Impact of Ergodic and Nonergodic Ground Motion Estimation on the Earthquake Resilience of Shared Distributed Energy Resource Systems

Abstract

Distributed energy resource systems (DERs), such as rooftop solar panels, are gaining traction in the energy sector to improve infrastructure resilience to earthquakes by facilitating electricity sharing in seismic regions (e.g., California). The seismic risk assessment of DERs requires estimating ground motion intensity measures (IMs) using ground motion models (GMMs). In this context, a few existing efforts have used ergodic GMMs, which assume that the distribution of IMs over time (across multiple events) at a single site is the same as that of ground motion IMs over space (across multiple sites). However, with the advent of large ground motion databases, it has become evident that ground motions are influenced by location-specific repeatable effects, motivating a gradual transition into nonergodic approaches that can capture these effects. However, the impact of these approaches (i.e., ergodic and nonergodic) on the seismic risk assessment of DERs has not been assessed. This study considered areas with contrasting spatial extents to assess the impact of nonergodic approaches in the seismic risk assessments of DERs. Specifically, we investigated the risk of power outages in residential communities that have access to DERs and are exposed to a significant seismic hazard. The results indicate significant differences in the estimated risk (as much as 0.2 on a scale of 0–1) between ergodic and nonergodic estimates at locations where large intensity measures and significant repeatable effects are observed. Furthermore, the nonergodic approach is better equipped to capture the spatial variation of risk estimates across a large spatial extent, but more data are required to fully realize the potential of nonergodic approaches in community-scale regions.