·The role of energy storage in photovoltaic power generation
Photovoltaic is a device that converts the light energy of solar radiation into electrical energy, and has no energy storage function.
1. Photovoltaic power generation energy storage refers to photovoltaic power generation and grid-connected systems equipped with batteries, which can store and release electric energy, and are used to smooth the output of photovoltaic power generation systems, power supply under normal conditions, and emergency power supply.
2. Grid-connected photovoltaic energy storage system: the electricity generated by photovoltaics can be used during the day and night, and the distributed general metering is used during the day, and the grid electricity is still used at night. After adding energy storage, the energy storage system can be discharged at night.
·Photovoltaic power generation and energy storage
Because photovoltaics can only generate electricity during the day, human beings need more electricity at night, and need to store the electricity generated during the day and use it at night.
The essence of photovoltaic power generation is to use polycrystalline silicon wafers to absorb solar energy and convert it into electrical energy for human use. Because only sunlight is available during the day, photovoltaic power generation is only carried out during the day and will not generate electricity at night. Humans consume more electricity at night, so power generation during the day needs to be stored Down, for use at night, the process of storing electricity is energy storage.
·What is the role of energy storage in photovoltaic power generation
Photovoltaic energy storage system is a combination of photovoltaic power generation system and energy storage battery system. Network operation, peak cutting and valley filling” and other functional applications.
In layman's terms, an energy storage power station can be compared to a reservoir, which can store surplus water during low-peak electricity consumption and use it again during peak electricity consumption.
·The relationship between photovoltaics and energy storage
The difference is that photovoltaics do not store energy, and lithium batteries store energy. Photovoltaic power generation is divided into off-grid and grid-connected. Photovoltaic modules are only power generation devices and do not have the function of electricity storage. Grid-connected means that the electricity generated by photovoltaic modules is directly integrated into the national grid without energy storage. The off-grid is used alone. When the light is weak or there is no light, and when the electricity is not enough during the peak period of electricity consumption, it needs to rely on lithium batteries to provide electricity.
·What is the most suitable energy storage method for the electricity generated by photovoltaic power generation
How photovoltaic power generation stores electricity
First of all, if it is a 12V or 24V lead-acid battery, use it in combination according to your needs, because the output of the solar panel fluctuates, so it needs to be stored in the battery and then released for use.
The storage battery is generally a lead-acid battery. In a small and micro system, a nickel-hydrogen battery, a nickel-cadmium battery or a lithium battery can also be used. Generally, an inverter is also used to convert direct current into alternating current.
Finally, we need to provide 220VAC and 110VAC AC power in many cases. Due to the direct input of solar energy.
·What are the energy storage technologies in photovoltaic power generation systems?
The most suitable energy storage method for the electricity generated by photovoltaic power generation is the storage battery.
At present, most of the electric energy generated by photovoltaic power generation is directly connected to the grid and transmitted to the grid for consumption, and a large amount of storage requires large-scale energy storage equipment. At present, batteries include alum batteries, lead-acid batteries, lithium batteries and sodium batteries, etc. The technology of batteries has not broken through the bottleneck, and there are certain problems, either the volume is too large, or there are safety risks. In addition, if the storage of a large amount of electric energy is realized, the investment required is huge, and failures caused by insufficient maintenance in the later period will bring uncontrollable safety and economic risk factors to the solar power station.
·How photovoltaic energy storage works
1. Working principle of photovoltaic energy storage inverter
(1) During the peak period of electricity consumption during the day, under the irradiation of sunlight, the DC current generated by the solar cell module is transmitted to the inverter through the controller to convert it into AC power and then merged into the power grid.
(2) During the low electricity consumption period at night, when the electricity price is relatively low, the electric energy of the grid passes through the inverter charging and discharging controller to charge and store the battery;
(3) When the sunlight is insufficient or electricity is used during non-low-peak periods at night, the battery sends power to the inverter through the DC control system, and the inverter converts it into AC power for the AC load.
·What is the role of energy storage in photovoltaic power generation
Photovoltaic first generates electricity during the day, and it cannot cover all the peak power consumption during the day, and there may be imbalance or waste;
The second is that the peak power generation is affected by sunlight. Generally, it peaks at noon, and the curve changes greatly in the morning and evening. Even during the daytime, clouds and rain will have an impact. Difficult to control output. Therefore, energy storage is needed after photovoltaic power generation. First, it can reduce light abandonment. Second, it can achieve more flexible implementation of smooth adjustment and better adapt to changes in the power grid.
·Significance of developing photovoltaic power generation and energy storage
(1) Energy storage is used to smooth out power fluctuations. The fluctuation of distributed renewable power output such as wind power and photovoltaics will cause fluctuations in the power of the distribution network. Using the fast charging and discharging characteristics of the energy storage system can reduce the impact of renewable energy on the distribution network and enhance the reliability of the distribution network. Controllability.
