Hydropower representation in water and energy system models: a review of divergences and call for reconciliation

Abstract

Reservoir-based hydropower systems represent key interactions between water and energy systems and are being transformed under policy initiatives driven by increasing water and energy demand, the desire to reduce environmental impacts, and interacting effects of climate change. Such policies are often guided by complex system models, whereby divergence in system representations can potentially translate to incompatible planning outcomes, thereby undermining any planning that may rely on them. We review different approaches and assumptions in hydropower representation in water and energy systems. While the models and issues are relevant globally, the review focuses on applications in California given its extensive development of energy and water models for policy planning, but discusses the extent to which these observations apply to other regions. Structurally, both water-driven and energy-driven management models are similar. However, in energymodels, hydropower is often represented as a single-priority output. Watermanagement models typically allocate water for competing priorities, which aregenerally uninformed by dynamic electricity load demand, and often result in a lowerpriority for hydropower. In water models, constraints are increasingly resolved fornon-energy components (e.g., inflow hydrology and non-energy water demand); few analogues exist for energy models. These limitations may result in inadequate representations of each respective sector, and vastly different planning outcomes for the same facilities between the two different sectors. These divergent modeling approaches manifest themselves in California where poorly reconciled outcomes may affect decisions in hydropower licensing, electricity grid flexibility and decarbonization, and planning for environmental water. Fully integrated water-energy models are computationally intensive and specific to certain regions, but better representation of each domain in respective efforts would help reconcile divergences in planning and management efforts related to hydropower across energy and water systems.

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

“…These findings indicate that in the near future, hydropower generation could be enhanced by implementing optimization analyses that prioritize both sustainable ecological function and power generation. This can be more effectively achieved by the use of coupled water‐energy system models to better represent these conflicting water‐centric and energy‐centric operational priorities (Rheinheimer et al., 2023). In addition, physical modifications of reservoirs and their associated powerhouses could mitigate potential power losses tied to increased spill events (Forrest et al., 2018).…”

Models for a hydropower plant: a review

“…The earlier models were considered adequate for typical first swing stability simulations, but more issues like longer transient stability problems simulation, low frequency oscillations, islanded operation, load rejection, system restoration, water hammer dynamics, pump storage generation with complex hydraulic structures, etc. had to be addressed with the wide practise of using hydropower (de Mello et al, 1992;Fang et al, 2008;Acakpovi, Hagan and Fifatin, 2014;Yang et al, 2015;Guo and Yang, 2018;Rheinheimer et al, 2023). For the case with long penstocks, the pressure differences and water compressibility generate significant dynamic behaviour which must be taken into modelling consideration.…”

“…Some of them are developed for planning studies while others are developed for control, transient response, study of dynamics, condition monitoring, etc (de Mello et al, 1992;Kishor, Saini and Singh, 2007;Valavi and Nysveen, 2018a;Liu et al, 2019;Sapkota et al, 2022). A single hydropower has many components starting from water reservoir and flow regions, mechanical rotating parts to the static electric parts in general (Quiroga OD, 2000;Rheinheimer et al, 2023). Moreover, variable speed hydropower plants have converters as the additional elements and pump storage power plants have reversible pump-turbines (Nobile, Sari and Schwery, 2018a).…”

Modeling the Water Systems of the Western US to Support Climate‐Resilient Electricity System Planning

“…To that end, a number of studies have modeled varying aspects of climate change impacts on linked large‐scale electricity and water systems across the US and the WUS, including on water supply availability and demand management across different sectors (Hejazi et al., 2015; N. Voisin et al., 2013), changes in hydropower generation with statistical models or process‐based hydrology models (Bartos & Chester, 2015; Boehlert et al., 2016; Kao et al., 2015, 2022; Parkinson & Djilali, 2015; Wei et al., 2017; Zhao et al., 2021; Zhou et al., 2023), and impacts on coupled power systems operations and planning under climate change and associated extreme events (Cohen et al., 2022; Dyreson et al., 2022; S. W. D. Turner et al., 2019; N. Voisin et al., 2017). However, often hydropower impact models treat hydropower in isolation, without including climate change impacts on other dynamic aspects of the complex water systems that hydropower operates within, such as water demands for irrigation (Rheinheimer et al., 2023). Conversely, regional analyses of climate change impacts on water resources do not typically evaluate the electricity impacts of changing water resources.…”

“…Voisin et al, 2017). However, often hydropower impact models treat hydropower in isolation, without including climate change impacts on other dynamic aspects of the complex water systems that hydropower operates within, such as water demands for irrigation (Rheinheimer et al, 2023). Conversely, regional analyses of climate change impacts on water resources do not typically evaluate the electricity impacts of changing water resources.…”