Plug in solar panels

[CambridgeWorks]

Firstly I hope this is allowed and in the correct forums.

An announcement I saw today tells about plug in solar panels to help power your house. 
Placed on a balcony or anywhere else outside.
No installation required it says. Just plug into a socket.
Hopefully arriving in next few months and available from Amazon, Lidl etc.
How would this work, assuming you are also connected to your electricity supplier all the time?
Edit. 
It seems electrical installation regulations are changing to allow for this.
Rob

[MW0SEC]

I was wondering the same - it would clearly have to include an inverter which could sync with the mains and presumably have some method of detecting that it was plugged in and connected mains voltage, to avoid a live plug! After all of that, I am not sure that modern meters are able to 'discount' reverse supply. Obviously useless for a power-outage situation.

[boater sam]

There is a very serious point to consider.
A proper installation ensures that power is not fed back into the grid when there is work ongoing on the supply line. This is to ensure that we don't kill off the engineers.
Sounds like something that will be banned to me. Smart meters will discount the solar energy gain.

[CambridgeWorks]

I thought that as well.
Evidently the inverter output requires a supply present where it is plugged in to.
A YouTube clip showed that pulling the plug out of the socket instantly stopped the inverter.

The particular video had an 800W inverter, 6KW battery storage.
He calculated payback time of 7 years.
I assume providing nothing goes wrong or battery deteriorating,?
Rob

[Radio Fixer]

Dont see how it helps people with their energy costs? I picked up that you have to buy them so if they are struggling with costs how are they going to afford them. Another net zero nutty scheme to me.

Gary

[ppppenguin]

All G83 compliant inverters https://dcode.org.uk/assets/uploads/ENA_..._2019_.pdf stop generating if the mains supply fails.

I have had PV at home since 2011. On the very old FIT scheme I get paid on the basis of amount generated. The amount exported isn't measured. Modern meters won't go backwards.

At the Broadcast Engineering Museum we have had PV since 2022. We have a smart meter that measures both import and export. The export side has a separate MPAN. We sell any surplus under the SEG scheme. Our new contract starting in May will be for 15p/kWh export and 23p/kWh import (both exc VAT).

Batteries are usually stated to have a 10 year life. Usual rule of thumb is that a battery capacity in kWh should be twice the panel rating in kWp. Another rule of thumb is that you can save about half the energy that you would otherwise export. Take the difference between your import and export price. Multiply by the number of kWh you export (you won't know this until you had a system for a year) and compare to the cost of a battery. If you can't pay back the cost of the battery in under 10 years it's not worth having.

You can get some idea of the amount you export by assuming a specific yield of between 500 and 1000 kWh per kWp per year. Depends on orientation of panels. Then assume you export half of it.

I've no idea about export tariffs for plug-in panels.

PS: For the 30kWp array on the south facing roof of the Broadcast Engineering Museum our specific yield is about 1000kWh/kWp/year. We generate about 30,000kWh per year and export about 18,000. Batteries are not yet worth it for us. We're about to fit more PV that's north facing. The yield will be about half that of the south facing panels. The economics still work well for us.

[ppppenguin]

These "balcony PV" systems are very popular in Germany. They work well for rented properties.

I own my house and have been there for years. My 2kWp system fitted in 2011 was expensive but paid back its cost in under 10 years. The inflation linked FIT runs for 25 years. The Broadcast Engineering Museum system has an impressive payback time of about 6 years.

If I rented there's no way that I would fit a fixed PV system. If I was in a flat I probably couldn't fit PV even if I owned the flat. These balcony systems are a really good idea and well proven in other countries.

[Mike Watterson]

Our solar system didn't need any law change, certification or approved contractor. It saves money by reducing Grid demand. It has maybe 14kwH of LiFePO4 batteries and 12 main panels. In winter it can charge the batteries from the Grid, thus even in Dec/Jan there is about 12 hours of power for essential services during a power cut. During the summer the Solar UPS can cope with months without grid, inc. overnight. If we had a smart meter we could use the UPS / grid charging feature in winter to move cheap overnight rate to the daytime.

A plug in panel without sufficient battery is a waste. Also selling to the Grid is a poor return and viable for less than 1/2 the year.

The cheap microinverters for a panel that plugs in to the mains are also poor quality and give no power if the grid mains is off.

The panels are cheap. A decent inverter / charger is expensive. The batteries have come down a lot in price and might last 20 years with a daily deep cycle (LiFePO4). Lead Acid, Tesla Powerwalls and Li Ion make no sense,

[boater sam]

There is a very serious point to consider.
A proper installation ensures that power is not fed back into the grid when there is work ongoing on the supply line. This is to ensure that we don't kill off the engineers.
Sounds like something that will be banned to me. Smart meters will discount the solar energy gain.

[ppppenguin]

There is a very serious point to consider.
A proper installation ensures that power is not fed back into the grid when there is work ongoing on the supply line. This is to ensure that we don't kill off the engineers.
Sounds like something that will be banned to me. Smart meters will discount the solar energy gain.

As I said, all inverters used in the UK must be G83 compliant. This means they cannot feed power back to the grid when the mains fails. If your itsy bitsy inverter tries to power the neighbourhood when it shouldn't then it won't get very far. Some PV systems with batteries can run in island mode when the mains fails. This involves some very well designed switching to ensure you can't feed power back to a dead grid connection. There are also earthing implications, especially if you're on PME: https://electrical.theiet.org/wiring-mat...e-systems/

When you have PV, your gains are in two parts:
1: The electricity you don't import. Your meter never sees this.
2: The electricity you sell back to the grid. A smart meter can record this but unless you have an export MPAN there's no way to get paid for it.

If you have a battery then you can also do arbitrage - buy power from the grid at a cheap rate and sell it back at a high rate. Some tariffs are designed to allow this. On a bigger scale some electric cars and tariffs can do this sort of arbitrage. It's called V2G. https://en.wikipedia.org/wiki/Vehicle-to-grid This is potentially a very good way of meeting peak demand without using grid scale storage. It's not here yet but soon will be.