(2) Energy storage is used for load shaving and valley filling. The energy storage system is used to realize the time-space transfer of power loads and delay the capacity upgrade of power distribution equipment. Real-time optimization of peak-shaving and valley-filling of battery energy storage system based on dynamic programming, a real-time correction and optimization control strategy based on dynamic programming is proposed, which can introduce discontinuous constraints such as charge-discharge times limit and discharge depth limit into the optimization model, and Solve optimization problems with discontinuous constraints by discretizing battery power. A constant power charging and discharging strategy is used to control the energy storage, and the optimization model of energy storage peak-shaving and valley-filling is studied. Aiming at the nonlinear and variable discontinuity problems in the model constraints, a simplified calculation method suitable for the model is proposed. .
Energy storage is widely used in the field of load shaving and valley filling. The domestic user-side lithium battery energy storage power station has been built and put into operation. It participates in the peak-valley regulation of the power consumption side and tries peak-valley arbitrage, which can realize peak-shaving and valley-filling on the distribution network side. , frequency modulation, voltage regulation and island operation and other application functions.
(3) Energy storage is used to improve power quality. The energy storage system is connected to the distribution network, and its active power and reactive power are adjusted bidirectionally through the control strategy to stabilize the voltage at the common connection point of the distribution network and suppress its load fluctuations, thereby improving the power distribution network. quality. Taking the supercapacitor as the power quality regulator, the circuit topology is analyzed, and the non-isolated bidirectional DC/DC conversion is used to realize the DC voltage conversion, and the voltage source converter is used to realize the DC/AC conversion. The power quality conditioner can eliminate the influence of the sag, asymmetry and flicker of the power supply voltage on the load, and suppress the influence of the negative sequence current of the load on the power supply when the load is asymmetrical.
(4) Energy storage is used to improve the aggregation capacity of distributed power sources. The United States, Japan, Italy and other countries use energy storage to control the energy exchange between the substation and the upper-level power grid to reduce the power reverse problem caused by the grid-connected renewable energy. Through the unified management and control of a large number of energy storage units, a large-scale energy storage capacity is formed, but the two-way interaction capability is not fully reflected. For example: the centralized charging station can charge the batteries of multiple electric vehicles at the same time, can realize the storage of electric energy in low loads, feed back electric energy to the power grid in peak loads or emergency situations, and adjust peak and valley loads.
Power system needs are diverse and the application environment is complex. In order to meet the needs of different working conditions, the selection of energy storage should be combined with the technical characteristics of the main body. According to the length of discharge time, energy storage can be divided into power type and energy type, and the classification of energy storage type selection for different working conditions.
Utilization of energy storage technology
At present, energy storage technology is developing towards high conversion efficiency, high energy, high density and low application cost. As the research and application of energy storage technology become more and more mature, energy storage plays an increasingly important role in power peak regulation, voltage compensation, power quality management, etc., and improves the safety and stability of system operation. For power system applications, the basic characteristics of energy storage technology are reflected in the power level and its action time. The action time of energy storage is an important embodiment of the value of energy storage technology, and it is a significant sign that distinguishes it from traditional power system instant-on equipment. The application of energy storage technology will change the traditional mode of instantaneous balance of supply and demand in the existing power system, and play an important role in the energy revolution. With the development of distributed power and the construction of smart grid, energy storage technology shows the following application trends:
(1) Combining energy storage characteristics with self-regulating characteristics of renewable power sources. Utilize the two-way power characteristics and flexible adjustment capabilities of the energy storage system to improve the controllability of renewable energy generation such as wind power and photovoltaics, and improve the on-site consumption and reliable operation of renewable energy.
(2) The application function of energy storage system has developed from single to multiple. The application scenarios of energy storage are rich, and the action time covers seconds to hours, transitioning from a single time scale to multiple time scales. Compact, modular and fast response are the development direction of energy storage equipment, in order to give full play to the energy storage efficiency and improve the energy storage efficiency. economical to apply.
(3) Give full play to the convergence effect of the distributed energy storage system. The convergence effect of the energy storage system has been initially manifested in the V2G operation mode of electric vehicles. With the popularization of electric vehicles and the widespread application of distributed energy storage systems, the advantages of its convergence effect in promoting renewable energy access and user interaction will gradually become prominent.
(4) In the complementary and comprehensive utilization of multi-energy, energy storage has become a medium for flexible conversion of various types of energy. In the future, it will play a key role in improving the comprehensive energy efficiency of the user side and reducing pollutant emissions.
With the widespread application of distributed renewable energy generation and the two-way interaction of end users, the product development, integrated manufacturing and market application of energy storage technology have become a strategic choice. The multi-energy complementarity and two-way interaction based on distributed renewable energy generation and energy storage technology as the core will show the development vision of the third industrial revolution.