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Solar cell modules
Anyone know of any solar cell vendors that sell
solar cell modules that put out 6-9volt @ 100mA? TIA, Remove "HeadFromButt", before replying by email. |
I think Harbor Freight had something.
Lots of stuff from places like Electronic Goldmine, and others, real cheap. Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, |
I think Harbor Freight had something.
Lots of stuff from places like Electronic Goldmine, and others, real cheap. Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, |
maxfoo wrote:
Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Remove "HeadFromButt", before replying by email. JC Whitney sells 12 volt panels competitively. These are not as efficient when loaded to 6-9 volts, but they put out at least as much current as when run with a 12 volt load. http://www.jcwhitney.com/webapp/wcs/...X&appId=385939 -- John Popelish |
maxfoo wrote:
Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Remove "HeadFromButt", before replying by email. JC Whitney sells 12 volt panels competitively. These are not as efficient when loaded to 6-9 volts, but they put out at least as much current as when run with a 12 volt load. http://www.jcwhitney.com/webapp/wcs/...X&appId=385939 -- John Popelish |
Another option might be to use a different voltage panel,
whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. |
Another option might be to use a different voltage panel,
whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. |
maxfoo wrote in message . ..
Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Lots of solar panels for sale on ebay. Here's a 12 volt 200mA unit for 11 dollars. Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1 -Bill |
maxfoo wrote in message . ..
Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Lots of solar panels for sale on ebay. Here's a 12 volt 200mA unit for 11 dollars. Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1 -Bill |
You've asked for a module that puts out 6-9 volts @ 100 mA. A more
accurate description of a solar panel would be that it puts out 100 mA at 6-9 volts. Solar cells act a lot more like a current source than a voltage source. So a panel that's rated at 100 mA at 12 volts will also put out about 100 mA at 6 or 9 volts. (It'll be a bit more than 100 mA, but not a whole lot more.) The open circuit voltage of a "12 volt" solar panel (one intended to deliver current to a 12-14 volt load) will be somewhere around 18 or 20 volts, and one specifically designed to work at 6 volts will be about half that, 9 or 10 volts. So if you have a 6 - 9 volt device that you want to power with solar cells, you'll have to float the panel across a battery, or use a voltage regulator to limit the voltage. (A properly sized zener diode would be adequate for the power level you're dealing with.) A 12 volt panel will be physically larger than you need, but it might be easier to find and less expensive. If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. Roy Lewallen, W7EL Bill Bowden wrote: maxfoo wrote in message . .. Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Lots of solar panels for sale on ebay. Here's a 12 volt 200mA unit for 11 dollars. Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1 -Bill |
You've asked for a module that puts out 6-9 volts @ 100 mA. A more
accurate description of a solar panel would be that it puts out 100 mA at 6-9 volts. Solar cells act a lot more like a current source than a voltage source. So a panel that's rated at 100 mA at 12 volts will also put out about 100 mA at 6 or 9 volts. (It'll be a bit more than 100 mA, but not a whole lot more.) The open circuit voltage of a "12 volt" solar panel (one intended to deliver current to a 12-14 volt load) will be somewhere around 18 or 20 volts, and one specifically designed to work at 6 volts will be about half that, 9 or 10 volts. So if you have a 6 - 9 volt device that you want to power with solar cells, you'll have to float the panel across a battery, or use a voltage regulator to limit the voltage. (A properly sized zener diode would be adequate for the power level you're dealing with.) A 12 volt panel will be physically larger than you need, but it might be easier to find and less expensive. If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. Roy Lewallen, W7EL Bill Bowden wrote: maxfoo wrote in message . .. Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Lots of solar panels for sale on ebay. Here's a 12 volt 200mA unit for 11 dollars. Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1 -Bill |
Hi;
