Rather than spending a large amount on a solar fridge, you can you adapt a chest freezer to do the job for you. Best to get yourself an A++ rated chest freezer, or if your on a real budget you can get a second hand old one (try and get something as new as possible or something with at least an A+ rating).
The advantage of using a freezer is the insulation layer is much greater and top loading means that the cold doesn’t fall out every time you open it. They also tend to have a larger compressor so will have to run for less time to get the amount of cold you want.
Then you simply add one of our thermostats into the power for the fridge. There are 2 methods you can use for this:
Capillary Thermostat - Buy one here
This is a great way to do it as the thermostat is not powered so has absolutely zero drain on your solar power. It can work on any AC or DC powered freezer as it is just acting as a switch.
Simply Put the silver thermostat end in the bottom of the freezer. You can either simply tape it to the side at the bottom and then have the tube come up out of the top of the freezer, or you can drill a hole and insert it into the bottom if you want a neater/better job. Make sure you seal the hole up well afterwards. If you are putting it just out of the top of the freezer you will want to put a little protection around the tube that comes out the top so that you don’t squash it when you close the lid (the digital option below doesn’t have this issue).
Then you simply use the terminals on the thermostat as a switch. You can cut the positive wire on the power cable coming to the freezer and connect the incoming live side to the middle terminal, and the other side going to the freezer to the left hand terminal.
It’s a manual control from 0C so you can set it to the fridge temp you want.
220V AC Digital Thermostat - Buy one here
This is a really easy way to convert your standard AC powered freezer. Its power consumption is under 2W so isn’t really causing a drain on your system.
Simply put the silver thermostat end in the bottom of the freezer, you can either tape it to the side at the bottom and then have the cable come up out of the top of the freezer, or you can drill a hole and insert it into the bottom if you want a neater/better job. Make sure you seal the hole up well afterwards.
The digital controller then becomes your power switch. You can simply cut the incoming AC power cable coming to the freezer and connect the incoming power to the digital controller. Then connect the remaining cable going to the freezer to the controller as well. Follow the instructions that come with the unit for the correct wiring.
You can then set the digital controller to the temperature setting you want to run it as a fridge.