Lessons from Bangladesh’s Kaptai Reservoir

Author: Md. Moniruzzaman

Executive Engineer, Power Grid Bangladesh

As power systems worldwide integrate higher shares of solar and wind, long-duration energy storage has emerged as a central grid challenge. While new storage technologies often face land, cost, and permitting constraints, an underutilized opportunity already exists within legacy hydropower reservoirs.

A newly released technical eBook, "Kaptai Reservoir as Energy Storage: From Conventional Hydropower to a National Grid Asset," examines how Bangladesh's only large hydropower reservoir can be re-positioned as a grid-scale energy storage and balancing asset—without constructing new dams or additional inundation.

The case study focuses on the Kaptai Hydropower Project, commissioned decades before large-scale renewables were envisioned. Importantly, a historic feasibility assessment supported by the Japan International Cooperation Agency (JICA) had already identified the site's technical suitability for pumped storage operation, citing favorable reservoir-river topography and downstream regulating capacity.

What has changed since that study is not the geography, but the energy system context.
Bangladesh is now experiencing:
• Rapid grid-connected solar expansion,
• Increasing evening peak demand and flexibility requirements, and
• Heightened exposure to imported fossil fuel costs.

Under these conditions, the same physical characteristics identified in earlier studies now enable Kaptai to function as a multi-service national grid asset, capable of:
• Absorbing surplus renewable generation through pumped storage,
• Delivering dispatchable power during peak hours,
• Reducing forced monsoon spill and water-energy waste, and
• Supporting grid stability, reserves, and contingency operations.

The eBook frames Kaptai not as an isolated project, but as a representative example of a broader global opportunity. Many hydropower reservoirs worldwide were designed for energy generation alone. In today's renewable-heavy grids, these assets can often be upgraded to deliver storage, flexibility, and resilience—using infrastructure that already exists.

Rather than proposing a final design or investment decision, the publication serves as a system-level case study, connecting historic feasibility insights with modern grid requirements. It highlights how development partners, utilities, and policymakers can extract greater value from existing hydropower assets while minimizing environmental and social risk.

The full eBook is available here:
https://mmzbabu.gumroad.com/l/ckgiuk