My installation comprises 12 Hengdian 450 PV panels, Fox inverter and Fox IP12 battery.
Non-ideally (IMHO) the panels are split across two roof sections - 10 are situated on the main roof of our dwelling and 2 more on the roof out our garage. The garage roof is considerably lower than the main roof and hence subject to quite a bit of shading during the late afternoon, especially in the winter months. All of these panels are connected in one string which is connected to the inverter.
As stated above, there are times late in the day when the garage panels, due to their lower aspect, become shaded while the main roof panels are still well lit with the result that the overall output is dragged down (the effect on the real-time curve is like it falls off a cliff when this happens) so I am beginning to wonder if I could improve the situation by attaching optimizers to the two garage roof panels.
Is there any experience in the community with the use of partial fitments of optimizers? And more particularly which manufacturers? I'm wondering about TIGO optimizers.
Stupid idea? Genius at work? Do some homework? I'd would appreciate some feedback on this please.
Best regards,
Derrick.
Hi Derrick,
My 2p worth says that the cost of having scaffolding put up, panels removed to fit optimisers etc and refitted, would outweigh your savings.
Maybe see how it performs on a day of full sunshine at this time of year, and compare to others with similar output, or make adjustments. We have 14th Feb looking like a good candidate.
My 2p worth says that the cost of having scaffolding put up, panels removed to fit optimisers etc and refitted, would outweigh your savings.
Maybe see how it performs on a day of full sunshine at this time of year, and compare to others with similar output, or make adjustments. We have 14th Feb looking like a good candidate.
High again,
From my own numpty style reading I am led to understand that the bypass diodes (supposedly three in each of the 12 panels I have fitted) should, in the case of the two garage panels (when they become shaded) enable current to flow freely through them with a minimal drop in voltage (3 x 0.7V IIHIC) due to the series connection of the bypass diodes.
Given that, I'm struggling to understand how the output doesn't just reduce the slightly less than what 10 fully lit panels would produce - instead it drops like it fell off a cliff.
And then there's this little voice in the back of my head whispering (usually at very low volume) "it doesn't work like that".
I'm always grateful for indications as to how I can correct my reasoning.
Best regards,
Derrick.
From my own numpty style reading I am led to understand that the bypass diodes (supposedly three in each of the 12 panels I have fitted) should, in the case of the two garage panels (when they become shaded) enable current to flow freely through them with a minimal drop in voltage (3 x 0.7V IIHIC) due to the series connection of the bypass diodes.
Given that, I'm struggling to understand how the output doesn't just reduce the slightly less than what 10 fully lit panels would produce - instead it drops like it fell off a cliff.
And then there's this little voice in the back of my head whispering (usually at very low volume) "it doesn't work like that".
I'm always grateful for indications as to how I can correct my reasoning.
Best regards,
Derrick.
I think Dave or someone will come along and post a better answer as to why.
My guesstimate is the panels being shaded heavily drop the string Voltage down so low that it shuts down the whole string? But I have no idea if that is the correct answer.
Give it a few hours and hopefully someone can explain the behavior better.
My guesstimate is the panels being shaded heavily drop the string Voltage down so low that it shuts down the whole string? But I have no idea if that is the correct answer.
Give it a few hours and hopefully someone can explain the behavior better.
Thanks again,
The strings doesn't shut down completely, there is still an output but one that is substantially lower than that which preceded the shading.
I'm not arguing - just trying to comprehend and understand things a little better than I do right now - but it states on the spec sheet that there are three diodes, so I suppose that the panels is divided into three sections with a bypass diode for each section. A completely shaded panel then would look, to the incoming current, like three diodes in series and not, in my case 108, reverse biased cells in series resulting in a massive drop in current: that doesn't seem to happen.
I got my arithmetic wrong previously - for both shaded garage panels it would be 6 diodes in series not 3.
I'll see what happens this evening.
Roll on the often occurrennce of meteorological temperature inversions and blue skies!
Best regards,
Derrick.
The strings doesn't shut down completely, there is still an output but one that is substantially lower than that which preceded the shading.
