Battery energy storage systems (BESS) are gaining popularity with the demand rising for clean energy. Besides, they ensure a smooth supply of energy by storing it for use later when renewable sources fail due to fluctuating weather conditions.
By Potshangbam July
The energy storage segment in India is expected to become one of the fastest growing markets in view of the demand-supply gap, as well as the increasing requirement for 24×7 quality power and green electricity. There are many energy storage technologies available, but batteries have emerged as a key option, with the potential to transform the electricity system. They can play a crucial role in bringing about zero carbon emissions around the world.
Batteries enable effective integration of renewable energy, can store more energy and then deliver it when needed within milliseconds. They provide a lot more flexibility in power management, stabilise the electrical grid, handle peak load efficiently, and add resilience during extreme weather events. In the fifth edition of its India Stationary Energy Storage Market report, the India Energy Storage Alliance (IESA) predicts that the domestic market for energy storage will grow at a CAGR of 6.1 per cent up to 2026. As per the report, in 2018, the Indian energy storage market was worth US$ 2.8 billion.
How BESS scores over other storage technologies
There are many storage technologies available, such as battery energy storage systems (BESS), pumped hydro storage (PHS), compressed air energy storage (CAES), molten salt (thermal), hydrogen, flywheel, etc. BESS is by far the most popular among the many options, as it has a small footprint and can be installed anywhere with no restrictions on geographical locations. BESS uses lithium-ion technology, which is used in more than 90 per cent of the grid battery storage market globally. There are many other battery options, but lithium-ion batteries have emerged as the most widely deployed because of their higher energy density. With new technological advances, graphite is being replaced with silicon to increase the battery’s power capacity, which makes lithium-ion batteries even more effective for long-term storage.
| Table 1: Characteristics of energy storage technologies |
| Technology | Energy density (Wh/I) | Power density (W/I) | Lifetime or cycles | Efficiency (per cent) |
| Pumped hydro storage | 0.2-2 | 0.1-0.2 | 30 – 60 years | 70-85 |
| Compressed air energy storage | 2-6 | 0.2-0.6 | 20 – 40 years | 40-75 |
| Li-ion batteries | 200-400 | 1300-10000 | 1,000 – 10,000 cycles | 85-98 |
| Molten salt | 70-210 | N/S | 30 years | 80-90 |
| Hydrogen | 600 | 0.2-20 | 5 – 30 years | 25-45 |
| Flywheels | 20-80 | 5000 | 20,000 – 100,000 cycles | 70-95 |
Though lead-acid batteries were one of the first battery technologies used in energy storage, their efficiency is not adequate for grid storage. When compared with lithium-ion technology, they have low-energy density and a short life cycle. Flow batteries are an alternative to lithium-ion batteries but they are not as popular. These batteries have low energy densities and a long lifetime, which makes them good for supplying continuous power.
Pumped hydro storage, also known as ‘pumped hydroelectric storage’, is another kind of hydro power that has been in the market for many years. This storage has various advantages, such as achieving 80 per cent energy efficiency through a full cycle, which typically provides ten hours of power against six hours for lithium-ion batteries. Despite these advantages, it can only be used in limited locations, because factors such as altitude and water availability need to be considered, apart from transmission constraints. Further, the high initial capital costs, the complex procedures for getting permits and the lengthy construction process, put off investors.
Compressed air energy storage has lower efficiency and is less environment-friendly than other storage methods. In such storage systems, air is stored in an underground tank, when the energy is abundantly available during non-peak hours. The stored air is released back to the plant when the energy is required. The heating involved in the process uses natural gas, which emits harmful carbon. Despite being capable of storing huge amounts of energy, compressed air energy storage is less preferred in comparison with BESS.
Battery types used in BESS
There are various types of batteries for BESS with slightly different characteristics and functioning methods. They all store and then release energy but for varying durations, ranging from a few minutes to several hours.
