Big batteries capable of storing electricity on the order of megawatt-hours or even gigawatt-hours are becoming indispensable in a world rich of renewable energy. They buffer the variable output of wind and solar, stabilize frequency, defer fossil-fuel peaker plants, and enable grid operators to shift energy supply across hours or days.
In this article, we explore the technology and concept behind these large-scale Battery Energy Storage Systems (BESS),[1] their advantages and trade‑offs, and highlight five leading projects.
Overview of Grid‑Scale Battery Systems
Most existing large BESS rely on lithium‑ion battery chemistry—such as Tesla Megapack or similar modular units—optimized for high-power delivery over a few hours.
Batteries are defined by key metrics:
- Power rating (MW): peak instantaneous output
- Energy capacity (MWh / GWh): total energy stored
- Duration: length of discharge at rated power
- Round-trip efficiency (%): ratio of output energy to input energy
Lithium‑ion excels in short-term grid services—frequency regulation, peak shaving, arbitrage—but durations beyond 4 hours become expensive and less efficient.[2] Emerging alternatives like iron-air batteries,[3] notably from companies such as Form Energy, offer multi-day discharge durations with lower cost per kWh but with lower round-trip efficiency and greater technological immaturity. Vanadium redox flow batteries (VRFBs) offer long-duration discharge (typically 8–10 hours), long cycle life with minimal degradation, and easier scalability, but require large volumes and more complex infrastructure.[4]
Pros and Cons of Big Batteries
Pros:
- Smooth integration of variable renewables by time-shifting supply
Grid-scale batteries can store surplus electricity generated during sunny or windy periods and release it when production drops, ensuring a steady supply. This reduces curtailment of renewable output and helps balance the grid without relying on fossil fuel backup.
- Provide fast-response grid services
Large battery systems can respond to fluctuations in grid frequency within milliseconds, keeping the system stable. They can also provide reserve capacity during unexpected demand spikes and help restart parts of the grid after a blackout (black-start capability).
- Reduce electricity price volatility via arbitrage
Batteries can charge when electricity prices are low (often during high renewable output) and discharge during peak demand when prices are higher. This flattens extreme price swings and can lower overall costs for both utilities and consumers.
- Delay investments in transmission or peaking generation
By providing localized energy storage, batteries can reduce the need for expensive upgrades to transmission infrastructure or the construction of new peaker plants (for instance, pumped-storage hydropower or simple-cycle gas turbines. This defers major capital expenditures while still meeting reliability requirements.
Cons:
- Upfront investment
While large-scale battery projects have historically required substantial capital, costs are falling quickly thanks to mass production and technological improvements. By mid-2025, global average lithium-ion battery pack prices dropped below $100 / kWh, with China already achieving ~$94 / kWh.[5] What used to cost $139 / kWh end of 2023[6] now costs a fraction, making batteries increasingly competitive with conventional power technologies.
- Replacement after decades of service
All batteries gradually lose capacity and eventually need refurbishment or recycling—typically after 20–25 years. But this is hardly unique: gas turbines often require major overhauls after 10–15 years, and nuclear plants face billion-dollar refurbishment cycles. Compared to those, batteries are relatively straightforward and cost-effective to replace or repurpose.
- Safety management
Lithium-ion systems, like many energy technologies, carry risks such as overheating. However, engineering advances, monitoring systems, and fire suppression solutions are already standard practice. These measures make modern battery installations much safer than before.
- Regulatory fine-tuning
Every new technology faces permitting and standardization hurdles. These are less roadblocks and more “growing pains” of innovation. Just as wind and solar power once navigated evolving rules before becoming mainstream, battery storage is following the same trajectory. Regulations adapt, and what looks challenging today typically becomes routine tomorrow.
Top 5 Big‑Battery Projects
- The Edwards & Sanborn Solar + Energy Storage project is a large solar-plus-storage facility in Kern County, California, located on both private land and property leased from Edwards Air Force Base.[7] It includes around 875 MWdc of solar power and 3,287 MWh of battery storage, making it one of the largest systems of its kind in the world. Construction began in 2020, and the project became fully operational in January 2024. It supplies electricity to utilities such as Southern California Edison, PG&E, San Jose, and the Clean Power Alliance.
- Form Energy Iron‑Air long-duration battery (Lincoln, Maine, USA): ~85 MW / 8.5 GWh designed for ~100 hours discharge; under development with ~$147 million federal grant awarded in 2024. This pilot targets multi‑day storage as a new paradigm in renewable buffering.[8]
- Big Canberra Battery – Williamsdale BESS (ACT, Australia): 250 MW / 500 MWh; under construction, expected operational by 2026; ~$300 million+ investment by ACT Government and Eku Energy.[9][10] Will supply up to one‑third of Canberra for two hours during peak demand. Lithium-Ion battery technolgy.
