Project Solar quote / Install

Martyn1981

Exiled_Tyke wrote: »

Solar Edge is not needed here. Most inverters allow for two independent strings, so one dedicated to each roof in this set up.

Yep agree, but checked the inverter specs just in case for minimum MPPT voltage per string, and again you're right with 100V start up, 70V minimum range, and 80V minimum for MPPT(s), so 4+ panels are needed and 3+ panels per string. Quite a versatile range on that inverter.

So the question comes back to shading and how much that matters early in the morning for the SSE and later in the afternoon for the WNW.

Hellfire8

Do you mean shading/obstruction? there isn't any on either, except 0.1 winter only on the westerly portion, (roof 2)

Exiled_Tyke

Hellfire8 wrote: »

Do you mean shading/obstruction? there isn't any on either, except 0.1 winter only on the westerly portion, (roof 2)

I seriously don't understand why installers try to simplify the issue of the sun moving across the roof of a house into a single percentage figure. Each day the sun takes a different path. Where I live, on the shortest day the sun doesn't reach 13o above the horizon. The sun rises in the SE (131o) and sets at 229o (SW). During these days even the most distant tree manages to cast a shadow on my roof at some point. (In contrast by the way at the peak of summer the arc is 46o to 314o with the sun getting to just short of 60o above the horizon).

So what on earth does 0.1 mean? I really have no idea - is it an average of 10% shading - if so across what period of the year (what is defined as 'winter'). On a winter's day does the roof never get more than 90% or does it do better and worse at different times of they. I suppose the suggestion is that in 'winter' this roof will average 90% of an equivalent roof's generation - but that still isn't 10% of shading - strictly speaking.

Of course my real issue and experience is that an installer will come round have a quick look and then pluck at what will at best be a terribly poor estimate because they really haven't researched the detail for each individual roof, aspect and most importantly latitude. They've just had a look around and said 'Yup, there's a hedge over there, we'll knock 5% off for that'.

These are good tools to help understand the sun's path across the seasons.

https://www.timeanddate.com/sun/uk
http://suncalc.net/#/51.5074,-0.1278,10/2016.03.21/17:31

This last one has fallen foul of googlemaps new expensive regime to developers, but it still works adequately.

Ultimately though the only solution must surely be to go out and have a good look at your roof at different times of the day. Now is a good time of year to do that as there are days where you can still get decent generation but shading can become a problem. Much later in the year it matters less: 10% of almost zero generation is still almost zero.

Rant now over - with apologies where due.

Hellfire8

Hi,

Totally get what you mean, I'll look into it,


Another quote came in, quoted 285w (that's what I asked for, 4KW yesterday) but will speak about upping to 300w panels,

14 x Perlight 285w Mono Triple Black 3.99kwp with Solis 3.6 Dual Tracker Inverter
£5394.99 Inc VAT

Hellfire8

Okay, shopping around has worked, previous company I spoke to has sharpened his pencil.

£5,500 for

14, Perlight 300w panels
Growatt 3600
Geo Solo III

Appreciate it's on the higher end but speaking to some people in my area this company have a very good reputation for quality of work. So I don't mind paying the premium.

pinnks

Recommendation is always worth a premium in my mind.

Do you have an immersion tank? If so, perhaps you could get them to add an Eddi or iBoost or similar diverter to use some of your hot water from the panels. These things cost a few hundred retail, so as an add-on would soften the blow as it were. I would go for one even at full price to be honest...:beer:

Hellfire8

Thanks, we are gas heating and on a Combi boiler so no tank. :-)

pinnks

Oh well… you can also power underfloor heating or oil-filled radiators or anything else that is a pure resistive load using them too but any gains in those circumstances would be minimal as you only need that type of device in the shoulder or winter months when you generate far less anyway....

Hellfire8

Hi guys,

Thought I'd give you an update, So discussing with the engineer and surveyor we finally have it set out.

Plans are done, we've upped the panels to the 300w models, We've managed to fit an extra panel on the front so it'll be a 4500w system

9 panels at -25 degrees off south PVGIS estimates 2750 KW per year
6 panels at +65 degrees off south PVGIS estimates 1570 KW per year

Total is 4320 KW compared to the 3340 KW we were originally looking at, So an extra panel and upping them to 300w panels produces almost 1000 KW extra a year which is amazing.

What also makes it better is due to competitor quotes I managed to work this into the original price of £5500.

So I am super happy with this and will be confirming and paying the deposit down soon.

Any thoughts before I do?