Sun trackers get 3 times the suns energy than flat plate collectors. So
much so they are powering Stirling engines.

This doesn't add up. The amount of energy available per square meter
is the same for any collector. At the height of summer, this is about
800-1000W per square meter. A suntracker maintains alignment with sun
so it's exposed area does not diminish as the sun moves. It might also
be 10-20% more efficient than the cruder panels but this doesn't add
up to 3 x difference...

It does. It magnifies the suns rays.


What is your air heater you mentioned by the way? A commercially
produced one or a DIY one? I may yet look into an air heater because I
reckon I can make an 8 square meter one for under 200 pounds (not
including the fan - I have a spare extractor fan about 20cm diam)...

Nick