Do we really need the grid-scale energy storage systems?
The world is gradually shifting towards renewable energy sources, and there is a growing need for grid-scale energy storage systems to help integrate these sources into the electricity grid. The government of India has recently come up with multiple tenders on grid-scale energy storage from SECI, indicating the country’s focus on this issue.
Battery energy storage systems (BESS) have gained a lot of attention in recent years as a potential solution to the grid variability problem caused by renewables. However, there is an ongoing debate over whether BESS is the most economical way to address this issue. Studies and real-world experience have shown that interconnected power systems can safely and reliably integrate high levels of renewable energy from variable renewable energy (VRE) sources without new energy storage resources. In fact, battery storage is one of several technology options that can enhance power system flexibility and enable high levels of renewable energy integration.
The appropriate amount of grid-scale battery storage depends on system-specific characteristics, including the current and planned mix of generation technologies, flexibility in existing generation sources, interconnections with neighboring power systems, and the hourly, daily, and seasonal profile of electricity demand and VRE. Therefore, there is no rule-of-thumb for how much battery storage is needed to integrate high levels of renewable energy.
In many systems, battery storage may not be the most economic resource to help integrate renewable energy, and other sources of system flexibility can be explored. For example, China, Europe, Italy, and the USA are using alternative methods of grid-level energy storage such as potential energy-based systems, compressed air systems, and pumped hydro systems. These systems have been in use for decades and have proven to be effective in balancing the fluctuations in electricity generation.
Pumped-hydro storage works by pumping water uphill during times of low demand and releasing it to generate electricity during times of high demand. Compressed air energy storage works by compressing air and storing it in underground caverns or tanks. When electricity is needed, the compressed air is released and used to power a turbine.
A mix of multiple technologies can also address the variability of renewable energy sources in the electricity grid system. For example, a combination of wind, solar, and hydroelectric power can help to balance out the fluctuations in electricity generation. Additionally, demand-side management techniques, such as time-of-use pricing and energy efficiency programs, can help to reduce overall electricity demand and smooth out peaks and valleys in demand.
In conclusion, while battery energy storage systems have received a lot of attention as a potential solution to grid-scale energy storage, they are not always the most economic option. A range of other technologies and approaches can be used to enhance power system flexibility and enable high levels of renewable energy integration. The appropriate mix of technologies will depend on the specific characteristics of each power system. The recent tenders from the Government of India indicate the country’s focus on finding the best solution to this issue.
Summary of grid-scale energy storage technologies and their descriptions in a table format:
| Technology | Description |
|---|---|
| Battery Storage | Stores energy in chemical form and releases it as electricity when needed. Can be used for short-term or long-term storage. Popular battery chemistries include lithium-ion, flow batteries, and sodium-sulfur batteries. |
| Pumped Hydro Storage | Stores energy by pumping water uphill during times of low demand, and releasing it to generate electricity during times of high demand. One of the oldest and most commonly used forms of energy storage. |
| Compressed Air Storage | Stores energy by compressing air and storing it in underground caverns or tanks. When electricity is needed, the compressed air is released and used to power a turbine. |
| Flywheel Storage | Stores energy by spinning a rotor at high speeds, which maintains the energy as kinetic energy. When electricity is needed, the rotor is slowed down, and the kinetic energy is converted to electricity. Used for short-term storage. |
| Thermal Storage | Stores energy by heating or cooling a material, such as water or molten salt, which can be used to generate electricity when needed. Can be used for short-term or long-term storage, and is commonly used in conjunction with solar power. |
| Hydrogen Storage | Stores energy by converting electricity to hydrogen through electrolysis. The hydrogen can then be stored and used to generate electricity through fuel cells or combustion. Can be used for long-term storage, but is still a developing technology. |
| Supercapacitors | Stores energy in an electric field, rather than in chemical form like batteries. Can be charged and discharged much faster than batteries, but has lower energy density. Used for short-term storage and to provide bursts of power. |
| Kinetic Storage | Stores energy by lifting heavy objects, such as large blocks or weights, and releasing them to generate electricity. Can be used for short-term storage, and is still a developing technology. |