Pumped storage hydropower (PSH) operates like a giant rechargeable battery using two reservoirs at different elevations. It relies on two main phases to store and generate electricity efficiently within a pumped hydro energy storage system.

Pumping phase

When electricity supply exceeds demand, often due to surplus renewable energy, a pumped storage power plant uses this excess electricity to pump water from the lower reservoir to the upper reservoir. This process, a key aspect of pumped hydro storage design, converts electrical energy into gravitational potential energy, effectively storing power for later use.

Generating phase

During periods of high electricity demand, the stored water is released from the upper reservoir back down through turbines in the pumped storage hydro power plant. This generates electricity that supports grid stability and energy supply. The ability to switch quickly between pumping and generating modes is a key feature of pumped hydro storage systems.

The energy storage capacity of a pumped hydro storage system depends on the size and elevation difference between the two reservoirs, while the power output is determined by the turbine size. Using reversible turbines, these plants switch between pumping water uphill and generating power as needed.

Pumped storage hydropower is the world’s largest and most flexible long-duration energy storage technology, crucial for integrating variable renewables like solar and wind and maintaining grid reliability.

The pumped hydro storage system involves two reservoirs at different heights connected by tunnels, where water is pumped uphill to store energy and released downhill to generate electricity.

Important design aspects include:  

Reservoirs: Size and height difference affect storage capacity and power output. In India, many sites are located in hilly or mountainous regions, requiring careful adaptation to steep terrain and variable geology.

Turbines: Reversible pump-turbines allow switching between pumping and generating; variable-speed models improve flexibility. This is especially useful in India's grid with fluctuating renewable inputs.

Waterways: Penstocks and tunnels manage water flow with minimal losses. Indian pumped hydro storage design often incorporates rugged terrain to optimize tunnel length and minimize environmental disturbance.

Environmental factors: Site selection in India prioritizes minimizing ecological impact and navigating land acquisition challenges, especially near forested or protected areas.

Grid integration: Designs increasingly support hybrid setups with solar or wind power, which is critical in India’s push for renewable energy expansion and grid reliability.

Effective pumped hydro storage design maximizes energy storage and supports grid stability, essential for India’s growing renewable energy needs.

There are two types of pumped storage hydropower systems: open-loop pumped storage and closed-loop pumped storage. These categories are based on whether the system has a continuous connection to a natural water source. Each type, open-loop and closed-loop, plays a key role in energy storage and grid stability, with different designs suited for various environmental and operational conditions.
Here is how the two types of pumped storage hydropower systems are different from each other:

Open-loop pumped storage hydropower plant: An open-loop pumped storage hydropower plant has a continuous hydrologic connection to a natural water source such as a river or lake. In this type, either the upper or lower reservoir is connected to flowing water. Natural inflow contributes more than 5% of the water volume passing through the turbines annually.

The Bhivpuri pumped storage plant which is set to have an operation of 1000 MW operates with the Thokerwadi dam as the plant’s main source of water.

Closed-loop pumped storage hydropower plant: A closed-loop pumped storage hydropower plant consists of two reservoirs that are not connected to any external natural water bodies. Water is pumped solely between the upper and lower reservoirs by the pumping system, with natural inflow contributing less than 5% of the water volume passing through the turbines annually.

A comparison between open loop and closed loop control system for pumped hydro

As the world shifts toward cleaner energy, PSH offers multiple benefits that enhance grid stability, reduce emissions, and provide cost-effective long-duration storage on a large scale.

Here are the advantages of pumped storage hydropower plants in India:
 

• High energy efficiency for pumped hydro storage: Pumped storage hydropower plants operate at around 70–80% efficiency by continuously cycling water between reservoirs. This process in a pumped storage power plant converts most of the input energy back into electricity. PSH systems can start generating power within minutes, offering quick backup to balance intermittent renewable sources like solar and wind.
• Large-scale energy storage capacity of pumped hydro storage systems: Pumped hydro storage can store vast amounts of energy for long durations, often 11 hours or more, making it ideal for meeting daily or weekly demand cycles. This helps prevent curtailment of renewables and optimizes grid performance.
• Grid flexibility and stabilization by pumped storage hydro power plants: A pumped storage hydro power plant stabilizes the electrical grid by quickly balancing supply and demand. It provides essential grid services such as frequency control, voltage regulation, and reserve power, supporting the growing share of variable renewable energy.
• Reduction of CO₂ emissions through pumped hydro energy storage systems: By maximizing renewable energy use and reducing dependence on fossil fuels, pumped hydro energy storage systems significantly lower carbon emissions in the power sector, contributing to a cleaner energy future.
• Energy resilience and black-start capability of pumped storage hydropower: Pumped hydro storage systems can rapidly restart the grid after outages by using stored water to generate emergency power. This enhances overall energy security and grid reliability.
• Long asset life and low lifetime costs of pumped storage hydro plants: With operational lifespans exceeding 80 years, pumped storage hydro plants offer cost-effective energy storage with low maintenance requirements and no reliance on scarce raw materials like those used in batteries.
• Multi-functional benefits and applications of pumped hydro storage plants: Besides energy storage, pumped storage hydro power plants support water resource management, flood and drought control, irrigation, and can be combined with solar or wind power to create hybrid renewable energy systems.
• Retrofit and expansion potential for pumped hydro storage in India: Existing infrastructure, including disused mines, underground caverns, and non-powered dams, can be repurposed for pumped hydro storage in India and worldwide. This expands capacity sustainably while minimizing environmental impact.
• Mature and proven technology of pumped storage hydropower systems: Pumped storage hydropower is a well-established, reliable technology that has operated worldwide for decades. Its predictable performance lowers risks associated with new pumped hydro storage system projects.
• Fast response times in modern pumped storage hydro power plants: Especially with modern variable-speed technology, pumped storage hydro plants can adjust power output within seconds, providing critical grid support and real-time stability.
• Minimal environmental impact for closed-loop control system: Closed-loop pumped storage hydro plants, which are not connected to natural waterways, reduce ecological disruption compared to traditional hydropower systems.

