Plug in solar, what do you think?

[ericmark]

I tried to find out more, but at the moment this seems to be all we can find, most adverts have not been up-dated, so we have no idea what will be on offer, and what instructions will come with them.

 

[helplessowner]

Anybody reading this thread who is like me - know nothing about electrics, how it all works - and is unable to get their head around the idea of plug-in solar, I found the below link pretty helpful in explaining in simple terms what it is, how it works, and why it is not yet ready.
Of course, as I know nothing about electrics - I also cannot say how accurate the information is.
https://solarenergyconcepts.co.uk/post/plug-in-solar-uk/#amendment-4

 

[Harry Bloomfield]

Anybody reading this thread who is like me - know nothing about electrics, how it all works - and is unable to get their head around the idea of plug-in solar, I found the below link pretty helpful in explaining in simple terms what it is, how it works, and why it is not yet ready.
Of course, as I know nothing about electrics - I also cannot say how accurate the information is.
https://solarenergyconcepts.co.uk/post/plug-in-solar-uk/#amendment-4

It looks to be fairly accurate, and these systems might be something I might consider investing in, once I have done the calcs - I've avoided the roof type so far, because I'm not convinced by the idea they would be worth my while, on the roof, they would be out of my direct control to maintain them. However I have plenty of space for these 'balcony' solar panels, room for several, on my garage flat roof even.

 

[ericmark]

I could not supply whole house from a 5 kW generator as some items (the shower for example) use more than 5 kW so grid tie allows me to use solar/battery or grid with a seamless transfer.

However, I could split my home electric supply to essential and non-essential, so the essential is below what the inverter can deliver. So if I took say 2 radials from the battery pack

simple plugging them in, and in turn the battery pack plugged into the grid, and solar panels, I could run multiple items around the house from solar or grid or battery, without using any grid tie. It would be a pain running new cables, and grid tie is easier, but it could be done. And no problems with overloading, live pins on a plug, or any of the other objections.

So where using grid tie really comes into its own, is when the battery is full, and we are still producing solar, under this situation it allows us to export solar and get paid for it.

So at around 12 kWh per day that I use, with solar panels even in March on good days, producing 28 kWh, I want paying for export. May up to 38 kWh some days.

But if my panels were smaller, under 1.8 kWh, then with big enough batteries to last the day, I would not need to export. Without any change in regulations, by moving lights, and essentials to solar/battery power with some re-wiring, I could do all the plug in solar does, without grid tie.

This system has been used with narrow boats for years, system was simple, large inverter ran all from a large lead acid battery bank around 500 Ah or more, and when one had the option to plug into a shore supply, all it connected was a big battery charger, class II so no need to connect an earth, so no galvanic problem.

The main change is the lithium battery. Smaller than lead acid, charges faster, and discharges faster, so far lighter, so could also be used with caravans, which do not have a ton of ballast that can be replaced with lead acid batteries.

Now we are looking at our own home, the big question is for how long with todays' tariffs exist? I remember in the 70s, we saw the storage radiator, and electric overnight was very cheap, but this difference has over the years eroded. And we are seeing people who did use economy 7 moving to panel heaters, as heating as and when required, is working out cheaper to using storage radiators.

So at the moment I am sitting pretty, import overnight for 5 hours at 8.5p/kWh, export during the day at 12p/kWh, and should my battery run out, I have to pay an extra 7p/kWh i.e. 32p/kWh instead of 25p/kWh, and that does not happen enough to be a problem, but at the end of the day, for solar to pay for its self, we depend on the tariff.

We see again and again on this forum the problems with storage radiators, and the increased cost if you want cheap electric for over 5 hours, be it 7 or 10 hours, the off-peak gets more expensive.

It would seem, the cheap overnight electric is all down to government wanting to push for EVs, and the way to get cheap overnight electric is the EV tariff. What is marketed as a solar tariff, is nowhere near as good.

So I am crossing my fingers, that the tariffs which suit solar last for another 5 years.

At 800 watt, plug-in solar is not worried about the tariff not lasting, or export payments. The problem as I see it, is once one fits plug in solar, one is less likely to install a larger array that can export, maybe this is what the government wants, maybe they are seeing too many large solar arrays.

 

[JohnW2]

I have looked at our ring final <diagram> and what could happen, remember some homes only have one ring final, but with the old BS546 15 amp socket, we would have multi-circuits and still likely 20 amp cable, with 15 amp fuse, so what is shown is unlikely to cause a problem simular to what is shown, the same applies with continental system, it could still happen, but less likely.

Cannot "a problem similar to what is shown" not equally possibly arise even if there are NO 'plugged-in' solar panels, the possibility of cable of one leg of the ring being 'overloaded'depending only upon the magnitude of the loads and how close they are applied to an end of the ring (e.g. 40A worth of loads applied close to one end of the ring in your diagram) ? ....

