I suggest that you get a single solar cell, mount it in the same orientation as the heater, and measure its short circuit current while you are testing. This will give you an accurate measure of the insolation during the test. I guess you should monitor the air temperature and wind speed as well.
If you want to compare 2 water heaters, let them work at the same time, one near the other, but not to close! so one won't be a "wind shield" to the other.
Give them clean flat surface in the front 5 Meters, to avoid non-equal wind disturbances.
Of course, no shadowing on them while testing.
Mount them on the same declinment and direction to the sun, as recomended in your area.
At the begining, feel their tanks with cold water.
At the end, mix the water in every tank and mesure average temperature.
Initial cold water temperature minus the average temp' at the end is the comperative factor.
Hi there,
I have just joined this foruim, and when I saw your question I remembered that I did a diploma in solar energy. So I have few questions for you.
what are you comparing? Is two solar heaters or comparing solar heater with electrical heater?
I think from the given replies it is a comparasion with two solar heaters.
So the comparison will be based on :
- the reflectivity of the glass.
- the material of the absorption surface.
- the material and quality of the paint of the absorbion surface.
- The material of the insulation.
I hope these will be of help to you
Good luck
