You can build a small solar panel to power small appliances with readily available tools and materials for under $500. The foundation for the solar panel will be a two-foot by four-foot frame made from plywood, pegboard and plexiglass that will hold the solar cells. You can then use the solar panel to convert solar power into electricity.
Things You'll Need
- 36 3-inch by 6-inch mono-crystalline solar cells
- 12-inch by 4-foot piece of plywood
- 2-foot by 4-foot piece of 3/8-inch plywood
- 2-foot by 4-foot piece of pegboard
- 2-foot by 4-foot piece of plexiglass
- 4 1-inch by 1-inch by 6-foot pressure treated/weather resistant wood for framing strips
- 3 pieces of 1/2-inch by 2-inch pressure treated boards cut to 3-foot lengths
- Water-proof white deck paint
- Fine rosin-core solder
- Rosin flux
- Clear silicon caulk
- Tile spacers
- 3/4-inch and on1-inch wood screws for treated lumber
- 15 feet of bus wire
- 60 feet of tabbing wire
- 20 gauge red and black copper wire
- 400-watt inverter
- 12-volt deep cycle battery
- 12-volt ten-amp digital solar charge controller
- Solar pv junction box
- Thin leather work gloves
- Power drill
- power sander or manual sand paper
- Miter saw or jig saw
- 60-watt soldering iron
- Staple gun
- Rosin flux pen
- Digital multimeter
- Crimping pliers
Cut framing strips into four half-inch by one-inch by four-foot pieces and four half-inch by one-inch by one-foot-10-inch pieces. Lay out two of the four foot and two of the one-foot-10-inch framing strips on top of the plywood panel in a border and attach them with three-quarter-inch wood screws. Measure the pegboard to be one-foot-10-inches by three-feet-10-inches and cut it with the miter saw to fit inside the framing strips. Do not attach. Sand down the framed plywood including the solid surface of the plywood and the edges of the pegboard. Paint both pieces, pegboard and framed plywood, with two coats of white deck paint. When completely dry, fit the pegboard into the frame and screw it in along the edges (the solar cell strips will go inside so the screws need to be along the edges). Paint over the screws and any other unpainted corners or crevices. Also paint the other four pieces of framing wood to use over the plexiglass later. Drill two holes about half an inch apart in the bottom left corner of the frame, through the pegboard and through the back of the plywood. These will be for the positive and negative current connections.
Make a base from a four-foot by twelve-inch piece of plywood to connect solar cells into three evenly spaced strips.
Trace a solar cell onto a piece of cardboard or stiff paper and cut it out to use for tracing on the plywood. Using an L-square, about one-quarter inch from the bottom edge of the four-foot by 12-inch piece of plywood for an even margin, put the traced piece on the plywood, fitting it into the corner of the square. Trace it onto the plywood. At each corner of the traced pattern, place a tile spacer and trace it. Staple each spacer onto the plywood. Put the cardboard piece one-quarter inch above the first tracing, trace the cardboard piece and place four more spacers. Continue up the base, until you have twelve spaces traced out with tile spacers. Use the L-square to make sure the spacers are aligned.
Use the spaced base to place two solar cells into the spacers. Take the tabbing wire and measure a piece of it from the top to the bottom of one solar cell plus three-quarters of an inch and cut that length with pliers. Cut 32 more pieces the same length, using the first one as the guide. Then cut three more three-quarters of an inch longer than the rest and put them aside in a separate pile. These will be used on the last three solar cells at the top end of the strips so that the finished strips of 12 will have tabbing wire extending from both ends.
Wearing rubber or leather gloves, use the rosin flux pen (make sure it's wet) to make six spots (two lines of three spots) on the bottom (bottom is positive side, top is negative side) of the first solar cell. Place one strip of the measured tabbing on top of one line of flux, aligned with the top of the cell and extending down after the bottom edge, and solder gently over each of the spots. Do the same thing with the other line of spots, so there are two measured tabbing wires soldered onto the back of the first solar cell. Do this with each solar cell until all of them have two tabbing wires attached. Test each cell with the digital multimeter after the tabbing wire is attached to make sure they are giving about half a volt. Touch the red post to the solar cell and the black post to the tabbing for a reading.
Using the base again, place two tabbed solar cells into the first two spacers with the tabbing up, aligning the tabbing from the top one on top of the tabbing on the bottom one to solder together. Use the flux pen to adhere the tabbing and then gently solder together. Test the two connected solar cells with the multimeter to make sure they give one volt. Touch the red post to the lower solar cell and the black post to the tabbing on the upper solar cell for a reading.
Continue soldering and testing the cells until you have connected 12 of them into a strip. Make three strips in this way, using a total of 36 cells.
