Interannual Variability Analysis of Utility-Scale Solar Photovoltaic and Wind Power Resources in Arizona and New Mexic

Interannual variability (IAV) of wind and solar resources impacts multi-million-dollar power system decisions related to operations, planning, and investments. Decisions pertaining to power systems are usually made based on a limited number of years where the consequences of interannual variability are often neglected or reduced. As the electric sector transitions to a renewable energy future, larger shares of wind and solar will introduce more variability to the operation of the power system. Consequently, we use the National Radiation Database (1998--2015) as well as the WIND Toolkit (2007--2013) to create wind and solar photovoltaic power time series using NREL's System Advisor Model (SAM), and study the interannual variability of wind and solar resources in Arizona and New Mexico. We define IAV as half of the ratio between the range of capacity factor (CF) and the long-term mean in the time frame of interest, expressed as a percentage. Results show a +/-3--4% IAV of annual solar CF and +/-7--8% IAV of annual wind CF. IAV of annual wind CF is significantly impacted by geographical location, with larger IAV values in the Great Plains and southern Rocky Mountains. IAV of seasonal wind CF is calculated on the order of +/-11--26%, whereas IAV of seasonal solar CF was found to range from +/-6% to +/-16%. In both cases, IAV of wind and solar seasonal CF showed lower IAV values in summer and larger in winter. Extreme ramping events in aggregated wind and solar power time series are also studied. It is shown that extreme events can increase as much as 40% from year to year. Impacts on generation, transmission, and storage investments as well as impacts on operating reserves, transmission congestion, maintenance and seasonal storage scheduling are discussed.