New MCS MIS3002 and PV Guide

[Ian-LS]

We have quite often done this with a shading selector tool to assess the shading. Its fairly simple to do but you have to be careful to take into account the orientation of the roof, an east facing system with shading up until 10 am throughout the year would have a massive impact on the system potentially making it unsuitable. Whereas a south facing roof with shading up till 10 am the shading losses would be in the region of 5-10% roughly.

 

[Gavin A]

hmm.

There's a few things I'm not happy with in there...

Performance estimates are basically just an updating of the flawed SAP methods and are only marginally better, but fiendishly complex - they're certainly not going to stop any of the dodgy lying gits in the shiny suits from lying through their teeth about performance estimates then going bust before the liability claims roll in. As I read this they're at best around 15-20% accurate once you take into account the +/- 10% accuracy of the shading estimate, and the 15-20% varation from the average sunlight levels there is for our region (East Penines) between the east coast, and the Penine areas.

Fair enough if companies don't have a better system than this, then make them use this method, but it's ridiculous to make companies give greater prominance to such a flawed methodology than to a far more sophisticated and accurate method using 3d modelling for shading impact, and PVGIS for highly accurate localised sunlight and temperature data.

It also severely penalises those using more efficient inverter set ups as it makes no allowance for this at all that I can see, yet there can be a 5% performance advantage between an old style inverter and the latest high efficiency TL inverters operating at the peak efficiency point. The shading factor also makes no allowances for inverters with shading functions, or micro inverters, or system designs with dual trackers and correctly orinetated panels to minimise the shading impact, it's just a one size fits all package that means all companies will have to estimate the same output from all system designs, which will put more costly but better performing systems at a distinct disadvantage.

TBH I'm pretty well minded to tell them that we're going to refuse to comply with this guidance as we don't think companies should be penalised for using better equipment, better system designs, and much more accurate methods of producing performance estimates. Let's see them make that one stick in court if they dared to take it that far.

 

[SibertSolar]

Looks like the Kk value for projected yields (per postcode zone) have already been multiplied by 0.8. There are some "handy" disclaimers that the Guide recommends to be used when presenting your proposals to end-clients, but it's clear that what these techniques will effectively do is to remove any differentiators between panels/inverters from one manufacturer and another. Should you decide to also provide additional analytical information to your end-client, the provision of the below statement seems to be required:

3.7.9 Additional Estimates
Additional estimates may be provided using an alternative methodology, including proprietary
software packages, but any such estimates must clearly describe and justify the approach taken
and factors used and must not be given greater prominence than the standard MCS estimate. In
addition, it must be accompanied by a warning stating that it should be treated with caution if it is
significantly greater than the result given by the standard method.

 

[SibertSolar]

Anyone need one of these?......

 

[Gavin A]

I'd quite like the bubble putting back into one of them we've got, as the bubble escaped somewhere which makes it a bit hard to know if it's level or not.

 

[SibertSolar]

Oh dear, that's not good, always a bit tricky when the bubble escapes..... ;-)

 

[JulianC]

Anyone need one of these?......
View attachment 17126

Quite possibly! Would be grateful of a price, if you are offering them. Ta.

 

[SolarCity]

My fears are similar to Gavin's. While I am in favour of a more accurate survey procedure, it is obvious that the unscrupulous (and incompetent) surveyors will understate the shading involved. When a customer then compares quotes, they are fooled into thinking that the (often more expensive) quote which promises higher returns is a better option when it clearly isn't.

The method looks ok but to get an accurate idea of what is happening you would need to get on the roof. Working from a window just doesn't cut it in my opinion.

I'd still like to know why my empirically provable more accurate PV Sol Expert estimates can't be given more prominence than the SAP method.

 

[Gavin A]

yeah, still it's better than the other 2 that have developed legs and gone walkies

 

[Gavin A]

Quite possibly! Would be grateful of a price, if you are offering them. Ta.

with or without bubble?

I've got a great new line in second hand versions without a bubble....

 

[JulianC]

I might have a couple of spare bubbles in a drawer somewhere...

 

[whinmoor]

The method looks ok but to get an accurate idea of what is happening you would need to get on the roof. Working from a window just doesn't cut it in my opinion.

I doubt the salesmen in shiny suits even go in the loft so there's not much chance of them climbing a ladder to the roof. In fact, they probably wouldn't know how to tie a ladder to a roof-rack on their VW Golf.

 

[jerriais]

Solmetric SunEye

For anyone with £2K to hand this is really the canine kahunas ...

Use it with the extension kit and it should take just a few minutes to get the full shade picture without needing to hang out of an upstairs window.

 

[whinmoor]

Solmetric SunEye

For anyone with £2K to hand this is really the canine kahunas ...

Use it with the extension kit and it should take just a few minutes to get the full shade picture without needing to hang out of an upstairs window.

Damn - Santa's just been and didn't bring this... At least we all know what to ask for birthday presents this year!

 

[dansk]

other than the hand held tool - were do you buy a sun path diagramm to draw on?