|The upper mirrors are fixed and optimised for winter|
sun angles only, the lower ones are tiltable for all sun angles
I have thought about monitoring their effect specifically, rather than just hope and see (following the questioning on the Navitron forum, some constructive, but others bewilderingly hostile). I listen to all good advice, and if it's doable, I do it. That is how these whole boxes and collectors and the plumbing circuitry developed, by evolution and discussion.
One of the first suggestions from there was that of putting in foot mirrors, because there was misperception of how the top mirrors would work when their edge was pointing at 60º. These ideas gathered momentum. If the idea of mirrors is to boost winter performance, why wait till next May? Do it now! Get the kWh into the system now!
Considering their effect as a whole:
I now agree that quite soon, it would be an idea to consider having say, the left hand sunbox mirrors disabled for a while (the upper mirror muzzled with dark cloth, and the lower mirror tilted back or muzzled too) and have the datalogger measure the flow temperature (the same to each) and then measure the different return temperatures from each sunbox (different pipes that unite in the loft before going to the energy flowmeter. This would be easy to do if I have long enough datalogger wires (getting these is a problem) and made easier by the fact that the liquid pressure and flowrate is the same through each sunbox. Being two, they each have a different interior air temperature.
I was reluctant to do this earlier, as I am keen to grab every free kilowatt hour that is going, to establish a new low for the annual electricity consumption in 2010-2011. But there is a research case for doing it.
Perhaps it's time to get my own little USB dataloggers, as I don't know if Blaise will have time in his final year of writing up. I can't get data out of the ones I already have without his help as he has the software on his laptop. I do have a spare old laptop that could be configured for use.