| Author | Message | ||
     Jim Bell |
What a great project! My son and I have created the solar cell using copper flashing. We have a few questions regarding what is actually taking place and would like more information. 1. With our multi-meter we connected the black lead to the cuprous oxide sheet and connected the red lead to the copper sheet. Our test results always showed a negative value, why? 2. can you direct us to a web site that has a visualization (diagram, graphs, schematic, etc.) of what is taking place. 3. we noticed when we took the plates out of the salt water solution and were still holding them in our hands we were still getting a read out on the multi-meter. Is this because we became the conductor of electricity? 4. Beside the amount of light hitting the cuprous oxide what is controling the amount of generated electricity? Is it the size of the plates? Is it the amount salt water? Is it the distance between the two plates? 5. We made two solar cells in jars. one is generating more energy than the other. They are the same size but one was "cooked" a little (3-5min) longer than the other, could this be why? 6. We could generate up to .117volts and 185microamps. This is considerably more than what you were generating. Does this sound possible? Thanks for your help! | ||
| Simon Quellen Field (Sfield) |
Thanks! 1. In the dark, the cell is a battery. Depending on the purity of the starting materials, you may have one electrode more electronegative than the other, creating a small current. 2. I thought I had explained how it worked in the "How does it do that?" section. Was there a part you did not understand? 3. Yes, you had become part of the battery. 4. The distance between the plates probably has little to do with the output, although larger separations do increase the internal resistance. The effect is smaller than changes to the area, light intensity, or conductivity of the transparent electrode (salt water). 5. This is an area for experiment. I suspect the reproducibility is not all that good, as several variables are not controlled very well. 6. You are getting 0.000021645 watts (21.645 microwatts). I was using a meter that had a limit of 50 microamps, and sometimes I would "peg the meter", so I don't know how much over 50 microamps I was getting. The amperage is a function of the area that is illuminated, the intensity of the light, and the conductivity of the electrolyte. You can experiment with all three variables, although you must take care that your choice of electrolyte does not attack the electrodes (no nitric acid, or hydrochloric acid, etc.) I was getting more voltage than you were. This may be due to purity of materials, or strength of electrolyte. | ||
| Allan M. Christensen |
I have some question to your "How does it do that? " section... "When sunlight hits the electrons in the cuprous oxide, some of the electrons gain enough energy from the sunlight to jump past the bandgap and become free to conduct electricity." Why is these free electrons different from the free electrons in a conductor? In the conductor they're always free... What am i missing here? :/ "The free electrons move into the saltwater, then into the clean copper plate, into the wire, through the meter, and back to the cuprous oxide plate. " What makes the electrons travel towards the clean copper plate through the saltwater, instead of just going through the meter to the clean copper plate? | ||
| Simon Quellen Field (Sfield) |
The answer to both of your questions is that the junction of the cuprous oxide and the copper forms a diode -- a place where charges can only move in one direction. In a semiconductor diode there is a voltage gradient at the junction of two dissimilar materials. This gradient allows electrons to move in one direction but not another. There are many excellent references on solid state physics and how PN junctions work, so I won't go further into that here. | ||
| Allan M. Christensen |
Thx for you answer! Just one more think: The sunlight sensitive effect in the cuprous oxide, is that the photovoltaic effect? | ||
| Simon Quellen Field (Sfield) |
It sure is! Have fun ;-) | ||
| drewpoalino |
I have a ? iam doing a science project on a hydrolic remote control car it runds off a 9.6 volt barrty. i was wondering if I could use solar cells to make about enough juice to make that car go. and how many of the solar panals do i need. to make it go. please email me at my addres football4lifex@aol.com with the awnser if you know it thanks. | ||
| Simon Quellen Field (Sfield) |
It's easy to get 9.6 volts from solar cells. But you forgot to mention how much current you require. Without that, I can't tell you how big the solar panel would have to be. Put an ammeter in series with the battery, and post the reading here. | ||
| Martina Kratt Unregistered guest |
Great experiment,I´m doing it for a science project at school.I have a few questions. -Where exactly is the pn-junction? Is there really a space-charge-region in the solution between the copperplate and the copperoxideplate or is it between the Cu2O-surface and Cu-layer underneath inside the copperoxideplate? -Why is the cell also a battery? Is the battery current opposite to the photocurrent(from the copperplate to the Cu2O-plate), and does it include the movement of copper-ions in the solution? I´d be very glad for some answers since I´ve already searched several books on solar cells and the Internet without finding any clues explaining this experiment. My teachers don´t know how it works either. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 491 Registered: 12-2004 |
