Solar PV >>> technical question

Sterlingtimes

I have a quotation from a supplier who has made a proposal that I did not expect.

They intend to install 16 panels as follows:

10 panels on a roof at 200 degrees (i.e. facing 20 degrees west of south); and

6 more panels on a roof at 110 degrees (i.e. facing 20 degrees south of east).

This would use the full area of both rooves.

The inclination of each roof is 30 degrees.

There are some trees to the easterly aspect.

Does this proposal, subject to other variables, make sense?

Martyn1981

Hiya, sounds fine ..... subject to how much shading you'll get from the easterly trees. If minimal, and during the poorer months, then no worries.

If rooves are a little small, then using em all is fine. Just make sure all conversations involving the inverter mention that it's a 'dual MPPT' inverter, so that the rooves will connect to it separately, that way they won't effect each other.

I have a large Magnolia (and a neighbours house) directly in front of my ESE (also 110d) systems .... about 60ft & 100ft away respectively. My annual generation is still very close to the PVGIS guestimates without shading.

Personally, I've always thought that a SE+SW split (you're very close to that) is better than all south, as it'll spread generation a little flatter and wider through the day, so you can make better use of it.

Mart.

Sterlingtimes

Thank you Martyn, this is an encouraging response.

I did a separate test on the Energy Saving Trust website for the easterly facing roof and that seems to work.

The tree shading may be more than minimum so the suveyor would need to check.

I will ask the question in due course about the "dual MPPT" inverter.

Again, many thanks, Sterling.

Martyn1981

Sterlingtimes wrote: »

Thank you Martyn, this is an encouraging response.

I did a separate test on the Energy Saving Trust website for the easterly facing roof and that seems to work.

No probs, but, can I just warn you about a few things on the EST website, as I had a lovely chat with them on Friday, and they are going to revue some, but others they can't. Given that they were taking a call from a 'nobody' criticising their website, I think they were very fair and open, but for now:-

Firstly, the calculator suggests that there will be a tariff drop in October .... there won't be, the next drop is 3.5% on 1/1/15, as confirmed by OFGEM back in July. So if you saw that, don't rush.

Secondly, their calculator is a bit dodgy when it comes to leccy savings. It estimates 25% savings against generation estimate and at 13.5p. This works on the 1kW example, but not on the 4kW example, so something has gone wrong.

Thirdly, those leccy savings take no account of a small system covering baseload, so massively underestimates the savings from a small system. They acknowledged that this may be the case, but it's too hard to explain on their site (I agree).

Fourthly, they state average prices as being £6k to £7.4k. I suggested that these seem about 6 to 12 months behind. They confirmed that the prices are based on Aug 13 to July 14 prices (after removing the top and bottom 5%). So it doesn't really reflect the lower prices people on here have been reporting since Spring(ish).

All pedantic points, but worth being aware of if you've formed a gut feeling based on their info.

Mart.

Sterlingtimes

Great posting, Martyn.

It will be a few weeks until I have the cash to invest, but generally the figures work for me. As I get closer to retirement, my logic is that that tax-free and index-linked income combined with spending more day light hours at home looks like a sound investment.

I was confused by the October cut-off at the EST site.

Quotes seem to be relatively fixed at just under £6,000 for a 16 panel system. Clearly, competition has hit in and providers are price matching.

tunnel

Depending on the outcome from the surveyor concerning your trees(shading) why not ask to price up a system using a solaredge inverter with power optimisers. Both Mart and I have these but it would only be of benefit if the shading becomes a problem in the summer rather than low generation(low sun) winter months.

Sterlingtimes

tunnel wrote: »

Depending on the outcome from the surveyor concerning your trees(shading) why not ask to price up a system using a solaredge inverter with power optimisers. Both Mart and I have these but it would only be of benefit if the shading becomes a problem in the summer rather than low generation(low sun) winter months.

Thank you, I will ask these questions in due course. I will need to do a little research first.

Martyn1981

Sterlingtimes wrote: »

I was confused by the October cut-off at the EST site.

To be fair, well done to them for the warning, which did carry the disclaimer:

This tariff rate has not been confirmed and is provided for guidance only.

but not so well done for still displaying it 6 weeks after OFGEM had confirmed no qtr4 degression.

I've just knocked up a new section:- 12. FiT Degressions for the PV FAQ. Of course, now it's up to me to try to keep it up to date, so not so funny when the shoe's on the other foot!

Mart.

Sterlingtimes

tunnel wrote: »

Depending on the outcome from the surveyor concerning your trees(shading) why not ask to price up a system using a solaredge inverter with power optimisers. Both Mart and I have these but it would only be of benefit if the shading becomes a problem in the summer rather than low generation(low sun) winter months.

Thank you. I have followed-up your suggestion.

So the standard 16 panel quote is just £5,895 but with Solaredge plus optimisers adding £660. The additions, I am told, should add between 6% to 10% to the annual generation. The supplier will have another look at the trees and revert to me tomorrow evening.

Is this ok?

Regards, Sterling

tunnel

Hi Sterling(moss?)

The PO's should come in around £600 but not knowing what type of inverter you were quoted for originally its hard to say if its a good or bad deal

I'd like to think you could bring it in under £6k inc the solaredge, especially with some of the prices that's been banded about of late. Not really sure about the 6-10% improvement either unless you have some bad shading.

Obviously you may not need that type of inverter, best to check and double check, no point spending more than you need to

Sterlingtimes

Sorry all, here is another query.


I have been offered a 16 x 250 watt system, i.e. 4,000 watts.


Alongside this I have been offered a Solaredge 2200 inverter.


The data for the inverter indicates a maximum DC input of 2400 watts and an AC output of 2200 watts.


Is there a problem here?