Pumped-Storage Hydropower

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Pumped-storage hydropower (PSH) is a type of hydroelectric energy storage. It is a configuration of two water reservoirs at different elevations that can generate power (discharge) as water moves down through a turbine; this draws power as it pumps water (recharge) to the upper reservoir.

PSH capabilities can be characterized as open loop—where there is an ongoing hydrologic connection to a natural body of water—or closed loop, where the reservoirs are not connected to an outside body of water.

Illustration of open and closed loop pumped storage.

Pumped-storage currently accounts for 95% of all utility-scale energy storage in the United States.

The U.S. Department of Energy's (DOE's) Water Power Technologies Office (WPTO) invests in innovative pumped-storage technologies and research to understand and value the potential benefits of existing and prospective advanced pumped-storage facilities. WPTO is currently developing a research portfolio to evaluate and expand hydropower and pumped-storage’s contribution to grid resiliency and reliability. 

Learn more about WPTO’s past, present, and future work with PSH below.

Future Research

Requests for Information

WPTO released a Request for Information (RFI) that was open from February 22, 2018–April 6, 2018. This RFI focused on a variety of topics including hydropower capability, the role and value of hydropower in future power systems, current operations landscape, and additional research needs. Responses from the request will be used as a key basis for further development of PSH valuation guidance, strategy, and research and development initiatives.

Notices of Technical Assistance

WPTO released a Notice of Technical Assistance that opened April 27, 2018. This NOTA focuses on conducting techno-economic studies-including cost-benefit analyses, power market analyses, financial analyses, and a valuation analysis—to evaluate the long-term value of two selected PSH projects.

Notices of Intent

WPTO has issued a Notice of Intent (NOI) to release a funding opportunity for innovative design concepts for standard modular hydropower and pumped storage hydropower. The first topic area seeks to stimulate innovative design concepts for small, low-head hydropower plants capable of lowering the capital costs and reducing the environmental impacts of development at new stream-reach (i.e., greenfield) sites. The second topic area explores new use cases for pumped storage hydropower. The NOI indicates two areas of interest for pumped storage: one for technology concepts that address critical barriers or tap new value; and the other for analysis and modeling enhancements that illustrate how pumped storage can improve electricity system resilience, reliability, and economic efficiency. Read more.

Studies and Reports

Hydropower Vision

The Hydropower Vision report (2016) is the first comprehensive effort to analyze and evaluate pathways for future development of hydropower and PSH in the United States. The report contains a roadmap that defines a range of actions needed to realize the economic and social benefits of increased hydropower in the future. It is based on three foundational “pillars” that are critical to ensuring the integrity of the research, modeling, and analysis in the Hydropower Vision:

  • Optimization: Optimize the value and power generation contribution of the existing hydropower fleet within the nation’s energy mix to benefit national and regional economies, maintain critical national infrastructure, and improve energy security.
  • Growth: Explore the feasibility of credible long-term deployment scenarios for responsible growth of hydropower capacity and energy production.
  • Sustainability: Ensure that hydropower’s contributions toward meeting the nation’s energy needs are consistent with the objectives of environmental stewardship and water use management.

Among the list of key findings, it was determined that significant potential exists for new pumped-storage technologies to meet grid flexibility needs and support increased integration of variable generation resources.

Modeling Efforts

Argonne National Laboratory led several groundbreaking modeling efforts related to pumped storage hydropower.

Pumped Storage Hydropower: Benefits for Grid Reliability and Integration of Renewable Energy (2014)

Providing further support for the development of new PSH units and adjustable speed upgrades to existing PSH units will contribute to grid reliability and will facilitate a larger expansion of variable renewable energy. Further PSH developments can be encouraged through streamlined licensing, as proposed by HREA of 2013 for closed-loop projects. Moreover, key activities that can help accelerate U.S. PSH developments include (1) develop tools to allow owners/operators of pumped storage hydropower plants to evaluate the feasibility of conversion from fixed-speed to adjustable-speed technologies; and (2) investigate market mechanisms that would accurately compensate pumped storage hydropower for the full range of valuable services provided to the power grid. 

