Peak Sun-Hours

摘要

A reader writes, "The sun comes over the top of a ridge in the morning at about 8 a.m. and sets at about 8 p.m in Ocean View, Hawaii-12 hours of usable light. So I'm confused when some PV system users claim that there are only 4.3 to 5.2 hours of "available light." Is this due to the fact that their modules are fixed in place? What else may be the cause?" The daylight you are witnessing ("12 hours of usable light") and the available sun-hours for solar energy are indeed different. For making electricity, we use the way solar-electric modules work, and how they are tested and rated, to help us calculate what our site's solar resource (solar irradiance) will provide.