Many different tactics must be employed to work your way to independence off the grid but the first step towards off the grid living is the reduction of energy consumption. Using high efficiency technology and making a few simple lifestyle changes can have a large impact on your daily energy use and thereby drastically decrease the investment needed for an off grid energy supply such as wind or solar.
One of the technological improvements I have made that I am most happy with is my home made high efficiency refrigerator. Well, perhaps I should say home wired because it’s simply a chest freezer wired to keep food cool rather than frozen. This refrigerator has been my only refrigerator for 4 years and has operated flawlessly with extremely low power consumption.
My motivation to experiment with a new refrigeration strategy came from my experience with my old refrigerator. It was a fairly common style of stand up refrigerator with a freezer section on the top third and it consumed an outrageous total of 5-6kwh a day! The major flaw of the common refrigerator is that the doors are located on the side. A proper design should take into account the fact that cold air is more dense that the rest of the air in your house and will drop in height when given the chance. Well the cold air in your refrigerator gets that chance every time you open the door. As you gaze inside to select your next meal, all of the cold air rushes out by your feet and is replaced by warmer air from your living space that will now need to be cooled. Also, the magnetic door seals, no matter how air tight when they are new, will inevitably develop imperfections and allow the cooled air to seep through constantly.
An efficient regrigerator design must start with a well insulated chest style container. If you don’t want to build your own, you’re in luck because any chest freezer will work wonderfully. Cool air from within the unit will not leak because the door is located on the top. Also, each time you open the refrigerator to grab something to eat the cool air will stay inside and will not need to be recooled as soon as you shut the door.
The obvious problem with using a chest freezer as your regrigerator is that its thermostat is set for a temperature range far to low. To solve this problem, it is necessary to setup another circuit with a thermostat and relay switch to make sure the temperature stays at about 4 degrees celsius. Basically, this circuit must turn on the freezer compressor when the temperature rises above 4 degrees and turn off when the temperature drops below 4 degrees. The simplest option would be to find a cooling line voltage thermostat with a range of 0 – 10 C but I couldn’t find one so I had to use a regular heating thermostat with a range of about 0-30 C. If I set this heating thermostat at 4 C and hooked it up to my chest freezer, it would turn on the freezer when the temperature dropped below 4 C and this would only make it colder or if the temperature was above 4 C the thermostat would never turn on the freezer! More research was needed to solve this problem.
The solution I found was the SPDT relay switch shown above. An SPDT relay uses the electromagnetic force of a coil to control a switch in another circuit and when hooked up as shown below this relay allowed me to use a heating thermostat to correctly control freezer compressor. When the heating thermostat reads a temperature of 3 C it will close its circuit and this will allow current throug the relay coil and flip the switch to the off position. When the heating thermostat reads a temperature of 5 C, it will open its circuit and this will stop the current through the relay coil and close the other circuit thereby turning on the freezer compressor.
In order to get wires to the new thermostat inside the refrigerator, I opened up the drain plug at the bottom corner of the unit. The hole is taped shut with duct tape inside. The relay switch is just tucked away between the wall and the regrigerator for now. I’ll build a nice circuit box for it at some point.
I can keep all of the same foods in this chest refrigerator but the organization has changed because the door is on the top. I found two rubbermaid bins that fit the large storage area quite well. I stack one on top of the other and just pull out the top one when I want to get at stuff in the bottom. I thought this process might get annoying but I found that I rarely have to do this if I just put my long term storage items in the bottom container and all of my daily used items in the top container.
Since the main reason for this project was energy conservation I should fill you in on the performance of this chest refrigerator. I plugged in my electrical energy meter to this unit for a few days and found that it used about 200wh a day on average. That’s only 2 cents a day of electricity and a huge drop from my former energy sucking model that used 5-6 kwh a day. The most efficient refrigerators you can buy new today use around 1 kwh a day and this design uses only one fifth of that!
This difference in power consumption only means a few dolars a year on my power bill if you are already hooked up to the grid but if you consider buying solar panels to power your houshold technology then this difference in energy consumption means spending thousands of dollars less on solar panels so the simple change to a chest refrigerator makes living off the grid much more viable.
That’s all you need to know to setup your own chest refrigerator but if you want to strive for even higher efficiencies and have some technical experience to help you through the process then I would suggest having a look at this chest refrigerator project that uses a custom thermostat and draws an incredibly low 100wh a day.
