Grid Scale Storage - Moving away from Lithium

Newsletter - October 2024 Edition

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Grid Scale Storage

Energy storage plays a pivotal role in maintaining grid flexibility, balancing the fluctuations between surplus and deficit power generation. By 2030, India is projected to install approximately 34 gigawatts (GW) or 136 gigawatt-hours (GWh) of battery energy storage systems (BESS), according to the Central Electricity Authority (CEA).

However, the path forward is not without its challenges. Researchers working on battery energy storage technologies face significant hurdles, particularly in sourcing raw materials. Many of these materials, especially rare earth minerals, are scarce within India.

In response to this issue, the Indian government has introduced Viability Gap Funding, aimed at supporting the development of 4,000 megawatt-hours (MWh) of battery storage systems. Announced 2023’s  budget, the allocation of Rs 3,760 crore is intended to accelerate the integration of renewable energy into the national grid.

One approach to incorporating battery storage into the grid is the Behind the Meter Battery Energy Storage System (BESS). This system, primarily used to provide backup power during outages or to store excess energy from rooftop solar photovoltaic (PV) installations, serves both residential and commercial users.

India’s energy future looks ambitious. The International Energy Agency’s India Energy Outlook 2021 estimates that by 2040, the country could install 140 to 200 GW of battery energy storage capacity, potentially the largest such capacity globally.

Trends supporting the momentum

Several ongoing trends are set to bolster this momentum. The rapid deployment of renewable energy, a shift toward decentralized power systems, the growth of hybrid energy solutions, and the rising demand for grid stability, energy access, and energy security are all catalysts for increased energy storage deployment.

In the coming years, as investment rises, focus will expand beyond lithium to include other emerging technologies such as redox flow batteries, supercapacitors, and hydrogen energy storage systems.

India’s solar capacity is growing at a tremendous rate, contributing to 77% of total capacity additions in 2022-23. This underscores the critical role solar energy plays in the country’s power mix. However, with solar power’s intermittent nature, balancing resources will become increasingly necessary to maintain grid stability.

To address this, policymakers have been implementing strategies to ensure that energy storage systems will support this transition. According to the CEA’s ‘Optimal Generation Mix 2030’ report, India will require 60.63 GW of energy storage capacity by 2030. This figure includes 18.9 GW of pumped hydro storage (PHS) and 41.65 GW of BESS, amounting to 336.4 GWh in total.

As of March 2023, India’s installed PHS capacity stands at 4.7 GW, with an additional 2.7 GW under development. To meet future needs, an additional 11.4 GW of PHS will be required by 2030.

Looking further ahead, the National Renewable Energy Laboratory (NREL) anticipates a substantial boost to India’s BESS capacity by 2047, projecting an increase to 237 GW, accounting for 13% of the country’s total installed capacity.

This significant expansion of BESS post-2030 will be driven by falling capital costs and the continued rise of renewable energy sources. These projections underscore the importance of preparing India’s grid for the seamless integration of a large share of renewables into its energy mix.

Looking into non lithium potential technologies

As power utilities and industrial companies increasingly turn to renewable energy, the demand for grid-scale battery storage is rapidly accelerating. Emerging alternatives to lithium-ion batteries offer potential benefits in terms of environmental sustainability, labor practices, and safety. These innovative battery chemistries are opening doors in sectors like the electric grid and industrial applications where lithium-ion technology falls short.

Moving to non-lithium-based grid storage offers several advantages:

1.⁠ ⁠Resource Availability: Non-lithium technologies, such as sodium-ion or flow batteries, often utilize more abundant and less geographically concentrated materials, reducing supply chain risks.

2.⁠ ⁠Cost-Effectiveness: As non-lithium technologies mature, they can potentially offer lower costs due to cheaper raw materials and simpler manufacturing processes.

3.⁠ ⁠Environmental Impact: Non-lithium batteries typically have a lower environmental footprint, reducing the ecological damage associated with mining lithium and other critical minerals.

4.⁠ ⁠Safety and Stability: Some alternatives, like flow batteries, provide enhanced safety profiles and thermal stability, minimizing risks of fires or explosions.

5.⁠ ⁠Scalability and Longevity: Many non-lithium technologies can be designed for longer cycle life and greater scalability, making them suitable for larger energy storage applications.

6.⁠ ⁠Diverse Applications: Non-lithium systems can be tailored for various use cases, from grid stabilization to renewable energy integration, enhancing overall system flexibility.

