A Solar Resource Measurement Network for Solar Intermittency at High Spatio-Temporal Resolution
In 2008, we established a sensor network uniquely capable of studying the solar intermittency of dense urban rooftop PV. Continuous 1-second global horizontal incident irradiance (GHI) data is being collected at 8 stations located throughout the 1200-acre (5 square km) UC San Diego campus in coastal southern California. A Total Sky Imager takes hemispherical sky photographs, and a ceilometer records cloud height. Given an existing one-year dataset of 1-second and 5-minute GHI measurements, statistical properties of extreme ramp rate events for individual and aggregated sites on a virtual distribution feeder were derived. This analysis allows the estimation of benefits of energy storage systems and provides different probabilistic scenarios for input into PV system 91ÃÛÌÒ¸ó. Conditional averaging was employed to study the prelude and following of the largest ramp rate events. Reflection of solar radiation by approaching clouds was found to cause a strong increase in GHI prior to the shaded period, thereby increasing the ramp rate by more than 30%. This analysis provides critical information about how GHI varies during strong ramping events, which will aid the modeling of these phenomena.
Kleissl, J., Harper, J., & Dominguez, A. (2010). A solar resource measurement network for solar intermittency at high spatio-temporal resolution. In Proc. ASES Annual Conf., Phoenix, AZ.