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Author Topic: Newbie wanting advice on PV install  (Read 14103 times)
lisyloo
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« on: January 31, 2014, 10:25:43 AM »

Hiya - I'm a newbie and I'm looking into a PV install.
Our roof is a bit messy. We have 3 potential places where panels can go.

Main part of the roof (A) which faces SW at 230 degrees.
Gable end (B) which faces SE at 140 degrees.
Another large area (C) which faces SE at 140 degrees but has 2 dormer windows, 1 velux window and no roof space.

I've had 2 quotes so far, plus 1 company walk away (presumably because it's messy).

First quote is 5950 for 6 (Gallium 250W) panels on A, 4 panels on B and 2 on C. This design is aesthetically unpleasing as the 2 panels on C will be different orientations. I believe that B and C will use the same feed to the inverter and there will be lots of DC cable to reach C (It's a 5 bed house).

Second quote is for 8 (Axitec or BenQ) panels on A, 4 panels on B and this company don't recommend having lots of DC cable going to C.
Quotes are 6500 for 12 x 250W panels and 8400 for 12 x 325W panels.

I am waiting for an indicative quote frm another company with micro inverters.

We are hoping to sort things out relatively quickly (FIT payments being revised in April) but I also don't want to rush into it without doing sufficient research.
(We couldn't have started this process earlier unfortuantely as we haven't had the available cash due to circumstances).

At the moment we prefer the second quote and would go for the higher power option as logically it's a bigger/better investment.
We think option 2 is aesthetically better and have taken on board the comments abouts the DC cable - plus they've offered us the higher power option.

I would appreciate any comments/wisdom from more knowledgeable folks about options we should consider e.g. the micro inverters.
We are thinking of having a solar Iboost but that's not in the quotes for comaprison purposes.

Thanks in advance
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JohnS
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« Reply #1 on: January 31, 2014, 11:00:41 AM »

Some photos would help.

What annual output are they forecasting for each section of the roof?
Are there any shading issues, from dormers etc?
Is the gable end part going to be vertical?
what sort of inverters are they proposing and are these dual MPPT inverters?
Are the 325w panels bigger (area wise) than the 250w ones and will they fit ok or will they look crammed in?
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2.1kWp solar PV
lisyloo
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« Reply #2 on: January 31, 2014, 11:32:29 AM »

1st quote is 2167 but I don't have a breakdown or know if they did it as a single 3KW install.

2nd quote has

250W on A - 1450
250W on B -   713
Total -         2163

325W on A - 1876
325W on B     967
Total -         2823

First quote has a Sunrous HF DT Inverter
Second quote has a Power One PVI-3.6-OUTD (2 MPP) Inverter

Both have calculated 20% shading

The rooves are 40 degrees

The panels are not much different in size and are not really likely to be noticed on A & B but would be highly visible on C.

Trying to get some photos from google earth.
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lisyloo
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« Reply #3 on: January 31, 2014, 11:55:54 AM »

Fuzzy I'm afraid but you can see C with the dormers and how it's very visible if you're driving/walking towards the house.
There is only room on the LH end and above the velux (right of the dormers). Not enough room abover the dormers.
B can be identified as to the left of the chimney.
A is the hexagonal bit in the middle.
A&B won't be that visible from the ground from anywhere you'd normally stand/approach/drive.


* house copy.jpg (35.96 KB, 536x360 - viewed 545 times.)
« Last Edit: January 31, 2014, 12:01:10 PM by lisyloo » Logged
ianh64
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« Reply #4 on: January 31, 2014, 12:18:40 PM »

Shading and orientation mismatch can play havoc with PV production. Think of it like a hose pipe, you put a kink in it and everything is affected.

What you need to be looking for are solutions that mitigate the issue of one or more panels not producing optimally (ie the ones with the kink in them). This may involve using inverters with dual mppt, multiple inverters (such as micro inverters) or power optimisers (such as SolarEdge or Tigo Energy).

You don't mention the options that address these in your quotes other than you are waiting for a quote that uses micro inverters. In the mean time, I would be asking the people who supplied the quotes that you do have what they are doing to mitigate the difference in panel output due to dual aspect and shading.

Having such a short string on one aspect may limit your choices.

Long AC cable runs are potentially more of a problem than long DC runs.
« Last Edit: January 31, 2014, 12:21:43 PM by ianh64 » Logged
lisyloo
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« Reply #5 on: January 31, 2014, 12:31:37 PM »

Thanks Ian that's very useful.