I must say that this last responce was well writen and informitive, it was a pleasure to read. Thank you Mr. Lewallen On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote: You've asked for a module that puts out 6-9 volts @ 100 mA. A more accurate description of a solar panel would be that it puts out 100 mA at 6-9 volts. Solar cells act a lot more like a current source than a voltage source. So a panel that's rated at 100 mA at 12 volts will also put out about 100 mA at 6 or 9 volts. (It'll be a bit more than 100 mA, but not a whole lot more.) The open circuit voltage of a "12 volt" solar panel (one intended to deliver current to a 12-14 volt load) will be somewhere around 18 or 20 volts, and one specifically designed to work at 6 volts will be about half that, 9 or 10 volts. So if you have a 6 - 9 volt device that you want to power with solar cells, you'll have to float the panel across a battery, or use a voltage regulator to limit the voltage. (A properly sized zener diode would be adequate for the power level you're dealing with.) A 12 volt panel will be physically larger than you need, but it might be easier to find and less expensive. If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. Roy Lewallen, W7EL Bill Bowden wrote: maxfoo wrote in message . .. Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Lots of solar panels for sale on ebay. Here's a 12 volt 200mA unit for 11 dollars. Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1 -Bill |
Hi;
I must say that this last responce was well writen and informitive, it was a pleasure to read. Thank you Mr. Lewallen On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote: You've asked for a module that puts out 6-9 volts @ 100 mA. A more accurate description of a solar panel would be that it puts out 100 mA at 6-9 volts. Solar cells act a lot more like a current source than a voltage source. So a panel that's rated at 100 mA at 12 volts will also put out about 100 mA at 6 or 9 volts. (It'll be a bit more than 100 mA, but not a whole lot more.) The open circuit voltage of a "12 volt" solar panel (one intended to deliver current to a 12-14 volt load) will be somewhere around 18 or 20 volts, and one specifically designed to work at 6 volts will be about half that, 9 or 10 volts. So if you have a 6 - 9 volt device that you want to power with solar cells, you'll have to float the panel across a battery, or use a voltage regulator to limit the voltage. (A properly sized zener diode would be adequate for the power level you're dealing with.) A 12 volt panel will be physically larger than you need, but it might be easier to find and less expensive. If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. Roy Lewallen, W7EL Bill Bowden wrote: maxfoo wrote in message . .. Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? TIA, Lots of solar panels for sale on ebay. Here's a 12 volt 200mA unit for 11 dollars. Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1 -Bill |
On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote:
If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a battery pack with a 9v type clip. Wanted to be able to charge the batteries with solar cells basically. But after searching the web a bit it seems cheapest to buy individual cells then tie them in series...No? thanks, Remove "HeadFromButt", before replying by email. |
On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote:
If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a battery pack with a 9v type clip. Wanted to be able to charge the batteries with solar cells basically. But after searching the web a bit it seems cheapest to buy individual cells then tie them in series...No? thanks, Remove "HeadFromButt", before replying by email. |
maxfoo wrote:
Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? Try All ELectronics. www.allcorp.com. TIA, Remove "HeadFromButt", before replying by email. |
maxfoo wrote:
Anyone know of any solar cell vendors that sell solar cell modules that put out 6-9volt @ 100mA? Try All ELectronics. www.allcorp.com. TIA, Remove "HeadFromButt", before replying by email. |
Joerg wrote:
Another option might be to use a different voltage panel, whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. Seems foolhardy to me, to use a boost circuit, and waste a lot of power. Just put more PV cells in series to increase the voltage. |
Joerg wrote:
Another option might be to use a different voltage panel, whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. Seems foolhardy to me, to use a boost circuit, and waste a lot of power. Just put more PV cells in series to increase the voltage. |
Roy Lewallen wrote:
You've asked for a module that puts out 6-9 volts @ 100 mA. A more accurate description of a solar panel would be that it puts out 100 mA at 6-9 volts. Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. |
Roy Lewallen wrote:
You've asked for a module that puts out 6-9 volts @ 100 mA. A more accurate description of a solar panel would be that it puts out 100 mA at 6-9 volts. Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. |
Watson A.Name "Watt Sun - the Dark Remover" wrote:
Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! |
Watson A.Name "Watt Sun - the Dark Remover" wrote:
Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! |
In article , "Joel Kolstad"
