Impacts of changing snowfall on seasonal complementarity of hydroelectric and solar power

Abstract

Complementarity of variable renewable energy sources at multiple temporal scales is important in order to ensure reliability of a decarbonizing energy system. In this study, we investigate the hypothesis that a decrease in the fraction of precipitation falling as snow (SWE/P) would increase monthly complementarity of hydro and solar power generation in the western U.S. With a focus on 123 dams responsible for 93% of generation, we found that these resources are seasonally complementary at about half of dams, as indicated by the sign of correlation coefficients (ρ). As hypothesized, average SWE/P at individual dams was positively correlated with ρ, but the relationship was non-linear and SWE/P only explained a modest portion of the variance in complementarity. At each dam, the dependence of annual ρ on interannual variations in SWE/P between 2002-2020 was assessed; these relationships were positive at 72% of dams but not statistically significant at the level of individual dams. Finally, at the system scale ρ was significantly related to SWE/P, with a stronger relationship observed than the dependence of total hydropower generation on SWE/P. Notably, the system-scale relationship between ρ and SWE/P changed dramatically in the latter part of the temporal domain (2012-2020), with a much steeper slope and greater fraction of variance explained by SWE/P. These results illustrate the historical relationship between SWE/P, monthly complementarity of hydro and solar power, complexities of these relationships due to snow and watershed hydrology and reservoir management, and a change in the observed relationship between SWE/P and hydropower generation timing. To the extent that hydro and solar power generation complementarity is responsive to SWE/P, expected declines in SWE/P may indicate greater seasonal complementarity but reduced hydropower available for load-balancing when solar power generation is highest.

Stress Testing California's Hydroclimatic Whiplash: Potential Challenges, Trade‐Offs and Adaptations in Water Management and Hydropower Generation

“…Furthermore, water utilization patterns could be more balanced with the stochastic hydrologic processes comprised of random sequences of high flow and low flow periods (Nagy et al., 2013). For instance, taking advantage of hydro and solar power generation complementarity for load and peak demand‐balancing, therefore, producing more hydropower when water is naturally more available (Marshall & Chen, 2022).…”

Hydroelectricity Modeling for Low‐Carbon and No‐Carbon Grids: Empirical Operational Parameters for Optimization and Dispatch Models

“…Indeed, in the Pacific Northwest, empirical evidence suggests that reservoir operators have already increased spring hedging to mitigate potential low streamflow in the summer (Jones & Hammond, 2020). The earlier snowmelt (Marshall et al., 2019) and runoff timing (Stewart et al., 2004) expected under climate change in the western U.S. could create or exacerbate differences between water availability and energy demand timing by advancing streamflow timing by a month or more, though the magnitude will vary regionally and depend on emissions scenario, reservoir storage dynamics, and concurrent demands from a changing energy system (Chegwidden et al., 2019; Grubert & Marshall, 2022; Marshall & Chen, 2022).…”

The Severity of the 2014–2015 Snow Drought in the Oregon Cascades in a Multicentury Context

“…Further, aging reservoir and dam infrastructure and operational guidance are not adequately designed for recent shifts in the snow‐to‐rain ratio, earlier snowmelt timing, and unpredictable transitions from very dry to very wet years (climate “whiplash” events) (Li et al., 2017; Siirila‐Woodburn et al., 2021; Swain et al., 2018; Vicuna & Dracup, 2007). Projected declines in SWE will likely result in reduced hydroelectric generation, which is currently used to offset non‐renewable energy sources and supplement renewable sources, such as solar, in the peak demand season (mid‐to‐late summer) (A. Marshall & Chen, 2022).…”

“…Projected declines in SWE will likely result in reduced hydroelectric generation, which is currently used to offset non-renewable energy sources and supplement renewable sources, such as solar, in the peak demand season (mid-to-late summer) (A. Marshall & Chen, 2022).…”