- Why are battery energy storage systems (BESS) necessary as more renewable energy sources come online?
As the demand for energy continues to rise, the demand for renewable energy capture is also increasing. Americans consumed about 4 trillion kWh in 2023, up almost 4 percent from 2020. Renewable energy sources contributed about 25 percent of electricity generation in the U.S. last year and is expected to double by 2050.
As more renewable energy sources come online, the power grid needs to become more flexible to develop the capacity to maintain the supply-and-demand capacity. This is where long-duration energy storage is key. However, defining long-duration energy storage (LDES) presents several challenges.
- How is LDES currently defined?
One definition of long-duration energy storage is qualitative, referring to energy storage installations that can store renewable energy until needed. The necessary duration varies significantly depending on the use case. It can range from a few hours to multiple days depending on many factors.
The second use of the term is the quantitative definition – the length of time that a system can sustain its maximum discharge rate. The system’s rating outlines kilowatts (kW) and megawatts (MW), along with kilowatt-hours (kWh) and megawatt-hours (MWh). The duration varies at the rate at which it is discharged, so duration is usually stated as a range.
A consistent definition for LDES would create a common language and a shared understanding among stakeholders about the role of long-duration energy storage. The terminology will continue to evolve as technology advances and the need for energy resiliency increases.
- What are the different durations for BESS?
Short-duration energy storage systems can range from minutes up to two hours. These systems commonly act as a bridge providing maximum efficiency and reliable power for various applications, including uninterruptible power supply (UPS), data centers, telecom, utilities and emergency lighting.
Medium-duration applications require energy storage from two to four hours. As power demands on the aging grid increase, medium-duration BESS can help keep critical operations, such as military bases and hospitals, online in the event of a blackout. They can also power microgrids, both for isolated individuals disconnected from the wider grid who operate using renewable sources and for smaller buildings, neighborhoods or villages that still have access to the grid .
Long-duration can range from anywhere to six to 12 hours. Long-duration BESS is a crucial grid support tool, providing rapid response capabilities to mitigate fluctuations, stabilize voltage and enhance overall grid resilience. It also allows for renewable integration, storing excess energy during periods of high renewable generation and releasing it when demand peaks to ensure a balanced and sustainable energy supply.
- What are the different battery chemistries used in BESS? How sustainable are each of these chemistries?
The three battery chemistries most likely to be utilized are lead, lithium, vanadium or other flow battery technologies. Lead is the most commercially mature and has been the primary energy storage solution for over 100 years. Lead batteries can have a useful lifespan of up to 30 years, depending on the design and applications.
Lead batteries are the leader in sustainability, with a nearly 100 percent recycling rate. The lead battery industry has a well-developed circular economy that reuses and recycles the lead, electrolyte and plastic components of used batteries.
With its high energy density, lithium is currently the dominant battery technology for stationary energy storage. A lithium battery’s useful lifespan is about 10 to 15 years.
Currently, lithium is the least sustainable of the three chemistries. Due to the cost and complexity of the process, the recycling rate is less than five percent. While recycling processes are not yet widely available, this rapidly evolving area must improve the capture of critical materials from spent lithium batteries.
Vanadium is the least commercially mature but has the potential to become a leading solution for BESS. Vanadium battery technology has a near-infinite cycle life. This longevity complements the lifespan of wind and solar installations, which makes vanadium well-suited for long-duration energy storage.
The vanadium electrolyte that makes up the bulk of a vanadium BESS is almost infinitely recyclable. The best practices of the lead battery industry in the U.S. can serve as a blueprint for a domestic vanadium supply chain.
While vanadium is the leading flow battery technology, a growing number of other flow battery chemistries, such as zinc-bromine and all-iron redox flow batteries, are in the early stages of commercialization. Researchers are also exploring alternative technologies using common, easily synthesized materials.
- What applications are best suited for each of these battery technologies?
Lead BESS works best for short to medium durations, especially in situations where the depth of discharge is fairly shallow and low up-front cost is a major gating factor. It is possible to increase the duration by adding cells, but weight and space are significant factors to increase operation time.
Lithium is also appropriate for short to medium durations. Additional cells are added to the battery system to increase duration. These additions increase the footprint and the planning required to meet emergency access requirements should there be a safety event.
Vanadium is best suited for long-duration energy storage. It has a larger footprint, but it is easier to expand. To increase duration, more electrolyte is added to the battery system. Footprint and weight need to be considered for vanadium systems, but these systems can be packed closer together thanks to the high level of safety offered by them.
- What is Stryten Energy doing to accelerate the commercialization of BESS?
Stryten Energy is unique among battery manufacturers in that we are not betting on any one battery solution. Instead, we believe the future will involve a variety of technologies, depending on customer needs, and will include advanced lead, lithium and vanadium flow battery solutions.
In June 2024, in collaboration with Groundswell, Stryten Energy installed one of the first community-owned resilience hubs in Georgia. Community members will be able to access reliable power for their essential devices, continue to receive information as emergency situations develop, store medications sensitive to temperature, and safely gather in the aftermath of an emergency or severe weather event. The resilience hub will be powered by a 34.1 kW DC solar installation connected to 320 kWh of battery storage.
Stryten Energy and Snapping Shoals EMC celebrated the installation of the first vanadium redox flow battery (VRFB) system in August 2023. The 20 kW/120 kWh VRFB was specifically designed and sized for an initial evaluation phase to conduct long-duration testing that is six hours or more. The opportunity to test flow battery technology in a utility setting is extremely valuable for future R&D and scaling up to megawatt-hour systems. This project is the first VRFB energy storage system manufactured and installed in Georgia.
Stryten has been awarded MAKE IT Prize funding to build a domestic vanadium electrolyte manufacturing plant to support long-duration energy storage to build a domestic vanadium electrolyte manufacturing plant to support long-duration energy storage. The Securing America’s Vanadium Electrolyte Supply (SAVES) project will deploy Stryten’s proprietary reactor design to provide domestically produced, low-cost electrolyte.