writes: Watson A.Name "Watt Sun - the Dark Remover" wrote: Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! Ahem, Joel, consider the location of "the land of the midnight sun..." :-) Ackshully, based on a little bit of experience on Solar One, the first (of two) experimental 50 MWe solar plant in Barstow, CA, (in the middle desert of California with not much else), sunlight has a considerable variance in energy over the course of a day. A combined buck-boost switching power supply would be a consideration for reliable solar cell charging of a secondary battery during daylight. There are several different ICs just for the purpose of wide-voltage-range inputs from National, Linear, and Maxim along with application notes from all three. Roy Lewallen hit the subject nail on the head in saying, correctly, that solar cells behave more as constant-current sources than constant-voltage (as batteries are) sources. Those who care to test that will find out from connecting a fixed resistor to solar cell outputs and measuring the voltage during the course of daylight, especially the differences between clear and cloudy skies. Solar One was a boiler system, over 500 independent mirrors were used as a giant reflector array to focus sunlight on a central boiler made from the same stainless-steel-like tubing used in rocket engine bell structures. Rocketdyne Division of Rockwell International was the subcontractor to MacDonnell-Douglas that made the boiler and the underground steam-heat storage system of Solar One. The peak daylight energy was in excess of 100 MWe equivalent but the extra heat had to be stored overnight for the steam-turbine-powered generators to run 24/7. Rocketdyne, now purchased by Boeing, made the Space Shuttle Main Engines. Rocket engine bells are made from tubing to circulate fuel before entering combustion. That pre-warms the fuel as well as cooling down the tail of the engine's output. Not exactly what a QRP operator would need... :-) Len Anderson retired (from regular hours) electronic engineer person |
In article , "Joel Kolstad"
writes: Watson A.Name "Watt Sun - the Dark Remover" wrote: Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! Ahem, Joel, consider the location of "the land of the midnight sun..." :-) Ackshully, based on a little bit of experience on Solar One, the first (of two) experimental 50 MWe solar plant in Barstow, CA, (in the middle desert of California with not much else), sunlight has a considerable variance in energy over the course of a day. A combined buck-boost switching power supply would be a consideration for reliable solar cell charging of a secondary battery during daylight. There are several different ICs just for the purpose of wide-voltage-range inputs from National, Linear, and Maxim along with application notes from all three. Roy Lewallen hit the subject nail on the head in saying, correctly, that solar cells behave more as constant-current sources than constant-voltage (as batteries are) sources. Those who care to test that will find out from connecting a fixed resistor to solar cell outputs and measuring the voltage during the course of daylight, especially the differences between clear and cloudy skies. Solar One was a boiler system, over 500 independent mirrors were used as a giant reflector array to focus sunlight on a central boiler made from the same stainless-steel-like tubing used in rocket engine bell structures. Rocketdyne Division of Rockwell International was the subcontractor to MacDonnell-Douglas that made the boiler and the underground steam-heat storage system of Solar One. The peak daylight energy was in excess of 100 MWe equivalent but the extra heat had to be stored overnight for the steam-turbine-powered generators to run 24/7. Rocketdyne, now purchased by Boeing, made the Space Shuttle Main Engines. Rocket engine bells are made from tubing to circulate fuel before entering combustion. That pre-warms the fuel as well as cooling down the tail of the engine's output. Not exactly what a QRP operator would need... :-) Len Anderson retired (from regular hours) electronic engineer person |
maxfoo wrote:
On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote: If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a battery pack with a 9v type clip. Wanted to be able to charge the batteries with solar cells basically. But after searching the web a bit it seems cheapest to buy individual cells then tie them in series...No? For 6V, I would put two of these in series, along with a 1N5817 schottky diode to prevent reverse current. Each cell is encapsulated with epoxy and the wires can be soldered to the pads on the back. Each puts out an honest 30 mA, or more in bright sunlight. Price is reasonable too. http://www.allelectronics.com/cgi-bi...-60&type=store You can also put two pairs in parallel to get a faster charge. thanks, |
maxfoo wrote:
