Photovoltaic energy storage technology is a new type of resource-saving and clean power generation technology, whose basic principle is to convert solar energy into electricity. The use of energy storage technology in photovoltaic power generation systems not only ensures clean energy extraction, but also effectively achieves energy recovery. With the support of photovoltaic power generation and energy storage technology, even in underdeveloped mountainous areas, power supply can be achieved. Energy storage units are a very important module in photovoltaic power generation systems, which can effectively store electrical energy and improve the stability and safety of photovoltaic power generation systems to a certain extent.
1. Classification of energy storage technologies
1.1 Battery Energy Storage Technology
Battery energy storage is currently the most mature and widely used energy storage technology, which can be classified into different types based on the use of different chemicals, including lithium-ion batteries, lead-acid batteries, all vanadium flow batteries, sodium sulfur batteries, and nickel hydrogen battery energy storage. Lead acid batteries have the characteristics of good performance, low cost, and large annual production capacity, and are widely used in small wind and solar power generation systems, electric vehicles, lighting, and communication equipment. Compared with lead-acid batteries and nickel hydrogen batteries, lithium-ion batteries have higher operating voltage, conversion efficiency, energy density, and longer cycle life. Due to its high price and the problems of being explosive, flammable, and polluting the environment, its scope of use is greatly limited, mainly concentrated in new energy electric vehicles, portable electronic products, and distributed power stations. All vanadium flow batteries and sodium sulfur batteries are a new type of energy storage battery that has developed in recent years. They are relatively expensive, but have a large capacity, and have good application prospects in the power industry.
1.2 Flywheel energy storage technology
Flywheel energy storage technology is an integrated energy storage device composed of multiple sub components, with a very complex structure, mainly including flywheels, magnetic shafts, generators, electric motors, transformation devices, electronic control devices, vacuum pumps, backup bearings, etc. The working mechanism of flywheel energy storage technology is as follows: the flywheel system absorbs energy to a certain extent and is powered by the external power grid. Under the influence of external electricity, the flywheel will rotate rapidly, continuously generating energy and storing energy during rotation. This technology can achieve effective conversion of electricity, enabling it to effectively output electricity. Using the high-speed rotation of the flywheel as the power transmission, the power transmission device outputs a series of electricity through an electric power conversion device, thereby converting mechanical energy into electrical energy. The advantages of flywheel energy storage technology are as follows:
(1) The energy conversion efficiency is high, and in some cases, mechanical energy can be converted into electrical energy, which is more than 90% of the electrical energy.
(2) Flywheel storage technology is adopted, which is a new energy storage technology that has been used for a longer time, is more environmentally friendly, and has lower noise. Storage technology is used in hybrid vehicles, which have a large cylinder and a gearbox that drives the flywheel to provide power to the vehicle.
1.3 Supercapacitor Energy Storage Technology
The supercapacitor energy storage technology first appeared in BECKER’s patent in 1957. After the development of relevant researchers, this technology and patent have been industrialized in production. Placing the electrode in the electrolyte can cause ions with significant surface charge differences to adsorb, resulting in the formation of a double layer. The charging and discharging of supercapacitors are both physical processes that do not undergo chemical conversion, ensuring that the battery can be charged and discharged multiple times, thereby extending its service life. However, the single supercapacitor currently used has low energy density and voltage, and once discharged, the voltage at both ends will undergo drastic changes, seriously restricting its large-scale application. Usually, multiple supercapacitors are used
The parallel connection method can meet the practical needs of high-power and high-capacity systems.
2. The positive role of energy storage technology in the application of photovoltaic power generation systems
2.1 Improving the stability of photovoltaic power generation systems
Applying energy storage technology to photovoltaic power generation systems can optimize and adjust the state of peak electricity consumption. Energy storage devices can adjust the electricity consumption during peak hours and store it. During peak electricity usage, the stored electricity can be released according to specific circumstances to reduce the level of electricity load. From this, it can be seen that the use of energy storage technology in photovoltaic power generation systems can effectively improve the stability of the system and avoid economic losses caused by insufficient power supply.
