Solar Powered Fan to aid ventilation?

A target of 85% RH is ideal for temps between 77F and 90F. You`ll find an overhead misting system very useful on hot days.

 

Ever thought about those fans that are used with inflatable xmas decorations, I had one once but didn't have a tunnel then.

 

Never had an inflatable xmas decoration, I assumed you blew them up with a bicycle pump or something. Live and learn!
I ended up buying a fan from pkgreen (via amazon, it was cheaper!) and I'm running it from an old leisure battery with a 20w solar panel and controller (which I already had). It is about 6 foot in from the front door hanging off a crop bar. Standing at the door you can just about feel the breeze. Don't think it makes any difference to the temperature (my min-max thermometer said 30deg C today) but hopefully a bit of air movement will do some good.
My next project is a version of the heat sink that they did on 'It's not easy being green'. My theory is that if you leave a hose pipe out in the sun, the water in it gets pretty hot. So how about hanging a hosepipe in the top of the polytunnel, put a water butt in the tunnel, and pump water from the butt through the pipe and back into the butt. Heat the water up during the day and give out the heat at night. The problem then is to find a pump capable of lifting the water and pushing it through x feet of pipe, with a continuous flow, (some pumps say run for a max of 15 minutes) somehow connecting it to the pipe without leaks, run it off 12volts, and all without breaking the bank. My builder has contributed a 10mm microbore copper pipe roll to the project (he's had it lying around his shed for years) and I've ordered a pump for about £15. Watch this space...

 

Thank you for that, yes, very interesting.

 

Dick always seemed to work backwards, he`d build whatever it was then try to figure why it didnt work, physics and thermodynamics arent his thing It would be great if a cubic metre of gravel/broken glass and a pc fan could heat and cool a greenhouse but tbh a hot cuppa tea (heating) and an icecream cone (cooling) would probably be just as effective.