Current situation with PV winter 2019?

Mr.Boy

We're about to build a 11x7m single storey log cabin in our garden with a dedicated electrical supply (already in). It has a low pitched roof, maybe 20 degrees and the cabin is South facing though only one half of the roof is likely to get good sun due to trees.

I'd been told there is no assistance/incentive for installing PV these days for residential or commercial, you just have to take the long view on savings. Is this correct?

I've also read that feed in tariffs are not very good, placing limits on how much you can sell to the Grid, but that this is starting to change? We expect electricity use to be near zero in summer and high in winter so this is quite a bit factor, I can see we'd potentially be contributing a lot in the summer.

I have no idea how many KW per square meter of roof is reasonable but Google seems to reckon about £1000 per KW which is quite a lot of cash.

We are required to comply with building regs due to the size and use of renewables can be a big help but still it's pricey.
Where are we at right now, what factors should we be considering when deciding how to proceed?

Thanks

Reed_Richards

d000hg wrote: »

I've also read that feed in tariffs are not very good, placing limits on how much you can sell to the Grid, but that this is starting to change?

The Feed-In Tariff was a government scheme that was discontinued earlier this year. It is due to be replaced by the Smart Export Guarantee which should come into force on 1st January 2020. Here is a link (not intended to endorse the particular website, just top of Google's list)
https://www.solarguide.co.uk/smart-export-guarantee-replace-fit#/

There is no limit on how much electricity you can sell but you need permission to export a current greater than 16 A which is equivalent to 3.68 kW of generation.

Martyn1981

Solaredge systems are excellent for dealing with shading, also, any chance you can build a mono-pitch roof to double the south facing available space?

ABrass

You probably mean you need to comply with permitted development rules, it's pedantic but different to building regs, which your building probably also has to meet depending on use. In which case don't forget the height you'd be adding on with panels.

That could mean your building would exceed the maximum height limit with the addition of panels.

Mr.Boy

Reed_Richards wrote: »

The Feed-In Tariff was a government scheme that was discontinued earlier this year. It is due to be replaced by the Smart Export Guarantee which should come into force on 1st January 2020. Here is a link (not intended to endorse the particular website, just top of Google's list)
https://www.solarguide.co.uk/smart-export-guarantee-replace-fit#/

There is no limit on how much electricity you can sell but you need permission to export a current greater than 16 A which is equivalent to 3.68 kW of generation.

Sorry I had thought "feed in" was a general term for selling energy back. What I'd heard was that you were restricted how much you could sell generally. If I was installing right now (before 1.1.2020) how should I proceed?
When you say I need permission, how will I know I'm doing this and would a system stop me? Or would they simply take it but not pay beyond that level?

Martyn1981 wrote: »

Solaredge systems are excellent for dealing with shading, also, any chance you can build a mono-pitch roof to double the south facing available space?

I wouldn't want to cover both sides of the roof realistically, the sunny side is the one pointing south anyway and would give I think 30m2 or more depending how tightly you can fill the roof(?) The cabin is already in our garden in pallets so the roof is as specced

ABrass wrote: »

You probably mean you need to comply with permitted development rules, it's pedantic but different to building regs, which your building probably also has to meet depending on use. In which case don't forget the height you'd be adding on with panels.

That could mean your building would exceed the maximum height limit with the addition of panels.

No, we had to go full planning permission and comply with BR via full plan submission to BC.

Mr.Boy

We are also having structural engineering sign off the cabin. How much do these things weigh, should we ask him to check this wouldn't be an issue at the same time? Or is it trivial?

Another basic question... do you need to lay additional high-current cables back to your meter for all this?
Our meter is actually 10m from the building and will have buried armoured cables. So is it sensible to bury a spare cable in advance. If so for the 5kW system we might be able to put in, what amp-rating is needed so I can choose the right size cable?

joefizz

d000hg wrote: »

We are also having structural engineering sign off the cabin. How much do these things weigh, should we ask him to check this wouldn't be an issue at the same time? Or is it trivial?

Definitely ask them. It may not be a big weight but it will depend on the loading of your cabin roof. Your roof might be sized for normal snow loading and maybe 2 person loading but add in the solar panels and possible wind loading (depending on placement, angles etc) then it might very well be an issue.
None of us can give you a definite answer on this, your own structural engineer would be the best to judge.

d000hg wrote: »

Another basic question... do you need to lay additional high-current cables back to your meter for all this?
Our meter is actually 10m from the building and will have buried armoured cables. So is it sensible to bury a spare cable in advance. If so for the 5kW system we might be able to put in, what amp-rating is needed so I can choose the right size cable?

Thats another it depends question that your electrician will answer. If your inverter is in the house then you might possibly get away with 10m DC cables, but if its in your cabin then it will depend on the loads you have in your cabin plus the max possible that the inverter can supply. Your electrician will give you a better idea of the rated figures for cables for that load. Ive always oversized my underground cables in the past allowing for expansion without digging the ground up but you would need to talk to whoever is doing the installation/planning about it for your particular instance.

Mr.Boy

To clarify, this is totally separate to our house, it's a separate building on its own supply. The powergrid guys put the meter on a wall of our drive for us to lay the cable to the cabin, because "it'll cost you 10X as much if we do it". So a 10m trench from supply to cabin.

What I'm asking is if the input from your PV goes back down same cables or has an entirely separate circuit back to the supply box? I kind of assume it must be the latter, your electricity meter effectively ends up having IN and OUT cables instead of just OUT?

I need to look up the basic anatomy of a PV setup but I think everything would be in the cabin and in that case there'd be a single chunky extra cable back to the supply?

ABrass

On the BC side adding solar panels requires BC sign off as an alteration. They add roughly 10-20kg per square meter to your roof. If you're going for something lighter than concrete tiles you're adding a large fraction of the roof weight.

If you've already submitted plans you'll probably need to amend them, if not then just include it in your plans. I believe you'll be saving VAT if you do it all as a new build rather than an alteration but that's outside my area of not-expertise.

Mr.Boy

We are kind of expecting BC to push us towards renewables for energy energy but absolutely, they will need to know. The plans are still being reviewed so good to alert them early.

Thanks.

joefizz

d000hg wrote: »

To clarify, this is totally separate to our house, it's a separate building on its own supply. The powergrid guys put the meter on a wall of our drive for us to lay the cable to the cabin, because "it'll cost you 10X as much if we do it". So a 10m trench from supply to cabin.

What I'm asking is if the input from your PV goes back down same cables or has an entirely separate circuit back to the supply box? I kind of assume it must be the latter, your electricity meter effectively ends up having IN and OUT cables instead of just OUT?

I need to look up the basic anatomy of a PV setup but I think everything would be in the cabin and in that case there'd be a single chunky extra cable back to the supply?

Ah ok, I have a similar setup but 4m away but have the panels feeding the inverter in the house (the panels on the garage were an extension to an existing system).


If your cabin is operating as an independent property with an independent supply from the grid then the supply installed should cope with the installation although you may need to contact your DNO for permission and if you want to sell electricity to the grid you may need an import/export meter. Still check with your electrician but if its household supply armoured cable then you should be fine, if its something like 10A then you wont be.
Leave it to them to source the cable etc.