The Fine City of Norwich has 5 park and ride sites. Since Covid, only 4 have returned to operation, as the number of users is a long way down; the council can’t afford the subsidies to keep the fifth going.

Last week, it was reported that the County Council wants to build six “solar-powered electric vehicle charging ports” at one of the 4 extant park and rides.

On the face of it, the usual absurd virtue-signalling waste of other people’s money. Because we both know that the solar PV is not going to produce enough juice to reliably charge an EV. More on that in a moment. But what took my eye was this:

Said Graham Plant, the cabinet member for transport, trees and guinea pig farming:

“It’s the first scheme of its kind for the council but we’re hopeful that if the trial is a success we can seek further grants to install them at other park and ride sites.

“We currently have eight EV charging sockets across our park and ride sites which have provided over 4mWh [sic] of energy to electric vehicles over the last year.

“We continue to roll out more public EV charging facilities across the county which support our wider strategy to reduce the carbon footprint of our county.”

I’m sure Graham meant MWh, not mWh; let us assume that the M was lost in translation. As it was put, the 8 chargers combined had output equivalent to four thousandths of a watt for one hour over the course of the year.

But let us not be churlish. Megawatt hours was meant, not milliwatt hours. It is a far more imposing figure – right?

4 MWh = 4000 kWh.

The internets says that the chargers are rated at 7 kW. Now, I’m going to posit that the owners of the EVs that parked in the park’n’rides were going shopping in the Fine City, and spent on average 4 hours there. Returning to their vehicles, the drivers found them topped up by 7 kW * 4 h = 28 kWh.

How many cars were charged?

4000 kWh / 28 kWh = 143

I can’t be bothered to find out how much the 8 charge points cost, or whether they also put 2 in at the mothballed site. However, I am going to say that charging 143 cars over a year is a paltry return. Remember, there are 8 chargers. So each charger put juice into 18 cars over twelve months, or 1.5 cars each month. Its utilisation time was…

72 h, or less than 1% of the hours in the year.

OK, so that’s dumb. What about the solar-powered charger thingy?

We want to provide 7 kW: how much area of panel do we need for that? According to renewableenergyhub, a standard 1.9 * 1 m panel has about 350 W (presumably peak power). That implies 1 kW = 5 m² and 7 kW = 35 m².

How big is a typical parking space? The AA says 2.4 * 4.8 m, about 1/3 of the 35 m² required for 7 kW; EV charge point spaces might be bigger yet. Of course, the panels on the car park are likely to be horizontal and therefore lower power than rooftop systems. Let’s call it 75% of the rooftop value, meaning that you now need about 45 m². It’s about 4 spaces worth for “one car’s worth” of solar charging.

Next, we must point out that the peak power provided is unlikely to be consistent. Even if the park’n’ride is only in use during the day, that is still the case, owing to seasons, mist, cloud, etc. This is a SWAG, but on the average, we might be looking at half of the rated power being delivered in the daylight hours.

So our 250 m² of panels (six PV chargers’ worth) should on average produce enough juice to charge 3 EVs. That is actually rather good, considering that 3 EVs * 365 days = c. 1,100 EVs over the course of the year.

The “but” is that the solar PV area is likely to be 1:1 with the parking space area, and therefore much smaller than required. Allowing an EV charging slot to be 50% larger than a regular one, gives us an area of 15 m² per solar charger. For six such slots we now have 90 m². According to the maths above, this should typically be enough to charge 1 EV, not 6. If 6 plug in: the lion’s share of the juice has to come from the grid.

At the moment, only 36 EVs per park’n’ride avail themselves of the chargers on site in a year, and if that low utilisation rate continues, there’s a good chance that our 90 m² solar array will usually be enough to charge every car that rolls up. Though if such cars were only plugged into the solar array, i.e. if there was no grid connection to fall back to, it would be unwise for EV owners to rely on a significant boost to their juice when they arrive back at the park’n’ride clutching twelve bags of shopping.

Editorial

This scheme seems to exemplify a problem with local authorities. It is funded by a grant. LAs apply for funding for specific projects, based on the parameters of the grant. Of course, there are valid reasons for wanting to receive a grant, even if the funded project itself is of limited value. For example, even a white elephant drives local employment; a local contractor builds it. So it is in LAs’ interests to apply, and equally it is in their interests to scratch around for any possible project on their turf that they can apply for funding for. Thus, close by us, there is a road scheme, built on top of a previous road scheme completed not that long ago, for a layout change that will have trivial effect on traffic flows. Similarly, one of Norwich’s main shopping streets has undergone a series of recent changes, each erasing the previous, expensive effort.

Let us contrast this situation with one in which the LA in question is given a certain share of money by default, and can decide by itself what its spending priorities are. In this case, the constant re-shaping of the same road would never be funded. Similarly, no LA would squander part of its pot of cash on chargers that are likely to be very under-utilised… or would they…?

See also Mark’s series on LA climate-related wasteful spending.

Personally, if I were to design a car park, I think I’d scratch the chargers and instead sacrifice 1 parking slot in 50 to plant an English oak. The summer shading this would provide in due course would be of more value to car park users, I should think, than the solar chargers.