Solar powered fridge

I live in the south of Spain, we get a lot of sun, so I was thinking of hooking up a solar panel on the roof to our fridge. Fridge runs on 220-240 volts AC 50/60Hz, 10 Amps. My current problem is to set it up to switch to the mains whenever there isn't enough sun to provide all the energy it needs.

I was thinking of using a volt meter as a sensor, because it seems straightforward enough, but I'm not sure how to do this

For the rest I was intending to use the "how to use the 5V relay on arduino" ( for the circuit and its program (with a few modifications)

Should it matter this is the panel i was going to buy:

look into getting a Tesla Power Wall.
there are home-brew versions so you can build your own much cheaper.

look at the power rating of the refrigerator and compare to the power rating of the relay to make sure they are compatible.

That's a 270W 37V DC panel. If you want to run a 2400W device (240V@10A) you're going to need a lot more than a single panel. And to convert the panels output to AC you're going to need an inverter and they're not cheap. A proper solar power inverter will manage the mains/solar switching for you.

But perhaps you just want to top up mains power a little which is a completely different matter. But you'll still need an inverter somewhere in the system to convert solar panel DC to AC.


A thing to watch out for with mains powered fridges is the enormous inrush current when the synchronous motor starts. I have a 1kW (2kW peak) inverter because an 800W (1.5kW peak) was not sufficient. Even with the 1kW inverter the fridge won't start immediately after it is stopped - presumably the intenal pressure is higher and puts a heavier load on the motor. When it doesn't start it can draw 40 amps or more from the 12v battery - which would deplete the battery very quickly, and is probably not good for the fridge either.


Fridge runs on 220-240 volts AC 50/60Hz, 10 Amps.

Our 1.8m tall (quite big) Bosch fridge and freezer are 90W each, under 1/2 an Amp. Maybe you need to get some more modern appliances.

My current problem..


Fridge runs on 220-240 volts AC 50/60Hz, 10 Amps.

That would be the circuit breaker specification. Unless it is a walk-in freezer, it uses less.

By the way the fridge I referred to in Reply #3 is (IIRC) rated at 40 watts.


Off topic for an Arduino forum, but some solar powered fridges use no electricity.
Google for "zeolite refrigeration system"