To a casual observer aluminium soda cans and solar energy would have seemingly little to do with one another. However with some ingenuity and a basic understanding of thermodynamics you can transform your beverage empties into a powerful and efficient passive solar energy cell. Passive means that it does not generate electricity directly, but rather passively assists a standard generator or serves as heating. There is a trick to it though, which comes in the form of thermally conductive black paint which covers each column of modified aluminium cans. The heat energy from the sun then transfers through the very conductive aluminium into the air inside.
- Skill level:
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Things you need
- Safety goggles
- Wash basin
- Warm water
- Phosphate-free dish soap
- Drill with metalworking bits
- Tin snips
- Needle nose pliers
- Heat resistant adhesive
- Duct tape
- Two window panels
- Treated lumber
- Wood screws
Fill a basin with warm water and some mild dish soap. Soak the aluminium soda cans in the hot water for at least two hours before rinsing them clean with hot water. Mark the centre of each of the bottoms of the soda cans with a pencil.
Drill a hole in the centre of the bottoms of all the soda cans, using progressively larger drill bits until you have a hole large enough to easily insert the end of the tin snips. Cut away the middle of the bottom of all the cans, leaving 1/2 inch remaining below the edge of the ridge of the can's bottom. It is important that the ridge remain intact, as it is where each can will join its neighbour. Use the tin snips to remove the same amount of material from the top side of the can. You should now have two holes of the same size on both the top and bottom of the can.
Cut six equally distanced notches on each end of each can with your tin snips. Bend them into a spiralled fin shape using needle nosed pliers. The fins will put a spin on the air, allowing for better circulation throughout the device.
Glue the prepared cans into columns using heat resistant metal adhesive. Once you have constructed enough columns to fill your cell casing you'll need to construct top and bottom caps. Build a soda can column, seal both ends with duct tape and use tin snips to cut holes into the sides of the cans so that the holes fit over the top and bottom of each column. Cut one final hole for the air intake and air output, which will be a single can that sticks out the top and bottom of the frame. The final configuration will be that of a series of columns with a single row on the top and the bottom. Seal any air leaks with duct tape.
Paint the can assembly a deep shade of true black, using a thermally conductive paint. The dark shade is what converts the solar energy into heat which can be harnessed in the form of flowing hot air.
Drill pilot holes before using wood screws and a drill to assemble the wooden frame, using two window panels as the front and back, allowing the panel to collect energy from the sun regardless of its direction so long as it is not placed in shade. Cut out an air intake and hot air output hole at the top and bottom of your cell frame, and then seal it with duct tape.
Tips and warnings
- Begin with the end in mind and draw a diagram on graph paper before you start; it will save time when assembling the frame.
- By attaching the hot air output to your home heating with a one-way vent you can save on winter heating bills. You can even use your indoor air as the air intake to further enhance efficiency.
- By attaching the hot air output to an air turbine generator you can produce cheap, green electricity.
- Always wear safety goggles when working with wood or metal.
- Consult local building codes when attaching this device to your home heating or a generator.
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