I have been thinking about the extremes in the tunnel & I have moved my citrus down there now as they are too big for the greenhouse or inside. They will enjoy being outside down there during the summer, but have aborted some of their wee fruit being in the tunnel which I think might be the -4C to +27C in 24hrs. (This is not usual I might add, well not to date)!
Also when there is no breeze at all in the summer I thought if a got a small combined fan & heater it would be good for winter warmth as closed up & would move the air around a bit in summer as even though the vents open it does not cool much if there is no breeze & I realise it would not do much to drop the temp with the doors open as well but might deter pest build up with better ventilation.
I will add I know nought about solar, but kinda think it is a panel & a car battery & some cable to plug into, but you see people set up solar stuff when camping off wee tiny panels so got do be doable even for me! (Or my handy next door plot holder)!
![Smile :)](./images/smilies/icon_smile.gif)