The switch to electric cars

Much has been written about autonomous, driverless vehicles. Though they will undoubtedly have a huge impact as artificial intelligence (AI) develops, the shift to electric cars is equally important, and will have all sorts of consequences for the United Kingdom. The carbon dioxide emissions from petrol and diesel cars account for about 10% of the global energy-related CO₂ emissions, and the UK government has recently announced that all new cars sold in the UK after 2040 should be electric.

Contrary to some misconceptions, electric cars are effective in lowering emissions, as long as the electricity used to charge them is clean enough. While the carbon intensity (gCO₂ emitted per kWh generated) of Britain’s electricity averaged 740 g/kWh in the 1980s and 500 g/kWh in the 2000s, it was just below 200 g/kWh during the period April-June 2017. This reduction has come from the switch from coal to gas and biomass fired power stations, and the significant increase in generation from wind and solar. The carbon intensity is now often below 100 g/kWh for short periods. The result is that, assuming electric cars are charged throughout the day with the current mix of generators, their CO₂ emissions per mile are now less than half that of the best petrol or diesel cars. And this will get better as more renewable generation comes online.

Besides helping to reach the UK targets for reducing climate change, switching to electric cars cuts out the harmful particulates and nitrous oxides, emitted in particular by diesel engines. Since electric cars brake mainly by using their motors as generators, there are few particulates emitted from braking. However, the amount from tyre wear is similar to that from petrol or diesel cars, but this can be improved by reducing acceleration, deceleration, and weight. Autonomous driving, which is being promoted by electric cars, will help.

To provide the electricity for recharging the batteries of electric cars, the National Grid in their Future Energy Scenarios estimate that their generating capacity will need to increase significantly. In their lowest CO₂ emission scenario, called ‘Two-Degrees’, an additional six gigawatts would be needed by 2050, when effectively all cars in the United Kingdom will be electric. The United Kingdom is fortunate in having very good wind resources, and electricity from on-shore wind farms is now as cheap as that from fossil fuel plants; within a few years it will be just as economic from off-shore wind farms, where space and visual impact are not such a concern. Together with solar and biomass, wind power can give the extra generating capacity the United Kingdom will need, but handling the variability in supply will require investment in energy storage, smart grids, and interconnectors.

There are several other factors that must be improved to speed up the switch to electric cars. Their performance is very good; but at present, they are too expensive, have too short a range, and recharge too slowly. Moreover, there are far too few charging points available. The UK government has started to address the lack of number of charging points, and some new electric cars are now equipped with batteries that give 300 miles range, which is similar to that of many present cars. These improvements should remove the ‘range anxiety’ that currently makes electric cars unattractive to some customers.

The time it takes to top up a lithium-ion battery also needs to be improved. Typically, it takes around 20-30 minutes. Faster charging batteries, one, for example, with the potential to charge in five minutes, are under development. To cope with many cars recharging at once, ‘filling’ stations with banks of batteries will be needed to smooth out the load. Also smart chargers in each electric car would enable the demand to be spread out over time, and help in deciding where to recharge.

The main hurdle to switching to electric cars is the cost. Electric cars have many fewer components than petrol and diesel cars, mainly because of the simplicity of electric motors, but their high price is primarily due to the cost of the battery. Research and development are driving down battery costs, and as global production increases, prices are falling; this is particularly true for lithium-ion batteries. There is a well-established link between production and cost called the ‘experience’ or ‘learning curve’: there is an approximately constant percentage fall in cost for each doubling in global production. This percentage is called the ‘learning rate’ and is typically around 20% for developing technologies.

For lithium-ion battery packs the learning rate was 19% during 2010-2016, and in 2016 their average cost was $273/kWh when the cumulative global production was ~40 GWh. Assuming the same learning rate, then by 2026 production is estimated to be ~1 TWh and the cost ~$100/kWh, and by 2031 ~3 TWh and ~$70/kWh. This would mean that by the end of the 2020s electric vehicles will be economically competitive with internal combustion engine cars.

So the performance and cost of car batteries look likely to be attractive enough for there to be a significant switch to electric cars over the next decade. Hybrid and plug-in hybrid cars will have a share of the market initially, but their complexity makes them expensive, and pure electric cars—such as the Nissan Leaf currently produced in Sunderland—will quickly dominate as battery prices fall. Many of these will be autonomous and shared, improving safety, and lowering the cost of travel, and will herald a new age of car transport.

Featured image credit: Charging Station by Mark Turnauckas. CC BY 2.0 via Flickr.