Modeling and Analysis of Value of Advanced Pumped Storage Hydropower in the United States (2014)

This study’s purpose was to develop detailed simulation models of advanced pumped-storage technologies in order to analyze their technical capabilities to provide various grid services and assess the value of these services under different market structures and for different levels of renewable generation resources integrated with in the power system. The main objectives were:

  • Improve modeling representation of advanced PSH and conventional hydropower (CH) plants in power system and electricity market models
  • Quantify technical capabilities of advanced PSH plants to provide various grid services
  • Analyze the value of these services under different market conditions and levels of variable renewable generation (wind and solar) in the power system
  • Provide information on the full range of benefits and value of PSH plants.

Much of the nation’s 22 gigawatts (GW) of PSH was initiated during the mid- to late-1970s. Projects were economically justified for daily energy arbitrage based on the high cost of peaking oil and natural gas-fired generation, low-cost coal and nuclear power during the off-peak periods, and capital costs that were similar to those of combined cycle plants. Today, with natural gas on the margin much of the time and with the increased efficiency and decreased relative capital costs associated with combustion turbines and combined-cycle plants, energy arbitrage is typically not sufficient to justify new pumped-storage plants. However, storage provides additional flexibility benefits for the power system, and the need for that flexibility is getting even larger as a result of the increase in variable wind and solar generation. Moreover, restructuring has led the Federal Energy Regulatory Commission (FERC) to explicitly define A/S, which help quantify and price the flexibility requirements.

Simulation of the Secondary Frequency Control Capability of the Advanced PSH Technology and Its Application to the SMUD System (2013)

This is one of several reports developed for the DOE study Modeling and Analysis of Value of Advanced Pumped Storage Hydropower in the United States. The study is led by Argonne National Laboratory in collaboration with Siemens PTI, Energy Exemplar, MWH Americas, and the National Renewable Energy Laboratory. The scope of work for the study has two main components: (1) development of vendor-neutral dynamic simulation models for advanced pumped storage hydropower technologies, and (2) production cost and revenue analyses to assess the value of PSH in the power system.

A variety of simulations were performed using a system based roughly on the Sacramento Municipal Utility District (SMUD). The intent was to use the SMUD system, as a typical balancing authority and project team member, to test the models of the advanced pump storage hydro technology newly developed in the course of the DOE project and to demonstrate the potential benefits of this technology. The simulations showed that the advanced pump storage technologies can improve secondary frequency control capabilities. The advantages of both ternary and adjustable speed technologies were demonstrated.

Testing Dynamic Simulation Models for Different Types of Advanced Pumped Storage Hydro Units (2013)

This report is one of several reports developed for the DOE study Modeling and Analysis of Value of Advanced Pumped Storage Hydropower in the United States. The study is led by Argonne National Laboratory in collaboration with Siemens PTI, Energy Exemplar, MWH Americas, and the National Renewable Energy Laboratory. The scope of work for the study has two main components: (1) development of vendor-neutral dynamic simulation models for advanced pumped-storage hydropower technologies, and (2) production cost and revenue analyses to assess the value of PSH in the power system.

The following new dynamic simulation models have been developed and tested in the course of this project: 

  • A model of an adjustable speed pumped-storage hydro (AS PSH) unit operating as a turbine 
  • A model of an AS PSH unit operating as a pump
  • A combined model of a ternary PSH unit that can be used for simulation of any of three modes of operation of this type of unit, namely: 
    • As a conventional hydro turbine
    • As a conventional hydro pump
    • As a ternary unit operating in the hydraulic short-circuit mode.

Three tests were conducted that demonstrated that the new models performed well and can be used for the typical dynamic simulation analyses required by planning and interconnection studies. The tests also demonstrated the new capabilities available in these models (e.g., the use of an adjustable speed pumped-storage plant to provide regulation services in the pump mode) and showed the improved equipment capabilities such as the faster response to system events. These new models fill a major need in the transmission system interconnection activity with regard to system dynamic performance studies for new pumped-storage plants with adjustable speed or ternary pumped-storage units. These models will be very useful in studies investigating how these technologies can be implemented to help address concerns related to the increasing integration of wind and solar photovoltaic renewable resources.

