in theory, if one could find a way to waterproof the back of a PV cell it could be used as the heat-side plate in this concentrator/boiler found at (or after) http://www.ida.net/users/tetonsl/solar/page_46.htm you could safely increase the power range of a smaller PV cell without too horrible of a heat loss. the problem is finding a sealing substance that wont melt or burn under these 1200*F temperatures.
----- Original Message ----- From: "logan vilas" <[EMAIL PROTECTED]> To: <Biofuel@sustainablelists.org> Sent: Friday, May 12, 2006 4:54 PM Subject: Re: [Biofuel] Solar Concentrator & PV Modules >I am working with the idea of building my own Concentrator with about 50 > times the mirror space then collector space. That Is why the question was > asked in the first place I was wondering if placeing a 50watt solar panel > at > the focal point would increase the power output. I've read that it is more > then 100% liner increase in power output when increasing the amount of > light > on it. a normal panel at 50 watts would be 2500 watts at 50 suns. I know > it > would need to be kept cool. due to the fact that they are only 20-30% > efficent, but I could use the coolant to heat my biodiesel processor, then > the hot water going into my home before a tankless heater. If I were to > get > a grid tied inverter It would suppliment my normal power useage and maby > with netmetering it might come close to canceling out my power > requirements > alltogther. a simple temp sensor could be used so if the temp is over 150f > in the coolant it will shut down and not collect the sun anymore. As for a > solar tracker that is relative easy with very simple electronics. The > setup > to hold everything would be a simple build for most people who can make > their own biodiesel processor. And If I base it off a 7 meter dish I can > get > those free. I just have to use the labor to remove it. > > Logan Vilas > ----- Original Message ----- > From: "Zeke Yewdall" <[EMAIL PROTECTED]> > To: <Biofuel@sustainablelists.org> > Sent: Friday, May 12, 2006 3:59 PM > Subject: Re: [Biofuel] Solar Concentrator & PV Modules > > >>I am speaking mostly from experience, from what I have seen work and >> fail in the field, and what I can buy to install for my clients. The >> reason I talk about trackers on large poles is because that is what is >> commercially sold right now (at least in the US, europe is ahead of us >> in many areas). And the biggest reason I see for failed systems is >> lack of maintenance (mostly batteries, but also anything that moves). >> Also, the number of new innovative PV systems that I have seen come on >> the market over the years, only to dissapear within another year... >> We're still basically doing the same thing as PV was in the 70's, with >> incremental improvements in efficiency and incremental cost decreases. >> I called the concrentrating PV exotic merely because I can't call up >> one of 200 some suppliers and buy one that meets all current >> electrical code, whereas I can with silicon PV modules. Maybe another >> breakthrough is coming, but in the mean time, alot of people will keep >> using coal generated power because they are waiting for those >> breakthroughs. I would rather see working PV systems going in today, >> even if they aren't all that high tech, rather than people thinking >> they have to wait before solar energy can work for them -- and in the >> mean time continuing to support coal and oil. It's not that I want >> to limit the new technology, but what I have seen is that the >> layperson holds out the possibility of a paradigm shift in the >> technology in the future as a reason to do absolutely nothing now. >> And if I recall, the original question was about concentrating >> sunlight on a normal old PV module -- which isn't the best idea -- >> they tried that at the carrizo solar plant in the early 80's, and a >> few years later, a whole lot of used Mud-lams (because the encapsulant >> turned varying shades of brown) flooded the market for off-grid use. >> >> I do admit that this list's members are not your average layperson, >> and most of us won't just use the news of new inventions as an excuse >> for procrastinating, so I apologize for that. >> >> Zeke >> >> >> On 5/12/06, Michael Redler <[EMAIL PROTECTED]> wrote: >>> >>> By now, you may have noticed my resistance to "conventional wisdom" >>> whenever >>> someone gives negative feedback about a particular energy scheme. Here >>> is >>> an >>> example. >>> >>> The idea of concentrating light onto PV cells is a relatively new idea >>> in >>> some circles. What to do about waste heat is a natural progression in >>> the >>> discussion of such technology. But, why is it seen as such an obstacle - >>> especially when schemes for harvesting waste heat are so abundant in >>> energy >>> related discussions? >>> >>> You wrote: "...regular PV is cheap enough that the simplicity of not >>> having >>> >>> moving parts will probably outweigh any advantage of trying to get more >>> from >>> the same amount of silicon." >>> >>> >>> The sweeping statements are getting old Zeke. Adding trackers become >>> advantageous when you run out of roof. By the way PV that works on >>> concentrated sunlight isn't so exotic and will probably become the PV of >>> choice in a large percentage of applications. The large cost of >>> concentrating PV is likely