With the increasingly severe global climate change problem and the gradual reduction of fossil fuel resources, new energy technologies have received more and more attention and investment. Due to the influence of natural conditions such as wind speed and solar radiation on the supply of new energy, its power generation has strong uncertainty and volatility. This requires the power system to have strong flexibility in order to efficiently utilize these renewable energy sources while ensuring the stable operation of the power grid. Energy storage system technology has therefore become a key link in solving this problem.
1. The role of energy storage system technology in large-scale grid connection
1.1 Ensuring stable operation of the power grid
With the increasing proportion of renewable energy, the power grid faces many challenges, including power fluctuations, frequency instability, and supply-demand imbalance. Energy storage systems can provide the necessary flexibility for the power grid to adapt to these new challenges. Energy storage system technology can be used for frequency regulation. The energy storage system can monitor the frequency of the power grid in real time and maintain the grid frequency within a stable range by quickly storing or releasing electricity. In the case of supply-demand imbalance, energy storage systems can quickly release stored electricity to meet short-term high demand, or store excess electricity when demand is low. This rapid response capability not only improves the operational stability of the power grid, but also reduces reliance on traditional thermal power plants. Energy storage systems can also serve as part of the emergency response mechanism of the power grid. In extreme weather conditions or other emergency situations, energy storage systems can provide critical backup power to ensure the continuous operation of infrastructure such as hospitals and emergency services.
1.2 Optimizing Power System Dispatch
The traditional power system mainly relies on basic load power plants and peak power plants to allocate power resources, but this model faces challenges when facing a large number of highly volatile and non dispatchable new energy access. Energy storage system technology, especially energy storage devices with fast response capabilities, can play an important role in this regard. The energy storage system can monitor and analyze the status of the power grid in real-time, in order to quickly make scheduling decisions in the event of sudden changes in power demand or unstable new energy output. This greatly improves the scheduling flexibility and response speed of the power grid. Energy storage devices can operate as virtual power plants in the power grid, releasing energy during peak demand periods and storing energy during low demand periods. This ability enables power grid operators to more effectively arrange electricity resources, reduce peak and valley electricity price differences, and thus improve the economic benefits of the entire system. Through advanced data analysis and control algorithms, energy storage systems can be deeply integrated with renewable energy generation equipment, demand side management systems, and other power grid equipment (such as substations, transmission lines, etc.) to achieve more complex and intelligent power system scheduling.
1.3 Improving Energy Efficiency
Energy storage system technology can greatly improve energy utilization efficiency, especially in highly complex and variable modern power systems. By storing electricity locally or globally, energy waste caused by supply-demand mismatch can be minimized to the greatest extent possible. This means that when renewable energy output exceeds demand, excess electricity no longer needs to be “abandoned” or “abandoned”, but can be stored for future use. In addition to facilitating more effective supply-demand matching, energy storage systems can also optimize the operation of motors and other industrial equipment by providing more operational flexibility. For example, without affecting production efficiency, factories can store electricity when electricity prices are low and use it when electricity prices are high or demand increases dramatically. Energy storage system technology also makes demand side management more efficient, such as storing electricity during low electricity periods through smart home systems and then using it during high electricity or high demand periods. This can not only reduce electricity bills, but also reduce the load on the power grid during high demand periods, thereby improving overall energy utilization efficiency. Energy storage systems can be combined with other energy management systems (EMS) or building automation systems (BAS) to further improve the comprehensive utilization efficiency of electricity and thermal energy.
2. Types of energy storage system technologies in large-scale grid connection
2.1 Chemical energy storage system
In the large-scale grid connection of new energy, various energy storage system technologies are applied to solve problems such as supply-demand imbalance, improve grid stability and efficiency. Among them, chemical energy storage system technologies such as batteries and fuel cells play a crucial role. The battery energy storage system stores and releases electrical energy through electrochemical reactions. In a typical lithium-ion battery, there are two electrodes: the positive electrode is usually composed of lithium compounds, and the negative electrode is usually composed of carbon (such as graphite). When the battery is charged, lithium ions move from the positive electrode to the negative electrode and are stored at the negative electrode. When the battery is discharged, lithium ions move back from the negative electrode to the positive electrode, while releasing electrical energy. This process is reversible, so the battery can be charged and discharged multiple times. Lithium ion batteries are particularly suitable for power grid energy storage systems due to their high energy density, long lifespan, and fast response characteristics. A fuel cell is an electrochemical device that directly converts the oxygen in fuel (usually hydrogen) and oxygen (or air) into electricity and water through chemical reactions. During this process, hydrogen gas is oxidized to protons (H+) and electrons (e -) at the anode. Protons migrate to the cathode through electrolytes (usually solid oxides or proton exchange membranes), while electrons move through external circuits, generating current. At the cathode, oxygen, water, and protons combine to produce more water. Both batteries and fuel cells convert energy through electrochemical reactions, but they differ in application, scale, and efficiency. Batteries are more suitable for fast response and small to medium-sized energy storage system requirements, while fuel cells are more commonly used for large-scale energy storage systems and long-term energy output.
