Solar PV

[Click4B]

Looking to install some solar PV, but understand it needs building notification.

just wondered what notifications I need to make and if anybody had any experience getting it signed off.

not worried about MCS Export guarantee payments.

electrical will be covered as property is being rewired so will just add the electrical wiring for the PV prior to part p sign off so it’s all under same umbrella. Got an electrician I’m working with who has 3rd party sign off and is happy to do that.

but don’t know what other notifications I need, going to submit a g98 to DNO.

thanks

 

[ajstoneservices]

BC will want you to comply with part A. An mcs registered business can self certify compliance.

 

[Click4B]

Thanks,

so if I get a structural engineer to provide calculations, and then submit then under a building notice for part A and get it inspected will that cover that then?

I would use an MCS certified person, but they won’t sign off something they haven’t installed and I want to supply my own MCS certified panels.

If they was willing to inspect and sign off my work then I would happily hand them the money rather than the local authority. But they don’t want to know.

 

[ajstoneservices]

Where are you getting your pv kit from ? If you get it from midsummer they have a computer program called easy-pv which will cut out the need for an se as it produces all the calculations you need.

 

[Click4B]

Where are you getting your pv kit from ? If you get it from midsummer they have a computer program called easy-pv which will cut out the need for an se as it produces all the calculations you need.

I don’t know yet. I did price it up with midsummer, but then found ITS technologies cheaper.

but I’ve since made enquiries sourcing the quantity of panels I want direct from China from a JA solar distributor and even with tax it’s cheaper still and they sell 400W Bifacial JA solar panels, which neither midsummer or ITS technologies list.

the part P bit isn’t an issue as house is being rewired so that will be covered with that.

just the other notifications.

As above I would use an MCS installer.

But as I’m working with an electrician on the rewire part p aspect and I want the 400W panels which they can’t / wont supply for the same price I can get them for.

they aren’t interested as they want to understandably supply and install everything due to paper trail and liability.

which is going to cost more than the cost of notifying direct to building control. If they was willing to sign off MCs certified panels they hadn’t fitted after an inspection I would otherwise prefer to give them the money than building control, but because of paper trail and liability nobody understandably wants to know. So I’m just trying to focus on keeping it legal with building control.

I found a seller on eBay that signs off MCs for extra money if you buy from them... but I don’t like the spec they are supplying and for same price I can spec a better system.

Hence doing it as a DIY install.

 

[IT Minion]

How big? Over 3.68kw and you need to notify your DNO and ask for permission to go higher.

I'm thinking of getting a system shortly as well so a write-up in the projects forum would be interesting if you've got the time.

 

[Click4B]

How big? Over 3.68kw and you need to notify your DNO and ask for permission to go higher.

I'm thinking of getting a system shortly as well so a write-up in the projects forum would be interesting if you've got the time.

that limit is only for export.

If you limit export to 16amp / 3.6kw there is no limit on the size.

I’m looking to install around 10kw, basically want to fill both sides of the roof with panels to offset running costs of a 9kw electric boiler.

Im going to do a G98 with the DNO anyway to see what they say, but if they decline I will just limit it to 3.6kw export.

 

[garyo]

What does the payback time look like at the moment, click4b? I've wondered about this myself but it seems you need to know how to play the game and I had too much on...

 

[Click4B]

What does the payback time look like at the moment, click4b? I've wondered about this myself but it seems you need to know how to play the game and I had too much on...

haven't worked this out, but cost wise,

panels are around about, £3298 roughly (dependant on shipping costs) for 10kw worth of 400W Bifacial panels in bulk direct from China distributor.

then rest of the cost would depend on choice of inverter But 2x 4kw solis inverters are around around £1026.

so that’s £4324 then you have the roof fitting kit and cable, isolators, connectors and other electrical accessories so a little over £5000 or thereabouts for a 10kw system.

to get one installed from an MCS certified installer could be easily half that amount again, even a diy 10kw kit with everything included is £6595 online.

but the problem is if not MCS certified you can’t reclaim money for export from the soon to arrive export guarantee so you don’t get money back that way... only way to recoup costs is with the reduction in electricity bills.

In our case, don’t have an electric boiler yet, still on gas.

but our electric bill is presently 10kw/h a day on average, 310kw/h a month on average.

a 10kw/h system, this time of the year would probably (from my research) generate around 5kw/h for around about 7-8 hours a day which would be around 35-40kw/h a day so it would certainly reduce our daytime consumption to 0 as long as it’s not cloudy outside... in summer would be likely around 8-9kw/h

add battery backup, and could probably go off grid completely.

so at that rate it would take 15 years to break even.

however, if you then went and got an electric vehicle as next vehicle and charged the vehicle off solar. Then you would also be saving on fuel costs also and with that factored in you could recoup costs in as little as 4 years (based on £5 a day fuel, 5 days a week, 50 weeks a year £1,300 which would be very low consumption compared to many.)

so it does depend on individual circumstances how long it takes and how much of the generated electricity you use vs how much is exported. If you use more of it then you will recoup costs quicker.

If MCS signed off you will recoup quicker because they will pay you a few pence for every kw you export.

 

[IT Minion]

that limit is only for export.

If you limit export to 16amp / 3.6kw there is no limit on the size.

I’m looking to install around 10kw, basically want to fill both sides of the roof with panels to offset running costs of a 9kw electric boiler.