On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote: If you're looking for a module that includes a built in voltage regulator to limit the voltage to 6 - 9 volts, you need to make it clear. Most of the responses seem to be referring to 12 volt panels, which will be fine if you limit the voltage, but won't be suitable if you need voltage regulation to be included in the external module. my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a battery pack with a 9v type clip. Wanted to be able to charge the batteries with solar cells basically. But after searching the web a bit it seems cheapest to buy individual cells then tie them in series...No? For 6V, I would put two of these in series, along with a 1N5817 schottky diode to prevent reverse current. Each cell is encapsulated with epoxy and the wires can be soldered to the pads on the back. Each puts out an honest 30 mA, or more in bright sunlight. Price is reasonable too. http://www.allelectronics.com/cgi-bi...-60&type=store You can also put two pairs in parallel to get a faster charge. thanks, |
Avery Fineman wrote:
In article , "Joel Kolstad" writes: He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! Ahem, Joel, consider the location of "the land of the midnight sun..." That's why I said 'during the periods when the sun never sets' -- it's about half the year with no light, and half with no darkness, no? :-) After all, during the 'no light' periods he doesn't have to run the air condtioner anyway, right? Just kidding! |
Avery Fineman wrote:
In article , "Joel Kolstad" writes: He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! Ahem, Joel, consider the location of "the land of the midnight sun..." That's why I said 'during the periods when the sun never sets' -- it's about half the year with no light, and half with no darkness, no? :-) After all, during the 'no light' periods he doesn't have to run the air condtioner anyway, right? Just kidding! |
But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No? thanks, My experience with tying together solar cells is that you'll probably destroy a few along the way (the pads lift very easily when heated with soldering iron), so either get extras or go with a solution which does not require you to solder cells together (or be more careful than I was, I guess). |
But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No? thanks, My experience with tying together solar cells is that you'll probably destroy a few along the way (the pads lift very easily when heated with soldering iron), so either get extras or go with a solution which does not require you to solder cells together (or be more careful than I was, I guess). |
On Mon, 12 Apr 2004 13:02:38 -0700, "Watson A.Name \"Watt Sun - the
Dark Remover\"" wrote: Joerg wrote: Another option might be to use a different voltage panel, whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. Seems foolhardy to me, to use a boost circuit, and waste a lot of power. Just put more PV cells in series to increase the voltage. The solar cell operates as a (badly) regulated power supply with current limiting. At low load currents, the cell operates nearly as a constant voltage source, but after a specific current (for a given illumination) it operates nearly as a constant current source and deliver approximately that current even into a short circuit. The largest power from the cell (for a specific illumination) is obtained at the point it switches from constant voltage to constant current mode, in which both the voltage is quite close (within 30 %) of both the maximum voltage (as measured at open circuit) and maximum current (as measured at short circuit). This maximum power point varies with illumination, but if the switcher always loads the cell at this maximum power point, the largest available energy at a specific time is extracted from the cell independent of illumination. Even if the losses in the maximum power point tracker is 10-20 %, usually more energy can be obtained than running the module in some non-optimal constant voltage or constant current mode. Paul |
On Mon, 12 Apr 2004 13:02:38 -0700, "Watson A.Name \"Watt Sun - the
Dark Remover\"" wrote: Joerg wrote: Another option might be to use a different voltage panel, whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. Seems foolhardy to me, to use a boost circuit, and waste a lot of power. Just put more PV cells in series to increase the voltage. The solar cell operates as a (badly) regulated power supply with current limiting. At low load currents, the cell operates nearly as a constant voltage source, but after a specific current (for a given illumination) it operates nearly as a constant current source and deliver approximately that current even into a short circuit. The largest power from the cell (for a specific illumination) is obtained at the point it switches from constant voltage to constant current mode, in which both the voltage is quite close (within 30 %) of both the maximum voltage (as measured at open circuit) and maximum current (as measured at short circuit). This maximum power point varies with illumination, but if the switcher always loads the cell at this maximum power point, the largest available energy at a specific time is extracted from the cell independent of illumination. Even if the losses in the maximum power point tracker is 10-20 %, usually more energy can be obtained than running the module in some non-optimal constant voltage or constant current mode. Paul |
