I recently installed a muffin fan and adjustable snap disk thermostat. We had a clear day yesterday with no shade on the panel all day, max. 25 degrees outside, perfect for logging the temperature.
The graph tells the story and I am very impressed. I look forward to tweaking the fan and thermostat as I learn more of the response times and air flow etc.
The speed at which the panel heated up to 120F degrees is amazing and even at the sun angle of 9:30 AM. (these are mounted vertical flat against the South wall) The fan kicked on at 120F and off at 100F. The hot air out rose to 159F degrees even with the fan continously running. This was an unusual day in that there was never any shading all day.
The yellow line is room temperature and the bumps are my furnace cycling indicating about 1/2 degree F fluxuation. This is due to the air escaping around the closed off room vents. The panel held and actually upped the room temperature over 2 degrees from 72 to over 74F for 12 hours. The outdoor temperature range was 16F - 25F max.
The fan is 120 VAC 20 watts Max. and 65 CFM. Learning from the data I'll be playing with the fan size and thermostat etc. but for now it's a great start. About 2 cents of grid power to heat my 12x16 room 72-74 degrees F as well as spill off into the adjoining room by leaving the door open. Actually is was easily free, my 16' wind generator more than made up for that heating my water yesterday besides. More graphs and updates to follow, I can't wait to get the other one mounted and running as well. Dave B.