Off-grid Personal Refrigerator

This device is a charcoal-based refrigerator. This refrigerator utilizes evaporative cooling (instead of electricity) to create a cool space to store food. We utilize scrap wood, chicken wire, mesh and charcoal to construct the device, as well as water collected in a rain barrel to catalyze this evaporative cooling process. This is a great off-grid option to refrigeration technology that can be implemented in areas where electricity is scarce, or individuals would like to reduce their electricity consumption and carbon footprint.

Materials Needed:

2 by 4's (wood): one 20'', two 24'', eight 26'', one 32''

scrap-wood

1 slab plywood (to fit 20'' X 24'' bottom)

black mesh fabric (12 ft by at least 32'')

Chicken Wire (15 ft by at least 32'')

Charcoal (four 7.7Lb bags)

Zip-Ties

2 hinges

PVC flexible pipe (1 in diameter)

bucket with adjustable valve

screws and staples

WD40

Equipment Needed:

Drill Press

Power Drill

Staple Gun

Hammer

Saw (preferably a power-saw)

The first step is to construct the outer frame of the fridge (for the walls) with scrap wood. To do this, cut the 2 by 4s into individual pieces: one 20” piece, two 24” pieces, eight 26” pieces, and one 32” piece. All the 26” pieces are for the vertical pillars of the fridge. The other 4 pieces are used for the bases of each of the wall frames of the refrigerator.

Next, construct the sides into U-shapes (leaving the top lateral sections open for the irrigation system to be installed). The lengths of the bottom lateral pieces of each wall vary for a reason. The 2 side sections utilize the two 24” pieces allowing these walls to be the exact same length. The back piece uses the shorter 20” piece which permits it to be situated within the two sidepieces. The longer 32” piece is used for the door so it can lay on top of the ends of the two sidewalls. This is important so the door can be attached using a hinge and fully close without creating a gap. Each of these U-shaped sides is constructed in a similar fashion.

Using a drill press, drill two side-by-side holes about an inch from each end of the base on each lateral bottom limb. Nect, use a power drill and screws to attach each end to one of the 26” wood pillar pieces (using these pre-drilled holes). After doing this, 4 U-shaped wall frames should be formed. These are the main components of the skeleton for all the walls of the refrigerator.

Next, the lining of the walls needs to be attached. Make sure the fabric is greater than 32” in length (so that it fits the walls). Cut 8 slabs of the fabric into pieces equal in area to the U-shaped wall frames. The dimensions of these slabs consisted of four 24” by 26” pieces, two 20” by 26” pieces, and two 32” by 26” pieces. Initially, two of these pieces were attached to each side of the 3 wall frames and were stapled into the wood beams of the frames about every 3 inches. Therefore, these 3 wall frames create pouch like structures. The door piece is only covered on one side at this point to allow for some flexibility while attaching the door and the hydration apparatus. These fabric pouches are used to hold the charcoal in place within the walls.

To reinforce the structure of the wall we attached chicken wire lining to the outside of each wall frame to give the pouches some more structure and strength. Similarly to the fabric lining, the chicken wire lining was cut to fit both sides of each of the four wall frames. The dimensions of the chicken wire lining again consisted of four 24” by 26” pieces, two 20” by 26” pieces, and two 32” by 26” pieces. Only initially attaching the lining to one side of the door frame is an important step to allow for flexibility. Staple the chicken wire to the frame about every 3 inches on top of the fabric. Since the chicken wire is a much stronger material than the planting fabric, it is useful to actually hammer in all of the staples afterwards because the staple gun has trouble actually piercing the wood, fabric, and holding the thicker wire in place.

Depending on how large your walls are, you may need to reinforce them. When putting the charcoal into the walls the chicken wire will have trouble supporting the weight the larger the walls are. We suggest two options for this, the first is to line the walls with wood planks to give the walls more structure. The other option is to use zip ties to hold the walls together.

Now it is time to connect the wall frames together to form the refrigerator structure. The two sides should be attached to the back piece first. To do this, the side pieces should be situated on the outfacing sides of the laterally shorter back piece. At this point we simply screw each pillar of the side pieces into the pillars of the back piece. The first screw should be screwed in two inches from the base and then every 6 inches after that. Four screws should be put into each set of pillars. After doing this, there should now be a three-sided structure that can stand on its own.

Next the door needs to be attached with hinges. Two hinges are attached on the top and bottom of either side of one of the pillars (of one of the sidewalls), depending on which direction one wishes the door to swing. The hinges are screwed in two inches from the top and two inches from the bottom to distribute the weight of the door properly. The door is then attached to the hinges in a similar fashion as the hinge was attached to the side pillar. The hinges should be loosened with a lubricant like WD40 to allows the hinges to work more freely and swing. The bottoms of the chicken wire may have to be trimmed to reduce friction.

The next step is to fill the walls with the charcoal. Fill all the walls up with four 7.7 Lb bags of charcoal (makes the walls extremely heavy and sturdy).

Next, it is time to attach the water apparatus. Attach a PVC pipe lining around the top of the refrigerator. This is a flexible fluid line type of PVC pipe that can be bent and stretched to fit whatever shape or contour is needed. The open tops allow the pipe to have exposure to the charcoal in the pouches of the walls.

Drill a whole every one inch of the pipe along the same plane (measure of avoid drilling holes around corners). Make holes using a drill press. Face the holes downward towards the charcoal. The pipe is then held in place with zip ties, stringing it across the top of the walls. The fluid line is attached to the joint pillar of the left side and back piece. From here the line is attached to a bucket which is the designated water source. There is a valve attached to the pipe to control the water flow and determine the amount of fluid allowed to drip onto the charcoal beds in the walls.

Finally, the floor and ceiling of the refrigerator need to be added to complete the refrigerator. This was simply done by cutting a 32” by 26” slab of plywood and attaching it to the bases of each of the joint pillars to make the floor. The slab is attached with a single screw at this point. The screws are situated on the outermost post of each joint pillar so that the weight of the plywood is as evenly distributed as possible. The ceiling is made using the exact same process but using the fabric instead of plywood. The ceiling and floor serve two main purposes, the first being to reduce the amount of cool air that flows out of the fridge. The second is that is gives the fridge a solid base to stand on. Depending on where the fridge is located, the floor may or may not be needed.

And now you're done!