2.2 Mechanical energy storage system
Mechanical energy storage system is a method of converting electrical energy into mechanical energy for storage. This conversion is usually reversible, meaning that mechanical energy can be converted back into electrical energy for future use. Pumped storage and flywheel energy storage systems are the two most commonly used and mature technologies in mechanical energy storage systems. Pumped storage is a large-scale energy storage system mainly used in power grid systems. This method involves two reservoirs: one located at a higher location and the other at a lower location. When there is low electricity demand or sufficient electricity supply (such as high wind or solar power output), excess electricity is used to pump water from low to high reservoirs. When the demand for electricity increases, the stored water flows back to the lower reservoir through gravity and drives the turbine to generate electricity during this process. Due to its large scale, pumped storage energy is mainly used for large-scale energy storage systems at the grid level. The flywheel energy storage system utilizes a high-speed rotating flywheel to store energy. Simply put, a flywheel is a heavy wheel, typically made of high-strength materials such as carbon fiber composites or titanium alloys, suspended or suspended in magnetic or vacuum environments to reduce friction. When there is excess
When using electricity, this energy is used to drive the flywheel to rotate, thereby storing it as mechanical energy. When electrical energy is needed, the rotational energy of the flywheel is converted back into electrical energy through the motor (which is then used as a generator). Due to their extremely fast charging and discharging rates and high cycle life, flywheel systems are commonly used in applications that require rapid response. Pumped storage and flywheel energy storage systems both convert electrical energy into other forms of mechanical energy for storage, but their application scenarios and scales vary greatly. Pumped storage is more suitable for large-scale, long-term energy storage systems, while flywheel energy storage systems are more suitable for short-term, high-frequency power regulation needs.
2.3 Thermal energy storage system
Thermal energy storage system is a method of energy storage and release that utilizes heat. Compared to other energy storage system technologies, thermal energy storage systems are typically used to capture and store waste heat or other low-grade heat sources. Molten salt energy storage system and phase change energy storage system are two very promising technologies in this field. Molten salt energy storage system technology is commonly used in large-scale cogeneration systems or solar thermal power plants. This technology uses specific types of salts (such as nitrates or chlorides) as thermal storage media. When collecting heat, these salts are heated to a molten state and stored in insulated containers. When energy needs to be released, the molten salt flows through a heat exchanger, transferring heat to water or other fluids, which in turn generates steam to drive a turbine for power generation. Due to its high specific heat capacity and thermal conductivity, molten salts can store a large amount of thermal energy in a relatively stable and efficient process. Phase change energy storage systems utilize substances to absorb or release latent heat during the conversion between different phases (usually solid and liquid). For example, certain specific types of salts or organic compounds will melt or solidify at a certain temperature. During this process, they can absorb or release a large amount of heat. These substances are encapsulated in containers or microcapsules and can be used as heat exchange media to store energy from solar energy, industrial waste heat, or other heat sources. Compared to molten salt energy storage systems, phase change energy storage systems are usually suitable for small to medium-sized applications and can respond more quickly to load changes. Molten salt energy storage systems and phase-change energy storage systems each have their own advantages and disadvantages, but their commonality lies in their ability to effectively store and utilize thermal energy, which contributes to the stable operation of the power grid and the high proportion of renewable energy integration.