Investing in these alternatives can create a more resilient and sustainable energy future.

Vanadium redox flow batteries

Flow batteries operate using liquid or gaseous electrolytes that pass through cells from storage tanks. The chemical reaction that converts energy into electrical and stored chemical energy occurs within electrochemical cells. According to the International Flow Battery Forum, these batteries are built from low-cost materials like thermoplastics and carbon, many of which can be recycled. The electrolyte itself can be recovered and reused, leading to a lower cost of ownership.

VRFBs store energy in liquid electrolytes containing vanadium ions of different oxidation states. Unlike traditional batteries, where energy is stored in solid electrodes, VRFBs use a liquid electrolyte that flows through the system. The energy is stored and released through the reversible oxidation and reduction reactions of vanadium ions in different states (V²⁺/V³⁺ in the negative half-cell and V⁵⁺/V⁴⁺ in the positive half-cell).

Positive half-reaction (in the positive electrolyte): 

Negative half-reaction (in the negative electrolyte): 

Operating Characterstics

• Power and Energy Decoupling: In VRFBs, the power is determined by the size of the cell stack (number of cells) while the energy capacity is determined by the size of the electrolyte tanks. This allows for easy scaling by increasing the size of tanks for higher energy storage without changing the power characteristics.

•  Efficiency: VRFBs typically have a round-trip efficiency between 65% and 85%. The efficiency depends on the system design, operational conditions, and the membrane properties used.

•  Lifespan: VRFBs can last over 20 years and have an almost unlimited cycle life with proper maintenance. They can endure thousands of full charge and discharge cycles without significant degradation since the electrochemical reactions do not involve solid-state phase changes, which typically wear out conventional batteries.

• Response Time: VRFBs can respond quickly to changes in demand, providing fast balancing and load management for the grid. Their response time is typically in the range of milliseconds to seconds, depending on system configuration.

Economic Viability

1.    Capital Costs – 

The cost of VRFB systems can range between $400 to $600 per kilowatt-hour (kWh), compared to around $200–$400/kWh for lithium-ion batteries. However, this gap narrows when considering the total cost of ownership over time, given VRFB’s longer life and lack of degradation.

2.    Operational Costs – 

Maintenance: VRFB systems are relatively low-maintenance. Routine inspection of pumps, monitoring electrolyte balance, and periodic cleaning are the main tasks. Since there is no degradation in the electrolytes, they do not require replacement, further reducing long-term operational costs.

Energy Costs: While VRFBs are less efficient (65%–85%) than lithium-ion batteries (85%–95%), they do not require replacement over time, which helps maintain their cost-effectiveness for long-term grid applications.

Recycling and End of Life: VRFBs have significant recycling advantages. The vanadium electrolyte can be fully recovered and reused at the end of the battery’s life, unlike lithium-ion batteries, where recycling is more complex and expensive. The rest of the components (tanks, electrodes, membranes) are made from materials that can be relatively easily repurposed or recycled.

3.    Levelized Cost of Storage (LCOS)

While VRFBs have higher upfront costs, their Levelized Cost of Storage (LCOS), which accounts for lifetime costs including capital, operation, and maintenance, is competitive for long-duration storage applications. For applications requiring frequent, deep cycling over many years, the LCOS of VRFBs becomes comparable or even lower than lithium-ion, thanks to their longevity and minimal degradation.

Estimates for the LCOS of VRFBs range from $0.10 to $0.15 per kWh over the system’s life, depending on the specific application and operating conditions. By comparison, the LCOS of lithium-ion batteries typically falls between $0.05 to $0.20 per kWh but increases as the number of charge/discharge cycles increases and degradation becomes a factor.

Market Potential (Key markets)

Utility-Scale Energy Storage: VRFBs are well-suited for utility companies looking for long-duration storage solutions. They can store excess renewable energy during periods of low demand and release it during peak hours.

Off-Grid and Microgrid Applications: VRFBs are attractive in remote or island locations where the grid is weak or nonexistent. Their ability to provide consistent, reliable storage without degradation over time makes them ideal for off-grid solar or wind systems.

Renewable Energy Integration: With their ability to store energy for long periods and discharge it steadily, VRFBs are ideal for smoothing out the fluctuations of renewable energy sources like wind and solar, helping to integrate these intermittent sources into the grid.

