Solar hot water - 30°C

This morning it was 8 °C outside in the world when I started the test. The maximum temperature for the day was 9.8 °C.

Air temp in the collector was 18°C

Air temperature within the poly pipe collector was around 23 °C
And the temperature within the water tank was around 9 °C

The water tank has developed a very slight leak so the water wasn't circulating until I topped it up, thus the temperature difference. Once flowing you can actually see it flow. You see it as heat haze emited from the inlet hose and as a current swirling little bits of gunk that I failed to clean out of the hoses.

An hour and a half later and it reached 30°C inside the water tank, and 33°C within the collector.

As far as I know, my water didn't get any hotter than 30°C, but It stayed at that temperature, and still is at that temperature, even though the day became overcast and colder.

I took the temperature at the bottom of the storage tank as well and found it to be only 1°C less than at the top. This might mean I need a bigger storage tank to allow the heat to rise to the top. The flow might be enough to be stirring the water and mixing it too much. If it was a deeper tank, or the flow was less I might be seeing higher temperatures. Slowing the flow would be as easy as adding a tap. I'm not sure that I'll bother on this small test system. I think I have made the correct number of errors to allow myself to move on to the bigger version, and actually do something with the collected heat. 30°C is still 9 degrees short of my target but I think with a better made, and larger unit, 39°C should be achievable on a day like today.


  1. This is hilarious. I'm enjoying your approach and your writing and it'll be interesting to hear what happens as you scale up. It saves me trying this stuff myself.

    From an aspiring Dandy!


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