I'm not arguing - just trying to comprehend and understand things a little better than I do right now - but it states on the spec sheet that there are three diodes, so I suppose that the panels is divided into three sections with a bypass diode for each section. A completely shaded panel then would look, to the incoming current, like three diodes in series and not, in my case 108, reverse biased cells in series resulting in a massive drop in current: that doesn't seem to happen.
I got my arithmetic wrong previously - for both shaded garage panels it would be 6 diodes in series not 3.
I'll see what happens this evening.
Roll on the often occurrennce of meteorological temperature inversions and blue skies!
Best regards,
Derrick.
Hi all,
Now that things are running into the evening the shading on the garage panels is starting to bite with the primary effect being that the output from the whole array starts its fall of a cliff at about 15:00 - see attached analysis image, where the generation starts to take off at about 09:00, and satellite view showing sun rays. From about 15:00 onward the house at the back of us partially shades the garage panels while the roof panels are still fully lit.
I could be wrong in my estimation, but the reduced illumination of the garage panels definitely seems to be having a gross effect when the shape of the real time curve in the morning is compared to that in the evening.
Our house is oriented so that the Western side of the roof is facing approximately WSW - the line of the roof being 30 degrees West of North.
Best regards,
Derrick.
Now that things are running into the evening the shading on the garage panels is starting to bite with the primary effect being that the output from the whole array starts its fall of a cliff at about 15:00 - see attached analysis image, where the generation starts to take off at about 09:00, and satellite view showing sun rays. From about 15:00 onward the house at the back of us partially shades the garage panels while the roof panels are still fully lit.
I could be wrong in my estimation, but the reduced illumination of the garage panels definitely seems to be having a gross effect when the shape of the real time curve in the morning is compared to that in the evening.
Our house is oriented so that the Western side of the roof is facing approximately WSW - the line of the roof being 30 degrees West of North.
Best regards,
Derrick.
Attachments:
I made a whopping 18.70kWh today, in mostly blue skies, did get clouds this afternoon sadly that affected the overall.
If I adjust the size of my array to yours, then in theory in similar conditions you might have made around 16kWh of production. If you panels are aimed at a different angle to mine, then this will skew the figures of course.
My angles are here, 186° and 27° pitch
What sort of skies have you have up to now, and how much did you produce to around 16:00?
If I adjust the size of my array to yours, then in theory in similar conditions you might have made around 16kWh of production. If you panels are aimed at a different angle to mine, then this will skew the figures of course.
My angles are here, 186° and 27° pitch
What sort of skies have you have up to now, and how much did you produce to around 16:00?
This can be a complex subject to answer simply because there are so many panel types, some having 2 or 3 bypass diodes, other modern and more expensive panels can have considerably more.
The short answer is it depends on how the shade is applied to the panel, bypass diodes aren’t there to help you optimise the panel, their purpose is to protect the panel from hot spots because of high resistance when shade blocks a portion of the panel. Rather than me blather on, this is a very good review of how and why you might choose a Tigo optimiser over standard panels https://mcelectrical.com.au/blog/tigo- ... ptimisers/
I suspect I have a similar problem to you in that I have 8 panels on one roof but when the sun is at low elevation the gable end puts a hard shadow across 2 of the panels, sadly I didn’t install Tigo’s on that roof and output is badly affected by hard shade on 2 panels. Much like @MB said, getting up to the panels and fitting Tigo’s would need scaffold (I have solarskirt fitted) and so i’ve not gone to the extra expense of fitting them as I doubt I could ever recover that cost.
The short answer is it depends on how the shade is applied to the panel, bypass diodes aren’t there to help you optimise the panel, their purpose is to protect the panel from hot spots because of high resistance when shade blocks a portion of the panel. Rather than me blather on, this is a very good review of how and why you might choose a Tigo optimiser over standard panels https://mcelectrical.com.au/blog/tigo- ... ptimisers/
I suspect I have a similar problem to you in that I have 8 panels on one roof but when the sun is at low elevation the gable end puts a hard shadow across 2 of the panels, sadly I didn’t install Tigo’s on that roof and output is badly affected by hard shade on 2 panels. Much like @MB said, getting up to the panels and fitting Tigo’s would need scaffold (I have solarskirt fitted) and so i’ve not gone to the extra expense of fitting them as I doubt I could ever recover that cost.
