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Solar Resource Characterization

Researchers:  Richard Perez

The initial activities in this field consisted of developing and validating solar radiation algorithms capable of generating the solar resource parameters needed by engineers for specific applications from quantities that are more commonly available. For instance, one of these models converts measured global and direct irradiance into irradiance received by plane surface of arbitrary tilt and orientation such as a roof. Another model reproduces the distribution of daylight luminance in the sky as a function of measured global and direct irradiance.

In recent years, the solar resource characterization activities have focused on satellite-based solar resource assessment. The rationale for this is the following: however dense a solar radiation measurement network may be, there will always be a need for solar resource information between the stations. Some countries such as Switzerland, have very dense networks, most countries do not. In the US, for instance, there are only 26 stations in the national network. Many countries do not have any measurements. Because weather satellites monitor the earth's cloud cover continuously in time and space, they provide an effective proxy measurement of solar resource information where this is not available by conventional measurements.

Our group pursues several issues relative to satellite data:

Archiving of satellite-derived solar radiation data

Enhancement and validation of models converting satellite images into irradiances

Application of satellite-derived irradiance to the modeling of solar systems

Our ongoing projects in solar resource characterization are sponsored by the National Renewable Energy laboratory, the USDOE and the University of Oregon. These projects include the validation and improvement of satellite-to-direct irradiance models for the detection of solar microclimates in the southwestern US - this will be used for the optimum deployment of solar thermal power plants -- and the mapping of solar radiation components in the Pacific Northwest states.