Just spoke to a 4th company.
He said the problem with micro-invertors is that if/when they go wrong then you need scaffolding to fix them and that's going to be expensive and our roof access is not easy.

He coming out on Monday to actually get up and measure the roof.
He is sceptical so it'll be interesting to see what he says.
« Last Edit: January 31, 2014, 01:37:07 PM by lisyloo » Logged
M
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« Reply #6 on: January 31, 2014, 01:36:10 PM »

Hiya - I'm a newbie and I'm looking into a PV install.

Hiya lisyloo.

Probably a little too late for you, but this thread has general info on PV that you might find useful:

http://www.navitron.org.uk/forum/index.php/topic,19989.0.html


We are hoping to sort things out relatively quickly (FIT payments being revised in April) but I also don't want to rush into it without doing sufficient research.
(We couldn't have started this process earlier unfortuantely as we haven't had the available cash due to circumstances).

Obviously you don't want to miss out on a better rate, but the April tariff drop is only 3.5% on the FiT (export and leccy savings not affected), so the rate will change from 14.9p to about 14.4p. So keep one eye on the date, but don't rush if you're not confident, and wait till you know everything ...... ok, we'll never know everything, but the drop isn't enough to risk rushing.

Happy hunting.

Mart.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
lisyloo
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« Reply #7 on: January 31, 2014, 01:39:35 PM »

Quote
but the drop isn't enough to risk rushing

Totally agree - but we still need to do this research anyway whether it's sooner or later.
« Last Edit: January 31, 2014, 01:42:00 PM by lisyloo » Logged
dan_b
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« Reply #8 on: January 31, 2014, 03:17:01 PM »

I'm not an installer, but I'd say your roof is the perfect definition of "tricky" - different orientations, different angles, and shading hazards. Different roof arrays with different outputs at different times of the day. Selection of inverter technology and how the panels are configured will be very important.
I have a tricky roof and went with SolarEdge in order to mitigate as much as possible against the significant impact that shading has on output. I would say it would be preferable for your system too.
If you (or your installer) don't want power optimisers or micro-inverters on the outside of the roof, could they be located inside in the loft space instead? It's not strictly necessary to have them outside underneath the panels...
If the higher output panels are the same size, get them. They will always generate more power, which means more FiT.
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3.06kWp SolarEdge system with a split array:
2.18kWp 10x South facing, plus 4x West facing 880W

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lisyloo
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« Reply #9 on: January 31, 2014, 04:48:53 PM »

I've just spoken to number 1 about Solar Edge.
He said he wouldn't recommend it.
He said there are 4 diodes per Gallium panel and that they would be treated as 4 groups of 3 panels (and mentioned dual trackers).
So his professional opinion is that the set up he's recommended is the best for our situation.
He also says we'll get most shading issues when there's not much power generated anyway i.e. sun is slow.

Just spoken to number 3.
He's raving about micro inverters. These have to go outside but are monitored and can be fixed remotely and even if they need scaffolding they have a 20 year (manufacturers) warranty.
I am aware that manufacturers warranties suffer from the problem of manufacturers going out of business (don't know Enphase).
His quote is 8,500, but allowing for 20% shading the output is 2408 (2189 plus 10% for the micro inverters).
He says the the micro inverters will give us the best solution, but the estimate shows less power for more cost compared with number 2's 325kw system (8400 @ 2823).
I appreciate those are estimates, but the micro inverters would have to be performing at an extra 29% (2189 -> 2823) which is outperforming the highest 25% estimates to match the 325w panels output.

My gut feeling is that number 2 is ahead with the 325w panels, but I need to question them about how their solution copes with shading issues.
« Last Edit: January 31, 2014, 04:56:39 PM by lisyloo » Logged
ianh64
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« Reply #10 on: January 31, 2014, 05:10:30 PM »

Most warranties associated with Solar only cover parts not the costs associated with replacing it on the roof.
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JohnS
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« Reply #11 on: January 31, 2014, 05:27:47 PM »

A quick google on panels showed that the higher power panels are bigger.  Eg for the Axitec panels, the length went up from 1,640mm to ~2,000mm for a higher power panel.  For the Benq, the width increased.

