Cloud Speed Impact on Solar Variability Scaling - Application to the Wavelet Variability Model

The wavelet variability model (WVM) for simulating solar photovoltaic (PV) powerplant output given a single irradiance sensor as input has been developed and validated previously. Central to the WVM method is a correlation scaling coefficient ( ) that calibrates the decay of correlation of the clear sky index as a function of distance and timescale, and which varies by day and geographic location. Previously, a local irradiance sensor network was required to derive . In this work, we determine from cloud speeds. Cloud simulator results indicated that the value is linearly proportional to the cloud speed ( ): . Cloud speeds from a numerical weather model (NWM) were then used to create a database of daily values for North America. For validation, the WVM was run to simulate a 48MW PV plant with both NWM values and with ground values found from a sensor network. Both WVM methods closely matched the distribution of ramp rates (RRs) of measured power, and were a strong improvement over linearly scaling up a point sensor. The incremental error in using NWM values over ground values was small. The ability to use NWM-derived values means that the WVM can be used to simulate a PV plant anywhere a single highfrequency irradiance sensor exits. This can greatly assist in module siting, plant sizing, and storage decisions for prospective PV plants.