A homeowner is considering putting a horizontal solar panel on her roof to heat water for domestic use. An average increase of water temperature each day from 60oF to 20oF is wanted for 50 gallons. How large a panel would be needed on a clear winter day at 40o latitude if the overall efficiency is 50%?
Here's a typical 4' x 8' collector rating. 40 degree latitude would be a cool climate, so you look at row D, water heating in a cool climate. Probably take the middle rating, mildly sunny day, and it is 0,000BTU per panel per day (it's 9,000 on a sunny day). 38,700 BTU / 0,000 BTU = 3.87, they'd need about 3 to 4 panels. If you used the sunny day number, you'd only need 2, but 3 is more realistic, as it is not always a sunny day.
Good points. I'm new to the solar energy world, but solar just makes sense. Who wouldn't want to make it work? The more I learn the more I think its a great alternative to some of the energy we use. This info really helps.
