High-elevation, Renewable Co-Generation

Large "Water Battery" Projects in the U.S.

- Pump-Storage Using Energy Production / Pricing Spreads

Pump Back Hydro Diagram

Rather than run-of-the-river or storage-based conventional hydropower, pump-storage projects (a.k.a. pumped-storage hydroelectricity - PSH or pumped hydroelectric energy storage - PHES / "water battery") use turbines in reverse to pump back water from a position of lower elevation to a water body of higher elevation when energy is cheap to provide peaking power / load balancing by running the water back down through the turbines when energy is more expensive and less available. "Pump-back" systems are designed on existing reservoir stream systems, whereas "off-stream" systems (the closed loop system shown of interest) utilizes an off-stream upper reservoir to operate independently of multi-purpose water flow needs. In such a "closed-loop" PSH system, the water can be reused, rather than flow downstream, to perpetually store and release energy on demand.

Pump-storage hydro is sometimes called a "water battery", but most systems continue to work in conjunction with steady round-the-clock base load fossil fuel and nuclear plants, just to meet daytime peaks. Storing renewables, intermittent energy production sources like wind and solar for periods when the sun isn't shining and the wind isn't blowing or natural disasters or maintenance prevent their regular operations, would be more difficult. Most PSH systems can only maintain a few hours of massive elease of gravity-flow reservoir storage, so it wouldn't work for long term gray days or winter use, without an alternative cheap recharge source, but during such situations, that recharge source would no longer be cheap.

See international examples installed around the world for various options.

Ten of the largest U.S. based pumped hydropower projects are described in detail below:

