Posted By radsol on 12/29/2007 1:18 AM
I am just starting to research solar water heating for a radiant floor heating system in a mild climate. I am amazed that I haven't been able to find
any books that focus on this topic. Are there any recent ones?
That's probably because solar hasn't made much inroad for space heating, and I think that is because of cost and aesthetics. Over a year ago when I started my house project I considered solar as a possible primary heat source, or even just to augment another heat source. Essentially what I came to realize is the efficiency of solar collectors is lowest when the heat demand is highest, i.e., winter time. You end with a lot of solar collector area, hence cost, to capture the btus necessary for space heating. Pictures I saw of apparently successful space heating solar systems show solar collectors covering almost the entire roof of a home. Not very attractive in appearance. Most solar is use for domestic water heating and swimming pool heating because the demand of those systems is much less than space heating, coincides better with higher solar radiation levels, and don't require extensive arrays of collectors.
Another consideration for mild climates is the need for air conditioning. To have AC along with solar space heating you end up with two space heat energy transfer systems, one for input, solar, and one for extraction, AC. I didn't do a lot of number crunching, but it became apparent fairly quickly that solar plus AC is an expensive way to go.
Also think about the fact that radiant heating is a relatively small portion of all residential heating systems, and solar would be a small portion of that. Consequently, solar source radiant heating systems are going to be a miniscule portion of the total residential heating industry. Companies don't like to focus on tiny market segments. I say that's why there's no books on the subject.