Build Your Own Solar Panel

4 Apr

Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect.

Solar Panel Array

Solar Panel Array

  • The structural (load carrying) member of a module can either be the top layer or the back layer.
  • The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon.
  • The conducting wires that take the current off the panels may contain silver, copper or other non-magnetic conductive transition metals.
  • The cells must be connected electrically to one another and to the rest of the system.
  • Cells must also be protected from mechanical damage and moisture.
  • Most solar panels are rigid, but semi-flexible ones are available, based on thin-film cells.
  • Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability.
  • Separate diodes may be needed to avoid reverse currents, in case of partial or total shading, and at night.
  • The p-n junctions of mono-crystalline silicon cells may have adequate reverse current characteristics that these are not necessary. Reverse currents waste power and can also lead to overheating of shaded cells.
  • Solar cells become less efficient at higher temperatures and installers try to provide good ventilation behind solar panels.
  • Some recent solar panel designs include concentrators in which light is focused by lenses or mirrors onto an array of smaller cells.
  • The best achieved sunlight conversion rate (solar panel efficiency) is around 21% in commercial products.

Types of Solar Cells

  1. Silicon Photovoltaic Cells.  Most solar modules are currently produced from. These are typically categorized as Monocrystalline or Polycrystalline Modules.
  • Monocrystalline Photovoltaic Cells. A single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries. The absence of the defects associated with grain boundaries can give monocrystals unique properties, particularly mechanical, optical and electrical, which can also be anisotropic, depending on the type of crystallographic structure.
  • Polycrystalline Photovoltaic Cells. Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random (called random texture) or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter.
  1. Thin-Film Cells. Third generation solar cells are advanced Thin-Film Cells. They produce high-efficiency conversion at low cost.

Material Required

Solar cells, Plywood, Plexiglass/Acrylic Sheet, Tabbing Wire, Silicon, Solder, Rosin Flux Pen, UV Protector, Volt Meter/Multimeter, ABS Sheet, Vinyl Acetate (EVA) Sheet

Assembling of Solar Panel

Solar Cell

  1. Grab a Multimeter capable of measuring fractions of DC voltage and your collection of solar cells.
  2. Position a light source near your collection of Solar Cells; this will enable to you get a consistent measurement of voltage output of each one of your Solar Cellswith a light source that has constant output and is a fixed distance away.

    Multimeter

  3. Set the Multimeter to measure DC voltage.
  4. Place the negative test lead (usually black) on the side of the Solar Cell which indicates negative voltage (usually the front).
  5. Place the positive test lead (usually red) on the side of the Solar Cell which indicates Positive Voltage (Usually the Back).
  6. Observe the maximum voltage output. Don’t move the Solar Cell around to try to get a higher reading since you will be grouping the solar cells together according to how much voltage they generate at the same position from your light source.
  7. Separate your Solar Cells into groupings of .05 volt increments as you are taking voltage measurements.
  8. This will allow you to take maximum advantage of Solar Cell output by grouping solar cells together (each group would be a solar panel). For example, if you had 35 Solar Cells which had an output of .45 volts and you had one which had an output of .35 volts; the output of your solar panel will suffer.

    String Tabbing Wire

  9. We need to connect our solar cells together with  Interconnection Wire. In order to do this, we’ll need to take the spool of Interconnection Wire and cut it into 10.5 inch lengths for the six inch solar cells.
  10. Each length of  Interconnection Wire must have solder added to it. This is done by adding solder to 5.25 inches of the wire starting at one end. Then flip the wire length over and add solderto 5.25 inches of the wire starting at the opposite end.
  11. Solder a length of the interconnection wire to each connection strip that is on the front of each solar cell (in this case, three lengths of interconnection wire are used per solar cell).
  12. Connecting solar cells together in series using the six inch solar cells
  13. In order to solder the solar cells together, one will be placed face-down.
  14. Take another solar cell, face down, and place the interconnection wires on top of the previous solar cell (leave approximately 1/16 inch space between the solar cells) and solder those interconnection wires to the previous solar cell.
  15. Now that you’ve seen how to solder solar cells together, you’ll need to know the sequence of soldering the 36 solar cells together into a compact form .