Thanks to both of you.
In answer to @MB - up to around 16:30 yesterday the array produced 12.4kWh and filled the 11.5kWh EP12 battery to 91% while also running the house - lights, computers, cooking, washing, etc. The inclination of my roof, if I've measured the pitch of my roof correctly, is about 50 degrees tilted back from the vertical or 40 degrees lifted up from horizontal as another way of looking at it.
I found an Aussie site uttering cautionary words about optimizers and especially TIGO, another video had some harsh words about ENPHASE.
https://mcelectrical.com.au/blog/tigo-o ... all/#issue
https://mcelectrical.com.au/blog/tigo-optimiser-recall/
As to fitting - the roofers special type of ladder was sufficient to fit them because they were an afterthought given that there wasn't room on the main roof to fit the 12 panels originally spec'd and stay within MCS guidelines (although British Gas fitted the same size, but different manufacturer, panels on an identical neighbours house last year). So, it may not be that expensive to have them fitted given that a ladder is sufficient to do the work - but then there's the Electrician and cups of coffee and cakes and ...
I think I'm just gnashing my teeth a bit about how did the neighbour doesn't have these shading issues.
What I'll take from this is "More thought required".
Best regards,
Derrick.
In answer to @MB - up to around 16:30 yesterday the array produced 12.4kWh and filled the 11.5kWh EP12 battery to 91% while also running the house - lights, computers, cooking, washing, etc. The inclination of my roof, if I've measured the pitch of my roof correctly, is about 50 degrees tilted back from the vertical or 40 degrees lifted up from horizontal as another way of looking at it.
I found an Aussie site uttering cautionary words about optimizers and especially TIGO, another video had some harsh words about ENPHASE.
https://mcelectrical.com.au/blog/tigo-o ... all/#issue
https://mcelectrical.com.au/blog/tigo-optimiser-recall/
As to fitting - the roofers special type of ladder was sufficient to fit them because they were an afterthought given that there wasn't room on the main roof to fit the 12 panels originally spec'd and stay within MCS guidelines (although British Gas fitted the same size, but different manufacturer, panels on an identical neighbours house last year). So, it may not be that expensive to have them fitted given that a ladder is sufficient to do the work - but then there's the Electrician and cups of coffee and cakes and ...
I think I'm just gnashing my teeth a bit about how did the neighbour doesn't have these shading issues.
What I'll take from this is "More thought required".
Best regards,
Derrick.
To both again,
Something I forgot - the skies were mostly clear, but, as can be seen from the real-time plot I posted, there were some big gaps due to some fairly big passing lumps of cu.
Best regards,
Derrick.
Something I forgot - the skies were mostly clear, but, as can be seen from the real-time plot I posted, there were some big gaps due to some fairly big passing lumps of cu.
Best regards,
Derrick.
I think your production figure sounds good to me, given your orientation, pitch and a bunch of fluffly clouds that went over. There are a lot of factors, but 12.4kWh production could be bang on the money.
The difference of 3.6kWh from my guesstimate is not bad, and would only compare if you had same 186° almost due South orientation and my same pitch, with identical cloud cover.
The difference of 3.6kWh from my guesstimate is not bad, and would only compare if you had same 186° almost due South orientation and my same pitch, with identical cloud cover.
Hi all, again.
I was perhaps a Dog in a previous life and this is a bone I can't stop chewing on.
It's turned quite bright this afternoon and the roof panels are experiencing period of intense light, yet, from ten brightly lit panels and two shaded panels I am getting 242 Watts.
Just prior to the shading the twelve panels were churning out, in bright periods, around 3kW.
And now I'm experiencing severe arithmetic failure - if the bypass diodes are working why am I not seeing something around 2.5 kW?? (on the basis of 10/12 of the total panel output).
It should be 10 panels worth less the effect of the bypass diodes, shouldn't it? Where's the error in my reasoning?
Best regards,
Derrick.
I was perhaps a Dog in a previous life and this is a bone I can't stop chewing on.
