Getting quotes for solar pv - but what panels are decent

[Tabraz Khan]

Shading can cause complex problems. Some people insist on a system of the largest size that can be squeezed on a roof, when, in fact, reducing the number of panels by one or two might make it work so much better. With shading, it can only take one or two panels to be affected for it to knock-on to all the others.


Can you use google maps to get a zoomed-in aerial view of your roof plus the nearby buildings, and post the picture here?

Clicking on this picture should take you to 8 snapshots i've taken from google earth.



here is the direct link : http://imageupper.com/g/?galID=S020001007O13773508651996751&n=1

I was concerned the the neighbour house (Dr Surgery) being taller than mine would cause shading in early hours - whilst this might be true looking at different images on google earth (from different years and months) it seems to be ok - however the sun path feature on google earth shows a different picture.

Space wise seems i have 5.1 metre diameter upto chimney (got more space on lower rows) and approx 4.6 metre in height from front to ridge.

I also have a the possibility of the dorma which is 2.6*1.8m.

So seems I can have a 2.75 system if i fit 11 250 panel on front - possibly 3.25kw if dorma is used (can 2 panels go there?) or 12 panel 4kw without using dorma if i opt for sunpower 327 panel which are smaller size - what kind of premium would that be ?

 

[Earthstore]

Hi, I think you need to get some help from a decent company, personally I would not use the dormer for a few reasons, as to Sunpower, which are the best on the market you really have to do your sums on that to see if the extra outlay can be justified in the return, which can get very complex due to your energy usage.

Why not just get someone from here to quote for you, there are some very good companies here??

 

[Tabraz Khan]

Hi, I think you need to get some help from a decent company, personally I would not use the dormer for a few reasons, as to Sunpower, which are the best on the market you really have to do your sums on that to see if the extra outlay can be justified in the return, which can get very complex due to your energy usage.

Why not just get someone from here to quote for you, there are some very good companies here??

I have approached a couple of people via the forum to quote me. If anyone else is local to Birmingham and/or wishes to quote please private message me and I shall give you my details.

Tabraz

 

[FB.]

The panels will be free from shading at peak generation time from late-morning to mid-afternoon. That's a good thing, and your problems will be relatively minor.

The height difference between your house and the slightly taller building next door won't cause much of a problem - probably no more than 5% loss of output and no losses at peak generation time (lunchtime) nor on cloudy days when it is just light reflecting off the clouds above that powers the panels.

The chimney is slightly more of a concern, with it casting a "hard shadow". There will be no shading from the chimney until 1pm in summer (2pm in winter due to clock change, but by then the sun will be close to setting and weak by the time the chimney causes a problem).
In summer, from 2pm onwards the upper row of panels will suffer gradually more shading as the sun moves round. By about 5pm you could have two or three panels dropping-out of the string due to shading. The chimney might well knock 10-15% off the annual total generation by confusing the inverter from mid-afternoon, but won't affect the ability to reach peak output of 2.5kW around mid-day.
Panels on the upper row near the chimney might benefit from being in portrait layout, which will knock out less of the panel from shading than in landscape layout, due to the way the bypass diodes are arranged. A few panels - such as Panasonic/Sanyo have a different layout of the cells relative to the bypass diodes.

Some inverters have a setting which helps to more regularly scan a wider optimum voltage range than older or lower-tech inverters. This can overcome panels dropping-out of the string due to hard shading, and with a suitable inverter you'd probably be under 5% losses from the chimney.

If the roof was larger (or the panels smaller), it might have been possible to fit the panels as two strings - say 6 or 7 in each row, operated by two independent processors in the inverter so that at least the lower panels aren't impaired by shading on the upper panels. But smaller strings of about five panels often don't have enough voltage to meet an inverter's startup requirement.

Putting panels on the rear roof extension might cause more problems than it's worth because of the flat roof presenting a very different angle to the sun compared to the sloped roof on the front of the house. It'd be similar to partially shading some panels in the string, and is an example of where, sometimes, "less is more".

