That’s a beautiful install. Nice work!
That’s what I was thinking too. Maybe a shade (platform above) would help.
I was also contemplating something like this:
https://www.1-act.com/spot-cooling-heat-pipes/
I also tried to exchange heat using copper pipes and heatsinks but the temperature difference was something around 5oC, still high
Probably need a shield to protect against direct sunlight. For example, set the receiver in the shadow of a satellite dish
Love that setup. Perfect.
Depending on availability, rangehood filter paper may be a good choice for this. It ‘should’ offer a low flow restriction.
In my opinion the problem with the number of insects “per inch” 
.
Perhaps the problem would be solved by connecting a perforated pipe as an external coarse filter.
That would certainly provide a very large surface area to draw air through.