- China has completed the world’s largest vanadium redox flow battery (VRFB) plant in Jimusar County, Xinjiang.[11] Developed by China Huaneng Group, it provides 200 MW / 1 GWh of storage and is part of a 1 GW solar-plus-storage project. Built with an investment of about CNY 3.8 billion (USD 520 million), the facility can discharge electricity for up to five hours and is expected to produce 1.72 TWh of clean power annually, offsetting over 1.6 million tonnes of CO₂ emissions.
- Lovech BESS (northern Bulgaria): ~500 MWh capacity in 111 battery containers; newly inaugurated in 2025 aimed at price and grid stability in Bulgaria’s system; initial step toward 10,000 MWh national storage goal .[12]
Long‑Duration Alternatives: Iron‑Air and Vanadium Flow
Beyond lithium‑ion, iron‑air batteries offer exceptionally long discharge durations (100 hours plus), ideal for seasonal storage or extended calm periods when renewables underperform. Form Energy’s Maine project exemplifies this vision;[8] it may fundamentally change energy storage economics once scaled.
Vanadium redox flow batteries use liquid electrolytes in external tanks and support large capacities with minimal degradation. Europe has recently commissioned its largest VRFB pilot at Fraunhofer ICT in Pfinztal, Germany: 2 MW / 20 MWh facility serving as an R&D testbed.[13]
Europe is also set to construct a massive 800 MW / 1.6 GWh redox flow battery facility in Laufenburg, Switzerland, the largest of its kind, with construction approval granted for operation around 2028.[14]
Major companies like Invinity are advancing UK and Hungary projects totaling ~31.5 MWh, with a 20.7 MWh project expected online by 2026.[15]
Conclusion
Battery energy storage is becoming a cornerstone of the Solarpunk future: smoothing renewable variability, strengthening resilience, and easing price spikes. Costs that once seemed daunting have plunged—global averages fell below $100/kWh in 2025, with China near $94/kWh. Regulation is evolving as it once did for solar and wind, while new chemistries like iron-air and vanadium flow reduce reliance on critical and supply-constrained materials.
As Europe scales storage from tens of gigawatt-hours today to hundreds by 2029, technology diversity will be vital. Large-scale BESS—lithium-ion, iron-air, or, vanadium flow—are not just enablers of a resilient, decarbonized grid; they reflect the Solarpunk ideals of decentralization, ecological balance, and resilient systems.
Sources:
[1] https://en.wikipedia.org/wiki/Battery_energy_storage_system
[2] https://en.wikipedia.org/wiki/Lithium-ion_battery
[3] https://en.wikipedia.org/wiki/Metal%E2%80%93air_electrochemical_cell
[4] https://en.wikipedia.org/wiki/Vanadium_redox_battery
[5] https://www.marketresearchfuture.com/news/ev-revolution-battery-prices-drop-below-usd-100-kwh-amid-china-s-dominance-of-the-market-in-2025
[6] https://about.bnef.com/insights/clean-energy/lithium-ion-battery-pack-prices-hit-record-low-of-139-kwh/
[7] https://www.renewableenergyworld.com/solar/weve-got-a-new-champ-worlds-largest-solar-storage-facility-fully-operational-in-california/
[8] https://pv-magazine-usa.com/2024/08/16/form-energy-iron-air-battery-in-maine-granted-147-million/
[9] https://www.act.gov.au/builtforcbr/browse-all-projects/climate-action-energy-and-environment/Big-Canberra-Battery-Williamsdale-BESS/
[10] https://www.energy-storage.news/eku-energy-secures-development-approval-for-500mwh-bess-in-the-australian-capital-territory/
[11] https://www.ess-news.com/2025/07/04/china-completes-worlds-largest-vanadium-flow-battery-plant/
[12] https://www.energy-storage.news/largest-bess-in-eu-inaugurated-in-bulgaria/.
[13] https://www.pv-magazine.com/2025/07/01/fraunhofer-activates-europes-biggest-vanadium-flow-battery/
[14] https://www.energy-storage.news/construction-approval-for-1-6gwh-flow-battery-in-switzerland-about-time-we-brought-this-scale-to-europe/
[15] https://renewablesnow.com/news/invinity-advances-32-mwh-of-vanadium-flow-battery-projects-in-europe-1279592/
