PV; what's it like in winter?

[Threeracers]

I wonder if someone can give me an idea of what to expect in winter in the UK? I have recently finished my electrical installation adding solar panels only a couple of weeks ago. Prior to that I was topping up through hook up on my weekly pit stop for laundry and fluids in and out.

I have been pleasantly surprised by the output and this morning I was producing as much as I was using by a little after 8am and each day the batteries are back to 100% by early afternoon. But I appreciate this is August and I am not going to see this level over the winter. What can I expect? Someone suggested that the level of production in a bleak winter month can drop to about the same produced on one good summer day, is it that much of a drop?

TIA

Mark

 

[Geistguy]

We live in northern Scotland where winter daylight hours are very short but we still manage to keep off grid. Solar will be virtually useless but we usually just overnight and move on, a 50 mile drive will usually top up our battery. For this coming winter we have upgraded to a 300ah lithium but our previous 120ah liesure battery never let us down.

 

[Threeracers]

Are you full time? From my guesstimates I think I can remain off grid all year.

I do have two Victron 17 amps battery to battery chargers but I haven't really tested them yet so don't quite know what to expect from them.

M

 

[St3v3]

Unless you can tilt your panels solar is rubbish in the winter. Even then, it's not great.

 

[Threeracers]

I did look into tilting mechanisms but I bought some fairly chunky panels, 2m x 1m, and getting up to the top of the truck to adjust them wouldn't be an easy task so I dropped that idea.

Fairly happy with them them flat in August though, I was back up to 100% at noon today.

M

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[Howard B]

In Nov, Dec ,Jan & Feb my home PV generates about a quater of what it does in May, June July August.

 

[Threeracers]

In Nov, Dec ,Jan & Feb my home PV generates about a quater of what it does in May, June July August.

Thank you Howard, that's very useful and not quite as bad as I thought it might be!

Regards

Mark

 

[RedFrame]

Thank you Howard, that's very useful and not quite as bad as I thought it might be!

Regards

Mark

But... His home PV is likely to be tilted...

Personally, when designing our van I didn't factor in Solar for winter use as, in my experience (flat), it provides negligible power.

Cheers
Red.

 

[Howard B]

But... His home PV is likely to be tilted...

Personally, when designing our van I didn't factor in Solar for winter use as, in my experience (flat), it provides negligible power.

Cheers
Red.

What does being tilted have to do with it?

 

[RedFrame]

What does being tilted have to do with it?

Really, is that a serious question? If it is I'll give you a synopsis of my testing from a couple of years ago...

Cheers
Red.

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[Insider]

What does being tilted have to do with it?

think of shooting something. If you point the gun at it directly then the bullet goes through it causing big damage. If you shoot it at an angle then the bullet glances off causing little damage. Same with sun light. Sun goes high in the summer so light hits a flat roof at a perpendicular angle leaving all its useable energy on the solar panel. Sun goes low in winter so light hits at lets say 20° leaving only a fraction of its energy on the panel.

Tilting the panel in winter towards the sun brings you back to perpendicular getting all the useable energy but being winter its only for a few hours and you would have to change the angle of the tilt frequently to maximise the amount of energy whereas in summer the sun is high for a long period therefore is perpendicular for a lot of the day.

 

[chesterfield hooligan]

In winter we had a folding solar panels which we pointed at the sun in Portugal if heading north there's a possibility of snow so that must be taken into consideration clearing the panels.

 

[Lyrick]

150w of solar keeps both 100ah leisure batteries and engine battery topped up over winter, but my drive is on a slope and facing South West.

 

[Raul]

Nov, dec, jan, expect as little as 1/8 -1/4 of PV installed. As in 1kwp PV, can yield 125-250wh daily. Some days are brighter than others.

 

[Threeracers]

Nov, dec, jan, expect as little as 1/8 -1/4 of PV installed. As in 1kwp PV, can yield 125-250wh daily. Some days are brighter than others.

Many thanks Raul, similar numbers to Howard and gives me a good idea of what to expect.

I still need a campsite with facilities for laundry and loo emptying every ten days or so, I might need to plug in occasionally when I do.

Mark

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[Raul]

Here is a nice tool for you to try. Put in the relevant details and location on map, make sure slope is 0 for flat panels, and you will get a pretty accurate estimate for your system. I have used that site many times and it’s spot on.

JRC Photovoltaic Geographical Information System (PVGIS) - European Commission

Photovoltaic Geographical Information System (PVGIS)

re.jrc.ec.europa.eu

 

[St3v3]

What does being tilted have to do with it?

You get a much greater yield when the sun is low in the sky (winter)

 

[Raul]

You get a much greater yield when the sun is low in the sky (winter)

If you tilt

 

[Threeracers]

Thanks, I will look at that.

Victron have a daily forecast thing based on location - you can see it in the graph on my first post - which seems a good daily guide.

M

 

[Howard B]

Really, is that a serious question? If it is I'll give you a synopsis of my testing from a couple of years ago...

Cheers
Red.