 

[ebee]

I think John might have a point there!.
The difference between a spur or a plug in for one is you can easily move the socket used therefore which part of the ring it introduces at.
With a spur it is more of a fixed place, providing you at least do a "back of a fag packet" rough calc you can find a half reasonable place to feed in and with luck it might be fairly reasonable all considered much of the time.
With a plug in you might adopt a system of easy change suits more variables (times of day, seasons of year etc etc), with both alternatives so long as you are aware of things and keep a good regime up, the plug in can be greater benefit. If not the spur might serve better in the long run overall scheme of use.
Some of us on here might be better on plug in scenario and the rest of the population fixed by the position taken for the spur.
Horsy coursey.
Somebody like Eric would probably have it down to the nearest farthing.

 

[ericmark]

Cannot "a problem similar to what is shown" not equally possibly arise even if there are NO 'plugged-in' solar panels,

We have to use the ratings of the protective device, yes I know we can draw more than 32 amp from a 32 amp RCBO, but not for an extended time. So with 40 amps the RCBO should in fullness of time trip. Fullness of time meaning before the cable overheats.

There is a problem with the ring final in that high loads near to origin can overload the cable, which is why it says non-portable equipment over 2 kW should have a dedicated circuit.

The problem item is the washer/drier, as often on wheels, so classed as portable, and the drier can draw over 2 kW for an extended period. Ovens, dishwashers, hobs, etc, are normally thermostatically controlled, so even over 2 kW it is not for long, and the stand-alone tumble drier normally does not have wheels, so is not called as portable, as over 18 kg in the main, so should not be used on a ring final. The same goes for an immersion heater as a tumble drier, unless the tumble drier is under 2 kW.

With radials, we need to use far more circuits, even with 20 amp radials, a ring final (32 amp) can have 106 meters of 2.5 mm cable, and a 20 amp radial 32 meters, so you need three radials to replace one ring final. So in general there are fewer outputs on the radial, so chances of an overload is reduced.

With the non-fused plug, we need an over-load to suit the plugs rating, so down to a 16 amp over load on a circuit able to take 20 amps, so in Germany as long as only one solar plugged in per radial the cable will only be loaded to 19.5 amps. So the only danger is equipment can draw 19.5 amps before the overload trips. We don't have this problem as we have fuses in the plug, so in other words the problems Germany to UK are completely different, and saying Germany are doing it so we can too, does not make any sense.

So at the moment, without breaking any rules, I can run a circuit from an inverter around my house to power what ever I want. The inverter does not need to be fixed, I can simply plug into it, and the battery/inverter pack can also connect to a solar panel. What we can't do is grid tie the inverter, so the load is part from inverter and part from the grid. It is either the inverter pack or grid, not both without G98 etc. And we are not permitted to feed into a socket.

Looking at base load of my own house, under 0.2 kW I would not export without a battery, and under 1.9 kW I would not export with a battery, so at 800 watt, average export will be zero, so no one needs to worry about upgrading the supply network to be able to accept the export.

So to get people to only have 800 watt of solar, will save the government a lot of money as once they have 800 watt, unlikely to replace it with 6 kW.

If everyone did as I have done, and fitted 6 kW of solar panels, at today's tariffs, there would be a major problem, as my net cost for electric for 10 months is around £200, and dropping, they need to get people to fit smaller arrays, or there will be a problem, so get the builder to fit 2 kW to new builds, then new owners will not be tempered to fit a 6 kW array.

 

[Harry Bloomfield]

So to get people to only have 800 watt of solar, will save the government a lot of money as once they have 800 watt, unlikely to replace it with 6 kW.

If everyone did as I have done, and fitted 6 kW of solar panels, at today's tariffs, there would be a major problem, as my net cost for electric for 10 months is around £200, and dropping, they need to get people to fit smaller arrays, or there will be a problem, so get the builder to fit 2 kW to new builds, then new owners will not be tempered to fit a 6 kW array.

My daytime load is around 100 to 300watts, and so a 800w panel should match it, during daylight, but would it be worth it?

 

[ericmark]

My daytime load is around 100 to 300watts, and so a 800w panel should match it, during daylight, but would it be worth it?

It is not a clearly cut figure, my roof solar will likely get the sun for longer, fitted Sept 2023 today 12.76 MWh with 6 kW panels so approx 300 kWh per month, divide by 6 times 0.8 = 40 kWh per month x 0.24p/kWh = £9.50 a month or £114 per year.

So from that I would say an 800 watt panel could save £100 a year. But it depends on how much of what it produces you use. In the main we need a battery as well, and the question is at just 800 watt is it worth it? In the main it is the combination of off-peak and solar, not just solar, I am not sure which saves me the most.