  1. Bath County Pumped Storage Station
    • Location: SE of Eastern Continental Divide near border with WV near Warm Springs, Bath County, VA (43°53′37″N,86°26′43″W) - MAP
    • Capacity: 3,003 / 2,772 MW, Storage: 24K MWh / 35.6K AF (Powers about 750K Homes for 11 hours), From Year: 1985     
    • Owner: Dominion Energy [60%]; LS Power [24%]; First Energy [16%]
    • Source: Upper Reservoir on Little Back Creek / Lower Reservoir on Back Creek (HUC8 - 2080201)
    • Design: 6 turbines 480/500 MW each, 3-3,100 to 3,600 feet long conduits bifurcate into 6-900 foot shafts, Elev Dif: 460 feet, 79% efficiency
    • Description: Until 2021, Bath County Hydroelectric Power Generation was considered one of the largest pump-storage systems worldwide, storing energy for a 13-state region to allow traditional coal, nuclear and gas base power plants to operate at peak efficiency steadily, while  it covered the region's peak energy needs.  Sited on a small creek, rather than a huge river like the Tennessee used by Racoon Mt (3), this system works well because unlike conventional hydropower, it only needs to replace water loss due to evaporation, seepage or transport losses, as it can continually pump between the upper and lower reservoir otherwise.  Evaporation can be reduced by including floating solar or other mechanisms of shading or cooling, such as solar-powered aeration systems, that will also improve oxygen levels and reduce harmful algae blooms (HABs / cyanobacteria).
  2. Ludington Pumped Storage Power Plant
    • Location: Elevated Sand Dune on east shore of Lake Michigan near Ludington, Mason County, MI (35°02′55″N,85°23′48″W ) - MAP
    • Capacity: 2,172 / 1,979 MW, Storage: 82.9 AF, From Year: 1973
    • Owner: Consumers Energy [51%]; DTE Electric [49%]
    • Source: Lined Upper Reservoir / Lake Michigan (HUC8 - 4060101)
    • Design: 6 turbines 312 MW each, 1,100 feet long tunnel to turbines, Elevation Difference: 363 feet
    • Description: Water is pumped from Lake Michigan up to a holding reservoir above a natural sand dune to level area nuclear production. The design won an award upon completion as an alternative to building fossil fuel peaking plants during the 1970s energy crisis. It is unclear why more of the world's largest lakes do not produce similar projects - or between large lakes of different elevations, like Lake Erie and Ontario.
  3. Raccoon Mountain Pumped Storage Plant
    • Location: Just SE of Chattanooga, Hamilton County, TN (38°12′32″N, 79°48′00″W) - MAP
    • Capacity: 1,652 / 1,714 MW, Storage: 328K AF (generates up to 22 hours after filled in 28), From Year: 1973
    • Owner: Tennessee Valley Authority (TVA)
    • Source: Racoon Mt / NickjackLake on Tennessee River (HUC8 - 6020001)
    • Design: 4 turbines 413MW each, 5,800 foot long rock fill dam longest in TVA System, Elevation Difference: 230 feet
    • Description: Peak power generation and grid balancing on TVA reservoir system, Racoon Mt was the "Rube Goldberg" engineering wonder of its day, as the entire mountain was carved out up top to create a high-elevation reservoir from which to pump up the Tennessee River through a tunnel drilled right through to the bottom for critical periods of peaking power need that other on-stream reservoirs in the system simply cannot provide. There are also large mountain caves in the region that could potentially serve as underground PSH sites.
  4. Castaic (Pumped Storage) Power Plant
    • Location: 22 miles N of LA, Castaic, Los Angeles County, CA (34°35′14″N,118°39′23″W) - MAP
    • Capacity: 1,682 MW, Storage: 20K MWh (3-6 hr/day winter, 6-10 hr/day summer), From Year: 1972 auxillary unit, through 1978 turbine 6
    • Owner: Los Angeles Department of Water & Power (LADWP); California Department of Water Resources
    • Source: Pyramid Lake, West Branch of the California State Aqueduct (HUC8 - 18070102)
    • Design: 6-250 MW turbines  and 1-55MW auxillary turbine, Elevation Difference: 1,060 feet
    • Description: A very complex system with high friction losses, so not really used as envisioned, but rather for conventional peaking hydropower generation most of the time, only resorting to pump-back when extra duration is needed a few percent of the time.
  5. Helms Pumped Storage Plant
    • Location: 50 miles E of Fresno in Sierra MT on Shaver Lake, Fresno County, CA (37°02′13.78″N, 118°57′53.63″W) - MAP
    • Capacity: 1,212 MW, Storage: 129K AF, From Year: 1984
    • Owner: Pacific Gas & Electric CO (PGE)
    • Source: Courtright Reservoir, Wishon Reservoir (near underground power station) in Helms Creek Canyon (HUC8 - 18030010)
    • Design: 3-404 MW turbines, 3,797 foot tunnel, Elevation Difference: 1,625-1,634 feet depending on reservoir levels, Can Peak in 8 minutes!
    • Description: Tunnel connects the two reservoirs through an underground station. It allows Diablo Canyon Nuclear Power Plant to operate near peak efficiency through a dedicated peaking power line.