 

[series530]

As a consumer there is also another way to consider this purchase: we've taken the micro inverter route as we suffer from shading at certain times of the day. I'm not, for one moment, suggesting that this is the route that you should take as this adds tremendously to the cost and complexity. We took the micro inverter route because we saw the installation as a longer term investment rather than a short term money earner. We bought when the FIT was paying the most but, conversely, the cost of the systems were highest. Each year, the return we get we see as a kind of annuity payment as opposed to anything else. Averaged out over 25 years, even poor performing panels will, hopefully, pay for themselves and a lot more besides. Thus, having some shading may not be an issue as it simply means that the shaded panels take longer to pay the investment costs.

This approach, however, requires extremely careful up front system design. You cannot simply wack a load of panels on a roof which suffers from shading for all of the very good reasons outlined in previous posts because you need to bear in mind that any shading will affect overall performance: a small amount of dappled shading may be handled successfully by a decent inverter. A modest amount of heavy shading could kill a badly installed system output. Careful system design, thus, is vital.

One other consideration is aesthetics: how many times have you driven along a road and comment how ugly an installation looks? I've done it many times. While a badly installed system may give a return through the FIT it could knock twice as much off the value of the property and is, thus, a very unsound investment unless the owner has no intention of ever selling the property.

We found that the cheapest system are cheap for a reason: they often use inferior components which, as pointed out, won't drastically affect you ROI but, if those components are simply thrown up on the roof without careful thought to system design (efficiency working together, quality of cable runs, remote monitoring, shading analysis, load bearing analysis, functionality of the roof in conditions of high wind and rain) and if the system comes without an insurance backed guarantee, it could be a false economy in the long run.

 

[SolarCity]

Just a thought on micro-inverters/optimisers:

We recently replaced a Solar Edge optimiser on an install where the original installer ceased trading. It cost the homeowner our labour and a scaffold erection to rectify it. He has 15 other optimisers on that install - each of them at risk of failing in the future. Replacing these can be expensive.

We will only install these as an exclusion to our warranty. Simple fact is, we cannot afford to erect a scaffold every time a Solar Edge optimisers fails - which they demonstrably do.

Margins are too small now and if Solar Edge can't support their product better - by including labour and scaffold under their warranty - then they simply are no longer an option.

 

[series530]

Just a thought on micro-inverters/optimisers:

We recently replaced a Solar Edge optimiser on an install where the original installer ceased trading. It cost the homeowner our labour and a scaffold erection to rectify it. He has 15 other optimisers on that install - each of them at risk of failing in the future. Replacing these can be expensive.

We will only install these as an exclusion to our warranty. Simple fact is, we cannot afford to erect a scaffold every time a Solar Edge optimisers fails - which they demonstrably do.

Margins are too small now and if Solar Edge can't support their product better - by including labour and scaffold under their warranty - then they simply are no longer an option.

I agree, any individual component comes with risk of failure and provision needs to be made. In our case, like anybody else, the solar panels are on the roof and subject to the same risks as any other panel. I deliberately specified having the micro inverters inside the roof space and easily accessible. I got written confirmation from the micro inverter manufacturer that they were rated for usage inside a roof space. Finally, I specified an insurance backed guarantee so as to provide some third party coverage in the event that my installer ceased trading.

A good installer who has longer term customer satisfaction in mind in addition to costs which would be attributed to him in the event of a call out will consider risks and counter measures at the design stage and price the job accordingly. A pile high sell cheap installer will not. Sadly though, the public is easily seduced by cheap pricing structures and this works against the advantages and costs of good up front design. In some ways, the public get what they deserve.

In my case, being an engineer by profession, I am seduced by the technical design and longer term pay back of the system and not simply by a cheap upfront cost. A few share my approach to capital purchases but so many people simply see the financial bottom line at the point of purchase and pick the cheapest.

 

[FB.]

I saw a house for sale on Rightmove about a week ago (now sold) and it has solar panels in a curious layout that detract from the look of the property (IMO) - see picture 16.

4 bedroom detached house for sale in Holly Bush Way, Linton, CB21

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[series530]

I saw a house for sale on Rightmove about a week ago (now sold) and it has solar panels in a curious layout that detract from the look of the property (IMO) - see picture 16.

4 bedroom detached house for sale in Holly Bush Way, Linton, CB21

.

I have to agree! I cant help but wonder why the majority of the panels were not arranged in a line along the base of the roof. I also hope that there is sufficient clearance along the bottom so that rainwater reliably finds its way into the guttering system.

 

[Worcester]

Bet they didn't spilt it into two strings for the portrait and landscape panels as well...and they probably paid well over the odds for it ...