Zeke, Thermal solar panels can reach surface temperatures around 400 degree Celsius, but with pump or thermal driven circulation the water temperatures will not reach boiling temperature and open system can be used. I have such a system on my roof. Generally the efficiency is around 35%. The normal PV cells have 8 to 12% efficiency and the new high efficient ones around 34% efficiency, need cooling in concentrator applications. If the concentrator is not too efficient, they can be mounted on an air cooling device, similar to what is used for electronic components, otherwise they must have liquid cooling.
Design criteria for thermal solar panels was researched by Spanish and Swedish Universities in Almeria, Spain, in 1960's. This was used by a Swedish company, that now deliver 70% of the world market for commercial thermal solar elements. They are delivered in rolls, cut to size and the space for the liquid is then expanded with air pressure. This is my understanding of the quite interesting current technological situation. Since you did your master on solar panels, it would be very interesting to get your view on where this is moving and perspective on future possibilities. Hakan At 00:29 14/05/2006, you wrote: >This is exactly what I did my master's thesis on. The concept works >pretty well from a theoretical perspective. I was just investigating >using water cooling for non-concrentrating PV, but it would work even >better for concentrating PV. You shouldn't really have to deal with >1200F, at least if you are talking about water, because the maximum >working temp for a water based fluid is probably about 400F or so?? >(assuming antifreeze additives and increased pressure). Depends on >how much pressure you are talking about I guess. > >On 5/13/06, Jason & Katie <[EMAIL PROTECTED]> wrote: > > 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 _______________________________________________ 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/