  6. Blenheim Gilboa Hydroelectric Power Station
    • Location: Catskill Mts downstream from Gilboa, Schoharie County, NY (42°27′18″N, 74°27′29″W) - MAP
    • Capacity: 1,100 MW, Storage: 12K MWh after store 17K AF, From Year: 1973
    • Owner: New York Power Authority (NYPA)
    • Source: Schoharie Creek (HUC8 - 2020005)
    • Design: 4 Hitachi 286 (upgraded) MW turbines, Elevation Difference: 1,066 - 1,142 feet depending on reservoir levels
    • Description: Underwater structure using concrete shaft penstock, with about 73% efficiency. The visitors center / science & tech museum is housed in a 18th century dairy barn near the historic Lansing Manor House and Mine Kill State Park.
  7. Rocky Mountain Pumped Hydroelectric Plant
    • Location: 10 miles NW of Rome, Floyd County, GA (34°21′20″N, 85°18′14″W) - MAP
    • Capacity: 1.095 MW, Storage: 10.65K AF (about 50K homes for 7 hours), From Year: 1995
    • Owner: Oglethorpe Power [75%]; Georgia Power [25%]
    • Source: Upper Reservoir on Rocky Mt / Heath Creek (HUC8 - 3150103)
    • Design:  4 turbines upgraded in 2011 from 283-365MW, 889 foot penstock, Elevation Difference: 682 feet
    • Description: During drought, two auxiliary reservoir can be used to continue to power the plant and also sustain wildlife.
  8. Northfield Mountain Hydroelectric Facility
    • Location: Northfield, Franklin County, MS about 6 miles upstream of Turners Falls Dam (42°36′36.51″N, 72°26′50.63″W) - MAP
    • Capacity: 1,168 MW, Storage: 17K AF (about 1M homes for 7.5 hours), From Year: 1972 - largest in NE
    • Owner: First Light Power Resources INC / Operated by
    • Source: Upper Reservoir / Vernon Dam on Connecticut River (HUC8 - 1080201)
    • Design: Built Underground, 4 turbines operate along 2,500 foot Northfield Mt Tailrace Tunnel, Elevation Difference: 800 feet
    • Description: Despite opposition during the energy transition, before potential additional benefits of storing new renewables became obvious in this massive water battery, Northfield Mt. continues to serve as the largest New England reserve.
  9. Muddy Run Pumped Storage Plant
    • Location: Drumore, Lancaster County, PN (39°48′29″N,76°17′54″W) - MAP
    • Capacity: 1,072 MW, Storage: 1K AF, From Year: 1968 - largest at time built
    • Owner: Constellation Energy CORP, Operated by Susquehanna Electric Company
    • Design: 8 reversible turbines, 4,800 foot tunnel, Elevation Difference: 343-500 feet
      Source: Muddy River Reservoir / Conowingo Reservoir on Susquehanna River (HUC8 - 2050306)
    • Description: One of the first in the U.S., Muddy Run was designed by Grand Coulee Dam designer Eugene Whitney. Unlike BESS with a relatively short lifespan and end-of-use disposal challenges, water batteries can provide storage for decades, if not centuries, as elevating water is the simplest mine-free recharge mechanism. Existing Lakes can be important wildlife and recreational amenities, if the change in elevation can be effectively managed, like here in Susquehannock State Park.
  10. Bad Creek Hydroelectric Station
    • Location: 8 miles N of Salem, Oconee County, SC (35°0′40.02″N, 83°0′52.23″W) - MAP
    • Capacity: 1,400 / 1,065 MW (335 MW planned Phase II), Storage: 1.4K MWh, From Year: 1991
    • Owner: Duke Energy Carolinas LLC
    • Design: 4 reversible turbines/266 MW each, 1 mile tunnel, powerhouse 600 feet underground
    • Source: Upper Reservoir on Bad Creek / Lower is Lake Jocassee (HUC8 - 3060101), Elevation Difference: 1,110 feet
    • Description: Lake Jocassee is the lower reservoir, while low-flow dammed Bad/West Bad Creeks serve as the upper reservoir. After the upgrade to increase capacity, it will be able to store as much as most nationwide BESS projects did overall in 2020! This higher capacity allows for longer, higher energy storage. The ease at which an existing system can be upgraded to double its already phenomenal capacity is one of the best reasons to consider pumped storage!

These pump-back storage projects store water potential energy for later use. Although large systems can provide more energy over longer periods than most traditional battery storage projects that require lithium and precious metal mining and manufacture, PSH has much higher and longer upfront development costs and massive material and construction components. So most systems can only be developed at existing reservoir projects or as existing PSH system expansion. Regulatory and environmental concerns waste both time and money in development, but unlike conventional hydropower, the fact the water can be reused - only requiring evaporative water loss replacement - can reduce these issues. Underground PSH systems that use mined out caverns or existing caves could reduce evaporative losses.

Even if upfront costs are steep, the longer life and capacity and lower cost than current BESS alternatives and the potential replacement of fossil fuel powered peaking plants are major reasons to continue to develop PSH whereever possible.