I took the car to the carwash at the weekend and had an idea. I bought some Turtle wax. I would have preferred some T-Cut, so that the surface might actually be smoothed, but I suspect that T-Cut cuts paint films but not bare metal.
My mirrors will never have an optical mirror finish because they are a brushed finish - aluminium tarnishes to a stable level of matt shininess and if you want a much brighter finish you need stainless steel. But the foot mirrors have got dirty and they are a major contributor to thermal harvest. They could do with being cleaner and shinier.
I put some Turtle wax on a test piece of aluminium and when water is trickled onto them, it forms into droplets and runs off. On the remainder of the piece, the water is more of a flat sheet. So now, I have been up the ladder and polished both the foot mirrors, leaving just 30 cm unpolished....
1. because I couldn't reach it without falling off or moving ladder, and 2. to leave a bit un-waxed, so I can compare their appearance a couple months on, into the summer.
Monday was very sunny, but with reduced activity from the GSHP, the Sunboxes don't capture so much either. This is another reason to give those mirrors a polish - get more sun in! the PV had its highest score of the year so far, over 16 kWh, meaning that most of the Sunshine was delivered in the morning.
PS: I fitted up the right hand (easterly) pipe cover, so now the panels are symmetrical! Let's hope that reduces long term maintenance.