Not sure if I chose exactly the panels you were quoted for, but it is worth asking the installer for detailed spec sheets.  In general you can get a small range of outputs from the same size panel eg 230-250w.  There are manufacturing variances and the manufacturer tests them and, depending on the test result, lables them 230, 240 or 250.

Therefore there may be an issue shoe horning the bigger panels in.

Panasonic panels (previously Sanyo until Sanyo sold their PV business to Panasonic) use a slightly different silicon and are more efficient per unit area, but at an increased cost.  Only worthwhile when area is a resticting factor.
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2.1kWp solar PV
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« Reply #12 on: January 31, 2014, 05:28:31 PM »

Quote
but the drop isn't enough to risk rushing

Totally agree - but we still need to do this research anyway whether it's sooner or later.

Keep going, and when your brain starts to hurt, you'll know you're making progress.

Regarding SolarEdge, just like Ian and Dan, I've also got a SolarEdge system (only on the WNW system). Last year my ESE systems managed 102% of target, the WNW got 108% of target, but here's the fun bit, my targets are straight off PVGIS, I didn't deduct for shading, as I wanted to see how the system performed against 'maximum'. The ESE has a small amount of shading, but the WNW has quite a bit.

If you don't have shading, don't bother with micro's or PO's (power optimisers), but if you have to, SolarEdge is fun, allows any combination of panel orientation, pitch, type, size etc, all running through an extremely efficient inverter (~98%) and with great monitoring too.

Youtube SolarEdge for 3 videos on how they work, part 1 should lead to pts 2 & 3, about 10 mins all in.

Regarding the companies and the market, there seems to be a lot of confidence looking forward:

GTM: Microinverter and optimiser market to increase fivefold

http://www.pv-tech.org/news/gtm_microinverter_and_optimiser_market_to_increase_fivefold

Mart.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
lisyloo
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« Reply #13 on: January 31, 2014, 05:49:50 PM »

Number 1 and Number 2 who've been here believe the shading issues are minor.
I'm not qualified except living here for 11 years but I tend to agree.

The Axitec panels are 1640 x 992
The BenQ panels are 1559 x 1046
So the higher powered panels are indeed wider.
Number 2 has confirmed they are sure the panels will fit.

Number 2 has now said that whilst the benefits of solaredge are marginal as we don't have a big shading issue, they can add it to the Axitec quote for nothing (because the inverter price changes) and for 400 to the 325W BenQ quote.
My feeling is that whilst the benefits are not certain, it would reduce the risk of us having issues from shading and is probably worthwhile for the relatively low cost.

Number 4 is going up on the roof on Monday so I'll see what he says and try to get his measurements.

Number 3 agreed that 8 panels (phono) could go up but I'm not sure of the size.

Thanks for all the help so far.
« Last Edit: January 31, 2014, 09:12:22 PM by lisyloo » Logged
ianh64
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« Reply #14 on: February 01, 2014, 07:03:30 AM »

The additional cost of SolarEdge is in line with mine. For me it added about 400-450 on a 17 panel system vs an SMA Sunnyboy system. At 0 IMHO, its a no brainer but even at 400 its a worth while addition as it gives online monitoring at panel level free for 25 years which can often be offset against the cost a monitoring system. Even at 400, that's only 20/year for the FIT lifetime which would pay for itself if SE only gave 5% extra generation.

As for 20% shading. Did they use a telescope type thing and plot the readings on a curved graph?

If this method was used, that is quite a lot no matter what anyone says IMHO. I've got a shading factor of 0.86 which is 14% shading so less than yours but thankfully most of my shading is few months either side of winter so whilst I'm losing significant percentage of not a lot (based on Jan figures I lost 50% so financially about 10 down for the month), but if yours is all year round, you will be losing out on much more available light so your potential losses are more.

If you do go with SolarEdge, be aware of minimum string length (number of optimisers connected together) is 8 optimisers which with a traditional inverter you probably would not comply with due to it being two relatively small split over two aspects. However with SolarEdge, both aspects can be wired on same string without the normal disadvantages so this limitation can be avoided.

One bit of advice I learned early on when I researched Solar was put as much KWp on the roof as you can afford/fit (within 4KWp fit). Majority of the cost of Solar is in the inverter, fitting hardware, scaffold and labour. That's pretty much a fixed price whether you fit 8 panels or 16. The cost of an additional panel or more efficient panel (more KWp in same space) is relatively small and will easily pay for itself and shorten the repayment period for the whole system.
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