|The Green Power Team join Matt and Ray, sheltering from a shower in the polytunnel.|
The idea of the heat sink came originally from the Centre for Alternative Technology (CAT) in Wales, where they use a big pile of slate to hold the heat in their polytunnel. It heats up during the day, and gives off the heat at night, so that the temperature isn't too hot by day and isn't too cold by night. This can mean a few extra weeks of growing time in Spring and Autumn without putting in a heater in the tunnel. Our version is a bit more complicated. This one uses a solar-powered computer fan to push hot air from the top of the polytunnel, down a tube into an insulated box of rocks, to store the heat. At least that's the theory! After today - all we have is a hole, but hopefully it will be big enough to make a difference.
|The team start to dig the hole for the heat sink.|
|The team working on the bench site.|