Advice on PV Installation costs.

[mac1]

I am new to MCS, A customer want me to give a price to fit a 10 KW PV system to a flat roof ( 3 phase supply available). Is it better to fit 3 x single phase systems or use a 3 phase inverter?
I know prices of panels vary but can anyone give me an idea of what a reasonable cost for fitting a 10 KW PV system to a large flat roof would be. No special access is required because there is access to the roof within the building.
Can anyone recommend a type of panel to use in this situation.
Thanks.

 

[Worcester]

When fitting to flat roof, bear in mind that the roof needs to last for 25 years also, otherwise the sytem may not be compliant ....

Just got one case where he's going to have to replace it all first, it probably has 10 years worth of life left in it, if he doesn't replace we will put loads of riders and waivers in the contract!

Most are sensible about it since this is a £40 - £50k investment depending upon loads of factors, and he's in danger of messing up his ROI if he doesn't, also remember unless unusal circumstances it'll be 20% VAT.

 

[mac1]

Hi thank you for that info, I never thought of how long the roof will last?? It is in good condition and fibre Glass but I agree to have wavers in the contract about the roof.
Would you fit 3 x single phase inverters or one 3 phase? . I think 3 single phase inverters would be more reliable. If one stops at least the other 2 carry on but if a 3 phase inverter stops working it all goes down!
What is the cut off point for 5% vat on an installation?

 

[Worcester]

The VAT is not down to size, it's the type of customer.

The reduced rate applies to the installation of certain specified energy-saving
materials (see paragraph 2.5) in:
• residential accommodation (see paragraph 2.16); or
• a building used solely for a relevant charitable purpose (see
paragraph 2.17).

Full details here: HM Revenue & Customs


3 Phase inverters / 3 x 1 there are others on this forum far more qualified rhan I am to answer that one!

 

[Worcester]

OK, here’s my stab at one inverter or three.

Three inverters, - You've basically got three separate systems here, so you'll need to make sure they are balanced, and put equal amounts into each phase, as you are only allowed so much imbalance.

So your panel layout needs to make sure that each array gets similar amounts of sun, shading, orientation, etc (and needs to be a multiple of 3, or maybe 6 or maybe 9 or 12 depending upon the inverter you choose)

Single inverter actually generates three phases, so you don't necessarily need to be a multiplier of 3, that gives you lots more flexibility on the number of panels that you can install to match the roof layout. e.g. Fronius IG120 Plus will take 4 strings of 10 panels and equally distribute the generated output across three phases.

 

[mac1]

(10 kw PV system fitted to flat roof) Hi thanks for the advice, I am buying the kit from a company called Waxman they have recommended using a Sunny Boy STP-10000TL 3 phase inverter which sounds ok but has designed it to have 2 strings - 1 string with 23 x 240w panels and the 2nd string with 18 x 240w panels. I would appreciate any comments on this design. Is there any software I can use to design it myself?

 

[edexlab]

Sunny design its free from manufacturer
and 2 strings is fine this configuration would be 1 string on each input as they are unequal no of modules but you need to check for yourself as you are responsible for the design as the installer
what modules are you using?

 

[BruceB]

Download Sunny Design from SMA to do it yourself. That has all the inverters and panels built in. However for soime reason it thinks the Sunny Tripower 10000TL is not certified for UK and so will not offer it as an option unless you insist. I think there is a good chance the 10000TL has got a G83 certificate because a) it is sold here and b) all the Tripower sizes are listed on the certificate that is on the SMA website.

Regards
Bruce

 

[edexlab]

Download Sunny Design from SMA to do it yourself. That has all the inverters and panels built in. However for soime reason it thinks the Sunny Tripower 10000TL is not certified for UK and so will not offer it as an option unless you insist. I think there is a good chance the 10000TL has got a G83 certificate because a) it is sold here and b) all the Tripower sizes are listed on the certificate that is on the SMA website.

Regards
Bruce

Leave the country settings on Germany and go back and change to uk after design is done or you can alter the settings but this will give you every inverter that they make( the majority do not have G83)

 

[SolarCity]

Three inverters, - You've basically got three separate systems here, so you'll need to make sure they are balanced, and put equal amounts into each phase, as you are only allowed so much imbalance.

I never knew this was such an issue. I would have thought keeping systems seperate so that shaded areas only affect one inverter would be far more desirable than unbalanced 3 phase load. Unless the system was very large and the shading was severe.

 

[beefheart]

me too, how much imbalance is allowed?