It's turned quite bright this afternoon and the roof panels are experiencing period of intense light, yet, from ten brightly lit panels and two shaded panels I am getting 242 Watts.
Just prior to the shading the twelve panels were churning out, in bright periods, around 3kW.
And now I'm experiencing severe arithmetic failure - if the bypass diodes are working why am I not seeing something around 2.5 kW?? (on the basis of 10/12 of the total panel output).
It should be 10 panels worth less the effect of the bypass diodes, shouldn't it? Where's the error in my reasoning?
Best regards,
Derrick.
It might be worth comparing how much long term output you achieve, let's say you loose 1hr a day for shading, it does add up, but the cost of buying/fitting the optimisers might not make up for what you could gain.
If you spent a £1,000 to fix this, but gain £100pa, that's 10 years to pay back. Can you approach the firm that fitted and ask what they would charge to do the work?
If you spent a £1,000 to fix this, but gain £100pa, that's 10 years to pay back. Can you approach the firm that fitted and ask what they would charge to do the work?
Hi MB,
I spoke with them today and they are going to take at a look at monitoring it with the same idea you have - do some long term monitoring of its behaviour, I agree with that.
I'm still curious about the bypass diodes modes of operation given, from what I've read, that it's really under the control of the inverter and its control of the string voltage using the MPPT.
Fascinating stuff, almost as mysterious as quantum mechanical entanglement like an itch I can't scratch.
Best regards,
Derrick.
I spoke with them today and they are going to take at a look at monitoring it with the same idea you have - do some long term monitoring of its behaviour, I agree with that.
I'm still curious about the bypass diodes modes of operation given, from what I've read, that it's really under the control of the inverter and its control of the string voltage using the MPPT.
Fascinating stuff, almost as mysterious as quantum mechanical entanglement like an itch I can't scratch.
Best regards,
Derrick.
I agree that long term picture is what is best for your system.
Meanwhile, do you have something like this in your quotes for your system?
I am curious to your values for a possible comparison (the other day the 16kWh guess was done with your size of system to mine)
Meanwhile, do you have something like this in your quotes for your system?
I am curious to your values for a possible comparison (the other day the 16kWh guess was done with your size of system to mine)
Hi MB,
Yes I have a very extensive table with similarities to yours:
There are some foibles with it - although the proposal cited 12 panels on the roof, when the roofer made detailed measurements after he was able to access it via the scaffolding he refused to install them due to MCS guidelines compliance issues (in his view) so I agreed to having the remaining two panels put on the garage.
There are some other orientation foibles:
Degrees from South I put at 60 degrees - I know this because I did a little bit of astronomy some time ago and knowing where North is helps in finding Polaris.
Inclination I put at 40 degrees by checking the angle of the joists.
The irradience postcode is a nonsense to me - neither your 11 nor my 1 looks anything like a postcode.
The shade factor is obviously off a bit due to the garage panels, but that was my OK on that.
The annual output estimate is a "Well, we'll see about that" given the garage panels but so far the system seems to be going quite well given what it's produced so far (387kWh) against consumption (about 1.2MWh).
It's a journey.
Best regards,
Derrick.
Yes I have a very extensive table with similarities to yours:
There are some foibles with it - although the proposal cited 12 panels on the roof, when the roofer made detailed measurements after he was able to access it via the scaffolding he refused to install them due to MCS guidelines compliance issues (in his view) so I agreed to having the remaining two panels put on the garage.
There are some other orientation foibles:
Degrees from South I put at 60 degrees - I know this because I did a little bit of astronomy some time ago and knowing where North is helps in finding Polaris.
Inclination I put at 40 degrees by checking the angle of the joists.
The irradience postcode is a nonsense to me - neither your 11 nor my 1 looks anything like a postcode.
The shade factor is obviously off a bit due to the garage panels, but that was my OK on that.
The annual output estimate is a "Well, we'll see about that" given the garage panels but so far the system seems to be going quite well given what it's produced so far (387kWh) against consumption (about 1.2MWh).
It's a journey.
Best regards,
Derrick.
Attachments:
I was looking to compare your possible output annually 4756kWh compared to mine of 5226kWh, and this gives a 91% rough comparison.