2.2 Improving the power generation efficiency of photovoltaic power generation systems
There are a large number of undeveloped light energy resources in the western region of China, which result in low photoelectric conversion efficiency. It is urgent to adopt energy storage technology to improve its photoelectric conversion efficiency. After photovoltaic power generation was abandoned in western China, it seriously affected the utilization rate of solar energy. Energy storage technology can convert stored energy into solar energy when the photovoltaic power generation capacity is insufficient, which is of great significance for improving the power generation efficiency and increasing the revenue of photovoltaic power generation systems.
2.3 Improving the Safety of Photovoltaic Power Generation Systems
Microgrid is a core component of photovoltaic power generation systems, and the introduction of energy storage technology can improve its safety. The operation speed of microgrids is very fast, so they are also relatively reliable when the power supply load is high, and can play a role in stabilizing the voltage of photovoltaic power generation systems and reducing line losses of photovoltaic power generation systems. Applying energy storage technology to photovoltaic power generation microgrid systems can continuously provide electricity when the photovoltaic power generation system is separated from the microgrid, with high safety performance.
3. The specific application of energy storage technology in photovoltaic power generation systems
3.1 Application in Power Peak shaving
The purpose of electricity peak shaving is to ensure urban and industrial electricity consumption as much as possible during peak periods, especially under heavy load conditions. At the same time, the power consumption structure should also be adjusted appropriately to achieve the goal of reducing the load on the power grid. According to the characteristics of storage devices in the power system, storage devices in the power system should have some flexibility. When the power load of the power grid is low, it can store the electricity generated by the photovoltaic power generation system during actual operation, and greatly improve the reliability of power supply during peak load, ensuring the safety of power supply and effectively preventing power supply failure caused by excessive power supply. Therefore, while ensuring the stability of power supply, it can achieve the maximization of regional power supply. Across the country, there are certain peaks and valleys in the total electricity consumption, which is a common phenomenon and a concern for the entire society. During the peak period of electricity consumption, in order to ensure the supply of electricity, a large amount of electricity is required, which increases the load on the power grid. Once a fault occurs in the operation of the power grid, it will to some extent cause power interruption, which will not only affect people’s production and life, but also reduce people’s trust in power supply enterprises and their market competitiveness in a certain sense. Therefore, utilizing energy storage technology can not only effectively reduce the load borne by the system during peak electricity consumption periods. At the same time, it can also ensure the normal operation of the power grid during peak and valley periods, effectively compensating for the impact of power supply adjustments on the power system during different periods of peak and valley, ensuring that the photovoltaic power generation system can maintain stable operation and reduce the occurrence of power generation failures.
3.2 Application in Power Quality Control of Power Grid
Solar cells are an important component of solar panels, and applying energy storage technology to solar panels can ensure their stable operation. In the actual work process, the photovoltaic grid connected power generation system can effectively control the quality of the electricity generated, and in this process, the energy storage control system is crucial. By adjusting the active filter, voltage stability can be achieved, ensuring that the phase angle is within a reasonable range, and real-time adjustment can be made in case of deviation, thereby ensuring the quality of power output. In the past, there were a large number of faults in the power system, which were difficult to detect in a timely manner and had a significant negative impact on the power system. Especially during peak and valley periods of electricity consumption, although the power supply can be manually adjusted, it is difficult to ensure the quality of power supply. Applying energy storage technology to the power grid can effectively solve the above problems. This method can effectively avoid significant changes in power supply in a short period of time, thus avoiding significant impacts on the power system. This not only ensures the stability of power supply, but also reduces regional power outages caused by power system failures, effectively solving people’s needs for power supply and improving the overall quality of power supply.
