رؤية الشركة: الشحن من أجل مستقبل مستدام
Why Do Charging Stations Need to Be Equipped with Energy Storage?
- Transmission and distribution side
The application of energy storage in transmission and distribution side mainly includes three types: alleviating transmission and distribution congestion, delaying the capacity expansion of transmission and distribution equipment, and reactive power support. Compared with the application on the power generation side, the application types in transmission and distribution side are fewer, and from the perspective of the effect, it is more of the substitution effect.
- Alleviating transmission and distribution congestion
Line congestion means that the line load exceeds the line capacity, and the energy storage system is installed upstream of the line. When the line congestion occurs, the energy that cannot be transported can be stored in the energy storage equipment, and when the line load is less than the line capacity, the energy storage system will discharge to the line. Generally, the discharge time of energy storage system is required to be in the order of hours, and the operation times are about 50~100 times. It belongs to energy application, and has certain requirements on response time, so it needs to respond in the order of minutes.
- Delayingthe capacity expansion of transmission and distribution equipment
The cost of traditional power grid planning or grid upgrading and expansion is very high. In a power transmission and distribution system with a load close to the equipment capacity, if the load supply can be met most of the year, and the situation where the capacity is lower than the load only occurs during some specific peak periods, the energy storage system can be used to effectively improve the power transmission and distribution capacity of the power grid through a relatively small installed capacity, thus delaying the cost of building new power transmission and distribution facilities and extending the service life of the original equipment. Compared with alleviating transmission and distribution congestion , the working frequency of delaying the capacity expansion of transmission and distribution equipment is lower. Considering the aging of batteries, the actual variable cost is higher, so higher requirements are put forward for the economy of batteries.
- Reactive power support
Reactive power support refers to adjusting the transmission voltage by injecting or absorbing reactive power on the transmission and distribution lines. Insufficient or excessive reactive power will cause voltage fluctuation of power grid, affect power quality and even damage electrical equipment. With the help of dynamic inverter, communication and control equipment, the battery can adjust the voltage of transmission and distribution lines by adjusting the magnitude of the output reactive power. Reactive power support is a typical power-based application, with a relatively short discharge time but high operation frequency.
- Power consumption side
The electricity consumption side is the terminal of electricity use, and the users are the consumers and users of electricity. The costs and benefits of power generation and transmission and distribution side are expressed in the form of electricity price, which is converted into the costs of users, so the level of electricity price will affect the demand of users.
- User time-of-use electricity price management
The electric power department divides 24 hours a day into multiple periods such as peak, flat and off-peak, and sets different electricity price levels for each period, which is the time-of-use electricity price. User time-of-use electricity price management is similar to energy time-shift, the only difference is that user time-of-use electricity price management is based on time-of-use electricity price system to adjust power load, while energy time-shift is based on power load curve to adjust power generation.
- Capacity cost management
The power supply department implements a two-part electricity price for large industrial enterprises: the electricity quantity price refers to the electricity price calculated according to the actual transaction electricity quantity, and the capacity price mainly depends on the highest value of the user's electricity consumption power. Capacity cost management means that, without affecting normal production, the capacity cost is reduced by reducing the highest electricity consumption power. Users can use the energy storage system to store energy during the the low electricity load period and discharge during the peak period, thus reducing the overall load and achieving the purpose of reducing capacity cost.
- Improve power quality
Due to the variable nature of power system operating load and nonlinear equipment load, the power obtained by users has problems such as voltage, current change or frequency deviation, and the power quality is poor at this time. System frequency modulation and reactive power support are the ways to improve power quality on the power generation side and transmission and distribution side. On the user side, the energy storage system can also smooth voltage and frequency fluctuations. For example, the energy storage system can be used to solve problems such as voltage rise, sudden drop, and flicker in the distributed photovoltaic system. Improving power quality belongs to a typical power-based application. The specific discharge time and operation frequency vary according to the actual application scenario, but generally, the response time is required to be at the millisecond level..
- Improve the reliability of power supply
Energy storage is used to improve the reliability of microgrid power supply, which means when a power outage fault occurs, the energy storage can supply the stored energy to end-users, avoiding the interruption of electricity during the fault repair process to ensure power supply reliability. The energy storage equipment in this application must meet the requirements of high quality and high reliability, and the specific discharge time is mainly related to the installation location.
Which charging stations are suitable for installing energy storage?
Whether a charging station is suitable for installing energy storage needs to be considered from both internal and external aspects.
- External factors
On the one hand, it depends on the local peak-valley price difference. For example, in China, the National Development and Reform Commission once issued a notice requiring that in places where the maximum system peak-valley difference rate in the previous year or the expected rate in the current year exceeds 40%, the peak-valley electricity price difference should generally not be lower than 4:1; in other places, it should generally not be lower than 3:1. Such a price difference setting can, to a certain extent, help promote the development of energy storage.
On the other hand, it depends on the local management policy and approval process for energy storage. If the requirements are too high, the hidden cost is too high and it is not suitable.
- Internal factors
Mainly focus on the limitations of the charging station itself. First, energy storage requires a certain area. Therefore, it is best to have some spare corner spaces in the charging station, such as on the side of the box transformer or in the green belt. If itneeds to occupy a parking space alone, it will increase the additional cost. Secondly, the energy storage at the charging station should have a stable charging volume during peak hours, and how much energy can be stored depends largely on how much charging volume the charging station can have during peak hours. The stored electricity is charged at the time of low electricity price. If it cannot be consumed at the time of high electricity price, it is not suitable for installing energy storage. In other words, to achieve arbitrage, the charging station must have sufficient charging demand at a high electricity price.
Take Zhuhai, China as an example. It takes 2 hours in the morning and 5 hours in the afternoon, and there is 7 hours of consumption time. Charging can be carried out during the periods other than the peak discharge period. The peak-valley electricity price difference is: RMB 1.2638/kWh. If the stable charging volume during peak hours in a day is 500 kWh and 500 kWh of energy storage is configured, a profit of more than 600 yuan can be obtained through the price difference, and that is RMB 18,000 a month.
In addition, the virtual capacity expansion function of energy storage, combined with integrated EMS management system for unified management, can reduce the peak power consumption of the load, reduce the demand for power distribution, and the energy management of the station will be more flexible. With the increase in the installed capacity of renewable energy, the peak-valley price difference of electricity price tends to increase gradually. From the perspective of industrial development law and economy, the integrated mode of " photovoltaic-storage-charging-inspection-service" is a model and technology to help maximize the utilization of energy resources in the future.
