Long Duration 200 kW Energy Storage with Aquifer Pumped Hydro
Antelope Valley Water Storage, LLC
Recipient
Lancaster, CA
Recipient Location
21st
Senate District
39th
Assembly District
$883,546
Amount Spent
Active
Project Status
Project Update
The 200 kW Aquifer Pumped Hydro (APH) system design and construction tasks are in progress, as well as production well retrofitting. Remaining site preparation tasks include: interconnection with the utility, installation of containers for housing equipment, microgrid construction, pipeline system connection, surface storage pond construction, and final inspection of equipment.
A survey to assess the statewide applicability of this technology, as well as the feasibility of deploying in disadvantaged communities is ongoing in parallel.
The relevant regional water quality board staff has approved the project team’s water reinjection quality monitoring program, and final approval is pending.
In 2025, work was paused on this project for 6 months due to a potential regulatory issue with the Federal Energy Regulatory Commission (FERC). Following discussions with FERC, this issue was resolved and work has resumed.
In 2026, construction of the microgrid and surface pond will advance, and a water quality monitoring plan will be approved before operations begin.
The Issue
The increased emphasis on energy resilience in the state is driving the need for longer duration energy storage backup capabilities. Longer duration energy storage and energy discharge is needed to respond to unplanned grid outages, curtailment risk, Public Safety Power Shutoffs (PSPS) and to increase renewables penetration. Disadvantaged and Low-Income Communities are especially vulnerable to preemptive shutoffs. As wildfires become more common, new energy storage/discharge technologies are needed that provide economical, standalone power.
The California grid is facing three issues that could benefit from longer duration energy storage:
1. Evening Ramp Up: There is not enough power for the grid during the 5-hour evening ramp up (from 4:00 to 9:00 p.m.) as solar goes offline but consumers turn on appliances. The 2–4-hour discharge of lithium batteries has trouble covering the 5-6 hour ramp up period.
2. Public Safety Power Shutoffs: Increased wildfire risks have forced Investor-Owned Utilities to shut down transmission lines during high wind events. For example, in October of 2019, power to 800,000 customers (2.5-3.0 million people) was shut off due to wildfire risks. These preemptive shutoffs created major disruptions and may have contributed to at least one death.
3. Overgeneration: In non-summer months, especially in the springtime, there is a glut of solar energy in the afternoons and a dearth of generation in the early evening hours. This creates risks of overgeneration and curtailment of renewables.
Over 90 percent of the energy storage systems built to date in California use lithium-ion batteries. Excessive reliance on lithium batteries can create materials and minerals shortages, and safety issues from thermal runaway. Consumed lithium-ion batteries can also create a disposal problem.
Project Innovation
This project will demonstrate and define the necessary technical, financial, and operational resources to assess the potential of energy storage and discharge with APH to provide continuous energy discharge during grid outages, during peak periods, and during PSPS events, which provide end-user benefits that may drive wide-scale adoption of the technology in California.
A groundwater storage facility in eastern Kern County, Willow Spring Water Bank (WSWB), will be used for demonstration. Groundwater will be used to fill and drain a small surface reservoir. Five existing wells at WSWB with nameplate capacities ranging from 112 kW (150 HP) to 225 kW (300 HP) will be retrofitted to also act as generators. At 30 percent generation efficiency, each individual WSWB well will produce 34kW to 67 kW of power. The technology is behind-the-meter and will require a Net Energy Metering (NEM) interconnection agreement with Southern California Edison (SCE). For the demonstration, the stored energy will be discharged to provide on-peak power to SCE during the evening ramp up and recharged off-peak. The end-user customer, WSWB, will benefit from the differential between on and off-peak SCE rates.
Please also see EPC-19-058 project information to better understand the scaling of this technology.
Project Goals
Project Benefits
This project is part of a broader initiative to explore non-lithium energy storage technologies in California, in order to diversify the state’s energy storage portfolio, develop cheaper and more efficient energy storage systems, and mitigate the potential safety issues associated with lithium-ion batteries.
Aquifer pumped hydro technology is promising in its potential to use pre-existing infrastructure widely available in California, deliver long discharge and storage durations (to fill challenging seasonal energy storage roles on the grid) with limited capacity degradation, and avoid the use of critical minerals.
This project (along with EPC-19-058 occurring in parallel), will provide valuable operational data for this concept, to allow stakeholders to better understand the role that APH can play in the state’s longer-term energy transition, and specifically test the capacities in which it could compete with Li-ion technologies most effectively.
Affordability
Aquifer pumped hydro is estimated to cost less than a lithium-ion battery which can lead to lower costs for energy storage and eventually translate to bill savings. This is because it relies on existing infrastructure (wells) and proven technology.
Reliability
The 10-hour discharge duration can provide peak power during the evening ramp up five days in a row, increasing electric reliability. It can also absorb surplus renewables during the spring period of renewables overgeneration risk.
