Technology Overview

Hydro pumped storage is an energy storage technology that uses two water reservoirs at different elevations to store and generate electricity. The basic operating principle involves pumping water to the upper reservoir during periods of low electricity demand and releasing it to generate electricity during peak demand periods. The primary purpose of pumped storage is to store surplus energy and maintain grid stability, thereby supporting the integration of renewable energy sources.

Technical Characteristics

Pumped storage technology is divided into two main types: closed-loop systems (off-river) and combined systems that use both pumped water and natural inflows. System efficiency typically ranges from 70–85%, and despite energy losses, it remains one of the most effective large-scale energy storage solutions available today.

Feature	Off-river Pumped Storage	Combined Pumped Storage
Efficiency	70–85%	70–85%
Advantages	Does not require continuous natural water supply	Utilizes natural water sources
Disadvantages	Dependent on geographical conditions	Requires management of natural water flows
Cost	High	High

The initial capital cost (CAPEX) for new pumped storage projects, including dam construction, is very high, and construction time is long. However, if an existing hydropower plant is expanded to include pumped storage capability, the investment cost per installed MW is significantly lower, and construction time is typically around 2–3 years.

Application in Vietnam

In Vietnam, this technology is being implemented through the Bac Ai hydro pumped storage plant in Khanh Hoa province, with a planned installed capacity of 1,200 MW. This is the first and only pumped storage project currently under construction in Vietnam as of 2025.

Overall, hydro pumped storage can provide ancillary services such as frequency regulation, fast start-up, and voltage support, thereby enhancing system flexibility and stability. However, deployment requires careful consideration of environmental and social impacts, particularly when constructing new reservoirs.