I get about the yield being better with tilted panels. However mine are fixed on the roof of my house producing X in the summer months & Y in the winter months. ( mine average 16kWh ( X) per day in sumer and 3-4 kWh (Y) per day in winter). On some days in February I was producing 14kWh.
Are Threeracers panels which are flat on his van roof ( I presume), not likley to produce a similar X & Y ratio based on the size of his panels.
As an aside,

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[Raul]

I get about the yield being better with tilted panels. However mine are fixed on the roof of my house producing X in the summer months & Y in the winter months. ( mine average 16kWh ( X) per day in sumer and 3-4 kWh (Y) per day in winter). On some days in February I was producing 14kWh.
Are Threeracers panels which are flat on his van roof ( I presume), not likley to produce a similar X & Y ratio based on the size of his panels.
As an aside,

The van roof is flat horizontal, is your house roof flat? Or pitched?

 

[Howard B]

The van roof is flat horizontal, is your house roof flat? Or pitched?

My house is pitched.

 

[St3v3]

.
Are Threeracers panels which are flat on his van roof ( I presume), not likley to produce a similar X & Y ratio based on the size of his panels.

No, because the summer sun is brighter, the angle isn't as important.

 

[Raul]

My house is pitched.

If roof is pitched then, and panels follow the roof elevation, it will be at least 30 deg tilt. Massive difference in winter harvest compared to flat panels. Your panels are doing much better then a flat install.

 

[St3v3]

If you tilt

Read the quote and my reply together

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[busbuddy]

Fairly happy with them them flat in August though, I was back up to 100% at noon today.

Can I ask, what exactly (electrical) are you using onboard?
I have 320w of solar flat on roof feeding 2 old school lead acid leisure batteries...in august I can use my inverter to power the kettle, toaster, solar replenishing that and the overnight power usage and if this wasnt 100% full by 10am at the very latest I would be concerned something was wrong with my set up.
Normally, in the summer, my batteries are back at 100% before I get out of bed

 

[MichaelT]

Can I ask, what exactly (electrical) are you using onboard?
I have 320w of solar flat on roof feeding 2 old school lead acid leisure batteries...in august I can use my inverter to power the kettle, toaster, solar replenishing that and the overnight power usage and if this wasnt 100% full by 10am at the very latest I would be concerned something was wrong with my set up.
Normally, in the summer, my batteries are back at 100% before I get out of bed

We have 150w solar panel and 200a lithium and even with 36c sunshine we are struggling to charge. Getting about 5a during the day once sun is up but we are using the air fryer or slow cooker a lot plus fans going 24*7 to try and keep cool. Down to 28% this morning (it was 30% last night) and we are not going to use electrical appliances today except the fans and normal stuff like fridge and pump etc. so will see what its like tonight. We are getting 5ish hours of sun here in Jaca and we've been here since last Tuesday and battery has been up to 100% but its now lowest its ever been. Thinking we may need another panel but not sure its worth it as we are thinking of trading in in a couple of years and we are only here 10 days due to a medical issue so would normally be moving either everyday or every 2 or 3 days so its a one off situation maybe.

 

[funflair]

Can I ask, what exactly (electrical) are you using onboard?
I have 320w of solar flat on roof feeding 2 old school lead acid leisure batteries...in august I can use my inverter to power the kettle, toaster, solar replenishing that and the overnight power usage and if this wasnt 100% full by 10am at the very latest I would be concerned something was wrong with my set up.
Normally, in the summer, my batteries are back at 100% before I get out of bed

I have no doubt that your inverter/batteries "can" power a kettle and toaster as you say but I would doubt if you are doing that very often with your charge sitting so close to 100%.

We have 520 watts of solar and use all the things you mention and possibly more but we struggle to stay at 100% (not worried as we have a lot of LiFePO4 as well)

This shows that yesterday in sunny "ish" Scarborough we made 1.5Kwh so about 110ah but this morning the batteries are down by 95ah, I did cook on the induction last night though and boiled the kettle a couple of times.

And to answer the OP's question, in winter I would expect a fraction of the summer performance so we rely on the battery capacity and B2B when we move.

 

[busbuddy]

I just use toaster/kettle the once on summer mornings if the boss requires them but I was just wondering what the start state % of the op's batteries were before the new day starts charging them and what was being used to deplete them because,to me, that's the bigger issue

 

[Threeracers]

Can I ask, what exactly (electrical) are you using onboard?
I have 320w of solar flat on roof feeding 2 old school lead acid leisure batteries...in august I can use my inverter to power the kettle, toaster, solar replenishing that and the overnight power usage and if this wasnt 100% full by 10am at the very latest I would be concerned something was wrong with my set up.
Normally, in the summer, my batteries are back at 100% before I get out of bed

Good morning, I have 1080 watts on the roof with 3 x 360 w Victron Mono panels in series and 2 x 230 ah 24 volt Roamer batteries. It seems they seldom drop below 75/80% and usually get replenished by 10/11 am if I get clear sun. My earlier post was from a position next to a farm building which you can see in the background in the photo above and it was casting a shadow which meant that the sun needed to be up for it all to work, hence my earlier post regarding being replenished by noon. It's all a learning curve.

This is a good example from a couple of days ago. A bit of sun from 6'ish, the spike is my espresso machine warming up, and back up to 100% fairly shortly afterwards.

Regards

Mark

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