Power output variability of PV system fleets in three utility service territories in New Jersey and California

Abstract

The recent growth of the number and cumulative size of PV installations in regions with solar-friendly programs has raised the profile of those systems' potential impact on the electric grid. As grid-tied PV systems are a variable resource, it is important to characterize the variability of their output when aggregated over fleets within a service territory. SunEdison operates more than 300 systems ranging from 30 to 9,000 kWp across North America and monitors the power output of each one with a 1-minute resolution. We present an analysis of the observed power output variability of 67 PV systems across 3 utility service territories in California and New Jersey, during days of variable solar resource. One of the metrics is the standard deviation of the power output's change over 1-minute intervals across 4 hours near the solar peak. By aggregating power output over fleets of constant rated capacity but different make up, we show that variability is affected by both mean system size and fleet composition.