It is hard to compare cloudy days, but once you get a full day of Sun on your panels, where your PV output looks like a whale, and if I had the same uninterrupted sunshine, the theoretical 91% should translate.
So if I made 10kWh, you should have made 9.1kWh.
It is all fag paper maths, proof will be in your results.
The irradience postcode is a lookup table for MCS calculations, Scotland will get less sun than Devon, so the Country is divided up into bands of lattitude.
It is hard to compare cloudy days, but once you get a full day of Sun on your panels, where your PV output looks like a whale, and if I had the same uninterrupted sunshine, the theoretical 91% should translate.
So if I made 10kWh, you should have made 9.1kWh.
It is all fag paper maths, proof will be in your results.
The irradience postcode is a lookup table for MCS calculations, Scotland will get less sun than Devon, so the Country is divided up into bands of lattitude.
Well, I've been doing some reading about inverter MPPTs and what a horrible life they lead.
I'm starting to think that my shading problem may be due to some some possible inadequacies in the inverter's MPPT tracking algorithm (not simplifying, it's a very complicated problem when there are a few fully shaded panels in a long string) and the difficulties involved in persuading the bypass diodes to activate. Because, if the diodes are not activated the shaded panel(s) will drag the whole string down to the shaded panel amperage and I think that is what is happening in my case.
I'm not done reading and digesting yet, but the only way out seems to be the incorporation of a couple of optimisers, one to each of the garage panels.`
There's too much high cirrus today, maybe in the next few days I'll get full output.
per ardua ad perfection.
Still - Watch and deduce is what I have to do.
Best regards,
Derrick.
I'm starting to think that my shading problem may be due to some some possible inadequacies in the inverter's MPPT tracking algorithm (not simplifying, it's a very complicated problem when there are a few fully shaded panels in a long string) and the difficulties involved in persuading the bypass diodes to activate. Because, if the diodes are not activated the shaded panel(s) will drag the whole string down to the shaded panel amperage and I think that is what is happening in my case.
I'm not done reading and digesting yet, but the only way out seems to be the incorporation of a couple of optimisers, one to each of the garage panels.`
There's too much high cirrus today, maybe in the next few days I'll get full output.
per ardua ad perfection.
Still - Watch and deduce is what I have to do.
Best regards,
Derrick.
It's just a regional grouping, defined by the MCS. https://mcscertified.com/?standard=irradiance-datasets
So for example someone in the south-west will have higher irradiation than someone in Aberdeen.
Nothing to do with actual postcodes so I don't know why they called it that.
Thank you WyndStryke!
Initially the 1 and the 11 still make no sense when referring to the table unless one sees that the table has numbered tabs (per location) and row/column values per tab - so reading from the table under Zone 1 - London, the value at the intersection of row 43 (slope = 40) and column o (orientation = 60 from South) I get an irradiance value of 879 from it, but I am not in London! and I assume that it would be possible to interpolate values read from the intersection to deduce an irradiance value for my location. MB could then read his irradiance value from the row/column intersection under the tab for his "postcode".
So, on the assumption that MK lies midway between London and Birmingham then the irradiance value is (839+879)/2 = 859. That alters the projected figures I was given based on the Open Solar report. That's a little over 2%! I'm shocked (NOT).
Many thanks for your help, the veil is lifting.
Best regards,
Derrick.
Initially the 1 and the 11 still make no sense when referring to the table unless one sees that the table has numbered tabs (per location) and row/column values per tab - so reading from the table under Zone 1 - London, the value at the intersection of row 43 (slope = 40) and column o (orientation = 60 from South) I get an irradiance value of 879 from it, but I am not in London! and I assume that it would be possible to interpolate values read from the intersection to deduce an irradiance value for my location. MB could then read his irradiance value from the row/column intersection under the tab for his "postcode".
So, on the assumption that MK lies midway between London and Birmingham then the irradiance value is (839+879)/2 = 859. That alters the projected figures I was given based on the Open Solar report. That's a little over 2%! I'm shocked (NOT).
Many thanks for your help, the veil is lifting.
Best regards,
Derrick.