is clearly a localised one. In south east Scotland, EU limits are exceeded only at three places, all busy streets in Edinburgh. There are no issues with small towns or trunk roads. It would thus seem perverse to remove petrol and diesel vehicles from everywhere when local solutions are almost certainly possible.

However, the political aim now seems to have shifted from improving urban air quality to eliminating fossil fuels from transport in pursuit of 'decarbonisation' and the Government's self imposed and notionally 'legally binding' emissions targets. 

The earliest European proposals for removing fossil fuels from transport focussed on biofuels. Brazil has a successful programme for the production of ethanol from sugar cane dating back to the 1970s. (The aims of this were economic rather than environmental, predating that country's discovery of significant offshore oil.) The EU set a target that by 2020 ten per cent of vehicle fuel should be from 'renewable resources'. Alas, Europe is not Brazil and Britain is even less so. Brazil's success depends of having lots of land and sunshine to grow a crop readily converted to a fuel. We lack all of these. Britain does not have enough spare arable land to produce even 10 per cent of its vehicle fuel by the least improbable route, from oilseed rape to biodiesel. Biodiesel has emission characteristics very similar to petroleum diesel and so would not significantly help to reduce urban air pollution.

The penny seems to have dropped concerning the implausibility of European biofuels unless there is a breakthrough in the conversion of the cellulose and lignin, which make up the bulk of plant material. As well as their slow growth in a temperate climate the major problem is that current technology can only convert a small proportion of the plant to a liquid fuel. The big idea now is electric vehicles.

From an engineering standpoint, electric vehicles (EVs) have much to recommend them. An electric motor is simpler, cheaper, more reliable and should be longer lasting than an internal combustion engine. It can also eliminate the need for a gearbox and differential. The problem however is a portable supply of electricity. The earliest reasonably practical EVs, which appeared towards the end of the nineteenth century, used lead-acid batteries that were heavy and gave a very limited range. The search for an improved battery continued sporadically through the twentieth century, some exotic chemistries, e.g. with molten sulphur and liquid chlorine, being proposed, without much success.

The advent of practical hydrogen fuel cells suggested an alternative approach: to generate electricity from stored hydrogen. Fuel cells and electric motors are not heat engines and so the second law of thermodynamics does not restrict their performance. Their efficiency can be around 70 per cent while an IC engine in a car will struggle to get half of this. Hydrogen however, is a most unsatisfactory fuel. It does not occur in nature and must be manufactured. It has the lowest energy per unit volume of any combustible material. To obtain a range comparable to a conventionally fueled vehicle, hydrogen has to be stored in a tank compressed to several hundred atmospheres. I find the prospect of these travelling at 70 mph on crowded roads frankly scary. Only three manufacturers (Honda, Toyota and Hyundai) sell a small number of hydrogen cars. Any hydrogen car owner in Scotland would struggle to refuel their vehicle; there is one hydrogen filling station in he country, in Aberdeen. The nearest in England is in Manchester. 

Hydrogen for cars does seem now to have been pre-empted by straight battery-powered EVs. This is because the lithium batteries developed for computers and mobile phones can be scaled up to capacities useful for vehicles. It is now possible to consider the large-scale use of electric cars.

Possible, but how practical? How would a move to EVs affect the security, reliability or affordability of our transport system?

Securitymeans that in the medium to long term we can be sure that we be able to continue to use our vehicles. In practice, this means that we can be sure of obtaining fuel for them. Reliabilitymeans that at we will be able to use them, i.e. have enough fuel for them, at any time. If the fuel we need cannot be stored, reliability amounts to the same thing as security. And affordabilitymeans that both individuals and the country can afford to pay to buy, maintain and run them.

Security:Petrol and diesel are manufactured from crude oil (petroleum) of which the UK is now a net importer, to the tune of about 10 million tonnes a year, against a consumption of around 70 million tonnes. Most of our imports come from Norway, which is a stable, nearby and friendly country, but there are other sources including the Middle East, Africa and North America. Only twice since the end of fuel rationing in WW2 has there been a significant interruption in oil supplies. Both times the Middle East was effectively our only major source of supply and the restrictions followed wars there in 1956 and 1973. Under EU rules Britain is obliged to keep 90 days of oil supplies in storage.