On Mon, 12 Apr 2004 13:52:35 -0700, "Joel Kolstad"
wrote: Watson A.Name "Watt Sun - the Dark Remover" wrote: Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. The difference for panels perpendicular to the sun on the equator and the arctic circle in the summer noon is about 10-15 %, due to the atmospheric absorbtion. The difference between the equator and pole is about 30 % in the same conditions. If the panel is tracking the sun, the panel on the pole during the summer will produce electricity for 24 h each day, while the other panel on the equator will produce for less than 12 h. On the arctic circle about 18-20 h each day will give usable electric output. Exactly at the arctic circle, the midnight sunlight is strongly attenuated by the atmosphere, so you can look at it even with your naked eyes or ordinary sunglasses, thus the electric output is also minimal. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! The silicon cell behaves quite in the same way as a silicon diode which has a 0,7 V threshold voltage and -2 mV/C temperature constant, thus the cell output voltage (and hence power) drops with temperature. However, the cells are heated by solar radiation at nearly at constant flux on the equator and arctic circle, thus, the main issue is how well the heat will be removed from the cell to the environment. At the arctic summer the air temperature can be well over 20 C for longer periods of time, so this does not help a lot in keeping the cells cool. Paul |
On Mon, 12 Apr 2004 13:52:35 -0700, "Joel Kolstad"
wrote: Watson A.Name "Watt Sun - the Dark Remover" wrote: Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. The difference for panels perpendicular to the sun on the equator and the arctic circle in the summer noon is about 10-15 %, due to the atmospheric absorbtion. The difference between the equator and pole is about 30 % in the same conditions. If the panel is tracking the sun, the panel on the pole during the summer will produce electricity for 24 h each day, while the other panel on the equator will produce for less than 12 h. On the arctic circle about 18-20 h each day will give usable electric output. Exactly at the arctic circle, the midnight sunlight is strongly attenuated by the atmosphere, so you can look at it even with your naked eyes or ordinary sunglasses, thus the electric output is also minimal. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! The silicon cell behaves quite in the same way as a silicon diode which has a 0,7 V threshold voltage and -2 mV/C temperature constant, thus the cell output voltage (and hence power) drops with temperature. However, the cells are heated by solar radiation at nearly at constant flux on the equator and arctic circle, thus, the main issue is how well the heat will be removed from the cell to the environment. At the arctic summer the air temperature can be well over 20 C for longer periods of time, so this does not help a lot in keeping the cells cool. Paul |
Paul Keinanen wrote:
At the arctic summer the air temperature can be well over 20 C for longer periods of time, so this does not help a lot in keeping the cells cool. ....and the windchill is also reasonably comparable? I didn't realize the arctic could be so 'balmy!' Thanks for the info. I suppose that if you wanted to push the issue, a heat pipe stuck in the ice going back to a metal layer on the back of the panel would be quite effective in cooling the panel... |
Paul Keinanen wrote:
At the arctic summer the air temperature can be well over 20 C for longer periods of time, so this does not help a lot in keeping the cells cool. ....and the windchill is also reasonably comparable? I didn't realize the arctic could be so 'balmy!' Thanks for the info. I suppose that if you wanted to push the issue, a heat pipe stuck in the ice going back to a metal layer on the back of the panel would be quite effective in cooling the panel... |
