Improved Representations of Water-Power System Interactions to Inform Clean Energy Transition for Mainland Southeast Asia

Power systems are inherently water dependent. Future energy development needs to jointly consider the interaction between power and water systems, especially the stream dynamics related to both water temperature and availability. Such connection is particularly pronounced in thermal and hydro power plants, where once-through cooling systems face disruptions from high intake water temperature and water scarcity, and hydropower generation is affected by drought conditions. Equally important is the impact of power system operations on water temperature and availability. For instance, warm water discharged from thermal power plants can increase water temperature, while cool water released from reservoir bottoms can cause temperature declines. Additionally, hydropower operations can alter water availability through changes in reservoir storage. Despite the importance of those factors, existing electricity capacity expansion models typically do not fully consider such feedbacks between stream dynamics and power system operations, as they lack the capability to accurately represent cascade reservoir operations and cooling processes for thermal power plants at sufficiently high spatial-temporal resolutions. To address this research gap, we develop an integrated model coupling a hydrological model (Community Water Model, CWatM), a stream temperature model (River Basin Model, RBM), and a novel electricity capacity expansion model (Pathways for Renewable Energy Planning coupling Short-term Hydropower OperaTion, PREP-SHOT, https://github.com/PREP-NexT/PREP-SHOT) to better represent the two-way feedback between stream dynamics and power system operations. The coupled model, applied in Mainland Southeast Asia featured by a diverse array of hydropower reservoirs and thermal power plants, supports informed, sustainable, and environmentally friendly planning for future energy development in the region.