Vanadium Redox Flow Batteries represent a compelling solution for long-duration, large-scale energy storage. Their scalability, long life, and safety make them a strong candidate for applications like grid balancing, renewable integration, and off-grid storage. Despite higher upfront costs, the long lifespan, minimal degradation, and lower total cost of ownership make VRFBs an economically attractive option for utilities and renewable

Zinc Bromine Flow Batteries

Zinc-Bromine Flow Batteries (ZBFBs) are another promising energy storage technology designed for grid-scale and large-scale applications. These batteries, while less established than vanadium redox flow batteries (VRFBs), have distinct characteristics that make them a viable alternative for specific use cases. ZBFBs offer the potential for relatively low costs, decent energy density, and inherent safety advantages, positioning them well for long-duration energy storage solutions.

Redflow has been manufacturing zinc-bromine flow batteries since 2010. Unlike lithium-ion batteries, zinc-bromine batteries don’t rely on critical minerals, many of which are sourced from regions with labor and geopolitical risks. Instead, these batteries use affordable and readily available materials.

Charging and discharging take place within the stack, where zinc is plated onto a carbon surface during charging and dissolves back into the electrolyte during discharging. The zinc-bromine electrolyte, long used in the oil and gas industry, poses no fire risk, and all components of the battery are recyclable.

Working Principle

Operating Characterstics

Power and Energy Decoupling: Like other flow batteries, power (kW) and energy (kWh) are decoupled, meaning the system’s power output is determined by the cell stack, while the energy capacity depends on the volume of the electrolyte tanks. This makes it easy to scale energy capacity independently of the power rating.

Energy Density: ZBFBs typically have energy densities between 30–70 Wh/kg, which is lower than lithium-ion batteries (100–250 Wh/kg) but comparable to other flow battery technologies. This lower energy density limits ZBFBs’ use in space-constrained applications but makes them well-suited for stationary grid storage.

Efficiency: The round-trip efficiency of zinc-bromine flow batteries generally ranges between 60% and 75%. This is lower than lithium-ion batteries (85%-95%) but typical for flow batteries.

Lifespan and Cycle Life: ZBFBs have a cycle life of approximately 2,000–5,000 cycles, depending on operating conditions. This lifespan is significantly shorter than VRFBs but still longer than many conventional battery chemistries, particularly when deep discharge cycles are required.

Economic Viability

1.    Capital Costs – 

Estimates place ZBFB costs in the range of $300 to $500 per kWh, which is lower than VRFBs but higher than lithium-ion batteries. However, the lack of degradation and long-term stability can make them more cost-competitive in specific applications that require frequent deep cycling or long-duration storage.

2.    Operational Costs – 

Maintenance: ZBFBs require regular maintenance due to the challenges associated with bromine management and zinc dendrite formation. However, these maintenance needs are offset by the battery’s long cycle life and deep discharge capabilities.

Energy Costs: With a lower round-trip efficiency (60-75%) than lithium-ion batteries, more energy is lost during each charge/discharge cycle, which can increase operational costs, particularly in applications where efficiency is paramount.

End of Life: Despite lower initial capital costs, ZBFBs have a shorter lifespan (about 2,000-5,000 cycles) compared to VRFBs, which means that they may need to be replaced more frequently. However, their ability to deeply discharge without degradation can make them more cost-effective for applications where full cycling is common.

3.    Levelized Cost of Storage (LCOS)

For applications requiring long-duration storage and deep discharge, ZBFBs offer a competitive Levelized Cost of Storage (LCOS). Estimates place their LCOS between $0.10 and $0.20 per kWh, depending on specific project configurations and operating conditions. This makes them competitive with other flow battery technologies and lithium-ion batteries when long-duration storage and frequent cycling are needed.

Key Markets

Utility-Scale Storage: ZBFBs are well-suited for large-scale utility applications that require frequent deep cycling and long-duration storage. 

Microgrids and Off-Grid Applications: For off-grid or microgrid installations that rely heavily on renewable energy, ZBFBs provide a cost-effective and reliable energy storage solution with deep discharge capabilities and long-term stability.

Renewable Energy Integration: ZBFBs are highly effective at smoothing out the intermittent supply of renewable energy sources, enabling better integration of renewables into the grid. They can store excess renewable energy (such as wind or solar) during low demand periods and discharge it during peak demand hours.

Sodium Sulfur (NaS) Batteries

Sodium Sulfur (NAS) batteries are high-temperature molten salt batteries used primarily for grid-scale and industrial energy storage. They have been in commercial use for decades and offer several advantages for large-scale energy storage, such as high energy density, long-duration storage, and excellent scalability. Originally developed by NGK Insulators, Ltd. in Japan, NAS batteries have demonstrated reliable performance in numerous projects worldwide, especially in load leveling, renewable energy integration, and peak shaving applications.

