A solar cell is a device for converting solar energy into electricity. High performance solar cells, which you can buy at Radio Shack and other stores, are made from specially treated silicon and require huge factories, high temperatures, special cleaning and a lot of money.
If we want to sacrifice efficiency for the ability to make our own solar panels in the kitchen from materials from a hardware store, we can demonstrate a working solar panel in about an hour.
Our solar cell is made of copper oxide instead of silicon. Copper oxide is one of the first materials in which scientists discovered the photoelectric effect, in which light causes electricity to flow through the material.
Thoughts on how to explain the photoelectric effect is what led Albert Einstein to the Nobel Prize in physics and the theory of relativity.
1. Copper sheet from the hardware store. It usually costs about 150 rubles. for 0.9 square meters. We need about 45 sq. cm.
2Two clips "crocodile".
3. A sensitive microammeter, which can measure gaps between 10 and 50 microamperes. Radio Shack sells small multimeters with a LCD MONITOR. But you can also use a regular one.
4. Electric oven. My kitchen stove is a gas stove, so I bought a small electric stove with one spiral for about 750 rubles. The small 700 watt burners probably won't work - you need at least 1100 watts to turn the burner red.
5. Plastic bottle with a cut neck. I used a 2 liter bottle of mineral water.
6. Table salt. We will need a couple of tablespoons.
7. Water from the tap.
8. Sandpaper or drill with such a nozzle (abrasive)
9. Sheet metal.
Here is a burner.
First you need to cut off some of the copper so that it is the size of an electric stove. Wash your hands to avoid greasy or other stains. Also wash the copper sheet with detergent to wash away grease or other stains from it. Use sandpaper or an abrasive brush to completely remove the copper sheeting so that any sulfide or other light corrosion is removed.
Then put a clean copper sheet on the tile (electric) and turn it on to the maximum.
Copper will begin to heat and oxidize, you will see beautiful red-orange spots on its surface.
When the copper heats up even more, the multi-colored spots will begin to be replaced with black copper oxide color.
All colors fade when the helix is already red.
When the burner burns, the copper sheet will be coated with black copper oxide. Allow it to fry for another half hour, so the black coating will be thick. This is important, since the thick coating will peel off easily, while the thin coating will remain, sticking to the copper.
After half an hour of cooking, turn off the burner. Leave the hot copper on the burner to cool slowly. If you cool it too quickly, the black oxide film will stick to the copper.
As the copper cools, it shrinks. Black copper oxide also shrinks. But they are compressed at different speeds, which causes the black copper oxide to peel off.
Soon big pieces will fall off, it's fun to watch))
When the copper has cooled to room temperature (it takes about 20 minutes), most of the black oxide film will go away.Easy cleansing with your hands under running water will remove most of the small pieces. DO NOT ATTEMPT to tear off resistant stains and do not bend the sheet - you may damage a thin layer of copper oxide, but we need it
The rest of the assembly is very fast and easy.
Cut the second sheet of copper to the size with the first (heated). GENTLY bend the two pieces so that they enter the plastic bottle without touching each other.
Hook "crocodiles" to both plates. Connect the wire from pure copper to plus and the wire from the plate with oxide to the minus.
Now mix a couple of tablespoons of salt in a small amount of hot tap water. Stir until all the salt has dissolved. Carefully pour the mixture into the bottle (where the plates are), leaving about 2.5 cm from the edges of the plates.
In the photo above is a ready-made solar battery. In the shade, the ammeter shows approximately 6 miliamps. But even in the dark this battery will give several milliamps))
This photo shows the battery in the light, and the ammeter shows 34 miles, sometimes the battery can give 50 mA or even more.
How it works?
Copper oxide is a semiconductor.It is an intermediate conductor, where electricity can flow freely, and an insulator, where electrons are strongly connected to their atoms and do not flow freely.
In a semiconductor, there is a gap called the band gap between electrons that are strongly associated with an atom and electrons that are farther from an atom that can move freely and conduct electricity.
