In reply to Stephen A. Lawrence's message of Mon, 06 Jul 2009 22:00:31 -0400: Hi,
I agree there is somewhat of a performance improvement at high intensity, however this still pales by comparison to the cost savings achieved through the much higher concentration. I.e. at 80 Suns, a 1 cm^2 cell gets 80 cm^2 worth of sunlight, while at 500 Suns it gets 500 cm^2 worth. To get the same amount at 80 Suns, it would need to be 500/80 = 6.25 times larger and hence also 6 times as dear. This is a much larger effect than the small increase in efficiency. It might also be interesting to know how the new printed solar cells fare in concentrated sunlight (especially if they can made with a metal backing). > > >[email protected] wrote: >> In reply to Stephen A. Lawrence's message of Mon, 06 Jul 2009 15:42:15 >> -0400: >> Hi, >> >> I think you may be reaching a bit to far. I think it's just a matter of >> economics. By going to 500 Suns, they reduce the size of the solar cell >> required, and hence also the cost. Of course the temperature would be >> prohibitive without cooling, so they may also be extracting useful energy >> from >> the cooling fluid. (Energy concentrators are much cheaper / m^2 than solar >> cells). A trough only concentrates in 1 dimension as it were, whereas a >> circular >> parabolic mirror of Fresnel lens will concentrate in 2 dimensions, which is >> why >> a trough will only achieve about 80 Suns, while the others can get up into >> hundreds of Suns, depending on the accuracy and quality of the reflective >> surface. >> >Well I actually tried googling it, and I found this: > >http://pvcdrom.pveducation.org/CELLOPER/LIGHT.HTM > >If this is accurate, then there is a *slight* efficiency increase with >increasing intensity, due to a slightly peculiar effect: The current a >cell can produce varies linearly with the light intensity (as you might >expect -- my "two-shot-to-go" guess appears to be dead wrong). But, the >(open circuit) voltage varies with the light intensity, also -- it goes >up as the log of the intensity. The result is that the maximum power >the cell can put out goes up nonlinearly. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/Project.html
