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Beermonster

Solar panel & fridge

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We are on a seasonal pitch and was thinking of putting the fridge on battery when we aren’t here, will the solar panel keep the battery charged enough to keep the fridge working?

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Is that a 12v fridge or a 3 way fridge. If a pure 12v with a big enough panel it might work.

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10 minutes ago, Odd days said:

Is that a 12v fridge or a 3 way fridge. If a pure 12v with a big enough panel it might work.

 

It’s the fridge that’s in the caravan :D we have an Unicorn Cadiz S4 and it comes with a solar panel, not sure of the watts 

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Unless you have a non-standard set up the fridge will only work on 12v when connected to the car with the engine running.

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3 minutes ago, Weather Watcher said:

Unless you have a non-standard set up the fridge will only work on 12v when connected to the car with the engine running.

 

Thanks, that makes sense, we just have a standard setup, I thought it would have been a good way to keep my beers cool :)

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Posted (edited)
38 minutes ago, Beermonster said:

We are on a seasonal pitch and was thinking of putting the fridge on battery when we aren’t here, will the solar panel keep the battery charged enough to keep the fridge working?

Probably not.

 

You'd need to wire the fridge to the battery and depending on what size fridge you've got they take between 10-15amps (120-180 watts). Generally the the fridge stat only works on mains or gas so you've got to assume that it will be consuming say 150  watts continuosly = 3600watt hours. assume you've lashed out and got 200watts of solar panels and the sun shines continuously for ten hours a day you could hope to get 2000watt hours (you wont because you wont get 200watts and the sun wont shine for 10 hours).

 

The fridge in the Cadiz takes around 170 watts

 

That means the battery would have to supply 170watts for 14 hours min = 2400watt hours which means that not only have your solar panel got to supply 1700watthours for the fridge, they also got to supply 2400 to recharge the batteries.  Just for one night you'd need a 300a/h battery (to avoid discharging it  much below 50%)

 

You need oversized batteries to cope for the cloudy days (possible 4-5 in a row) and oversized solar panels to put all the energy back into the batteries and to keep the fridge running whilst so doing. You'd probably need around 5 x 100wat solar panels, optimally positioned - not flat on the van roof but pointed south and at the correct angle- and in a place where there's no possibility of shadows falling across the panels

 

 

 

Edited by matelodave
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1 hour ago, Beermonster said:

We are on a seasonal pitch and was thinking of putting the fridge on battery when we aren’t here, will the solar panel keep the battery charged enough to keep the fridge working?

The short answer is "No", normal batteries and solar panels are simply not up to the job.

To do this you would need multiple large batteries and multiple large panels.

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And people wonder why I'm so anti the stupidity that is absorption fridges.  They're very energy inefficient... A modern 12v compressor fridge is a much better option, and will run on a small average current of less than 2A.  My boat has a 12v compressor fridge, and the panels will keep that running for well in excess of a week without electrical hook up

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4 minutes ago, Guzzilazz said:

And people wonder why I'm so anti the stupidity that is absorption fridges.  They're very energy inefficient... A modern 12v compressor fridge is a much better option, and will run on a small average current of less than 2A.  My boat has a 12v compressor fridge, and the panels will keep that running for well in excess of a week without electrical hook up

But can you get a compressor fridge that runs on gas?

Even a 2A average current represents 48 Ah per day. A typical 100W solar panel in the UK, on a fixed mount will be very lucky to achieve 40W for10 hours per day which equates to 33Ah per day so fails to keep up even in good conditions before other electricity use is allowed for.

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18 hours ago, Stevan said:

But can you get a compressor fridge that runs on gas?

Even a 2A average current represents 48 Ah per day. A typical 100W solar panel in the UK, on a fixed mount will be very lucky to achieve 40W for10 hours per day which equates to 33Ah per day so fails to keep up even in good conditions before other electricity use is allowed for.

If you have an efficient compressor fridge, you don't NEED gas...15A for an absorption fridge run on 12V is ridiculous, and yes you can use gas, but the gas consumption likewise is ridiculous  (Nearly half a kg per day)... I wonder why we no longer use gas fridges domestically?

 

 

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4 minutes ago, Guzzilazz said:

If you have an efficient compressor fridge, you don't NEED gas...15A for an absorption fridge run on 12V is ridiculous, and yes you can use gas, but the gas consumption likewise is ridiculous  (Nearly half a kg per day)... I wonder why we no longer use gas fridges domestically?

 

 

Where does your "half a Kg per day" come from? Last year we used no more than that off grid for cooking, heating, hot water and fridge! 

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Dometic and Thetford Websites... 24hr consumption 420g...

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30 minutes ago, Guzzilazz said:

Dometic and Thetford Websites... 24hr consumption 420g...

We have a 10 year old more modest 60 litre fridge in our 2008 Folding Caravan. When the mains electric function failed shortly after arriving in Spain, we  had to switch to Camping Gaz 907 Bottles pending fridge repairs, so were grateful for the 260g consumption quoted in the Manual. In practice, we consumed a little less by switching the fridge off or down at night and letting the biting cold wind that whistles through the vents in the under sink cupboard provide natural cooling!

Steve

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Posted (edited)

I know of people that run compressor fridges on solar panels in good sunshine conditions but a absorption fridge you would have no chance . Even gas would only last a few weeks on a bottle and I think insurance and site rules might not be allowed left on for fire risk as some sites you have to disconnect your electric when leaving the caravan for more than 48 hours .

 

I always work gas out on half a kg a day then your lucky if you get a bit more . My fridge Thetford 190lt uses about 420g a day .

 

 

 

Dave

Edited by CommanderDave

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52 minutes ago, Guzzilazz said:

Dometic and Thetford Websites... 24hr consumption 420g...

Surely this is a projected figure for constant operation. In reality, in typical UK weather, the thermostat (which does work on gas operation) turns the flame off for most of the time. Normal gas consumption will therefore be significantly less than the 420g per day.

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Posted (edited)

I think you'll find that the quoted 420g/day is the average consumption which takes into account the operation of the thermostat rather than full on all the time.

 

Of course it will vary depending on the ambient temperature, the thermostat setting, how often you open & close the fridge door, the size of the fridge and what's in there  but half a kg a day is a good estimate.

 

Of course you could always go and do a definitive test and let us all know what it really is

Edited by matelodave

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25 minutes ago, matelodave said:

I think you'll find that the quoted 420g/day is the average consumption which takes into account the operation of the thermostat rather than full on all the time.

 

Of course it will vary depending on the ambient temperature, the thermostat setting, how often you open & close the fridge door, the size of the fridge and what's in there  but half a kg a day is a good estimate.

 

Of course you could always go and do a definitive test and let us all know what it really is

Last year we did a week off grid, using gas for heating, cooking, hot water and fridge and used around 3KG total. No way could the fridge have been using 400g per day.

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Posted (edited)

I've used part of a 4.5kg butane bottle on the boat in TWO YEARS... probably 60 nights aboard...,cooking only

Edited by Guzzilazz

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In the summer with no heating but fridge, hot water and cooking we use 6kg in 10 days and I believe the fridge to use 400 - 500 grams a day. Cooking does not use much gas. On the boat we cook a lot but a 2.7kg camping gas bottle lasts 6 - 8 weeks.

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