Solar variability zones have been defined by modeling solar variability across the United States using a combination of ground measured and satellite derived solar irradiance measurements [1,2]. The zones represent the magnitude of high-frequency (sub-minute) solar variability at each location. PV installations in locations with higher solar variability can, all else being equal, lead to larger voltage fluctuations on electric distribution grids than PV installations in areas of low solar variability. Thus, to understand and study the impact of PV installations in a specific location to distribution grid operations, it is important to know the solar variability at that location. To facilitate such studies, solar variability samples sorted by variability zones are provided.
This page describes how to retrieve a representative sample of high-frequency irradiance data using the solar variability zones.
1. Determine Solar Variability Zone
Solar variability zones are zones of similar high-frequency data. The first step is to determine the variability zone for your location of interest using the map below or this Google Earth file
Variability_Zones.zip (318 downloads)
2. Download High-Frequency Irradiance Sample
3. Use the Irradiance Sample for PV Integration Studies
The high-frequency irradiance samples can be converted to PV power output using an irradiance scaling model to account for spatial smoothing (e.g., the Wavelet Variability Model (WVM)) and an irradiance to PV power model (e.g., PVSyst or the Sandia Array Performance Model). Then, the PV power can be used in a grid integration study and will have representative PV variability.
- Broderick, R., Reno, M., Lave, M., and Quiroz, J. 2015. “Final Technical Report to DOE on Accelerating Cost- Effective Deployment of Solar Generation on the Distribution Grid.” Sandia National Laboratories.
- Lave, M., Broderick, R., Reno, M. 2016. “Solar Variability Zones.” To be submitted to Solar Energy.
Thanks to Idaho Power, SunPower Corporation, the Sacramento Municipal Utility District, and the University of California, San Diego for sharing high-frequency irradiance data.