Modeling Ternary Pumped Storage Units (2013)

This is one of several reports developed for the DOE study Modeling and Analysis of Value of Advanced Pumped Storage Hydropower in the United States. The study is led by Argonne National Laboratory in collaboration with Siemens PTI, Energy Exemplar, MWH Americas, and the National Renewable Energy Laboratory. The scope of work for the study has two main components: (1) development of vendor-neutral dynamic simulation models for advanced pumped-storage hydropower technologies, and (2) production cost and revenue analyses to assess the value of PSH in the power system.

The purpose of this report is to propose a power system dynamic simulation model structure for a ternary PSH unit employing a separate turbine and pump on a single shaft with the generator/motor. A companion report proposed a model structure for an adjustable speed PSH unit employing a doubly-fed induction machine (DFIM).

Modeling Adjustable Speed Pumped Storage Hydro Units Employing Doubly-Fed Induction Machines (2013)

This is one of several reports developed for the DOE study Modeling and Analysis of Value of Advanced Pumped Storage Hydropower in the United States. The study is led by Argonne National Laboratory in collaboration with Siemens PTI, Energy Exemplar, MWH Americas, and the National Renewable Energy Laboratory. The scope of work for the study has two main components: (1) development of vendor-neutral dynamic simulation models for advanced pumped-storage hydro technologies, and (2) production cost and revenue analyses to assess the value of PSH in the power system.

The purpose of this report is to propose a model structure for an adjustable speed pumped-storage hydropower unit employing a doubly-fed induction machine (DFIM).

Review of Existing Hydroelectric Turbine-Governor Simulation Models (2013)

This is one of several reports developed for the DOE study Modeling and Analysis of Value of Advanced Pumped Storage Hydropower in the United States. The study is led by Argonne National Laboratory in collaboration with Siemens PTI, Energy Exemplar, MWH Americas, and the National Renewable Energy Laboratory. The scope of work for the study has two main components: (1) development of vendor-neutral dynamic simulation models for advanced pumped-storage hydropower technologies, and (2) production cost and revenue analyses to assess the value of PSH in the power system.

This report includes an overview of the approaches to power system stability studies; a brief description of modeling of generators, excitation systems, and turbine-governors; a description of specific models extracted from the standard libraries of various software platforms; as well as a discussion on the approach to modeling conventional PSH units and plants.

The Role of Pumped Storage Hydro Resources in Electricity Market and Systems Operations (2013)

The most common form of utility-sized energy storage system is the pumped-storage hydro system. Originally, these types of storage systems were built to assist with providing generation during peak times with the energy they stored while pumping during night times, as well as a backup to nuclear power plants. Recent trends of differing electricity market design and increasing amounts of variable renewable generation have allowed for pumped-storage hydro to provide other services to support the power system, and earn additional revenue. While the market design topics have been evolving since their inception, there are still ways that the designs can be improved to better value all of the capabilities that pumped-storage hydro has to offer, while still maintaining a fair and impartial perspective. This paper introduces some of the issues that may limit the ability to fully value pumped-storage hydro plants in today’s markets and propose some solutions to those problems.

Much of the nation’s PSH plants were initiated during the mid- to late 1970s, at a time when they could assist in providing cheap power during peak periods that they stored during low-cost nighttime periods. In the United States, there have not been significant additions of PSH since this early time period. PSH can provide many services to the power system that are not captured in today’s market structure, such as increased flexibility, primary frequency response, following reserves, and fast-acting regulation reserves. A similar issue is that PSH is typically not adequately represented during the optimization of the commitment and dispatch formulations in most restructured electricity markets. These issues were discussed along with the current state of electricity market designs and how PSH is part of these designs. The way the market structure currently stands and the way PSH fits into that market structure was shown. Finally, potential market changes that can help PSH in today’s restructured markets were presented and discussed in this paper.
 

The Value of Hydropower Assets in a Changing Electric Grid

Quantifying the Value of Hydropower in the Electric Grid (2013)

The Electric Power Research Institute has released a report summarizing research to quantify the value of hydropower in the electric grid. This three year DOE study focused on defining value of hydropower assets in a changing electric grid. Methods are described for valuation and planning of pumped-storage and conventional hydropower.