Copper oxide on copper forms a Schottky barrier diode. You can Google for "schottky diode" to find articles like this one or this one that explain it in detail. The cell is a battery because one plate is different from the other. Two different conductors in an electrolyte make a battery. You can determine whether the battery effect adds to the photoelectric effect or not by measuring the dark current direction (place the cell in the dark and measure the current -- if the needle goes the wrong way, it is subtracting). Since we are measuring very small currents, very small impurities in the plates can cause the battery current to go either way. | ||
| zues (Unregistered Guest) Unregistered guest Posted From: 222.126.29.146 |
how many volts doe it takes to run an electric fan? how many solar cell (copper plates) does it takes to run an electric fun? is your solar panel/cell practical?why? thank you, by the way i am from the philippines..... any alternatives for silicon glue? | ||
| Chetana (Unregistered Guest) Unregistered guest Posted From: 204.248.240.161 |
Hey, its a neat experiment! My 4th grader tried it. But we didn't register any current in the multimeter. We tried very hot water with salt in it. Could it be he connected wrongly? +ve side of multimeter should be connected to the Cu2O on or the other copper flashing? He was sad after lot of work and no current! Can someone give me some hints? Thanks | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1733 Registered: 12-2004 |
The most likely problem is using the wrong setting on the multimeter. The current is microamperes. Using a milliampere setting will look like zero. Other problems would be a short circuit (easy to detect with the ohmmeter setting on the multimeter) or an open circuit (no connection). | ||
| Ryan Daniel Smith (Unregistered Guest) Unregistered guest Posted From: 75.71.95.186 |
What does the saltwater do exactley why cant u just use regular water | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1820 Registered: 12-2004 |
What we want is a transparent conductor. Salt water conducts electricity much better than plain water. A coating of indium-tin oxide would be better, but I don't know how to create that in my kitchen. | ||
| Syed Haider Abbas (Haider_abbas) Member Username: Haider_abbas Post Number: 18 Registered: 12-2007 |
Hello Simon, I am online after a very long time. I have to asked a question about the flat panel solar. 1.Where the salt water has to be poured. 2.I can,t understand the dark electrode. 3.you have showed the front of U shaped copper plate glued to a CD cover so where does the cupric oxide plate has to be pasted. 4.Do we have to use only 1 part of CD cover. 5.May i use both two parts. | ||
| chris obilor (Unregistered Guest) Unregistered guest Posted From: 82.206.136.83 |
I'm trying to build a photoelectric cell that could power my electric stove.I tried to use the setup I read from a physics text book where they used a photo sensitive material such as silver as the cathode where the sun strikes and a string of wire as anode which serves as the collector all connected to a cell,but failed.Please tell me what I didn't do wright. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1906 Registered: 12-2004 |
That kind of cell requires a vacuum between the cathode and the anode. Also, silver would not be as good a choice as selenium. But your real problem is power. An electric stove needs at least a kilowatt. There is a kilowatt of solar power in a square meter of sunlight at noon, but your solar cell is only about 0.01 percent efficient, so you would need 100 square meters of collection area. Using silicon solar cells that are 20% efficient, you would only need 5 square meters of collector. That would cost you about $5,000 at today's prices. It would be much less expensive to use a concave mirror to concentrate the sun onto a frying pan. It would be close to 100% efficient, and you would only need about a square meter of aluminum foil and some cardboard to make the parabolic surface. | ||
| scott (Ichyc) Senior Member Username: Ichyc Post Number: 189 Registered: 6-2006 |
I think it would be an awesome project to make a solar concintrator stove, it would use less co2 and other fourms of carbon, also it would have almost no atmospheric effects even in nano amounts because the only emission is gases of what ever you cook or burn with it. But on top of that all it would be very cool to make one. (= | ||
| Rohan (Digital) Senior Member Username: Digital Post Number: 118 Registered: 3-2008 |
yes haven't you seen the program "planet mechanics" in national gegraphic. in one episode of it they two( dick strawbridge and jems stansfield) made a solar powered paella. they were able to fry oil which means reaching temperature upto 20o degree centigrage which is great and enough to make omlet or toast your bread. | ||
| scott (Ichyc) Senior Member Username: Ichyc Post Number: 190 Registered: 6-2006 |
also it would be fun because there is so many ways to go with this, you could do a concave mirror, a solar DEATH RAY (my favorite), fresnel linse ECT. this makes the project funner and easier to gather materials. |
