Introduction: Solar Powered Refrigerator!
First Prize in the
Renewable Energy Contest
Here is an after the fact implementation of how I power my refrigerator from the sun. This off grid system has been working great since may 2013. It is truly reassuring to know my groceries are safely stored regardless of utility power.
I have fulfilled the electrical code requirements (NFPA 70, TTS-171 Part 1) and power utility mandates for my area. If you have to perform the same on your home, all relevant certifications and approvals are needed.
Remember for solar power systems, bigger is always better. Never go borderline else your system will not be reliable for off grid applications.
Grid tie is NOT ALLOWED in my country. Also don't ever assume you will have utility power during a nationwide disaster (bad weather, riots, energy rationing, terrorism etc).
Here is a detailed write up on how I solar powered my entire home: https://www.instructables.com/id/Solar-Powering-My-...
Step 1: The Refrigerator.
Ideally an inverter refrigerator is the best bet but my old refrigerator needs 300watts when on. Basically any fridge will do but the more energy efficient means a smaller solar setup is needed.
There are the rare dc powered refrigerators that are actually more efficient than the inverter types. However should this unit fail on me, there are none sold in my country. I want to be able to go to a store and buy a replacement or repair my unit if possible in the event of failure.
Step 2: The Solar Panels.
I use eight 225watt monocrystalline panels to power my home and by extension, the refrigerator. They are wired 4 in series and 2 strings in parallel. I harvest up to 8kwh per day with these panels.
Mounting the panels on the roof can be via manufacturer mounting solutions or you can make your own with rigid pvc. I actually did a hybrid approach.
Here is how I perform cleaning of my panels" https://www.instructables.com/id/Maintenance-cleani...
Step 3: The Charge Controller.
I have an outback fm80 charge controller to route energy from the panels to the batteries. Mppt chargers are more efficient and economical for large solar systems.
Step 4: The Batteries.
I use 16 lifepo4 batteries at 25.6v. They are all wired in parallel with an energy meter per pair of batteries. Each battery has a switch for isolation. For the work I did on my battery bank, please read: https://www.instructables.com/id/Lifepo4-solar-stor...
My refrigerator uses 1.2kwh per 24hour period. My battery bank has 4kwh capacity.
My country's climate is hot. Lead acid batteries, although cheaper, have failed in less than 10months of use. If your maximum temperature is below 25C then you should be able to use lead acids. I have long abandoned lead acid technology in my home and car. Lifepo4 is safe, powerful and environmentally friendly.
Step 5: DC Distribution.
With the appropriate sized conductors, I have circuit breakers to protect all my components and also provide easy isolation for maintenance.
The attached chart shows the conductors sizes for DC power.
Step 6: The Inverter.
To get 120vac from 25.6vdc I have a 1000watt power bright pure sine wave inverter. Always use pure sine wave especially for motor applications.
Step 7: The AC Distribution.
I made a panelboard with din circuit breakers to get power to my house loads. I have a breaker dedicated to the kitchen area. Since my refrigerator uses 2.5Amp the circuit breaker for it is 6Amp single Pole. Here is how I built the panelboard: https://www.instructables.com/id/DIY-Circuit-breake...
Also in the panelboard I have an automatic transfer switch (ATS) shown at the bottom of the pic. This switch is controlled by my home automation system which will switch to utility power if the batteries get depleted.
My local power utility is actually my backup power source.
The control system for my home is detailed here: https://www.instructables.com/id/Creating-a-home-au...
Step 8: Powering the Refrigerator.
The outlet for the fridge is protected with a motor protector. This is only needed should I switch to utility supply. The inverter gives clean power.
So that is how I powered my refrigerator via the sun!
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