Solar panels for fridge

[Hydrozoan]

Not a boat question specifically but I hope expertise here may help as I don't use solar panels. A UK neighbour who now lives mainly in Southern Africa is back home in the UK for a while and is thinking of acquiring solar panels to take back to run a 60W fridge in his 4x4 whilst camping. He is wondering what type/size of panel would be best to do that, and where he might best look to buy. Any relevant experience and advice I can pass on to him would be much appreciated.

 

[TQA]

The 60 w info is useful but you need to know the Amp Hour draw over 24 hours. 60 w is 5 amps at 12 volts, does the fridge run continuously at 5 amps?

If it does that is 120 a/h.

That is a lot my large 12 v fridge which makes ice in the tropics draws about 50 a/h in 24 hrs.

 

[William_H]

As said there are many variables to this question. For instance I found when touring outback Oz I was driving every day so running the (compressor) fridge when the engine was charging. The fridge working as a freezer stored enough cold overnight to not need to be run apart from when driving.
On the other hand for camping when not driving you need solar panels. The amount you need is again variable and will depend as much on what size you can carry and store as much as cost. I would not suggest he look at domestic 40v 200w panels as being the cheapest watts for dollar. However he will need a MPPT regulator to charge a 12v battery. Then again they can be pretty big to fit on a roof rack.
If he is going for 12v (20v) panels then there is a huge range of sizes all can be used with or without a regulator. 60w might be agood starting point. He could add more panels if it is found necessary in practice. But this all depends on him having a compressor type fridge not a paltier type which gobble current and don't get very cold. good luck olewill

 

[vyv_cox]

My 55 litre fridge on the boat in Greece consumes about 3 - 4 amps when running, which varies between about 1/3 and 1/2 the hours in the day, dependent upon ambient and water temperature (water cooled). In May June and July my 125 watts of solar panel will run it indefinitely, plus a few other consumers. In October it is just about coping but I need to run the engine every other day to top up batteries. I have three 100 Ah domestic batteries, when I had only two I doubt if they could have provided power for the fridge all night at this time of year.

 

[vyv_cox]

William H touched upon the fridge type, which is crucial. A compressor type will run on 12 volts quite happily, but many fridges in camper vans are adsorption types running on gas/mains/12 volt. Solar panels would not keep up with the consumption on 12 volts, which could be 10 amps plus. Peltier fridges consume about 4 amps constantly, no thermostat unless you buy a very expensive version, about x4 the price. Again, solar panels would not cope unless very large.

 

[Trundlebug]

Ultimately you could discuss for hours which is the perfect sized panel to match the consumption of a fridge.

However the determining factor in 99% of cases will be the size of the area available on which to fit the panel.
My advice would be, quite simply, measure up the space available and find a panel with the closest dimensions to fit it.
Semi flexible panels aren't heavy, so weight isn't an issue.
The solar regulator will not allow overcharging of the battery / batteries.
It's not likely that the panel will be too large and provide too much power anyway, as although there will be plenty of strong sunshine the fridge will need to work hard to cope with the raised temperatures.

Get the biggest you can fit and are willing to pay for, then you'll be worry free regardless of conditions.

 

[Hydrozoan]

Thanks to all for the information and advice - I will get some more information and get back here - if I may - with any further detailed questions. (He needs to look up the fridge details but tells me it's an Engel of about 80 litres capacity - though quite possibly not a current model, I suspect - and not gas switchable, so I'm guessing a compressor type.)

 

[rob2]

...adsorption types running on gas/mains/12 volt. Solar panels would not keep up with the consumption on 12 volts, which could be 10 amps plus.

All the three way fridges I've met with operate on a thermostat for mains and gas usage, but the 12V heater is assumed to be used only whilst running the engine, such as towing a caravan and connected to the auxiliary supply from the tow vehicle, so it runs continuously. After a good journey there is plenty of ice for the G&T and the beers are well chilled.

Rob.

P.S. Just realised that the Engel, being an Aussie is a very different beast. The only 60l one I found in a quick Google is a compressor type 240V/12V drawing up to 4 amps, so it comes down to duty cycle. Probably best for the owner to run it off the battery and find out what it is drawing under ambient conditions and for how long, then choose a panel and battery to suit.

 

[vyv_cox]

All the three way fridges I've met with operate on a thermostat for mains and gas usage, but the 12V heater is assumed to be used only whilst running the engine, such as towing a caravan and connected to the auxiliary supply from the tow vehicle, so it runs continuously. After a good journey there is plenty of ice for the G&T and the beers are well chilled.

Rob.

Yes, all the ones I have had in motorhomes would not run on batteries alone, needed the engine running before they would operate on nominal 12 volts. However, these were professionally fitted and it would presumably be perfectly possible to set it up to run on batteries in a DIY installation. If switching is voltage sensitive it might even go with solar panel input.

My present Dometic fridge freezer is far less efficient on 12 volts than it is on gas or mains.

 

[William_H]

All the three way fridges I've met with operate on a thermostat for mains and gas usage, but the 12V heater is assumed to be used only whilst running the engine, such as towing a caravan and connected to the auxiliary supply from the tow vehicle, so it runs continuously. After a good journey there is plenty of ice for the G&T and the beers are well chilled.

Rob.

P.S. Just realised that the Engel, being an Aussie is a very different beast. The only 60l one I found in a quick Google is a compressor type 240V/12V drawing up to 4 amps, so it comes down to duty cycle. Probably best for the owner to run it off the battery and find out what it is drawing under ambient conditions and for how long, then choose a panel and battery to suit.

Engel is very popular in Australia (but made in Japan) and was almost universal in the bush for many years. (there were not many Land Cruisers without one) until lately the other com,pressor types have been available. Even the Chinese have got into compressor types) The Engel is a compressor type using (or used to) a peculiar vibrating compressor.It would run on 50 hertz mains or from a built in 50 hertz inverter. They don't seem to draw more or less current than other compressor types. I did have one long ago but the compressor died. Failed flapper valves in the sealed compressor. Replacemnt was going to cost a large portion of new fridge cost so it was dumped. I now have a little WACO (not used in the boat but in the car) It also works well as a freezer but I must say when I lift it up and the bottom is very cold to touch I think insulation is not so good. In the end it is all about insulation. olewill