We have adequate oil refining capacity to process crude oil into finished fuel. Both crude and refined products are liquids that are easily stored and transported in bulk. It is fair to say that our supplies of petrol and diesel are reasonably secure.

The situation with electric vehicles would be very different. Electricity is expensive to transport and difficult to store in large quantities. In contrast to the 90 days of oil supplies, our electricity storage capability is a mere 45 minutes. Security of supply therefore depends on security of generation.

Without EVs, our electricity requirement varies between less that 30GW in the early hours of a summer morning and more than 50GW at around 7:30pm of a cold winter weekday. To meet this we have about 8GW of nuclear, 11GW of coal fired generation, 25GW of gas and 3GW of hydro. These 'dispatchable' facilities can just match our maximum demand. In addition we have cables to Europe through which we can import up to 3GW moreprovided it is not required by France or the Netherlands. We have wind turbines with a nominal output of around 18GW and 12GW of solar panels. However these are available only when the wind is blowing and the sun shining. Wind output can often drop to less than 1GW and solar will invariably be zero at 7:30pm in the winter. Our electricity supply is currently secure if we have enough coal and gas. Both of these now have to be imported, and while coal is plentiful and can be stockpiled, gas is harder to store and, having recently lost our major storage facility, there is a distinct possibility that we could run short in winter when most of it is required to heat homes. In early March we faced this very scenario and a number of large industrial consumers were required to shut down to preserve supplies for homes.

That is now; but what if in future all our cars were EVs? Clearly there would be more electricity consumption and so a need for more electricity generation. It is hard to put a precise figure on this since most of the time there is more generation capacity than immediate demand. If cars were allowed to recharge only when there was surplus capacity this would reduce the need for new power generation. But if everyone came back from work and immediately plugged in to recharge at the time of peak evening demand a great deal of new capacity would be needed. The first estimate from National Grid of 30GW new capacity was probably for this worst case. They have subsequently revised this down to 18GW by 2050, which agrees another independent estimate. To provide this would require 5 or 6 nuclear power stations the size of Hinkley C. If, as many would prefer, this were to be supplied by wind turbines which typically can produce only between 25 per cent and 35 per cent of their nominal power there would need to be about 60GW worth of them additional to 18GW currently operational. This would require 18,000 turbines onshore or 7,300 offshore. There are currently 3,274 onshore turbines in Scotland.

Even if space could be found for all these turbines our supply of electricity for vehicles would not be secure. At times of extended low wind output, and it may stay for three or four days at less than 10 per cent of nominal capacity, we would need several times these numbers of turbines, which would be both unaffordable and impractical. The only solution would be to expand dispatchable capacity, i.e. gas, coal or nuclear.

So is our government planning for such an expansion? On the contrary, they are proposing that we should close all our coal-fired power stations. All our operating nuclear power stations are scheduled to close between 2023 and 2035. Together these closures would remove nearly 20GW of reliable capacity. The only supposedly firm commitment to new nuclear is for 3.2GW from a type of reactor that has never yet been successfully built. Energy companies are not prepared to build gas generation as it cannot compete with subsidised renewables.

The conclusion must thus be that, without a large amount of new dispatchable generation an electric transport system would not be secure.


For a transport system to be reliable the resources needed for it to work must not only exist, but must be available whenever and wherever they are required. For cars, this means fuel must be available. 

Petrol and diesel are easily transported by road or rail to anywhere in the country. A typical roadside filling station will have four tanks of around 22,000 litres each, enough to refuel 2,000 cars. This represents more than 800MWh of energy. To store the same amount of electricity would require 44,000 Tesla powerwalls. There is probably more energy in the tanks of Edinburgh's filling stations than the combined capacity of Scotland's two pumped storage hydro schemes.

However, since in principle electricity would be supplied continuously to all recharging stations via the National Grid, there should be no requirement to store it there. There are two problems with this assumption. Firstly, the Grid, and more particularly its local distribution network was not designed to handle the demands of vehicle charging. It would require expansion, at an unknown cost. The problem would be exacerbated if, as seems likely, consumers demand fast charging which would take place in times comparable with refilling a petrol tank rather than between twenty minutes and several hours.

