YOUR GUIDE TO SOLAR ENERGY![]() |
THE BASIC INFORMATION ABOUT SUNLIGHT![]() You can see from this diagram that the amount of energy that is intercepted by the Earth at any give moment equals to solar constant times Earth's cross-sectional area Ac=π×d2/4, where d is the Earth diameter, π=3.14. Since the total surface area of a sphere is π×d2, the amount of sunlight power per unit area that reaches our atmosphere averaged over entire Earth's surface is ¼ of solar constant, or about 341 W/sq.m. From this amount about 29% is reflected back to space, 23% is absorbed in the atmosphere, and 48% reaches the surface. |
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Sponsored ads ![]() SOLAR INSOLATION INFORMATIONThe net amount of the sunlight received during a day varies significantly with geographical locations and the weather patterns. To calculate the average amount of electricity a residential PV system can generate, you need to know the characteristic called insolation (INcoming SOLar radiATION). Insolation levels represent an average solar energy density and are usually expressed in kilowatt-hours per square meter per day (kW-hr/m2/day), or as an amount of equivalent hours of "standard sun" 1000 W/sq.m. Numerically both values are the same. NASA maintain an extensive database on average solar energy density for most locations in the world. NREL laboratory has insolation maps for the US. Note that in today's non-concentrated PV systems for homes only less then 20% of the insolation can be practically converted to electricity (see: Solar power system efficiency). ADDITIONAL FACTS AND REFERENCE INFORMATION
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