    Vinyl Acetate (EVA) Sheet

  16. While it is not required, it is recommended that you sandwich the soldered solar cells inside of a protective thermoplastic material such as ethylene vinyl acetate (EVA) sheet or UV resistant Surlyn sheet. Over time, if there is oxygen or other contaminants inside the solar panel, your solar cells will degrade prematurely. If you have one of those types of sheet, place the sheet over the solar cells you’ve just soldered together and use the heat gun on the sheet so that it adheres to the solar cells.
  17. Place the solar cells on top of white paper and then soldered them together in advance of heating EVA sheet onto them. The reason for this is that the EVA sheet is a very adhesive material when heated (it also becomes approximately 100% transparent after heating). When flipping over the solar panel in a cardboard frame (so that the other side can have EVA sheet applied to it), the paper can be easily removed; without the paper between the solar panel and the cardboard it would be necessary to peel the inverted EVA sheet and solar panel from the rigid cardboard causing damage to individual solar cells. You will want to overcut the sheet since it will shrink as it is heated.
  18. Carefully turn the sheet of solar cells over, place the sheet over the top of the solar cells and use the heat gun on the sheet so that it adheres to the solar cells and the sheet.

    ABS White Sheet

  19. Take the 48 x 48 x 3/16 inch ABS white sheet and, using a cutting tool, cut it down to a 38 5/16 x 38 5/16 x 3/16 inch sheet. Then drill a 5/16 inch hole through the sheet six inches from the right-top edge and one inch down from the right-top edge.
  20. Place the 36 solar cells, which were soldered together, face up onto the ABS white sheet and center them on the sheet. Cut off excess EVA or Surlyn sheet (if you applied it to the solar cells) so that it is approximately an inch less on each side than the size of the ABS white sheet.
  21. Solder approximately 3 inches of the color-coded wire to the appropriate positive and negative interconnection wire on the #1 and #36 solar cells. Push the other end of the wires through the 5/16 inch drilled hole.
  22. Cut two 72 x 1/4 x 1/4 inch clear extruded acrylic bars to a length of 38.3125 inch. Cut the remaining two 72 x 1/4 x 1/4 inch clear extruded acrylic bars to a length of 37.8125 inch.
  23. Glue one 38.3125 inch clear extruded acrylic bar to the top of the ABS white sheet, lining the bar up with the edge of the ABS white sheet. Allow the glue to dry. Then take the second 38.3125 inch clear extruded acrylic bar to the bottom of the ABS white sheet, lining the bar up with the edge of the ABS white sheet. Allow the glue to dry.
  24. Glue one 37.8125 inch clear extruded acrylic bar to the left of the ABS white sheet, lining the bar up with the edge of the ABS white sheet. Allow the glue to dry. Then take the second 37.8125 inch clear extruded acrylic bar to the right of the ABS white sheet, lining the bar up with the edge of the ABS white sheet. Allow the glue to dry.
  25. Cut the remaining clear extruded acrylic bar into 1 x 1/4 x 1/4 inch blocks. Glue each block, centered, in between each solar cell in an alternating pattern (this will provide strength to the solar panel).
  26. Take the 48 x 48 x 1/8 inch Acrylite UV stabilized transparent sheet and, using a cutting tool, cut it down to a 38 5/16 x 38 5/16 x 3/16 inch sheet. Place glue along the top of the four acrylic bars which were glued to the ABS white sheet. Place glue on top of each of the 1 x 1/4 x 1/4 inch blocks. Line up the Acrylite sheet with the edges of the four acrylic bars and place it firmly on top. Allow the glue to dry.
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