Dr Simon Harrison, Mott MacDonald’s strategic development director, weighs up what the mass-electrification of vehicles would mean for electricity utilities.
First you need to understand how electricity supply works at the street level
The average demand of you and your house is about 1.5kW. The way the power system is designed assumes that people along your street are not all having electric showers at once – because people have different habits, power use is diverse and load is spread fairly evenly. But if everyone in your street turned on their electric showers at the same time and left them on for an hour, you’d cook the local distribution system. EVs are now visible on the high street. If, or when, we hit a tipping point and EVs become ubiquitous, then the local power system is going to be put under intense strain.
What happens when EVs enter the mix?
EVs have a high charging load which is there for a long time. Depending on charge rate, you might have 3-5kW for a slow charge or around 7-22kW of load for a fast charge. In the case of the 3-5kW load you will be charging for several hours. People who own electric vehicles are also more likely to have people who buy electric vehicles as neighbours. It won’t be long before we are seeing a large change in electricity demand at the very local level. More positively, if an EV is plugged in and not charging, it should in future be able to sell power back from its battery, making its owner some money when power is short.
How might that be met?
One option is to use a smart grid to control the timing of charging and to offer variable tariffs to incentivise charging when the neighbours aren’t. If the network companies invest in smart technologies, for a while at least, we won’t need to put a lot of additional cable in the ground to provide more capacity. Another is for owners or communities to install batteries at home that can help charge the vehicles and relieve the grid. You can buy these kinds of batteries today, they are expensive but will get much cheaper.
How far will that get us?
The issue is scale. If you electrified the whole of the UK vehicle fleet, you could be doubling national electricity use and having a big impact on peak demand. Additional generating, transmission and distribution capacity could be provided but at a hefty price and involving much disruption. Also there will need to be large scale street works to put in ubiquitous charging facilities for the large numbers of people who can’t park off-street.
Tricky!
Yes, but there’s an alternative scenario. As others have pointed out, there are technological and social revolutions afoot. If automation converges with sharing and people don’t own their own EVs, it may take pressure off the local parts of the power grid and the need for street works.
Why?
The key question is where are autonomous shared vehicles going to get their juice? The chances are that the fleet owner-operator will do a deal with somebody who has land and a stiff grid supply point next to it. It might be the local supermarket car park or a piece of land next to an electricity substation. What they won’t do is charge up outside people’s houses. The risk though is that we go through a phase of needing vehicle charging in streets before moving to autonomous shared vehicles a few years later – a lot of investment could be stranded.
How likely is this?
The bit that nobody has really got to grips with yet is how society is likely to react to this opportunity and what proportion of the population are going to take it up. You’ll probably have buy-in from all the people who aren’t independently mobile at the moment, such as the elderly, the disabled, for whom this could open up life changing opportunities. Young millennials and the noughties generation are less fixated on owning stuff and might go for it. Maybe the middle aged might still want to own a vehicle, but maybe not if the price is right. Maybe those living in the countryside might want to own a vehicle, shared vehicles might take too long to arrive.