Pumped storage hydropower (PSH) plays a crucial role in enhancing grid reliability and integrating renewable energy sources. While it is commonly assumed that hydroelectric power plants and pumped hydro plants have the same role in generating electricity, their uses can be very different. The key applications of pumped hydro storage plant in India include:
 

• Grid stability and ancillary services: Pumped storage hydro power plants provide vital grid services like frequency regulation, voltage control, and spinning reserves, ensuring a reliable and resilient electricity supply.
• Load balancing and peak shaving: Pumped hydro energy storage systems optimize energy use by shifting electricity consumption from peak to off-peak hours, reducing the need for fossil-fuel-based power plants.
• Rural electrification: Pumped storage hydro plants support off-grid and remote communities, especially in developing regions, by providing steady power supply and integrating with photovoltaic systems.
• Emergency backup and black start: Pumped storage hydropower plants can quickly restore power after outages, ensuring grid resilience.
• Water management: Beyond energy storage, pumped storage hydro power plants aid in flood control, irrigation, and water supply management, making them multifunctional assets.
• Hybrid renewable systems: Pumped hydro storage design allows integration with solar and wind farms, creating hybrid systems that maximize clean energy use.
• Scalable and sustainable development: With growing interest in pumped hydro storage in India and worldwide, pumped storage hydropower projects are expanding to meet increasing energy storage demands sustainably.

The International Forum on Pumped Storage Hydropoweropens in a new tab is a government-led global platform aimed at scaling up pumped hydro storage, often called the “world’s water batteries”, for rapid clean energy transition. Launched in 2020 by the International Hydropower Association (IHA) and the U.S. Department of Energy, it now brings together governments (including India), industry leaders, financiers, academia, and NGOs to shape policy, best practices, and financing strategies for expanding PSH worldwide.

The next Forum is scheduled for 9–10 September 2025 at UNESCO Headquarters in Paris, marking the culmination of a year-long global campaign to accelerate action. It will focus on unlocking 1,500 GW of energy storage by 2030, offering guidance on derisking investments, regional policy support, and sustainable project delivery.

Key themes include:
 

• Energy system integration and grid flexibility
• Policy frameworks and financing models
• Sustainability and environmental resilience
• Supply-chain and project delivery best practices

These discussions equip governments and developers, including India, to accelerate the deployment of pumped storage hydropower and realize its full potential in the global energy mix.

India is fast-tracking pumped storage hydropower (PSH) to support its ambitious clean energy goals. A recent ₹12,461 crore budgetary allocation will fund 31,350 MW of new hydropower capacity over eight years, including ~15,000 MW from pumped storage projects. The government has also introduced:
 

• Infrastructure support: Funding for transmission lines, access roads, and other facilities
• Fast-track project approvals: A single-window clearance mechanism has reduced project DPR approval times (e.g., Upper Sileru PSP from 90 to 70 days)
• Transmission-charge waivers: ISTS fee waivers extended to June 2028 to aid PSP integration

These initiatives lay the groundwork for unlocking India’s ~119 GW PSH potential, with plans to commission 39 pumped storage hydro power plants totaling 47 GW by 2029–30. The future of pumped storage in India looks promising as these efforts gain momentum.

Here’s what this means for India:
 

• Large-scale PSH deployment will enhance load balancing, renewable integration, and energy security.
• With continued policy support, India can tap its vast pumped hydro storage system potential to reach non-fossil fuel targets by 2030 and net-zero by 2070.
• States like Maharashtra and Andhra Pradesh, with projects like Upper Sileru and Bhivpuri, are leading the PSP push under this enabling framework.

India’s commitment to pumped storage hydropower, backed by significant policy support and investment, positions the country to scale up its pumped storage hydro plant rollout rapidly. As these projects take shape, the future of pumped storage in India will be a cornerstone of the nation's transition to a resilient, renewable-driven energy system.

As India accelerates its clean energy mission, Tata Power stands at the forefront of the pumped hydro storage revolution. Explore how Tata Power’s next-generation pumped storage power plants are driving grid stability, creating jobs, and enabling 24/7 renewable energy. Discover more!