Pumped Storage Hydropower

2024 ATB data for pumped storage hydropower (PSH) are shown above. Base year capital costs and resource characterizations are taken from a national closed-loop PSH resource assessment and cost model completed under the U.S. Department of Energy (DOE) HydroWIRES Project D1: Improving Hydropower and PSH Representations in Capacity Expansion Models. Resource assessment assumptions are documented by (Rosenlieb et al., 2022), and subsequent updates are described on the National Renewable Energy Laboratory's (NREL's) resource data web page Closed-Loop Pumped Storage Hydropower Supply Curves. The cost model used to estimate site-level capital costs is described in (Cohen et al., 2023). The ATB includes two PSH subtypes: 1) closed-loop systems with two new reservoirs and 2) systems that use one existing reservoir and one new off-river reservoir. Closed-loop systems are expected to have lower environmental impacts whereas systems using an existing reservoir can have lower costs. Operation and maintenance (O&M) costs and round-trip efficiency are based on estimates for a 1,000-megawatt (MW) system reported in the 2020 DOE Grid Energy Storage Technology Cost and Performance Assessment (Mongird et al., 2020). Projected changes in capital costs are based on the DOE Hydropower Vision study (DOE, 2016) and assume different degrees of technology improvement and technological learning. 

The three scenarios for technology innovation are as follows:

• Conservative Technology Innovation Scenario (Conservative Scenario): no change from baseline CAPEX and O&M costs through 2050
• Moderate Technology Innovation Scenario (Moderate Scenario): no change from baseline capital expenditures (CAPEX) and O&M costs through 2050, consistent with the Reference case in the DOE Hydropower Vision study (DOE, 2016)
• Advanced Technology Innovation Scenario (Advanced Scenario): CAPEX reductions of 12% by 2050 based on improved process and design improvements along with advanced manufacturing, new materials, and other technology improvements, consistent with Advanced Technology in the DOE Hydropower Vision study (DOE, 2016); no changes to O&M.

Resource Categorization

Resource categorization from a national closed-loop PSH resource assessment is described in detail by (Rosenlieb et al., 2022) with subsequent updates described on NREL's resource data web page Closed-Loop Pumped Storage Hydropower Supply Curves. Individual sites are identified using geospatial algorithms to delineate potential reservoir boundaries, exclude reservoirs that violate technical potential criteria (e.g., protected land, critical habitat), find all possible reservoir pairings, and then eliminate overlapping reservoirs to produce the least-cost set of nonoverlapping reservoir pairs. For sites that use existing reservoirs, we include the HydroLAKES data set of existing reservoirs in the set of total reservoirs used to find reservoir pairings. This procedure is done for alternative storage durations of 8, 10, and 12 hours. Underlying data are site-specific, but for the ATB, resource classes are binned by capital cost so that each class contains a roughly equal amount of total national PSH capacity potential. Binning is done at the national level for the data tables below; other representations use region-specific cost bins to better represent the distribution of site characteristics in each region. Physical characteristics and capital cost statistics for each ATB class and a 10-hour storage duration are included in the table below. 

Resource Class Capacity and Capital Costs

Resource Class Design Values

Scenario Descriptions

Cost reductions in the Advanced Scenario reflect various types of technology innovations that could be applied to PSH facilities. These potential innovations, which are discussed in the DOE Hydropower Vision Roadmap (DOE, 2016), are largely similar to technology pathways for hydropower without pumping.

Summary of Technology Innovation: Advanced Scenario

Scenario Assumptions

No explicit deployment assumptions or learning rates are used to define the Advanced Technology Innovation Scenario for PSH. All cost reductions are attributed to improved technology, processes, designs, and contracting along with advanced materials and improved construction practices. Deployed PSH capacity is 23 gigawatts (GW) in the Base Year (2021), and the rate of cost reduction is 0.6%/yr through 2035 and 0.2%/yr from 2035 to 2050.

Representative Technology

The resource assessment procedure requires several design specifications to be defined up-front, and for the resource included in the ATB, these include hydraulic heads of 200–750 m for closed-loop sites and 100–750 m for sites using existing reservoirs, a maximum reservoir distance of 12 times the head height, and dam heights of 40, 60, 80, or 100 m (Rosenlieb et al., 2022) and Closed-Loop Pumped Storage Hydropower Supply Curves (NREL). Upper and lower reservoir volumes are also assumed to be within 10% of one anther for closed-loop sites with no such restrictions when using existing reservoirs. Given the resulting technical specifications of each reservoir pair, the powerhouse (turbine, generator, and electrical equipment) can be sized flexibly for a given reservoir pair, and here data are included for a powerhouse sized to result in 8, 10, or 12 hours of storage duration (i.e., the maximum number of hours generating at rated capacity). 

Methodology

This section describes the methodology to develop assumptions for CAPEX, O&M, and round-trip efficiency. 

Capital Expenditures (CAPEX)

Capital costs are first calculated for each site using a bottom-up component-level PSH cost model developed at NREL with participation and engagement with hydropower industry stakeholders (Cohen et al., 2023). The cost model uses a detailed set of site specifications for the reservoirs, powerhouse, water conveyance, auxiliary components, and indirect costs to calculate technical specifications and component-level costs that are then aggregated into estimates for total direct and indirect costs for each site. Component costs are estimated largely by using procedures in the Electric Power Research Institute (EPRI) Pumped-Storage Planning and Evaluation Guide (EPRI, 1990) with market adjustment factors to reflect noninflation-based changes in relevant markets since the publication of the EPRI guide. Grid connection costs are added based on the distance from the powerhouse location (assumed at the lower reservoir) to the nearest high-voltage transmission line node (Maclaurin et al., 2021). One limitation of the capital costs estimated for single reservoir sites is that they do not include any additional costs to retrofit an existing facility; instead, they simply exclude one of the reservoir cost components. Thus, single reservoir site costs might be underestimates relative to what might be observed when deploying new PSH at existing reservoirs.

The maps below plot the median CAPEX in each state for each resource class for a PSH subtype when individual sites are binned by cost separately for each state. Some states have zero sites identified, largely because of insufficient elevation differences to meet the minimum head height criteria. The ratio of water conveyance length between reservoirs to head height (L/H ratio) is also shown for individual sites. The display includes links to a bar chart and a tabular display. The bar chart shows more granular data for each balancing area defined in the Regional Energy Deployment System (ReEDS) capacity expansion model (Ho et al., 2021) along with the state-average PSH capital cost. The table allows the data to be filtered by subtype, class, and balancing area to view region- or class-specific data.

Regional PSH Capital Cost by Class

Operation and Maintenance (O&M) Costs

(Mongird et al., 2020) characterize PSH O&M costs using a literature review of recently published sources of PSH cost and performance data. For the 2024 ATB, we use cost estimates for a 1,000-MW plant, which has lower labor costs per power output capacity compared to a smaller facility. O&M costs also include component costs for standard maintenance, refurbishment, and repair. O&M cost reductions are not projected for future years because the relevant technical components are assumed to be mature, so they are constant and identical across all scenarios.

Round-Trip Efficiency

Round-trip efficiency is also based on a literature review by (Mongird et al., 2020), who report a range of 70%–87% across several sources. The value of 80% is taken as a central estimate, and no improvements are projected either in (Mongird et al., 2020) or here because the relevant technical components are assumed to be mature. Thus, round-trip efficiency is constant and identical across all scenarios. 

References

The following references are specific to this page; for all references in this ATB, see References.