Electrons cannot remain in the forbidden zone. An electron can give only a little energy and move from the nucleus of an atom to the forbidden zone. The electron must receive enough energy to move further from the nucleus, outside the forbidden zone.
Similarly, an electron outside the forbidden zone cannot lose some energy and fall only a little closer to the nucleus. This should lose enough energy to fall past the forbidden zone into an area where electrons can be.
When sunlight hits electrons in copper oxide, some of the electrons get enough energy from sunlight to jump past the forbidden zone and become free to conduct electricity.
Free electrons are transferred to salt water, then to a clean copper plate, to a wire, through an ammeter, and back to the oxidized plate.
As the electrons travel through the ammeter, we see the work (ampere). When the shadow falls on the solar cell, the electrons move slower and the mile amps less.
A note about energy.
The battery produces 50 mA of 0.25 volts.
This is 0.0000125 watts (12.5 microwatts).
Do not try to light a light bulb))) would need acres of batteries to illuminate the house. Our model is experimental and can be used as a light sensor.
0.0000125 watts (12.5 microwatts) for a 0.01 square meter battery, or 1.25 milliwatts per square meter. To light a 100 watt bulb would require 80,000 square meters of copper oxide for the sunlit side, and 80,000 square meters of copper for the dark electrode. To operate a 1,000-watt kiln, you would need 800,000 square meters of copper oxide, and another 800,000 square meters of plain copper, or 1,600,000 square meters all together. If it were to be fixed on the roof of the house, each house would be 282 meters long and 282 meters wide, taking in all that they needed electricity, there was one oven.
At 1,600,000 square meters there are 17,222,256.7 square feet. If copper covering costs $ 5 per square foot, copper alone would cost $ 86,110,283.50 USD.By doing this one tenth of the thickness can reduce it to $ 8,611,028.35. Since you buy in bulk, you might get it for half of this, or about $ 4,300,000.00.
If you used silicon solar panels costing $ 4 per watt, then you could run the same furnace for $ 4,000.00. But the groups would only be about 10 square meters.
Or for about a dollar you can build a solar oven of aluminum foil and cardboard. For about $ 20, you can build a very good polished aluminum parabolic solar plate.
Flat solar battery
I made a more portable version of the solar battery in a flat form. I used the transparent plastic cover of the CD cover as a window and silicone glue (you can use a common sealant) to put the parts together and isolate them from each other.
First we make copper oxide, as in the first part. We solder an insulated copper wire to the corner of the oxide plate, this will be a minus (negative pole).
Positive plate - U figuratively cut a piece of pure copper in size slightly more oxide (hereinafter we understand in the pictures as))) we solder the wire to its corner, this time is a plus.
First, glue the copper plate U to the plastic window.Use a lot of silicone glue so salt water will not leak. Make sure that the solder joint is either completely covered with glue, or outside of glue U, as shown in the photo (completely covered with glue is better).
The photo below shows the back side of the solar panel (the side not facing the sun).
The photo below shows the front side of the solar panel (the side that will face the sun). Note that silicone glue does not completely cover the copper, as part of the copper must ultimately be in contact with salt water.
Smear glue plate of pure copper. This layer will act as an insulator between a clean copper plate and an oxide plate, and should be thick enough to leave a little space for salt water. Again, not all copper is covered, so there will be a lot of copper in contact with water.
Gently glue the oxide plate onto this layer. You must press hard enough to make sure the glue surrounds any gaps, but not so hard that the two plates touch.
The photo below shows the back side of the solar panel (the side not facing the sun).
The photo below shows the front side of the solar panel (the side that will face the sun). Note that I added extra glue to form a pipe on top to make it like pouring salt water.
The photo does not show additional coating with glue around the perimeter so that water could not seep through, but you must do it. Allow the glue to dry before proceeding to the next step.
Then, use a large pipette to add salt water. Fill the battery almost to the top of the copper plate so that the water is almost overflowing. Then seal the hole with a drop of glue and allow the glue to dry for at least half an hour.
In the photo above you can see a flat solar panel in action in bright sunshine. It gives about 36 microamps. You can also see an extra bead of glue around the edges of the plates, and filling the top of the pipe.