The work described herein is intended to help meet this need. Thus, utilities are seeking data to quantify the reliability of SHW systems. Moreover, utilities are responsible for replacing energy for loads that failed SHW system were supplying. If SHW systems routinely fail prematurely, then the utilities will have overpaid for grid-energy more » reduction performance that is unrealized. As these numbers increase, concern is growing about the systems dependability because installation rebates are often based on the assumption that all of the SHW systems will perform flawlessly for a 20-year period. In recent years thousands of new solar hot water (SHW) systems have been installed in some utility districts. This report presents the results of experimental tests of a concept for using infrared (IR) photos to identify non-operational systems based on their glazing temperatures operating systems have lower glazing temperatures than those in stagnation. The results of these comparisons and conclusions regarding the accuracy of the models are presented. To assess the accuracy of these models, data were obtained from several US National Weather Service Stations and other sources, used the models to estimate the solar-radiation, and then compared the modeled radiation values with observed radiation values. A study of the accuracy of these three solar radiation models is reported here. And, a third model, also an empirical one, predicts the hourly direct normal radiation from the hourly total horizontal radiation. A more » second model, an empirical one, predicts the hourly total horizontal radiation from meteorological variables. One of the models, a theoretical one, predicts the solar noon radiation for clear sky conditions from the optical air mass, precipitable water vapor and turbidity variables. Three of these solar radiation models have been used in developing the Augmented SOLMET Solar Data Tapes for the 26 SOLMET sites and the 222 ERSATZ Solar Data Tapes.
Some of these models have been used to generate data bases which are extensively used in the design and analysis of solar system. Several mathematical models have been developed within the past few years which estimate the solar radiation from other weather variables.
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