This study confirmed that hydropower resources across the United States contribute significantly to operation of the grid in terms of energy, capacity, and ancillary services. Many potential improvements to existing hydropower plants were found to be cost-effective. Pumped storage is the most likely form of large new hydro asset expansions in the United States; however, justifying investments in new pumped storage plants remains very challenging with current electricity market economics. Even over a wide range of possible energy futures, up to 2020, no energy future was found to bring quantifiable revenues sufficient to cover estimated costs of plant construction. 

Modular Pumped-Storage Hydropower

With funding provided by the Water Power Technologies Office, Oak Ridge National Laboratory has lead several efforts to investigate a number of different aspects of modular pumped-storage hydropower, such as feasibility, design effectiveness, economic viability, and more:

Development and Implications of a Predictive Cost Methodology for Modular Pumped Storage Hydropower Projects in the United States (2016)  

Since 2011, Oak Ridge National Lab has been exploring the economic viability of modular pumped storage hydropower (m-PSH) development through targeted case studies, revenue simulations, and analysis of innovative configurations and designs. This paper outlines the development and supporting analysis of a scalable, comprehensive cost modeling tool designed to simulate the initial capital costs for a variety of potential m-PSH projects and deployment scenarios. The tool is used to explore and determine innovative strategies that can improve the economic viability of m-PSH in U.S. markets.

Evaluation of the Feasibility and Viability of Modular Pumped Storage Hydro in the United States (2015)

The viability of m-PSH is examined in detail through the conceptual design, cost scoping, and economic analysis of three case studies. Modular PSH refers to both the compactness of the project design and the proposed nature of product fabrication and performance. A modular project is assumed to consist of pre-fabricated standardized components and equipment, tested and assembled into modules before arrival on site. This technology strategy could enable m-PSH projects to deploy with less substantial civil construction and equipment component costs. The concept of m-PSH is technically feasible using currently available conventional pumping and turbine equipment, and may offer a path to reducing the project development cycle from inception to commissioning.

U.S. Department of Energy Report to Congress

U.S. Department of Energy Report to Congress, Pumped Storage Hydropower and Potential Hydropower from Conduits (2015)

This U.S. Department of Energy Report to Congress, Pumped Storage Hydropower and Potential Hydropower from Conduits, analyzes the technical flexibility that existing pumped-storage facilities can offer to support intermittent renewable energy generation. This study assessed possible upgrades or retrofit of these facilities, the potential of existing and new pumped-storage facilities to provide grid reliability benefits, and the range of conduit hydropower opportunities available in the United States.

Hydropower Market Report 2017

The second ever Hydropower Market Report provides a snapshot of the distribution, characteristics, and trends of the current U.S. hydropower fleet. The report also highlights the flexibility and reliability services that hydropower and pumped storage hydropower provide to the grid, which are particularly important as the U.S. grid and generation mix continues to change.

Key findings from the 2017 Hydropower Market Report, developed by the Energy Department’s Oak Ridge National Laboratory, include:

  • U.S. hydropower grew nearly 2 GW over the past decade as owners optimized and upgraded existing assets and some new projects were constructed. Growth was seen in all regions of the country.
  • The value of hydropower’s flexibility is important and likely increasing. As the U.S. generation mix changes to include more variable renewable resources like wind and solar, hydropower provides necessary flexibility and reliability services to the grid. From 2005–2015, the use of variable renewables in the United States has increased from 2% to 11%. An analysis of many different U.S. electricity markets shows that hydropower assets are being utilized equally—and in many cases more intensely in providing ancillary services—than natural gas plants, one of the most flexible generation assets available.
  • The hydropower industry still faces challenges as the power sector evolves. Availability factors have decreased in the last decade, which presents a challenge to new hydropower development, increases operations and maintenance costs of aging infrastructure, and requires plants to be operated in new and different ways.
  • The United States has the third-largest hydropower and PSH fleet in the world, and the seventh-largest PSH pipeline.

