Western Power Distribution (WPD) has announced plans to develop a miniaturised off-the-shelf substation for connecting electric vehicle (EV) chargers at motorway service stations.
The “plug and play” substations will have a capacity of up to 20MW, allowing them to supply up to 40 rapid EV chargers, and will be compressed into two units, each the same size and shape as a standard shipping container.
The firm is investing £1 million in the Take Charge project, which it claims could save almost £0.5 million in connection costs per site.
Paul Jewell, DSO development manager and EV lead at WPD, said the idea is not entirely new: “Whenever we build an electricity supply to a standard housing estate, what we normally do is put in one of those distribution substations – the ones that fit in the surrounds – and we can knock those out as if they’re like cookies from a cutter.”
“It’s really simply,” he added. “Everybody knows what they’re doing. It’s a standard bit of kit that works. And what I wanted to do what get to a position where we could offer that same facility for motorway service operators.”
He said the big difference is that these new units will need to have a lot more capacity and do the job of a much larger substation: “Normally for a 33,000-volt-in/11,000-volt-out type substation… you’re probably looking at a 30 metre by 40 metre outdoor site, with fences, with security systems, with transformers, with overhead bus bars, with a switch room and lots and lots of assets, including lots of kit that needs to be built on site.
“So what we I was trying to come up with was a way we could shrink that all into something that was more compact and do all the work off site so you just deliver it to a motorway service area.”
WPD is now in the process of designing the miniaturised substation. It plans to start building a 12MW prototype in October and deploy it a service station in Exeter for a six-month trial beginning the following March.
The substation will be divided into two units, the first containing an 33kV/11kV transformer, and the second containing 33kV switchgear and 11kV circuit breakers.
Jewell said: “The plan is that you would get those two containers delivered on the back of a lorry and all you would need to onsite, apart from making the space for two shipping containers, is run the 33kV cables into the unit and then run the 11kV cables away to standard distribution substations that might be around the motorway service area site depending on where their car charging locations are.”
“It turns it into that very standard, pick it off the shelf, deliver it to site, and run some cables into it solution that we also offer for housing estates but at a bigger voltage and a bigger capacity.”
Jewell told Utility Week these pre-fabricated substations could also have further uses beyond just supplying EV chargers: “There’s the almost the potential that if you were thinking of fitting a primary substation on your network and you weren’t confident on load growth yet it would give you a bit of a stopgap.”
He said it would not fit the requirements for a permanent substation “as not everything is duplicated, obviously because we’re trying to fit it in a small box”.
“For motorway service charging, I think it’s reasonable because it’s a single customer with a large capacity,” he explained. “It’s a bit like saying to a factory or an industrial customer: are you happy to take different levels of risk? I think if you were doing it as a standard network solution that was maybe feeding 10,000 homes, you’d then be thinking to yourself: is this secure enough?
“But it might be something that gets you over a peak, gets you over a problem; which you use and them remove afterwards when you’ve built a permanent solution.”