to be offset by an increase in power >>> conversion >>> requiring the use of heliostats, tracking technology and those pesky >>> moving >>> parts. >>> >>> >>> Mike >>> >>> Zeke Yewdall <[EMAIL PROTECTED]> wrote: >>> >>> Most of the highest efficiency PV cells do use concentrators. These >>> are the 35% efficient super exotic ones that NREL and others are >>> working on. Compared to 20% which is about the highest commercial >>> single sun efficiency right now. In general the power produced by a >>> PV cell is linearly related to the energy input. More sun = more >>> power. So if you put 25 suns on it, you get 25 times the amount of >>> power from the same cell (assuming you don't change the spectral >>> composition of the l ight). It's not quite linear, so I think you >>> actually get a tiny bit more power at higher concentrations than just >>> the concentration ratio would imply -- say 28 instead of 25. The >>> problem is that a typical crystalline silicon cell also decreased its >>> power about 0.5% for each degree celsius the temperature goes up. So >>> if you increase the operating temperature of the cell from 60C >>> (typical for one sun) to 200C, you've just lost all the power you >>> gained by putting more light on it.... Plus if you get too hot, >>> you'll damage it -- usually the encapsulating material degrades well >>> before the temperature at which the actual PV cell is damaged though. >>> The other thing is that concentrators require tracking the sun usually >>> (at least to achieve more than 2 or 3 times concentration. This >>> introduces moving parts to the equation, and destroys one of the nice >>> features of PV. If it's a big central power station where you can >>> hire a full time maintenance operator, then go ahead. If for your own >>> house, regular PV is cheap enough that the simplicity of not having >>> moving parts will probably outweigh any advantage of trying to get >>> more from the same amount of silicon. >>> >>> Zeke >>> >>> On 5/12/06, Joe Street wrote: >>> > Actually mirrors can be used to concentrate the light from a large >>> > area >>> > onto a small high efficiency solar cell. It is being done. This is one >>> > of the justifications for the cost of high efficiency cells but the >>> > extra cost of the concentrators and the lengths one has to go to to >>> > keep >>> > from overheating the PV module unfortunately outstrip the savings the >>> > idea hopes to offer. Too bad but on the other hand if you are just >>> > fortunate to have access to heterojunction cells on the cheap then >>> > maybe >>> > you should go for it! You will need a liquid cooled backing plate for >>> > the cells but if you are crafty you might be able to use the rejected >>> > heat somehow as well! >>> > >>> > Joe >>> > >>> > Lugano Wilson wrote: >>> > >>> > > hi Logan. >>> > > >>> > > PV modules and solar concentrators are two different technologies >>> > > and >>> > > unfortunately, their individual energy capture principle is >>> > > contradicting to each other. consequently, they can not be used at >>> > > same >>> > > application. PV modules need to absorb all the solar radiation so as >>> > > to >>> > > generate electricity through the module cells where as solar >>> > > concentrators have to reflect all the solar radiation and direct it >>> > > at a >>> > > specific location (ie concentrated) for the purpose of heating a >>> > > medium >>> > > that can latter generate required energy. you therefore need to >>> > > choose >>> > > one for a specific application. however, when it comes to >>> > > electricity >>> > > the pv modules are good due to the fact that you can size them >>> > > depending >>> > > on your requirement starting with one module and increasing. >>> > > concentrators for electricity is a large scale project - not so >>> "modular". >>> > > >>> > > Lugano >>> > > >>> > > */Logan Vilas /* wrote: >>> > > >>> > > Would a standard PV module produce more when used with a Solar >>> > > Concentrator >>> > > or does it require a special PV module? >>> > > >>> > > Logan Vilas >>> >>> [snip] >>> _______________________________________________ >>> Biofuel mailing list >>> Biofuel@sustainablelists.org >>> http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org >>> >>> Biofuel at Journey to Forever: >>> http://journeytoforever.org/biofuel.html >>> >>> Search the combined Biofuel and Biofuels-biz list archives (50,000 >>> messages): >>> http://www.mail-archive.com/biofuel@sustainablelists.org/ >>> >>> >>> >>> >> >> _______________________________________________ >> Biofuel mailing list >> Biofuel@sustainablelists.org >> http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org >> >> Biofuel at Journey to Forever: >> http://journeytoforever.org/biofuel.html >> >> Search the combined Biofuel and Biofuels-biz list archives (50,000 >> messages): >> http://www.mail-archive.com/biofuel@sustainablelists.org/ >> >> > > > _______________________________________________ > Biofuel mailing list > Biofuel@sustainablelists.org > http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Search the combined Biofuel and Biofuels-biz list archives (50,000 > messages): > http://www.mail-archive.com/biofuel@sustainablelists.org/ > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.385 / Virus Database: 268.5.6/338 - Release Date: 5/12/2006 > > _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
