Solar panels (pv) efficiency in winter/cloudy/shade

1. How is the energy production in winter (central/east Europe) in the cloudy day without direct sun?
2. How is the energy production in summer (south Europe) in the cloudy day without direct sun?
3. How is the energy production in summer (south Europe) in the partly shaded spot, ie. under the tree or sth?

JakubMitkaJakubMitka said:

I am about to install a solar panels on the roof of my California Beach (85Ah leisure battery) for 2 reasons. In the summertime to stay off-grid with fridge working for few days or more (now, in 30 Celsius it runs approx ~48h). In the wintertime to stay of-grid with aux. heater working for few days or more (now, in -5 Celsius it runs approx ~48h).

Therefore, I have following questions.

1. How is the energy production in winter (central/east Europe) in the cloudy day without direct sun?
2. How is the energy production in summer (south Europe) in the cloudy day without direct sun?
3. How is the energy production in summer (south Europe) in the partly shaded spot, ie. under the tree or sth?

I know there are portable solar systems, energy banks, etc. In this thread I'm considering roof systems.

Thanks in advance for all support!

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dspuk said:

A veritable minefield of a question akin to "how long is a piece of string". We have a 100W "Roger" panel on our Ocean and it works great in the summer in the UK and pants in the winter.

These are useful for EU averages. There is no simple answer, depends on here you go, when, the position of the panel etc etc.

Solar Sun Hours | Average Daily Solar Insolation | Europe

www.hotspotenergy.com

File:Europe sunshine hours map.png - Wikimedia Commons

commons.wikimedia.org

Solar resource maps of Europe

The largest collection of free solar radiation maps. Download free maps of GHI, DNI, and PV power potential for various countries, continents and regions.

solargis.com

List of cities by sunshine duration - Wikipedia

en.wikipedia.org

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JakubMitkaJakubMitka said:

I might not asked precisely. I'd like to know how certain conditions affects the PV panels productivity. I know that even partial shade can switch off the whole panel, I know that thick clouds layer can lower the energy production to 5% on the roofs house, etc.

That's why I explained my needs to hear others subjective opinion based on their off-grid, wild camping experience

I might not asked precisely. I'd like to know how certain conditions affects the PV panels productivity. I know that even partial shade can switch off the whole panel, I know that thick clouds layer can lower the energy production to 5% on the house, etc.

That's why I explained my needs to hear others subjective opinion based on their off-grid, wild camping experience

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dspuk said:

Same answer TBH.

Works great in bright sun.
Works poorly in shade or thick cloud (in the UK, likely better in Southern Spain).
Does not work at all in the dark (you will be surprised how many people don't seem to know this).

You will get a cacophony of answers. Everyones individual setup and circumstances are different. Including yours. The best thing you can do is to get a setup that works for you and can be expanded.

We have one Roger 100W panel. May one day get two. But for us - no more than 3/4 days "off grid" works fine and one panel gives us more than enough. I'll ignore "wild camping" - most "wild campers" are car park warriors.

If you're worried just get a 200W setup. Just about everyone and their dog agree that is the ideal setup for a Cali.

For your setup question - 100W will get your Fridge working in poor weather for 4 to 5 days. 200W, in most weather, poor or blazing sun, should get you working almost indefinitely.

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Ch1pbutty said:

We have 3 of Rogers panels on our Beach & tend to have empty roof bars on when parked up on the drive. If we didn't have the roofbars then would have had 2 panels, but additional one more than compenstes for any shadow created by the roofbars & makes the roof look more uniform. We are based in South East UK and have alot of overcast days during the winter.

Dometic fridge runs 24/7 all year round, even in the winter. Never had a battery / power issue.

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Webbah_in_Switzerland said:

I'm in Switzerland and lately it's been cloudy most days with several rainy days. I can tell you the Solar in Winter is more or less useless unless you are using very few low watt consumers. I have 170 watts of panels on mine and while I get 150 on average in summer I only see 10-15 watts during Winter unless it's a rare sunny day. The sun is at a lower angle in winter as well so this affects as well unless you can change the angle of the panels to capture the few peak hours on a sunny day. See the pMax values below for reference of the last several days. Also only storing between 20-50wh's a day which is horrible.

This is why I installed a dedicated DC-DC booster from Victron. I know the Cali and Beach have a "Boost" mode but it isn't consistent. If you monitor the batteries you can see that. With a Victron BuckBoost you can leverage your alternator while driving and choose between 50A or 100A models. I went with the 100A BuckBoost which is a beast!

View attachment 103756

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Webbah_in_Switzerland said:

Victron BuckBoost you can leverage your alternator while driving and choose between 50A or 100A models. I went with the 100A BuckBoost which is a beast!

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yossarian said:

Assuming you have two AGM leisure batteries around 75Ah each you should consider reprogramming your Victron device's current limit to less than 45A. Research AGM battery C charge limit. It's typically 0.3C and a bit lower will improve battery life.

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