3. Specific application of energy storage system technology in large-scale grid connection
3.1 Frequency and voltage regulation
Frequency regulation and voltage stability are two crucial aspects in the operation of power systems. The frequency of the power grid usually needs to be maintained at a relatively fixed value (such as 50Hz or 60Hz) to ensure the stable operation of the power system. Any deviation from this benchmark value may lead to instability of the power system and even trigger large-scale power outages. For large-scale grid integration of new energy, the output of renewable energy sources such as wind and solar energy is often unstable and unpredictable, which may have an impact on grid frequency and voltage. To address this issue, various types of energy storage system technologies are used to achieve frequency regulation and voltage stability. The application of flywheel energy storage system in frequency regulation: Due to its fast charging and discharging characteristics, flywheel energy storage system is very suitable for short-term regulation of grid frequency. When the grid frequency drops (usually due to load increase), the flywheel system can release stored mechanical energy in a few seconds, convert it into electrical energy to supply the grid, and quickly restore the grid frequency. The role of lithium-ion batteries: Due to their high energy density and fast response ability, lithium-ion batteries can also be used for frequency regulation. Through real-time communication with the power grid management system, batteries can quickly charge and discharge when needed to maintain grid frequency. The application of pumped storage in voltage stability: Pumped storage power stations are usually connected to the high-voltage transmission system of the power grid. In the event of voltage drop, pumped storage power stations can quickly switch to power generation mode, using water stored in high-altitude reservoirs to generate electricity through turbines and output high voltage to stabilize the power grid. The combination of molten salt energy storage system and solar power plant: In solar power plants, molten salt energy storage system can be used to provide voltage support in case of insufficient sunlight. The stored molten salt heat energy can be quickly converted into electrical energy, and the power grid voltage can be adjusted in real time through the power plant’s transformers and phase regulators.
3.2 Peak valley balance and energy scheduling
Peak valley balance involves how to maintain a balance between electricity supply and demand during the highest (peak) and lowest (valley) periods of demand. Energy scheduling is the process of achieving this balance through targeted allocation of different types of energy resources. After the integration of new energy sources into the grid, especially wind and solar energy, which have high volatility, the issues of peak valley balance and energy scheduling are particularly prominent. Energy storage system technology plays a crucial role here. Firstly, the collaborative operation of solar power generation and energy storage systems. Daytime energy storage: In the case of sufficient sunlight during the day, solar power generation systems will generate a large amount of electricity. In addition to meeting real-time demand, excess electricity can be stored in lithium-ion batteries or molten salt energy storage systems. Peak release: When electricity demand reaches its peak, especially after sunset, energy storage systems can quickly release stored energy to meet peak electricity demand. Secondly, the coordinated operation of wind power generation and energy storage systems. Wind speed variability response: Wind power generation has great instability, and changes in wind speed can lead to fluctuations in power generation. When the wind speed is high enough and the power generation exceeds demand, excess energy can be stored through flywheel energy storage systems or pumped storage systems. In low wind speeds or increased demand, previously stored energy can be quickly released into the grid to balance supply and demand. Through these collaborative operation methods, solar and wind power generation systems can more effectively cooperate with various energy storage systems to achieve better peak valley balance and energy scheduling. This not only improves the stability and reliability of the power grid, but also helps to increase the proportion of renewable energy in the entire energy structure.
3.3 Large scale energy storage power plants
Large scale energy storage power stations have enormous potential in solving peak and valley problems in the power grid, providing emergency backup energy, and promoting the high proportion of renewable energy integration. These power stations typically use high capacity and fast response energy storage systems, such as lithium-ion batteries, sodium sulfur batteries, and emerging stone throwing energy storage systems. Lithium ion batteries store and release energy through rapid ion exchange between lithium ions and electrolytes, which have the characteristics of high energy density, long lifespan, and fast charging and discharging. Due to its high energy density and fast response characteristics, lithium-ion batteries are particularly suitable for emergency power supply, frequency regulation, and short-term peak valley balance. Sodium sulfur batteries operate under high temperature conditions and store energy through chemical reactions between sodium and sulfur. These batteries have high energy storage system efficiency and energy density, but need to operate in high-temperature environments. Due to its high energy storage system efficiency, sodium sulfur batteries are typically used for long-term energy storage, such as nighttime power supply or energy storage for wind and solar power generation. Energy storage by throwing stones utilizes heavy objects (such as boulders or concrete blocks) to store their potential in a gravity field. When energy needs to be released, heavy objects fall and generate electricity through linked generator sets. Due to its lower construction and maintenance costs, as well as good sustainability, the stone energy storage system is gradually being applied to large-scale energy storage and supply, especially in scenarios with a high proportion of renewable energy integration.
4. Summary
In summary, energy storage system technology plays a crucial role in the large-scale grid connection of new energy. It not only ensures the stable operation of the power grid, but also promotes the integration of more renewable energy into the grid, thereby achieving higher energy utilization efficiency. Power operators and policy makers need to keep up with technological trends and flexibly utilize various available energy storage system solutions, such as lithium-ion batteries, sodium sulfur batteries, and stone storage systems, to ensure the efficiency, reliability, and sustainability of the power system. Through comprehensive and in-depth research, promote the wider application of energy storage system technology in large-scale grid connection of new energy, and further strengthen the stability and sustainability of the power grid.