Plug-in Solar and the PV Detector Van
- Published
- in Smart Energy
Let’s start with the good news. It looks as if the UK is about to make it legal to buy and install plug-in solar panels. That’s basically a solar panel packaged with electronics, that lets you plug it directly into an ordinary 13A socket in your home to generate some of your own electricity. The bad news is that DESNZ ( the Department for Energy and Net Zero) want to regulate plug-in solar units in much the same way as TVs used to be regulated. These are DIY products which you can install yourself, but when you buy one, DESNZ wants to be notified, presumably so they can check that you’ve plugged it in properly and not broken anything. Their proposal reads like the old TV Licensing regime, which then sent detector vans around to make sure you had a licence. Except in this case, they’d be PV vans to check your Photo Voltaics.
There’s a consultation on whether that’s a good idea at https://www.gov.uk/government/consultations/plug-in-solar, but in typical DESNZ fashion, it opened last week and closes next week. So if you’ve got an opinion, you have until 30th June to respond.
The principle of plug-in solar is simple. You get a package which contains a solar panel, and an inverter – an electronic box which converts the low voltage, DC output of the solar panel into an AC mains supply. The inverter has a normal 13A mains plug on it, but when you plug it into one of your sockets it doesn’t take power out, it pushes the solar power into your home mains supply. That’s power you don’t need to pay for, which reduces your electricity bill. It’s as simple as that. Plug-in solar units are already popular in countries like Germany, where people install them on balconies and shed rooves, but so far, they’ve not been legal to install in the UK.
A typical system looks like this:
When the sun shines on the solar panel, 230V mains appears on the plug. That’s what’s worrying DESNZ. If you were to touch it, you’d get an electric shock, which is obviously a bad thing. To prevent this happening, the inverter needs to include something called anti-islanding protection. (Despite the name, this has nothing to do with Brexit.) It’s a way of sensing when a local electricity microgenerator is operating in isolation. Although you may not consider it, your plug-in solar panel and inverter is actually your own personal micro power station. If the anti-islanding circuitry doesn’t detect that a mains voltage is already present on the 13A plug, either from the grid or any other solar panels you might have, it isolates the 13A plug from the inverter in around 50 milliseconds. Even if you got a shock, that’s not long enough to do you any harm.
There’s a lot of other things that the inverter needs to do, such as tracking and synchronising to the mains voltage and frequency. This means that inverters for plug-in solar need to be quite sophisticated designs. However, issues with making them work reliably have been ironed out over the past few years in the German deployments, so there’s no real reason why well designed systems shouldn’t go on sale in the UK. Any extra power you generate beyond your own usage will find its way to the grid, unless you also install a battery. It’s debatable whether you’ll be paid for that electricity, as to do so would probably mean you’d need to get your meter changed. As these plug-in solar units are being limited to 800W, your utility probably isn’t interested in doing that. But plug-in solar should still save you money and pay back over 4 – 5 years.
That’s the theory. To test that premise, DESNZ commissioned a company called Arceio to look at current plug-in solar packages and assessed how well they worked. That’s been published at https://assets.publishing.service.gov.uk/media/6a32bfea0bea238415c9a1c0/Plug-in-solar-PV-study.pdf and forms the evidence behind the consultation.
It’s a thorough study, but there’s quite a big “BUT” about it. In the UK, we have a bit of a penchant for regulations. Where wiring is concerned, you’re not allowed to make any modification without notifying your local council’s building control before you start, or employing a registered electrician. There are building control regulations ,along with the IET’s wiring regulations which you’re meant to read and have to follow, even if you’re only replacing a socket. That’s the theory and DESNZ and the IET seem to believe it’s how things work. If you’ve ever walked into a B&Q or Screwfix you’ll know that you can buy almost any electrical product and take it home to install yourself. I assume that millions of people do, which makes quite a nonsense of any notification procedure.
This report ignores that reality and recommends that plug-in solar should be a notifiable device. In other words, if you buy one, the retailer has to tell the appropriate Government body, who can potentially check you’ve done it properly or that you’re “competent”. It’s the same principle that used to be applied to TVs. Every shop that sold a TV had to tell the TV licensing authority the address of the purchaser. They would then check if you had a TV licence and if not, they’d send around a TV detector van to see if it was working, after which they’d take you to court. Whether Ed Miliband is planning a fleet of electric PV detector vans is something we’re not told. As he can’t drive, at least he won’t be out chasing offenders himself.
What is more worrying, and something that say a lot about the people who did the testing, is that it is all viewed through the lens of wiring regulations. There’s virtually no mention of security. As that’s what the “S” in DESNZ stands for, that’s quite an omission. All of the microinverters that were tested come with an associated phone app, which presumably uses a Wi-Fi connection. That means they can potentially be hacked. If their firmware is changed, the anti-islanding function could be disabled, changing them from a money saving product to a life-threatening product.
Penetration testing, which measures a device’s susceptibility to hacking, should have been a key feature of the test, but it’s not. The report confines itself to the electrics and whether they’ll withstand typical British weather. It feels that it’s an exercise in applying IET wiring regulations, with no notion that the world has moved on. It’s not the first time we’ve seen this happen. In DESNZ’s former life as DECC, they made the same mistake with smart meters, which meant that the first million or so meters had to be replaced with secure ones after a GCHQ review found the inadequate.
It also skates over the real things that we should worry about with plug-in solar, which are the everyday ones. Will they be mounted properly? They are far more likely to kill someone by falling from a fifth floor balcony, where they’ve been tied on with a piece of string, than by electrocuting someone. Will people be able to modify them, as we’ve seen happen with electric scooters and bikes, and will we be able to prevent the sale of non-compliant devices. Those are already available to purchase from web retailers. Fixating on wiring regulations and the arcane considerations of technical guilds won’t help us save money on energy, or get to net zero. Germany has shown that plug-in solar can work. What the UK needs is to see them on sale in LIDL and Screwfix. Which is what we should be telling DESNZ.