Solar panel (for heating water)

Materials used for the first panel (all recycled materials):

  • A wood-styrofoam-aluminium sandwich, taken from the bottom of a trash caravan.
  • Copper tubing
  • A 3-layer thermo window


We tested the panel over the summer 2012 using an old 120 L hot water tank originally intended for electric heating and an old circulation pump. The temperature in the panel got up to approximately 100°C with no water circulating. With water circulating the themperature would go down to approximately 70°C, increasing up to 85°C as the incoming water temperature got up to 45-50°C. This took a few days of sunny weather. The tests were in no way scientific.
  By hand feeling the exiting water would be around 5-10°C hotter than the incoming water, much less than the ambient temperature in the panel. This points to a serious flaw in the current design: the thermal path from the black painted aluminium plate to the copper tube is not very good. The copper tube is pushed down against the aluminium plate with screws into the wooden frame that supports the aluminium plate. In some places the tube is even above the plate.
  Suggestions for solutions for this panel: thermal grease, aluminium powder to improve the thermal path.

Future plans for testing the first panel:

  • Temperature sensors on incoming/exiting water + ambient temperature in panel
  • Water flow sensor
  • Data logging
  • Controller to turn on the pump when it's sunny
  • Sun tracking
Project start: 
August, 2010