Active Initiatives, Innovations, Configurations, and Components

Valuation and Techno-Economic Assessments

WPTO is currently funding an extensive effort aimed at producing a comprehensive and objective methodology to assess the value of PSH analysis that can be widely used by stakeholders throughout the hydropower industry. This effort is partially driven by a lack of information related to the value and cost of providing PSH services, which leads to possible inefficiencies in how existing power and ancillary services are obtained and compensated. A WPTO-supported Hydropower Value Collaborative team comprised of five national laboratories is devoting extensive research efforts into advancing state-of-the-art value assessments of PSH plants and their role and contributions to the power system. The five national laboratories include: Argonne National Laboratory (project lead), Idaho National Laboratory, National Renewable Energy Laboratory, Oak Ridge National Laboratory, and Pacific Northwest National Laboratory. The specific goals of this effort are to:

  • Develop a comprehensive and transparent valuation methodology that will allow for consistent valuation assessments and comparisons of PSH projects
  • Test the PSH valuation methodology by applying it to two selected PSH projects
  • Transfer and disseminate the PSH valuation methodology and two project results assessment findings to the hydropower industry, PSH developers, and other stakeholders

The findings from this work can be used to value existing and proposed new PSH projects by industry plant owners/operators and project developers. Regulatory agencies and financial organizations will also benefit from enhanced understanding of how to more accurately value PSH.

Techno-economic assessments will be carried out in order to validate the proposed valuation guidance at two separate PSH sites with high levels of variable renewable energy generation in the United States. Techno-economic assessments will be carried out in order to validate the proposed valuation guidance at two separate PSH sites with high levels of variable renewable energy generation in the United States. To inform selection of these sites, WPTO has recently released both a DOE Request for Information as well as a Notice of Opportunity for Technical Assistance (NOTA) which will serve to solicit proposals for the techno-economic studies.

PSH flowchart: develop draft valuation methedology, then draft PSH valuation methedology, test valuation methedology, run several test cases, revise and publish the final PSH valuation methedology.
Next-Generation Hydropower Technologies

WPTO has recently awarded significant funding to several organizations with innovative technologies that can demonstrate the potential to lower capital costs and deployment timelines for pumped-storage technologies and non-powered dams. Stay up to date with recent developments by checking out the info below.

Obermeyer’s Cost Effective Small-Scale Pumped-Storage Configuration

DOE Funding: $1,180,000

  • Design, modeling, and analysis of a reversible pump turbine with submersible permanent magnet motor generators installed in vertical shafts.
  • This design reduces environmental footprint and eliminates the need for an underground powerhouse, reducing initial construction cost.

National Renewable Energy Laboratory's New Application of Ternary-Type Pumped Storage

DOE Funding: $1,250,000

  • Concept feasibility studies of a ternary pumped-storage hydropower system, a system that allows nearly instantaneous switching between generation and pumping, coupled with an innovative dynamic transmission system using transmission monitoring and control equipment.
  • Turbine, motor-generator, and pump are stacked on a single shaft. The system is able to pump and generate at the same time, and seamlessly move from pumping to generating at an estimated 20-40 MW/second.

Shell Energy's Hydro Battery

DOE Funding: $945,000

  • Investigate the feasibility of building a modular 5MW closed-loop PSH facility, the Hydro Battery.
  • The Hydro Battery consists of a corrugated steel tank as the upper reservoir, a floating membrane as the lower reservoir, and a floating powerhouse.
Illustration of Shell Energy's Hydro Battery.

Oak Ridge National Laboratory's GLIDES Grid-Scale Modular Pumped Storage Hydropower System

DOE Funding: $1,250,000

  • Evaluate the feasibility and value proposition of the novel Ground-Level Integrated Diverse Energy Storage (GLIDES) System as a modular PSH across multiple US regions and market segments.
  • With pressure vessels being the main cost driver (60–90+% of system capital costs), substantial effort will be dedicated toward analysis of pressure vessel manufacturing and potential alternative materials and processes to reduce cost.
Illustration of the Grid-Scale Modular Pumped-Storage Hydropower System.

More Information

Frequently Asked Questions

What is pumped-storage hydropower?

See the U.S. Department of Energy's "What is Pumped-Storage Hydropower?" video.

What are some typical characteristics of pumped-storage technologies?

PSH can be typically characterized as transmission interconnected, large systems (>100MW) that are utility owned and equipped with fixed speed pumps.

When was pumped-storage hydropower first put into use?

The first known use cases of pumped-storage were found in Italy and Switzerland in in the 1890s.

How many pumped-storage hydropower plants are there in the United States?

America currently has 43 PSH plants and can still add even larger amounts of new, flexible, low-cost PSH that could more than double its current PSH capacity.