DTI Guide Shade Analysis

[SRE]

So - P63 says - "The sunpath diagram below shall be used to produce a shading analysis for all estimates produced" :frown2: without wishing to spark another debate about the inadequacy of this method is anyone just ignoring it and providing PVsol shading analysis with quotes as usual? I don't have the luxury of 3d so mine would have to be 2d - with our business the way it is at the moment I couldn't justify the upgrade costs.

 

[Gavin A]

as their shadow analysis only works for south facing systems I'm ignoring it as not fit for purpose.

also IMO it falls foul of HSE working at height guidance as the only way to get accurate figures for close up shading is to be on the roof, and HSE states that the first step in working at heights is to avoid working at heights where other alternatives are available. HSE trumps MCS.

 

[SRE]

Ok- I concede - I'm obviously a sandwich short of a picnic!

Here are the photos of this afternoon's shade analysis using the solar path gadget. Once taken as Martin Cotteril suggests at window level and one from the gutter - completing ignoring any H&S at all.

The lines on the photo from the bottom up are 21st Dec, 21st Oct, 21st March, 21 April.

From the window there's significant shading until 21st March although not quite sure how clothes on a line below an array and decidous trees can make a huge difference.
From the gutter most of the shading has gone by 21st October.

In reality there's only one tree that provides a slight shade in the Winter if you look carefully you can see it's huge above the Summer House. Nothing else comes anywhere near the panels other than the telephone wire that runs right across the panels.

Using the window shade figures we should generate 2158 kwh/pa
Using the gutter figures we should generate 2565kwh/pa
Using PVsol figures we should generate are 2571 kwh/pa

We've had our panels installed since Nov 2010 - 943 days, generated 8051 kwh/943 days x 365 days gives a skewed actual generation of 3116 kwh not taking into account the next 6 months when we will generate the most.

What am I missing - I'll never sell anything using the new figures

 

[whinmoor]

No way am I doing that !!

 

[Worcester]

I hate heights (and I've got a cherry picker licence!), Also I was told on my first ever site saftey briefing (before the H&SE existed ...) "One in Three of you will get killed on the job" - At that moment I vowed that I wasn't going to be one of those....

As GavinA says HSE trumps MCS any day

 

[SolarCity]

I think I'll do a similar 'survey' on the job we're doing tomorrow and see how it goes.

 

[dansk]

I dont do enough solar to be bothered about this nonsense - SRE thanks for the photos, very interesting and a hat of Lawrence for risking his neck!

Ill carry on the way i have for the past few years.

 

[solarsavings]

All around me people are ignoring the rules with regards to the mcs and real malarky and getting away with it.(a company Jason mention on the open forum have directors that have been kicked off twice and are back for a third time) So after a nice relaxing holiday and a directors meeting with myself I've decided if you can't beat them.........................................---- em!!! I'm not using it.

 

[Gavin A]

good man.

 

[Gavin A]

bump - so is anyone at all using the MCS method?

 

[Worcester]

Er... not in full we will comply, however the horizon chart is so impractical to use ....
So we use it with the Solar Horizon Meter and a custom re-calibrated transaparency to fit it, - mark on it with a dry marker then scan it for the customer and records. I also use am iphone app to ascertain the real horizon - theodolite - my engineering helps understnad how to use that and relate it back to the real horizon that the roof 'sees' plus I take panoramic photographs, plus if nescessary then either import the info as a horizon file or 3D model in PV*Sol.

A lot of work I know, however to go that far I know i have already effectively got the order, - it's down to a) the way I get the prospects / clients in the first place, b) position us during the presentation / survey and c) sometimes I won't even bother quoting after the visit.

 

[Worcester]

Just done another full analysis of one site as above - MCS method using our Solar Horixon Meter said deduct 27%, detailed 3D analysis in PV*Sol says overall impact is ....... 28%

 

[Gavin A]

any idea how PVSol actually does those calculations?

28% sounds pretty high to me, or maybe we'd just have ruled those sites out from an initial remote survey before we even got to that stage / design around it.

Also do you know how PVSol predictions actually compare to reality in shaded conditions?

sorry for all the questions.

 

[Worcester]

Did it two ways in PV*Sol, so I'm happy that with a good 3D model, you should get similar results.
1) used the horizon model in PV*Sol, inputting the data manually - (there's got to be a way to import it from a csv file, just not found it yet)
and
2) Looking at the animation sequences at various intervals during the year and comparing with actual at the site - a) on the day and tie of the survey) and b) from photographic observations supplied by the client taken over the last year.

Doesn't mean that I'm happy with the new guide's horizon chart in all circumstances, it was good for this one as it faced due south and I could safely get up to bottom of first panel level.

 

[t4sltd]

I'm using the Cotterill shading method cos thats what I've been told I have to do.
I measure the locations and heights of obstacles using a laser level to work out wherre they feature on the solar horizon.
Its obviously rubbish (and open to varying intepretation) but I always try and avoid putting panels in the shade anyway.