Lithium-ion batteries: These batteries have many advantages—they can be charged/discharged many times in their lifetime and have good energy storage for their size. They are particularly suited for applications like consumer electronics and electric vehicles. According to reports, as on 2017, the cumulative global manufacturing capacity of lithium-ion batteries had crossed 100GWh a year and going forward, is expected to outstrip the lead acid battery market soon. In a recent report by Allied Market Research, the global lithium-ion battery market contributed $36.7 billion in 2019, and is estimated to reach $129.3 billion by 2027, growing at a CAGR of 18 per cent from 2020 to 2027.
| What you need to know about BESS: |
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Lead-acid batteries: These are the traditional rechargeable batteries and the most widely used battery technology worldwide. They also have a longer life span. In addition, they are not expensive in comparison with the new battery types. They have been in use for various purposes—backup power supplies, protection and control systems, grid energy storage, etc.
Advanced lead-acid batteries: These are of two types —the lead carbon variety and the bipolar lead acid type. Lead carbon batteries use carbon additives to improve the energy density, cycle life and have better charging-discharging properties than lead acid variants. Bipolar lead-acid batteries have bipolar plates and eliminate the high current density seen around the terminals in the conventional design. In the bipolar design, each point on an electrode is in contact with the current collector. These batteries have higher specific energy and energy density, have approximately a 40 per cent smaller footprint compared to monopolar type, and are made up of recyclable materials.
Sodium sulfur: These batteries are mainly used for large scale non-mobile applications because of their operating temperature and the highly corrosive nature of sodium polysulphides. Their applications include storing energy from renewable sources such as solar and wind. Besides, they are effective in stabilising wind farms and solar generation plants, peak shaving and time shifting.
Zinc-based batteries: They are known for their light weight, low cost and low toxicity. The potential applications include large-scale energy storage, with good levels of safety and environment-friendliness.
Flow batteries: These batteries work in a different way to conventional batteries. They store energy in the electrolyte (the fluid) instead of the electrodes. The system is complex, and these batteries have low energy and power densities. The other benefits of the batteries include easy scalability, no harmful effects of a deep discharge, very low self-discharge, long cycle life, etc. They are generally used for large-scale storage.
Challenges
Despite the growing popularity of battery energy storage systems, there are a few challenges associated with them. The use of batteries is not new to energy storage systems; what has changed are the new sizes, the chemistries used, as well as the energy and power density of the systems, which can lead to massive fire risks. Lithium-ion batteries are the most sought after technology when it comes to battery energy storage systems. The design complexity and the increased power density of lithium-ion come with arc-flash hazards. Due to the absence of reliable and harmonised standards with regard to short-circuit current calculations and safety, it is difficult to arrive at accurate calculations of arcing currents in energy storage systems.
Apart from the issue of technical standards, there are no uniform processes and policies governing the storage industry. This further creates confusion for investors as each project presents unique possibilities and challenges. The uncertain regulatory and market guidelines also discourage investors, and this has hampered the adoption of the technology
Market scenario
The BESS market has grown considerably in recent years due to increasing demand for renewable energy sources. Power generation from renewable energy plants is not reliable and tends to fluctuate if the weather conditions are not favourable. Therefore, battery energy storage systems are used to store the energy generated from renewable sources. The storage system ensures a smooth flow of electricity to the consumers. The increasing demand for grid-connected solutions is also one of the major factors boosting the BESS market. These systems provide grid stability and enhance the quality of power. With the gradual advancement in energy storage technology, the efficiency of battery energy storage systems has also increased.
Another major factor that drives the market is the high demand for lithium-ion batteries in the renewable energy industry. Lithium-ion batteries are preferred over other variants owing to their high energy and power densities, a long life span of five to 15 years, efficiency, light weight and minimal maintenance requirements. On a positive note, the falling price of lithium-ion batteries is expected to change the market scenario leading to higher demand for energy storage systems in the coming years. Some of the big global players in the BESS market are LG Chem, ABB Ltd, Exide Industries Ltd, AES Energy Storage, Tata Power, LLC, Schneider Electric, Beacon Power, BYD Company Limited, Convergent Energy and Power Inc., Greensmith Energy Management Systems, Eos Energy Storage, and Seeo Inc.
