| Spotlight The author says the study contributes to smart


energy research by reframing hydropower’s role in renewable electricity systems and emphasising the importance of system design.


Pumped sorage in Rwanda Another study has explored the advantages of


combining VRE with pumped storage hydropower for grid integration. It focuses on the 12MW Mukungwa hydropower reservoir in the northern province of Rwanda, which faces water level reduction due to weather variation in the dry season. A major waterway in the Musanze River Basin, the Mukungwa river is endowed with an abundance of solar, water resources and a medium wind speed. Its mainstream and tributaries have an estimated 48.4MW of undeveloped potential. Authors Niringiyimana et al say in their study published in Energy Strategy Reviews, that although hydropower plays a central role as a source of energy storage and balance to supplement highly intermittent and variable energy sources such as wind and PV energy, many reservoirs have already been burdened with multiple responsibilities for flood mitigation, water supply, power generation, the provision of downstream water flows for environmental protection, and recreation. Consequently, they add: ‘managing a hydropower


reservoir is already a complex mission and adding the new task of complementing wind/PV power represents both a significant opportunity and an outstanding challenge’.


However the authors believe the introduction of a pumped storage system will help provide adequate, stable and reliable power generation from Mukungwa hydropower, considering the intermittent nature of solar sources, wind sources and the demand fluctuations. Their analysis evaluated two distinct operational schemes: a baseline configuration without energy storage, and an enhanced configuration integrating pumped storage hydropower. A comparative techno-economic and environmental assessment was conducted to quantify the implications of storage integration. With the availability of resources, proximity to


hydropower infrastructure, and land constraints directly determining the least-cost technology mix, the authors’ results showed that the incorporation of pumped storage ‘yields a significant reduction in total system costs’, alongside a concurrent decrease in operational CO2


emissions. This dual


benefit underscores the role of pumped storage in enhancing both the economic viability and environmental sustainability of power systems with high renewable penetration, Niringiyimana et al add. Limitations of the study include considering various factors influencing the integration of pumped storage units, such as different ecological and geographical conditions (flat terrain, poor geology, or high sediment loads). It is also inapplicable in ecologically protected areas with legally binding environmental flow requirements, and distinct, varying load demand patterns which may result in different outcomes in different situations. Future research should also give consideration to evaporation losses due to atmospheric temperature variation.


Combined heat and power The urgent need for sustainable energy solutions has


led to a growing interest in the innovative integration of hydropower and thermal energy systems for combined heat and power (CHP) production. Research by Elkelawy et al has shown how such


hydro-thermal integration can achieve greenhouse gas emission reductions of up to 30%, significantly improving energy efficiency by 20-30% compared to conventional systems. Furthermore, integrating these systems can lead to cost savings of approximately 15-25% in operational expenses, primarily through enhanced fuel utilisation and reduced reliance on fossil fuels. Through an analysis of case studies and recent advancements in technology, the authors claim their review offers valuable insights for policymakers, researchers, and industry stakeholders aiming to implement sustainable energy solutions. However, they caution that various obstacles must also be overcome for this complex system design. To further reduce costs and emissions, their design and operational management requires sophisticated optimisation models, such as two-layer stochastic techniques that consider uncertainty in renewable energy and load demands. Because it entails managing start-up costs and operating restrictions that cannot be resolved by conventional approaches, the integration of mixed integer programming for hydro and thermal plants further complicates the planning process. The complex character of these energy solutions is highlighted by the need to balance operating efficiency, regulatory requirements, and environmental implications in the design of an effective hybrid system. Such obstacles can lead to high initial costs, technical complexity, and problems with water availability for hydropower generation. Despite this, the authors claim such hybrid systems


are becoming increasingly practical and affordable thanks to developments in energy storage, smart grid technology, and digital control systems. They add that hybrid hydropower-thermal systems have the potential to be a key component of the global shift to a more resilient and sustainable energy future, helping to meet rising energy demands while minimising environmental impact, provided that supportive policy frameworks, financial incentives, and ongoing technological innovation are in place.


President of the Philippines, Ferdinand Marcos Jr believes the recent acquisition of Caliraya- Botocan-Kalayann hydropower complex by The Thunder Consortium, “marks a deliberate step towards an energy system that is steadier in operation, smarter in design, and ready for the future” Image: Juergen Nowak/ Shutterstock.com


References


https://aboitizpower.com/news/ hydro/aboitizpower-led-thunder- consortium-acquires-797-mw-cbk- hydro-pumped-storage-complex


https://aboitizpower.com/news/ general/greater-flexibility-and- diversity-in-philippine-energy


Hydropower Dominance and Renewable Integration: System- level Flexibility Constraints in Canada. Ahmet Hakan Özkan. http://dx.doi.org/10.2139/ ssrn.6018994


Dispatch optimization by integrating wind, solar PV and hydropower energy generation with pumped storage by Emile Niringiyimana, Li Ji Qing, Xie Yutao, Xu Zehui. Energy Strategy Reviews 64 (2026) 102114. https:// doi.org/10.1016/j.esr.2026.102114


Innovative Integration of Hydropower and Thermal Energy for Combined Heat and Power Production: A Comprehensive Review by Medhat Elkelawy, Walaa AL-Ashmawy, Mustafa Mamdouh Sayed. Pharos Engineering Science Journal (PESJ). VOLUME 01, ISSUE 01 2025. https://doi.org/10.21608/ pesj.2025.344985.1008


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