Cloud shadow speed sensor

V. Fung, J. L. Bosch, S. W. Roberts, J. Kleissl
2014 Atmospheric Measurement Techniques  
<p><strong>Abstract.</strong> Changing cloud cover is a major source of solar radiation variability and poses challenges for the integration of solar energy. A compact and economical system is presented that measures cloud shadow motion vectors to estimate power plant ramp rates and provide short-term solar irradiance forecasts. The cloud shadow speed sensor (CSS) is constructed using an array of luminance sensors and a high-speed data acquisition system to resolve the progression of cloud
more » ... ssion of cloud passages across the sensor footprint. An embedded microcontroller acquires the sensor data and uses a cross-correlation algorithm to determine cloud shadow motion vectors. The CSS was validated against an artificial shading test apparatus, an alternative method of cloud motion detection from ground-measured irradiance (linear cloud edge, LCE), and a UC San Diego sky imager (USI). The CSS detected artificial shadow directions and speeds to within 15° and 6% accuracy, respectively. The CSS detected (real) cloud shadow directions and speeds with average weighted root-mean-square difference of 22° and 1.9 m s<sup>−1</sup> when compared to USI and 33° and 1.5 m s<sup>−1</sup> when compared to LCE results.</p>
doi:10.5194/amt-7-1693-2014 fatcat:av3eau2tdff7vlhibaiunf735a