solar lecture 4 - Solar Utilization...

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1 Solar Utilization Solar Radiation Instrumentation Radiant energy fluxes that are of importance to solar  thermal processes include: Beam solar radiation (shortwave) Diffuse solar radiation (shortwave) Reflected solar radiation (shortwave) Long wave radiation that comes from the sky, is reflected  from the surface and reradiates from the surface
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2 Solar Utilization Solar Radiation Instrumentation There are two major types of instrumentation for  measuring solar radiation: 1. pyrheliometers: uses a collimated detector for  measuring solar radiation from the sun and from a  small portion of the sky around the sun (beam  radiation) at normal incidence. Also called an  actinometer. 2. Pyranometer: an instrument for measuring total  hemispherical solar (beam and diffuse) radiation,  usually on a horizontal surface. Also called a  solarimeter.
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3 Solar Utilization Solar Radiation Instrumentation The pyranometer can be adapted with a shade ring or disk  to measure diffuse radiation: a shaded pyranometer. The standard and secondary solar radiation instruments  are all pyrheliometers. There has been quite a history for these instruments: Abbot in 1905: a cylindrical black cavity radiation admitted  through a collimating tube. Water flow around and over  the cavity was measured and the temperature  difference measured to determine absorbed energy  flux.
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4 Solar Utilization Solar Radiation Instrumentation Abbot 1932: modified the instrument with two thermally  identical chambers dividing the cooling water between  them. One chamber was heated electrically until its  temperature matched the chamber heated by solar  radiation.  The electrical input was measured and used  to indicate the solar radiation absorbed. Since primary instruments are difficult to use and very  expensive, secondary instruments have been  developed.  These instruments are still very difficult to  use and obtain constant readings.  There has been  much controversy in the development of the  Pyrheliometric Scale.
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5 Solar Utilization Solar Radiation Instrumentation Robinson (1966) and Coulson (1975) developed some of  the early documentation on this calibration procedure. Two secondary instruments are of importance: 1. Abbot silver disk pyrheliometer (circa 1902, modified in  1909 and 1927) 2. Angstrom compensation pyrheliometer (circa 1893) These instruments are used to calibrate the field  instruments that we use to measure solar radiation.
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This note was uploaded on 09/06/2011 for the course EML 4930 taught by Professor Staff during the Fall '08 term at University of Florida.

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solar lecture 4 - Solar Utilization...

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