3.3 Application in load transfer
When using energy storage technology for load conversion, its principle is similar to the peak shaving principle of the power grid, but overall it is more flexible. If solar cells can produce a large amount of electricity while there is very little available for human use, the overall load of solar cells will be very low. If operated improperly, it will not only lead to energy loss, but also increase the cost of solar cells. If people consume a lot of electricity but the overall power generation of solar panels is small, then they cannot meet their daily electricity needs. In order to meet people’s daily electricity needs, it is necessary to use energy storage technology on solar panels to balance the load of solar panels. When the load is relatively small, energy storage technology can be used to store excess electricity; When the daily electricity usage is high, the load of the photovoltaic power generation system will reach its maximum, which can release the stored energy to meet the needs of daily production and life, thereby achieving the goal of regulating the load of the entire photovoltaic power generation system and ensuring its smooth operation.
3.4 Application in load response
During operation, in order to ensure the stable operation of the system and reduce the probability of faults, it is often necessary to automatically adjust some larger loads. In order to ensure the safe and normal operation of the power system between different regions during peak electricity consumption, a solar cell energy storage system can be adopted, which can ensure the stability of power supply to the greatest extent. However, one issue that relevant personnel need to pay attention to during this process is that when connected to the load response control system, there must be a communication line that can work normally. This working mode can minimize the adverse effects of some high-power equipment on the normal operation of the photovoltaic power generation system, and achieve high-quality response to the load. Applying load response technology to photovoltaic power generation systems can achieve various types of grid connection, thereby reducing the probability of grid connection accidents. Through load response, high-power loads can be adjusted in a timely manner to operate within the critical range. While ensuring power supply stability, it can also reduce the adverse effects on the normal operation of the power grid during the adjustment of power supply to a certain extent, ensuring stable operation of the power grid and maximizing the overall power supply quality.
3.5 Application in composite energy storage photovoltaic power grid
In the past, the application process and methods of energy storage technology in photovoltaic power generation systems resulted in insufficient safety and stability of power operation. On the basis of existing applications, updating energy storage technology and applying it to composite energy storage photovoltaic power grids can significantly improve the power supply efficiency and quality of photovoltaic power generation systems. Composite energy storage technology has a wide range of applications in today’s society. Applying composite energy storage technology to photovoltaic power generation systems can directly reduce the harmonics in the network flow, thereby further ensuring the stability of power output in the power grid system. In addition, it can effectively reduce the impact of external factors on photovoltaic power generation systems. By applying photovoltaic power generation systems that are closer to the actual power generation situation, we can effectively ensure the smooth progress of China’s power grid construction work.
4. Future prospects of energy storage technology
At present, there are still many problems in the practical application of energy storage technology in China, such as the lack of a clear pricing system for energy storage business, resulting in fluctuations in energy storage costs, and a lack of relevant regulatory measures. At present, there are still significant safety hazards in the practical application of energy storage technology in China, such as fire, explosion and other accidents that may occur in the actual application of energy storage technology. Therefore, in future development, the power industry can optimize and upgrade energy storage technology based on its application scope and actual situation, and eliminate current safety hazards. The promotion of energy storage technology also has certain cost issues. Electric power enterprises should start from economic costs, strengthen the innovation and management of energy storage technology, so that it can better play its efficiency and more effectively reduce its operating costs. In the future, the country should provide active support for the development of energy storage technology, provide policy subsidies and financial support to relevant power enterprises, thereby promoting the upgrading and optimization of energy storage technology, so that it can better serve photovoltaic power generation systems.
5. Conclusion
In summary, the use of energy storage technology can not only effectively improve the stability and safety of the power grid in practical work, but also fully utilize the economic benefits of the power grid in operation, effectively ensure the quality of electricity consumption for users, and thus achieve the goal of sustainable development. According to the current situation in our country, although energy storage technology has made some progress, researchers should continue to research and develop new energy storage technologies in order to continue the development of photovoltaic power generation, expand its application areas, truly achieve the goal of green environmental protection, and reduce the negative impact of previous thermal power generation on the environment.