Fernando Cabral <[EMAIL PROTECTED]> writes: > Now I am planning to build a house for a small farm I have. I've > been thinking on how to take the best advantage of the solar > power. This includes where to have a garder with a nice sundial and > where to place the solar panels for water heating as well as > (perhaps) electricity (at least in Brazil solar panels for > electricity are very expensive). > > At 19 37' 57" S, it is clear that the panel should be facing North. > But what is the best angle with the horizon. And, if I can have > several panels, is there a practical to calculate the best angle of > each so as I can guarantee the highest possible insolation level? > > Say, if I have three panels, is it best to place them side by side, > with the same inclinatation and declination? Perhas if one is a > inclined towards the East with a certain angle and the other to the > West with a proper angle I can capture more light?
Goods questions, to which I don't have the answers. I would even question the basic assumption that the panels should face north. You may want to have fresh hot water as soon as you can in the morning, especially if you shower then, in which case the panel (or one of them) should face east. At midday and in the evening you can use the heat that has been collecting all day. By the same token, it is probably better to point the panel low to the horizon (angle between the normal and the vertical equal to 23.5 degrees minus the latitude, since you are in the tropics) because you will want to produce more hot water with less sunshine in the winter. (You may not have enough of a winter that that matters, but there may be similar considerations for rainy/dry season, afternoon thundershowers, etc.) If you determine the optimum angle simply by integration of the sunlight over some period, then that angle will be the same for every panel. If your use patterns are different and the storage characteristics poor, then you might want to do something like point one panel to the east for morning hot water and one to the west for evening hat water. Do you need some inclination to drive convection through the collectors? Or to prevent rain water from collecting on the panel? Since you say there is a great variety of orientations of panels in the city, can you get answers to some of your questions by interviewing residents with different orientations? Art Carlson
