question

Olivier Wouters avatar image
Olivier Wouters asked

Off grid winter optimum production with trees at 50m near Dublin

PVGIS-5_GridConnectedPV_53.556_-6.792_undefined_crystSi_1.44kWp_14_50deg_0deg.pdfHello,

I would like to optimise the production in winter of 3 solar panels (360W) horizontally put one above each other at a 60° slope (so the highest would be at about 3m high, and lowest at about 1m high). I live near Dublin in the countryside and I'll be off-grid.

I'm surrounded by trees, the house is 55m from the South, 20m from SE and 40m from SW (see below picture). The good thing is that they loose their leaves in winter and I would say they are more bushy at the bottom than the top.

The question is how do I connect these panels (in parallel or in serie), is there anything special I would need for this scenario ? How smoothly can I add an extra 3 panels to this system to put the number at 6 panels.

I attached some pictures and technical details (the panel would sit on the right of the door starting at the "gutter")

If I'm completely wrong at how to tackle this, you can tell me :). (I have a single slope roof at 11°, pretty bad for solar production in winter ...)

Thanks in advance !!

Olivier Wouters


screenshot-2022-07-29-at-083924.pngtiny-house.jpgPVGIS-5_GridConnectedPV_53.552_-6.643_undefined_crystSi_1.2kWp_14_60deg_0deg.pdf

offgridSolar Panel
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7 Answers
klim8skeptic avatar image
klim8skeptic answered ·

Shade is really detrimental to a solar panels output. You are better off having cloud cover, than shade...

You have looked at your sites solar harvesting potential, unshaded (the pdf review) and you can live on about 1kWh a day? That is enough for a fridge, a couple of led lights, and a phone charger??

I am mobile, and every site I stay at I use my phone and a sun position app to gain insight as to how much sun a site has potential for. Clouds permitting.

Some insights on how much energy you are expecting to use would be useful.

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Olivier Wouters avatar image
Olivier Wouters answered ·

I just updated the PVGIS report and would have on average 1.580 KWh per day in December. 1440W installation : 4 panels BlueSolar SPM043602400 Solar Panel 360W-24V Mono (seems like a good idea for shade).

By the way, I won't need a fridge (there is fresh beer at the pub) and this is a 4 year "temporary" situation ;). The house won't be moving.


About technical details :

* Should I connect those 4 panels in parallel to optimise in the mentioned shady environment ?

* Should I add panel optimisers ?

* Is there anything else I can do (apart from cutting some branches, moving the house, having the panels 200m away or oversizing the system :p ) ?


Cheers,

Olivier

3 comments
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klim8skeptic avatar image klim8skeptic ♦ commented ·

winter-2022.jpg

1350w of panels.

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winter-2022.jpg (100.0 KiB)
Olivier Wouters avatar image Olivier Wouters klim8skeptic ♦ commented ·

It seems like the production I would expect in winter. I would have 1440w of panels. Is it real data or simulation ? Why do you say it's winter and the graph shows data for June ? Thanks for sharing ;)

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klim8skeptic avatar image klim8skeptic ♦ Olivier Wouters commented ·

Real data from 33d south. Mostly unshaded, just ordinary weather.

winter-solstice-2022.png

Panels flat on roof.

20220621-123136a.jpg

Good luck.

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Olivier Wouters avatar image
Olivier Wouters answered ·

Hi everyone, just giving an update on how this all turned out :). I had to connect the four panels in series (otherwise the voltage was too low for the MPPT). It becomes hard in winter (from the 15th of November) : the sun is low so I get a lot of shade from the trees (I'm only producing after 12.30) and the weather is usually cloudy. I have a feeling it's sunnier in the morning (that's where the trees are ...). Right now, in practical terms, I only switch the inverter when required (2-4 hours a day, it uses 20W per hour when no load) and my computer is by far the most gluttonous. I added some graphs to show how the system is behaving over winter at the end ;).

Some stuff I still wonder if I need to do something about :

  • My battery will never get a good charge for 3 months in winter
  • My SOC is sometimes funny
  • The voltage seems lower in winter (BMS cell voltage and battery voltage) for an equivalent state of charge in good season
  • Any power under 40W does not seem to reach the battery


Past 90 days

screenshot-2023-12-14-at-114623.png

screenshot-2023-12-14-at-114829.png

screenshot-2023-12-14-at-114905.png


From yesterday (an unusual very sunny day for the entire day !!)

screenshot-2023-12-14-at-115812.png



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1234enough avatar image
1234enough answered ·

To get any meaningful power in the depths of winter, you need to way oversize panels, then in summer you'll have way too much.


PVWatts calculator below

screenshot-20231214-191107-chrome.jpg


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1234enough avatar image
1234enough answered ·

Yearly productionscreenshot-20231214-191056-chrome.jpg


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1234enough avatar image
1234enough answered ·

all calculated figures are average and some days you may get virtually nothing of use

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1234enough avatar image
1234enough answered ·

For example here is screenshot from a string on my system with 2 conservative days kWh kWh visable- south facing/ 33deg pitch/virtually zero shading/ rated at 1660w, vast difference between the daysscreenshot-20231214-191922-vrm.jpg


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