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Long-Duration Energy Storage:
Emerging Pilot Project Summaries
EPRI Insights | March 2024
Projected to have a 20-year project life, capable of over 20,000 cycles, with minimal loss of capacity due to cycling.
Abundant carbon-based molecules for the electrolyte have the potential to be low cost when manufactured at scale.
RTE of 75–80% with 100% depth of discharge, operating without capacity or power degradation with a projected 30+-year lifespan; energy density is 1.9 kWh/ft³.
Estimated capital costs at $150–220/kWh, with the levelized cost of storage projected under $100/MWh for early projects. Potential to reduce to $50–60/MWh.
This photo shows Energy Dome's 2.5 MW, 4 MWh CO2 Battery unit in Sardinia, which has been operational since May 2022. Energy Dome is also workingwith Alliant Energy, which as prime won a United States Department of Energy award in 2023 to install a commercial-scale Energy Dome system in Wisconsin.
Thermal
Storworks Power
Storworks Power (Storworks) develops systems to store energy using heat, focusing on thermal power plants. Stackable blocks made of concrete material store the heat. Charging occurs by passing either hot gas, steam or hot air through steel tubes in the concrete blocks. To use the stored energy, a fluid such as water or carbon dioxide is passed through separate tubes to recover the heat/deliver it to a power cycle.
Storworks anticipates the cost of a system exceeding 10 hours of duration retrofitted to an existing steam turbine asset would be $60–105/kWhe.
Using the concrete heat recovery steam generator (HRSG), the turbines can be sized smaller and run efficiently all day long, sending extra energy to the heat storage system.
The Storworks concrete modules are large, flat blocks with embedded pipes set into them. The modules, called "BolderBlocs," are about 40 feet (12 m) long.
Pilot
The CTES pilot plant is a 10-MWhe scale (2.5 MWe x 4 hours) system at Alabama Power's Plant Gaston in Wilsonville, AL. Lead by EPRI and funded by the U.S. Department of Energy, this facility is demonstrating the technology's performance for the steam-heated version by charging using supercritical steam at a pressure of 3500 psig (240 barg) from the host plant.
The Concrete Thermal Energy Storage (CTES) pilot plant consists of 7 layers of BolderBlocs stacked in a brickwork-like pattern along with an additional cooling block layer at the bottom needed to insulate the foundations during operation.
Chemical
RedoxBlox
RedoxBlox leverages magnesium-oxide (MgXO3) pellets, operating through two modes: charging and discharging. Charging: MgXO3 pellets are heated from 1830°F (1000°C) to 2730°F (1450°C) within a pressure vessel. Discharging: Pressurized air introduced into the vessel reacts with MgXO2, reversing the previous reaction and reforming MgXO3 to be used to produce electricity at 50-55 AC-AC% RTE when integrated with a combined-cycle gas turbine GT.
The production cost of its MgXO3 chemical pellets is anticipated to range from $600–800/ton (equivalent to $1.8–2.4/kWhth).
RedoxBlox is making its system directly compatible with commercial turbomachinery, by repurposing existing infrastructure.
Schematic of RedoxBlox's Thermochemical Energy Storage System
Pilot
Sub-Scale Prototype (pictured on the left): Features the advanced 10 kWhth capacity prototype, which underwent over 1400 hours of charge-discharge cycling in 2021, highlighting the system's chemical stability.
Small-Scale Pilot (pictured on the right): Features commercial-designed temperatures and pressures with simulated charge and discharge modes at 100 kWhth capacity, validating control strategies and capabilities.
The progression of RedoxBlox's technology from initial concept to larger-scale prototypes, with each step validating and refining the system's capabilities. The successful operation of earlier prototypes laid the groundwork for the development of a small-scale pilot, driving the technology's potential toward practical application.
EPRI Edge in LDES Innovation
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Pioneering Sustainable Energy Innovations Together
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