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Author Topic: New house - advice requested  (Read 994 times)
SnaxMuppet
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« on: July 13, 2017, 02:19:05 PM »

Hi all,

I am moving into a new house next month. The house has a 14 panel solar PV installation on a single string inverter. It was installed in Feb 2012 and so is on a high FiT rate. However, the generation has been lower than I would have expected for a 2.6kWp east-facing system. The roof is completely clear of all shadow except that there is a single chimney casting a hard shadow across one of the panels for half of the day. Unfortunately, the chimney is east of the panels and so it is when the panels are at their most generating.

I was wondering if it is something I might be able to improve without significant cost? For example, could I remove that panel from the string and give it its own micro-inverter thereby making the string more efficient? What about moving the affected panel to a different location on the same roof plane (there is plenty of room)? Could anything like this be cost effective? Would it affect my eligibility for the higher rate FiT?

Of course, even the reduce generation is worth having so I cold just leave it all well alone but I have had solar PV in the past and so I am interested in getting the most from it.

Any advise would be much appreciated.
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sam_cat
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« Reply #1 on: July 13, 2017, 02:51:34 PM »

That panel/panels in that area could have a Black magic microinverter (or similar) fitted.. But it might just breach your FIT agreement (change to the installation).. Worth checking before you make a change.

Or just do it and risk them stopping paying out.
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M
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« Reply #2 on: July 13, 2017, 04:11:04 PM »

You could go for a retro-fit SolarEdge system, but that will cost a fair bit, or I have heard of a system that works on individual panels, just the ones that concern you. It's the Tigo energy TS4-R.

If you are concerned about your FiT status then ask the FiT provider first, but as you aren't changing the panels, just optimizing it/them, then you aren't doing anything that couldn't have been done during the original install, such as a SolarEdge system.

I'm hoping to upgrade my ESE systems to a single SolarEdge system soon, and this won't affect my FiT, it'll just make my system less poor, IYSWIM.
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RIT
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« Reply #3 on: July 13, 2017, 05:24:49 PM »

I think the first thing to do is for you to post location and stats once you have access to the the inverter.

As a starting point you can use the stats for my 2.4Kw, East facing system in South London. These can be accessed via the public web site PVOutput at

        https://pvoutput.org/aggregate.jsp?id=49083&sid=44708&v=0&t=y
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TheFairway
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« Reply #4 on: July 13, 2017, 05:56:17 PM »

You could go for a retro-fit SolarEdge system, but that will cost a fair bit, or I have heard of a system that works on individual panels, just the ones that concern you. It's the Tigo energy TS4-R.

SolarEdge do/did an optimiser like the OPI300-LV that didn't need to be connected to a SolarEdge inverter. Not sure if to usilise this whether all panels needed to be optimised, or if you could just get away with the odd one. This may also have an effect on the working ranges of your inverter.

« Last Edit: July 13, 2017, 05:58:33 PM by TheFairway » Logged

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desperate
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« Reply #5 on: July 13, 2017, 05:58:30 PM »

Is the chimney being used? shared with the neighbour? can you get rid of it?

Desp
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Iain
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« Reply #6 on: July 13, 2017, 06:25:47 PM »

Hi
As a temp try taking the shaded panel totally out of circuit, you might find the losses are greater than the gains from the shaded panel. Worth a try if access is easy.
Is there room for the panel at the other end? Just move the one, Or can they all slide along? Moving the panels won't affect the FIT, good opportunity to check all the wiring and connectors!!

Iain
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gnarly
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« Reply #7 on: July 13, 2017, 08:17:42 PM »

Perhaps someone can explain to me.  Panels typically have 3 bypass diodes so these should kick in and just bypass those shaded cells.  The string voltage will drop but it shouldn't be too significant?

Key point is that this is a single string.  If you have two strings on one input them you can lose all the power from a whole string (if its voltage is lower than the other string then it won't contribute)
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RIT
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« Reply #8 on: July 13, 2017, 11:22:06 PM »

Perhaps someone can explain to me.  Panels typically have 3 bypass diodes so these should kick in and just bypass those shaded cells.  The string voltage will drop but it shouldn't be too significant?

Key point is that this is a single string.  If you have two strings on one input them you can lose all the power from a whole string (if its voltage is lower than the other string then it won't contribute)

The number of bypass diodes depends on the design of the panel, with many just having a single diode that allows the whole panel to be bypassed. If two strings have been connected in parallel to support a single string inverter, what is known as a blocking diode should have been installed on each of the parallel string. With luck, the installation docs should indicate if panels have been wired in parallel and such diodes were added. A nice overview can be found here

       www.electronics-tutorials.ws/diode/bypass-diodes.html

One open question for SnaxMuppet, is what inverter is currently installed? Depending on what it is you may or may not be able to get useful info from it, and it may or may not have a mppt controller which would handle shading better.

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SnaxMuppet
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« Reply #9 on: July 14, 2017, 09:26:23 AM »

Thanks for all that advice.

The chimney cannot be used... it is used by the wood burner in the lounge.

I am still unclear what inverter is installed. It is in the loft and we haven't yet moved in. I have asked a load of questions of the vendors but not yet got the replies. I shall post when I get the info Smiley I have asked for the installation diagram... I know this should have been left near the inverter when it was installed.

It sounds like there may be some things we could try. I shall have to check the FiT contract to see what is permitted before doing anything anyway.

Don't all MCS approved inverters have a mppt controller?
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Sean
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« Reply #10 on: July 14, 2017, 09:38:37 AM »

If two strings have been connected in parallel to support a single string inverter, what is known as a blocking diode should have been installed on each of the parallel string.



?
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RIT
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« Reply #11 on: July 14, 2017, 11:40:08 AM »

Don't all MCS approved inverters have a mppt controller?

The feature is just about standard now, but not back in 2012.
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djh
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« Reply #12 on: July 14, 2017, 12:59:42 PM »

I shall have to check the FiT contract to see what is permitted before doing anything anyway.

Unless your relationship with the vendor is stupendously good, I would try to get a copy of that and the installation details asap and before you make the completion payment.
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Cheers, Dave
RIT
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« Reply #13 on: July 14, 2017, 01:54:38 PM »

It would make sense for you to ask your solicitor to request all the information before completion anyway.

The original info pack left by the installers should include key docs

    - Insurance guarrantee
    - Part P certificate
    - Building Regulations Compliance certificate
    - MCS Installer Certificate

These are all key documents to prove that what has been placed on the house is correct and safe. It's not like you can arrange valid home insurance for the day you move in without proof that the house is safe and without all this info any future claim could become more complicated.

The info pack should also contain details of the equipment used, invoices raised during the installation and a diagram.

Asking your solicitor may slow the process down, but it also makes it is more formal as their solicitor will make it clear that it's all just part of the process required to sell the house. As will be the step of the seller completing the document required to transfer FITs payments to you which should happen at the same time as completion.
« Last Edit: July 14, 2017, 01:57:47 PM by RIT » Logged

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JohnS
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« Reply #14 on: July 14, 2017, 02:53:04 PM »

I suggest that you tell the solicitors that it is a condition of the sale that the FIT contract is transferred to you.  Perhaps ask your solicitor to require the vendor's solicitor to hold the equivalent of two years FIT income in escrow until the contract is transferred.

Also, I think that FIT holders are required to keep records of meter readings and dates for two ? years.  Ask for them.
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