This one is easy. Until 10 years ago, copper was used for 99% of all fins and the thickness was roughly .2mm+-. The biggest problem was the copper tube, aluminum fin connection which corroded a lot. It might have been good for a few years but the average panel with aluminum fins only lasted a few short years.
Now, with ultrasonic welding and laser welding, better aluminum (less reactive alloy) the joint is "supposed" to last as long as long as a copper fin. The thickness needed to have the same overall heat transfer for the same standard 150mm fin width is around .45-.5mm.
The surface prep is a bit different as well. The aluminum MUST be roughed up lightly and cleaned of any oxidation even more so than copper and just before the coating is put on.
Here is a spec by a company that makes both products. I toured their plant back in 05 in Germany. Interesting anecdote is that the head of the company took me out to lunch and we had fish from a river that used to have a NUC plant on it. 5 years after the NUC plant was decommissioned (thanks to solar PV, wind and Thermal), the fish were deemed safe to eat.
Note the absorption curve. This is with the coating, of course and it will be different from a painted coating that DIYers will have.
Last edited by Mikesolar; 04-03-13 at 06:33 AM..
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