Michael Kelly F.R.S. is Emeritus Prince Phillip Professor of Technology at the University of Cambridge. In a recent article he points out some unexpected difficulties with the coming transition to “clean green” energy. The gist of it is as follows:
Consider Dinorwig Power Station, the biggest hydropower energy-storage plant in the UK. If all UK cars were battery powered, the nine gigawatt hours of energy stored behind the dam would be capable of recharging the 60kWh batteries of about 150,000 small cars, or about 0.7% of the UK fleet. We are clearly going to need an extraordinary amount of electricity to convert all personal transport to batteries, even without considering the trucks and vans used in all the logistics that keep our supermarkets, high-streets, and industrial sites stocked.
Where will all this new clean green electricity come from? Something of the order of 70% of Britain’s entire existing electricity-supply capacity will be needed if we are to remain a mobile society. When we get coded messages from the Climate Change Committee, implying that we will have to rethink the extent to which we are going to be able to travel in future, it is the implausibility of meeting that vast gulf in energy sources that is motivating them to question our lifestyles.
And if we are to decarbonise the economy – so-called ‘net zero’ – we are also going to have to electrify the heating of buildings too. At present, this is mostly done cheaply and efficiently with natural gas. Converting everyone to heat pumps is going to bring about another huge surge in electricity demand. To repeat the earlier question, where will all this new electricity come from?
It is sometimes objected that we can charge battery cars at night, when demand is low. But the current day–night variation in electricity demand is of itself too small to handle the extra load, so charging at night is at best a partial solution. Another suggestion is that we can charge cars during the day, when solar power is high. But in the absence of storage, this would mean charging them from mid-morning to mid-afternoon on sunny days, wherever they happen to be. This is implausible too, and would be unreliable if we could make it happen.
The complete article can be downloaded here.
There are other unconsidered consequences of the large scale use of electric vehicles, chief among which are their effect on traffic flow. Electric motors have a radically different power curve from petrol engines in that they consume maximum current at zero revs, which is why electric cars have such excellent acceleration and don’t need gear boxes. It is also why poorly designed electrical gadgets, such as cheap sewing machines, tend to burn out during slow, difficult jobs. Likewise electric cars use more “fuel” when travelling slowly uphill, so that batteries are more likely to fail on hills in peak hour traffic, e.g. on Hobart’s Tasman Bridge around 9:00 am.
Add to this very slow recharging times. Kelly points out : Next time you stand for 90 seconds filling your petrol tank, you might think of the enormity of what is happening in energy terms. Chemical energy is entering your tank at a rate of typically 17 million Joules per second, or 17 megawatts – equivalent to the total energy given off by 17,000 one-bar electric heaters! Petrol is extraordinarily energy dense. But unfortunately for their proponents, electric vehicles are much less convenient, and recharging a car can take many hours. And before anyone suggests that rapid chargers can address this problem, it should be noted that these still take a long time and their use significantly reduces battery lifetimes.
Given that most people use their car for both socialising at night and commuting to work during the day, forgetting to recharge the family vehicle is likely to be a common occurrence.
How long before electric vehicles are banned from major routes during peak hour?
See also: The Guardian 28/11/2020