"Paul Keinanen" wrote in message ... On Mon, 12 Apr 2004 13:02:38 -0700, "Watson A.Name \"Watt Sun - the Dark Remover\"" wrote: Joerg wrote: Another option might be to use a different voltage panel, whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. Seems foolhardy to me, to use a boost circuit, and waste a lot of power. Just put more PV cells in series to increase the voltage. The solar cell operates as a (badly) regulated power supply with current limiting. At low load currents, the cell operates nearly as a constant voltage source, but after a specific current (for a given illumination) it operates nearly as a constant current source and deliver approximately that current even into a short circuit. The largest power from the cell (for a specific illumination) is obtained at the point it switches from constant voltage to constant current mode, in which both the voltage is quite close (within 30 %) of both the maximum voltage (as measured at open circuit) and maximum current (as measured at short circuit). This maximum power point varies with illumination, but if the switcher always loads the cell at this maximum power point, the largest available energy at a specific time is extracted from the cell independent of illumination. Even if the losses in the maximum power point tracker is 10-20 %, usually more energy can be obtained than running the module in some non-optimal constant voltage or constant current mode. Paul Yeah, I see what you mean, sort of like an impedance match, but at DC. But at the beginning or end of the day, or cloudy day, you can't pull any more energy out of the cells than there is there. What it looks to me is that you're adding circuitry to give a better match at the ends of the day or a cloudy day, and in return sacrificing a few percent overall. My attitude is that rather than try to do this (and in the process lose reliability), it's better to go supersize on the cells, add more area and overall capacity to get you thru the cloudy days, and have a higher capacity overall. |
"Paul Keinanen" wrote in message ... On Mon, 12 Apr 2004 13:02:38 -0700, "Watson A.Name \"Watt Sun - the Dark Remover\"" wrote: Joerg wrote: Another option might be to use a different voltage panel, whatever has a good price, and then use a small switcher to run the cells at their optimum load. Regards, Joerg. Seems foolhardy to me, to use a boost circuit, and waste a lot of power. Just put more PV cells in series to increase the voltage. The solar cell operates as a (badly) regulated power supply with current limiting. At low load currents, the cell operates nearly as a constant voltage source, but after a specific current (for a given illumination) it operates nearly as a constant current source and deliver approximately that current even into a short circuit. The largest power from the cell (for a specific illumination) is obtained at the point it switches from constant voltage to constant current mode, in which both the voltage is quite close (within 30 %) of both the maximum voltage (as measured at open circuit) and maximum current (as measured at short circuit). This maximum power point varies with illumination, but if the switcher always loads the cell at this maximum power point, the largest available energy at a specific time is extracted from the cell independent of illumination. Even if the losses in the maximum power point tracker is 10-20 %, usually more energy can be obtained than running the module in some non-optimal constant voltage or constant current mode. Paul Yeah, I see what you mean, sort of like an impedance match, but at DC. But at the beginning or end of the day, or cloudy day, you can't pull any more energy out of the cells than there is there. What it looks to me is that you're adding circuitry to give a better match at the ends of the day or a cloudy day, and in return sacrificing a few percent overall. My attitude is that rather than try to do this (and in the process lose reliability), it's better to go supersize on the cells, add more area and overall capacity to get you thru the cloudy days, and have a higher capacity overall. |
On Tue, 13 Apr 2004 09:18:00 +0300, Paul Keinanen
wrote: The solar cell operates as a (badly) regulated power supply with current limiting. At low load currents, the cell operates nearly as a constant voltage source, but after a specific current (for a given illumination) it operates nearly as a constant current source and deliver approximately that current even into a short circuit. The largest power from the cell (for a specific illumination) is obtained at the point it switches from constant voltage to constant current mode, in which both the voltage is quite close (within 30 %) of both the maximum voltage (as measured at open circuit) and maximum current (as measured at short circuit). This maximum power point varies with illumination, but if the switcher always loads the cell at this maximum power point, the largest available energy at a specific time is extracted from the cell independent of illumination. Even if the losses in the maximum power point tracker is 10-20 %, usually more energy can be obtained than running the module in some non-optimal constant voltage or constant current mode. Paul I have seen elegant ckts where a simple switcher was used, regulating the *input* voltage coming from the solar cell, keeping it in max efficiency mode at all loads. This obviously only works with flexible loads such as slow chargers or such. -- - René |
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