However, my DIY-fu is fairly strong, and my usual urge to try and do stuff in a somewhat hackish fashion kicked in…

I’m lucky enough to have a nice little stream outside, with a fairly decent flow rate and cold water. I had some copper microbore pipe left over from a plumbing project, and figured that I could rig up a heat exchanger in the room and in the stream, link them and pump water round the system, thus removing heat from the room.

I originally planned to buy some PVC tubing (flexible) but couldn’t find a local supplier, so I turned to garden hose. Very strong, quite flexible, and not too expensive. A 50 metre roll cost £40, and I had 20ish metres left over from another project, more than enough in total. All that remained was to get a heat exchanger and pump. The heat exchanger ended up being a radiator off a BMW from a breaker’s yard (£25), and the pump was a £60 central heating pump (including adaptors to convert the 1/12″ plumbing connectors to 15mm pipe).

The Diet Coke bottle is connected to the radiator overflow

The hoses fitted onto the 15mm pipe after being heated with hot water just fine, with jubilee clips to hold them on securely (likewise on the microbore). To get into the radiator I used a set of 22mm->15mm adaptors with self-algamating tape to pad the diameter out a bit, with jubilee clips clamping down the radiator hoses onto the fat end of the adaptors. Basically what I had kicking about.

The result? With 3 people and 4 (hot) computers in a room the system kept it not only comfortable but cold! For about £125 I not only have a cold room but for the fraction of the power draw- with a fan and the CH pump, it draws around 50 watts instead of the 800+ watts of most air conditioners.