Carefully place two solar cell strips next to each other on the pegboard, evenly spaced. Lifting the solar cell on the bottom of the first strip gently, put a quarter size drop of silicon caulk in the center of the back of it to glue it onto the pegboard and press it down gently. Glue each of the other solar cells in the same way. It may be easier to lift each one individually with a small rubber spatula or gently lift the whole strip from the tabbing wire at the top one. Either way, take care not to break a solar cell or the tabbing wire.
Once the cells are all glued onto the pegboard with caulk, connect them to create a path for the current. Make a negative connection by connecting the first two solar cell strips with bus wire at the top of the frame. Cut a piece of bus wire the length of four tabbing wires. Place it under the four tabbing wires at the top of the pegboard from the left and middle solar cell strips. Solder the tabbing to the bus wire using solder and the hottest setting on the soldering iron. Check to see that the soldering job is sturdy and cut off any excess tabbing wire that extends past the bus wire. Cut a piece of bus wire long enough to fit under four tabbing wires, place it under the tabbing wires of the left solar cell strip at the bottom of the frame and solder the tabbing to the bus wire.
Check the voltage--touch the red positive post from the multimeter to the bus wire at the bottom of the first strip in the left of the frame and the black negative post to the tabbing wire at the bottom of the second strip. The reading should be between 10 and 12 volts. If it's not, check the tabbing and bus wire connections to make sure they are soldered well.
Continue with the connections by placing the third strip of solar cells in the frame and gluing each cell to the pegboard with caulk. Cut another piece of bus wire the length of four tabbing wires, place it under the four tabbing wires at the bottom of the frame from the middle and right solar cells strips, and solder the tabbing to the bus wire. Cut to size and solder another piece of bus wire to the two tabbing wires at the top of the right solar cells strip.
Check the voltage of the connected solar cells strips. Now there is a completed path for the current to run through all the solar cells in the panel.
Take the end of the roll of 20-gauge black wire and strip the black coating off about half an inch of the end so the wires are exposed. Twist the wires together so none are loose or sticking out. Put the wire through the right hole at the bottom of the frame, from the back, and pull a length of it through. Do the same thing with the 20-gauge red wire, putting it through the hole next to the one the black wire is in. First take the red wire and pull it up to the top of the frame and over to the bus wire at the top of the third solar cell strip, pulling about half an inch longer to reach a little past the end of the strip. Tap staples from staple gun over the red wire a in a couple of places along the left and top sides of the frame, being careful not to tap staples into the wire. The end of the roll of red wire will be under the frame, coming out the back. Solder the wires of the 20-gauge red wire onto the bus wire near it at the top right of the frame. Take the black wire and pull about a half inch length, just enough to reach the bus wire near it at the bottom left corner of the frame with a little give in it, not pulled too tightly. Solder the wires of the 20-gauge black wire onto the bus wire near it at the bottom left corner of the frame. The end of the roll of black wire will be under the frame, coming out the back.
Test the voltage again, preferably with the frame in the sunlight. It should be close to 18 volts and about three and a half amps, especially if the frame is angled slightly to catch the most sunlight.
Place the plexiglass on top of the frame and mark where screws will be used, then pre-drill holes into the plexiglass carefully so it doesn't break or crack. Mark four pieces of framing wood in the same places and pre-drill also. Then place the plexiglass on top of the frame, place the framing wood on top of the plexiglass around the edges, and use the half inch screws to secure the plexiglass and framing. Drill slowly and carefully to avoid cracking the plexiglass. Carefully turn the panel over and attach the three-foot boards to the back of the panel, evenly spaced, so that six inches extend on each side for roof mounting.
The charge controller will have red and black connectors for the solar panel and red and black connectors for the battery, the inverter will also. The charge controller is connected to the red and black wires coming from the solar panel and to the battery, and the inverter is connected to the battery. A small appliance like a lamp or a laptop computer may be plugged into the inverter and run from the electricity generated by the solar panel.
Locate the positive and negative connectors in the junction box and place the junction box onto the back of the solar panel near where the red and black wires are coming through. Cut the black and red wires from the rolls, leaving enough length to reach the junction box for connecting. Strip off about one-fourth inch of the black and red covering to expose the wires and place the black wires in the positive connector in the junction box and the red wires in the negative connector. Now screw the junction box into the frame. The connectors can be soldered in the junction box, and the box can be closed and edges sealed with silicon caulk. Instead of directly connecting the charge controller to the solar panel, the junction box can be wired to the charge controller to run the charge from the solar panel through the controller into the battery, making electricity available to appliances plugged into the inverter.
Tips & Warnings
- Shop around for the best price on solar cells. Remember that red is positive and black is negative for electrical connections.
- Solar cells are fragile and can break easily. Handle them gently and with care to avoid breaking and having to replace any. Soldering can cause burns to fingers and hands, so rubber or leather gloves should be worn.
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