The other problem would be matching demand for charging to availability of electricity. Provided that enough electricity in total is available over a day, these can probably be matched by pricing: very expensive at peak times and cheap at 2.00am when other demand is minimal. However, as discussed above, if there is heavy reliance on wind generation and the wind drops for two or three days then the necessary power simply will simply not be available. 

An electric transport system is likely to be less reliable than one based on petrol and diesel.


Although electric cars are simpler than internal combustion vehicles, they are currently more expensive because of the cost of the battery. A new Nissan Leaf, the most widely sold EV, costs the purchaser at least £22,000 after a government grant of £4,500. Nissan's comparable conventional Pulsar hatchback starts at £13,275. The major cost of owning any vehicle is depreciation. Typically a car loses 60 per cent of its value in five years. If we assume equal rates of depreciation then annual depreciation on a £15,000 Pulsar would be £1,800 compared with £2,640 on a basic Leaf. Allowing for zero road tax, assuming half the annual servicing costs for an EV, the annual fixed costs (excepting insurance, assumed to be comparable) would be £2,740 for the Leaf compared with £2,140 for a Pulsar.

The final costs will depend on the annual mileage. Because domestic electricity is taxed at 5 per cent compared with nearly 70 per cent on petrol, fuel costs for an EV should be lower. For the average annual mileage of 10,000 petrol would cost about £1,100, while electricity, depending on the tariff available, would cost between £300 and £450. The owner would therefore save between £550 and £800. Any saving would at best be modest. It would disappear completely even with free electricity, if less than £600 a year were spent on petrol, corresponding to an annual mileage of about 5,500 miles.

So running an EV may not be more expensive than a conventional car and might even be cheaper. But this is not the whole story. The realprice of the vehicle is £4,500 more than the figures used above because the government provides this as a grant, which ultimately comes from the taxpayer. Also the government is losing road tax of £140 a year and the 70 per cent tax which would have paid on petrol is replaced by only 5 per cent on electricity. The annual loss of revenue for average annual mileage would be £855. The life of a car is about 14 years and so the average cost to the taxpayer of every EV currently put on the road will be more than £16,000. There are about 30 million cars and light vans in the UK. If the same generosity were shown to owners in replacement of all of them (which it surely could not be!) then the cost to the taxpayer would be nearly half a trillion pounds.

Then, as mentioned earlier, there are the infrastructure costs. Grid expansion, both to the national and local networks: cost unknowable but certainly into the billions. Provision of public charging points in cities for vehicles which park overnight in the street, and cost of vandalism to these: again unknowable. Additional generation capacity: say five Hinkley sized nuclear stations at £22Bn each, £110 billion. (Regardless of claims by the renewables industry, nuclear is still the cheapest proven non-fossil generation option.)

In summary, given present grants and electricity prices EVs would be affordable to their owners. However, they would not be affordable to the country as a whole.

And the Outcome

What started with the aim of improving air quality, which could in practice be achieved much more cheaply, simply and probably rapidly, has shifted to the 'decarbonisation' of most of the road transport sector. The objective of reducing carbon dioxide emissions is intended to minimise climate change. 

In reality, the relationship between atmospheric CO2and warming is very uncertain, but let us accept the IPCC figure of 4 degrees Celsius that would be caused by the current global emissions. These are about 36,000 megatonnes (Mte) a year. The UK's annual emissions are about 456 Mte. Those due to all transport are about 124 Mte of which cars produce around 68 Mte. UK cars are thus responsible for 0.18 per cent of global emissions, and so presumably the same proportion of temperature rise. That suggests that if we were to replace all petrol and diesel cars with EVs and ensure that that are supplied with non-fossil generated electricity we could reduce the 4 degree temperature rise by 0.18 per cent or 0.0072 of a degree. I believe that this is a so small as to be literally unmeasureable.

In Conclusion

A rapid move towards wide adoption of EVs would reduce both the securityand reliabilityof transport. While at current electricity prices and tax rates a government grant makes EVs affordable to the owner, the costs to the country as a whole are substantial and almost certainly unsustainable.

The benefits in terms of climate change amelioration are at best negligible.

Jack Ponton FREng


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