Im going to do a G98 with the DNO anyway to see what they say, but if they decline I will just limit it to 3.6kw export.

How do you plan to do that whilst still being able to use the full 10kw internally? Normally the Inverter acts as a limiter but do you have a better solution in mind?

The SEG is in force now, rates vary from 0.001p to 5.6p per kwh depending on supplier.

 

[Click4B]

How do you plan to do that whilst still being able to use the full 10kw internally? Normally the Inverter acts as a limiter but do you have a better solution in mind?

The SEG is in force now, rates vary from 0.001p to 5.6p per kwh depending on supplier.

I haven’t looked into how it works completely.

but it senses the export with a CT clamp.

If you create a demand by switching on something electrical, I’d imagine it senses the export has dropped and it ramps up the output to match demand, so if you was using hypothetically a full 10kw demand, that appliance would soak up the entire 10kw from the inverter so there wouldn’t be anything excess to go back to the grid.

 

[IT Minion]

Aha, I hadn't realised that inverters are that smart. Does 2 Solis inverters come out cheaper than a single 10kw one? I'd expect a single larger unit to be easier to work with and cheaper, but as demonstrated I clearly don't know that much.

https://onestepoffthegrid.com.au/solar-unlimited-use-inverters-get-past-export-limits/

 

[Click4B]

Aha, I hadn't realised that inverters are that smart. Does 2 Solis inverters come out cheaper than a single 10kw one? I'd expect a single larger unit to be easier to work with and cheaper, but as demonstrated I clearly don't know that much.

https://onestepoffthegrid.com.au/solar-unlimited-use-inverters-get-past-export-limits/

nope more expensive. Should be able to in most cases do it with 1 inverter.

but it depends on the panels you have and their total volts and amps and the inverter... I don’t know how true but was told it’s a good practice thing to have 1 per array so a roof with 2 sides would under that case use 2.. 1 for each side, although in practice I suspect vast majority only use 1.

Could be wrong, still learning myself and all relatively new to me also.

I’m planning on using SolarEdge inverters and optimisers which add quite a bit to the cost as the optimisers are £40 odd each.

But a basic inverter will work for most people and that’s all the vast majority fit and works out cheaper.

when you wire panels in series, the volts add up... so if you have 10v panel, and 6 of them it’s 10+10+10+10+10+10 which is 60v

and when you wire them in parallel the voltage stays the same, but the amperage adds up.

so it would be 10amp +10amp = 20amp

the spec on the panels I’m planning on using is,

50.02v each
10.24amps each

So say I had 9.6kw, that’s 24 panels.

50.02 * 24 = 1200.48v

But a 8kw SolarEdge inverter is listed as only being able to take a maximum of 480v on each input.

so even if you had split it into 2x 12 panel strings, that’s still 600.24v

Would need to split it into 4x 6 panel strings, that’s 300.12v which is within the inverter capability.

Then pair off them so you end up with 2 pairs of 2x series strings in parallel. If that makes any sense lol

So,

6 panels + 6 panels \
12 panels
12 panels
6 panels + 6 panels /

then when you look at amps.

and 10.24 + 10.24 becomes 20.48amps

which is only just within the capability of the inverter I’m using as it has a max of 20.5amp... but flip side is for reliability would you want to be running it right on the limit of its maximum capability?

ive listed 8kw, for 10kw array because apparently here in the UK it works better in lower light conditions if it’s under rated by 20%. Again don’t know how true but on an 8kw inverter it says it will handle up to 12.4kw so it’s fine.

but yes 1 is cheaper, and in most cases 1 should be enough. But it depends on the panels, inverter, and size of system.

 

[Aunsh]

Just a couple of points:

You have mixed up your use of the terms kW, kWh and kW/h, which does not bode well for the rest of your figures.

I think you are going to be extremely disappointed when the generated power fails to meet your expectations, by a long way.

Based on my knowledge of a 4kW system and extrapolating to your 10kW system, I would expect, for example, that your average daily output over the last three months to be around 6kWh, with an odd day/month popping in around 30kWh and a few days less than 1.5kWh. Of course, there will be no PV output if the panels are covered in snow.

Due to the nature of the PV output fluctuations, particularly with respect to varying cloud cover, I would still expect a daylight grid consumption of a few kWhs.

As to charging your electric car, I would suspect that the PV output fluctations would result in a significant proportion, if not the majority, of the charging current to come from the grid. There is also the unanswered question of how does the government replace the loss of income from the various fuel duties when electric cars become the majority.

 

[Click4B]

My interpretation, is that a 1kw system generates at a rate of 1 kw per hour.

same as a 1 kw appliance uses electric at a rate of 1 kw per hour

apologies though the way I wrote the terminology as kw/h rather than kWh.

I could be disappointed, but I would expect more than 1.5kw per hour from a 10kw per hour system still bearing in mind also I’m talking about fitting it to both east and west roofs also and system will have optimisers on each panel, plus be Bifacial to maximise generation.

I don’t have a daily average output? As I currently don’t have solar yet, not do I have an electric car.

Was just hypothesising.
But I never expect to be 100% off grid, it is possible though with batteries, was one on YouTube somebody documented with a 10kw system around this time of the year and they went off grid for 32 days with a few Tesla powerwalls.