This battery uses sulfur as the positive electrode and sodium as the negative electrode, with a beta-alumina ceramic tube serving as the electrolyte. The battery operates at high temperatures (around 300°C) and utilizes low-cost, widely available materials such as sodium, sulfur, oxygen, steel, and silica.

The NAS Battery has undergone extensive safety testing, including short-circuit, fire, and submersion tests, all of which confirmed its resilience without leakage or combustion. The batteries are packaged in 20-foot shipping containers, with each container holding six modules that together provide 1.45 megawatt-hours of storage.

The battery withstands heat, cold, and high-salinity environments, and NGK Insulators partners with recycling firms in Japan to handle end-of-life batteries, with efforts to expand this globally as more installations reach their lifecycle’s end.

Working Principle

NAS batteries operate at high temperatures, typically between 300°C and 350°C, and rely on a chemical reaction between sodium (Na) and sulfur (S). The battery consists of a molten sodium anode and a molten sulfur cathode, separated by a solid ceramic electrolyte made of beta-alumina. The electrolyte allows only sodium ions to pass through, preventing the direct mixing of sodium and sulfur, which would otherwise cause a highly exothermic reaction.

Charge Reaction:

Sodium at the anode releases electrons (oxidation), and sulfur at the cathode accepts electrons (reduction), forming sodium polysulfide (Na₂S₄).

Discharge Reaction:

Sodium ions are extracted from the polysulfide and returned to the anode while sulfur reforms at the cathode.

Operating Characterstics

High Energy Density: NAS batteries have an energy density of 150-250 Wh/kg, which is higher than many other stationary storage technologies, though lower than lithium-ion batteries.

Long Duration Storage: NAS batteries are capable of discharging continuously for 6–8 hours or more, making them suitable for daily cycling and long-duration applications.

Efficiency: The round-trip efficiency of NAS batteries ranges between 75% and 90%, which is comparable to other flow and high-temperature batteries but lower than lithium-ion batteries.

Lifespan and Cycle Life: NAS batteries typically have a 15-year lifespan and can endure 4,500 to 5,000 cycles, with minimal degradation even at deep discharge levels.

Temperature Requirement: A key characteristic of NAS batteries is their need to operate at high temperatures (300–350°C). While this can be a limitation in some environments, the thermal insulation of NAS battery systems minimizes energy loss to the environment.

Economic Viability

1.    Capital Costs – 

NAS battery systems are typically priced at around $300–$400 per kWh, which is higher than lithium-ion batteries (currently $200–$400 per kWh). However, NAS batteries offer greater cost-effectiveness for applications requiring long-duration storage due to their higher energy density and deep discharge capability.

2.    Operational Costs – 

Maintenance: NAS batteries require regular maintenance, primarily related to maintaining the high operating temperature. Insulation systems and heating mechanisms need to be monitored and replaced over time, which contributes to ongoing operational costs.

Energy Costs: : With a round-trip efficiency of 75-90%, NAS batteries experience higher energy losses than lithium-ion systems, which can impact the economics of energy-intensive applications.

Thermal Management: The need to maintain high temperatures even during standby leads to constant thermal losses, slightly increasing the operational expenses relative to other battery systems that operate at ambient temperatures.

3.    Levelized Cost of Storage (LCOS)

For long-duration storage applications, the Levelized Cost of Storage (LCOS) for NAS batteries is competitive, particularly when deep discharge cycles are frequently required. Estimates place the LCOS of NAS systems between $0.15 and $0.25 per kWh, making them a competitive option for grid-scale energy storage, renewable energy integration, and energy arbitrage projects.

Key Markets

Renewable Energy Integration: NAS batteries are particularly well-suited for balancing intermittent renewable energy sources such as solar and wind. Their ability to store energy for several hours makes them ideal for applications where energy must be stored during low-demand periods and discharged during high-demand periods.

Load Leveling and Peak Shaving: NAS batteries are commonly used by utilities for load leveling and peak shaving. They allow utilities to store excess energy during off-peak periods and discharge it during peak demand, improving grid efficiency and reducing reliance on expensive peaking power plants.

Remote and Island Communities: Due to their long duration and deep discharge capabilities, NAS batteries are ideal for off-grid and island applications where reliable, long-term energy storage is critical. They can store renewable energy generated in remote locations and provide stable power supply during periods of low generation.