Temperature dependence of Unisolar solar panels

I am interested in your Uni solar products, but I need a little advice.
I have a 50mm thick foam insulated (on the inside) flat, smooth, steel roof onto which I would like to mount two panels. The framed version needs to be raised and ventilated underneath for best results, but the self adhesive version must get much hotter being dark in colour and unable to dissipate heat from underneath; indeed, I understand that it must not exceed 85c.
My question is: Given that the PVL68 will get a lot hotter when compared to the framed version, how much difference in efficiency should one expect, given a hot summers day - if we get any?

Thanks for your advice. Jeff.

If you want a technical answer, the data sheet for the photovoltaic laminate series has some temperature coefficients for the different parameters, so you should be able to work out a loss of efficiency from those. See: http://www.uni-solar.com/uploadedFiles/0.1PVL-68%20AA4-3698-02.0601107.pdf, in particular the max power, which reduces by 0.21% per degree C. Note however that they say elsewhere that the temperature dependence is very non-linear, so I don't know how much reliance you can place on those figures at high temperatures. However, if a panel glued to the roof was, say, 10 degrees hotter than a ventilated framed panel, the difference in efficiency would only be 0.21 x 10, or 2.1%.

At the uni-solar web site (www.uni-solar.com) there are a few technical papers which might give you some help. Go to the home page, then select Resources > White Papers/Research reports. http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_2.pdf has a paragraph on temperature dependency for example.

If you want a practical answer, unisolar laminate panels are designed to be used in exactly your sort of situation, have a lower temperature dependence than conventional crystalline panels, and I've used unisolar panels in a very similar application myself for the last five years - on the steel roof of a narrowboat which is also insulated with foam underneath. Mine are laminate panels glued directly to the roof. I don't have any figures for the production at different temperatures, but on hot sunny days, when the roof can get too hot to touch, they are certainly kicking out a good current. I daresay there may be a little loss at high temperatures - but to be honest in any battery charging application I'd be a lot more concerned with the production at low light levels on colder days, as that is when the output is most likely to be struggling to keep up with demand.

In short, I personally wouldn't make the efficiency at high temperatures the deciding factor in deciding on the most suitable panel - the difference you notice will likely be minimal.