Collecting Solar Energy
To gather solar energy effectively, a solar collector (glass, solar panel, etc.) should be within about twenty degrees either side of perpendicular to the sun. Also, shades need to be placed, so that the building does not warm up too much in summer and then thus requires cooling. The farther from perpendicular, the lower the solar gain. More than thirty-five degrees from perpendicular results in a significant portion of sunlight being reflected off the solar collector surface.
An effective solar energy system (passive solar, active solar, building, equipment, etc.), takes into account the significant seasonal 47-degree solar elevation angle difference above the horizon, and the sunrise/sunset solar azimuth angle from summer to winter.
Precise knowledge of the path of the sun is essential to accurately model, and mathematically predict, annualized solar system performance - To explain, for example, why vertical equator-facing glass is cost-effective, the benefit of solar energy reflectivity off winter snow when the sun is low, and why roof-angled glass (in greenhouses, skylights and conservatories) can be a solar furnace during the summer, (when the sun is nearly perpendicular to the glass), and then lose more energy in the winter than it collects, (when the sun is 47-degrees lower on the horizon, and warm interior air rises and transfers heat out of the building on cold winter nights).
Read more about this topic: Sun Path
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—Logan Pearsall Smith (1865–1946)
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