Solar hot water - Poly pipe collector

It was a chilly and windy day in the hills today. But the sun was out for a while in the morning.

The ambient temperature was around 11°C as I added the rest of the T junctions to my new poly pipe collector, and I was almost confident that I'd sooner or later, be making some solar hot water. 

The water temperatere was around 10°C from my rainwater tank.

It was interesting to note the temperature of the collector was very close to the temperature of the storage tank, and the air temperature in the collector stayed low. (digital thermometer is testing water temperature and the glass one is testing air temp in the collector) 
No doubt this means that the heat exchange area of the black poly pipe is sufficient. This came as a bit of a surprise to me, although in hindsight it would appear that the transfer rate is self governing to some degree. The hotter the water gets, the faster it will flow and thus the more heat exchange will occur.

Final temp before it started raining and I went inside was only 22°C, and it didn't get any higher in the overcast, windy and rainy conditions, even when I went outside hours later. But, I think it was actually a success. I doubled the temperature of the water and it only took an hour and a half. 

Given I only used two sheets of corflute for insulation, and the insulation for the top, bottom, and sides was just tape, which isn't really insulation it's really just tape, It did about as well as I hoped.

The experiment served its purpose in that I learnt a few things and didn't cost anything as I'll be pulling it apart and using all the bits in the real thing.

Lessons learnt ...
  • Air bubbles are not your friend. Don't let them collect.
  • You don't need a lot of tubing to shift a lot of heat from a collector.
  • Insulation is amazingly important. (tape leaks heat so that you can feel it leaking)
  • A tube based solar siphon regulates itself, so there wont be any issues with the collector overheating.
  • Even at the rate this poorly constructed solar collector collected heat, it would still be worth using it as a bathroom heater or something*. On a bigger scale without changing anything except scale I could heat my house by building a wall out of water tank and simply circulating the water to my collector.
  • Collecting free energy is a worthwhile pastime.
  • I'm not very skilled at gluing.
  • there was a reason I collected all that 19mm poly pipe for all those years, even though it had holes in it every few metres, and kinks in the sections between the holes.
*Hmmm towel heater...


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