new performance estimates - comments on solar portal

[Gavin A]

erm right, so I've just gone and critiqued the new performance estimates and shading estimates methods in a comment on Martin Cotterells blog on solar power portal, and am now feeling slightly vulnerable for having stuck my neck out on there.

If anyone is thinking similar things about the performance estimates requirements, I'd appreciate it if you'd also stick a comment on there so I'm not seeming like so much of a long voice (it helps that the head of the solar design company has also written a guest blog saying much the same things, but some more installer input might help to get this changed before we're all forced to conduct complex additional performance estimates that are much less accurate than the estimates produced either via the method we use, or via the likes of PVSOL.

In the interim, the change I'd like to see made is for performance estimates made using more accurate methods approved by the MCS inspectors, to be allowed to be used instead of the MCS method.

ie that the MCS method becomes an absolute minimum standard, but methods that are more accurate are allowed to be used instead.

 

[whinmoor]

I went to visit a house recently that had no upstairs window beneath the roof where the panels would go. If I did a sunpath diagram from the ground, it would be 100% shaded due to a row of trees which were well below the guttering. I had a ladder with me but didn't fancy doing a silly sketch perched on it in the wind and rain so I'm going to stick with the old method for now.

Also, there was a chimney in the centre of the roof which wouldn't be visible from an upstairs window but would clearly affect output. I'm not sure if/how that is catered for in the new methodology.

 

[SolarCity]

Comment posted.

 

[Worcester]

It's a farce, and to help we've created a MCS overlay to go on the sunpath tool from test-meter.co.uk

I still haven't understood what your supposed to do on a roof that faces east - What shadow do you take for before 12 when the irradiance already covers that issue? Do I really have a shading factor of 0.6?

(Even resorted to buying a printed copy of the guidde as the pdf was unreadable in the way it cross references and jumps about)

 

[finchy]

To be honest I need to spend sometime looking at all this. I'm putting it off as long as possible.

 

[JulianC]

You and me both

 

[dansk]

Gavin im with you on this one - and Whinmoor, your more to the point about being perched on a ladder, turned around 180d to face the horizon then try and sketch something in the wind and rain of the ladder.

 

[dansk]

commented.

 

[zeljuga]

Citat"(We have a micro-inverter that has an input from two PV modules ... Looking at the new Guide (page 37, 2.1.12.4, bullet point 1) - does this mean it cannot be installed in the UK?

A: This inverter can be used. However, this clause means you will have to fit a DC isolator between the PV modules and the inverter )

??????????. More business for DC switch manufacturers.

 

[Gavin A]

Citat"(We have a micro-inverter that has an input from two PV modules ... Looking at the new Guide (page 37, 2.1.12.4, bullet point 1) - does this mean it cannot be installed in the UK?

A: This inverter can be used. However, this clause means you will have to fit a DC isolator between the PV modules and the inverter )

??????????. More business for DC switch manufacturers.

yeah that was on my hit list as well.

wtf is the point in making us install 2 x dc isolators per microinverter when the isolators would have to go behind the panel anyway, and it's going to create 4 x additional joints per panel plus the potential for none water proofing at the glands... or if they want the isolator mounted internally then that's 16 cable entry points per 4kWp system.

personally I have no intention at all of following that point, and think it makes a mockery of the entire guide to have ridiculous things like that in it.

 

[Somecamel]

What are you guys doing for Electricity saved? Still 50% of Ofgem average 3300kWPa @ 15p?

 

[SRE]

25% for 4kwp, 35% for 3kwp & 50% for anything 2 and under - unless there are specific circumstances that would justify a higher rate.

 

[finchy]

Is that your own guidance ? Or did I miss and update in the code. @25% makes the figures coming in lower. I do 50% across the board although a g59 job I did 100% due to amount of power usage. I did think about tracking new customers usage and go back after a week or so to give an accurate saving with obvious caveats time of yr etc, those were the days when solar customers were plentiful. Now it's price price price, as already said it was easier selling a 14k at 12% return than it is 6k with the same return.....

 

[SRE]

It's our guidance, we try to be realistic about savings - I'm beginning to think we're too honest!! EST did some research about 18 months ago showing that 25% was a fairly accurate assessment of savings and that 50% was too high. My own usage is about 25% and I'm in 80% of the time, working from home, diligently trying to use as much as I can.

 

[Somecamel]

I had a look at the new SAP performance the other day and being down south obviously get much better results than SAP 2009. I've been taking an energy monitor with me on appointments now to see what the customers baseload power is and working out bill savings on that a lot of the time. With prices going up and tariffs going down something has to give.