In the energy transition stage, energy storage technology needs to support the consumption of large amounts of renewable power and be fully integrated with related infrastructure to integrate industry, construction, and transportation to facilitate energy supply and reduce carbon emissions. With the increasing share of renewable energy, the whole energy storage system is changing from a highly centralized energy system to a decentralized, flexible, and renewable distributed energy system, which also makes energy storage technology have more and more extensive application scenarios.

1: Application field

Energy storage can be applied to the “generation-transmission-distribution-use” links of the power system and there are four main application fields currently.

1.1 The field of thermal power generation

By assisting the dynamic operation of the thermal power unit, the output fluctuation range of the thermal power unit can be reduced as much as possible, which can not only ensure that the thermal power unit is working in a state of close to the economic operation but also maintain the real-time balance between load and power generation, showing an excellent primary frequency modulation ability.

1.2 Renewable energy field

With millisecond response speed, it can track the planned output of new energy sources such as photovoltaics and wind power, smooth the power output, and ensure the power balance and operation safety of the grid; At the same time, it can reduce the rate of wind, light and water abandonment of new energy, reduce peak and fill the valley, and improve the power generation of new energy.

1.3 Grid auxiliary service field

According to the operational requirements of the power system, energy storage can provide peak and frequency regulation, black start services, and reserve capacity to the grid, which can effectively improve the safety and stability of the grid and regulate unreasonable grid loads.

1.4 Distributed Energy and Microgrid Field

Energy storage mainly plays a role in the effective management of TOU price and capacity cost, improving the reliability of power supply and the quality of electricity consumption, and replacing the self-supplied fuel power supply, etc.

2: Application scenarios

The main application scenarios of energy storage are the power generation side, power grid side, and user side. On the power generation side, it can play the functions of primary frequency modulation, reducing power abandonment and smoothing fluctuation. On the grid side can provide frequency modulation auxiliary services and peak clipping and valley filling functions; On the user side, electricity cost can be reduced by saving expansion rate, electricity response, peak-valley price difference, and so on.

2.1 Energy storage on the grid side

The power grid is a dynamic supply-demand balance system that is completed instantly by power generation, transmission, and distribution. In addition to the balance of power (including active power and reactive power), to ensure the safety of the power grid (including the safety of power load), the voltage fluctuation and frequency fluctuation of the power grid should also be controlled within a certain range. The equally important power quality parameters include grid harmonics and three-phase balance.

Before the appearance of large-scale battery energy storage application technology, the dispatchable resources for power grid dispatching were mainly rotary power generation equipment, such as thermal power generating units, hydroelectric units, gas generating units, and pumped storage power stations. Battery Storage Power Station (BESS), a new type of electric energy device combining power electronics technology and power battery technology, is not a power station in the traditional sense, but in a certain time and space, BESS can play the role of a power station. And because of its incomparable response speed and control accuracy, its frequency and peak modulation effect far exceeds all the traditional rotary power generation equipment; AGC and AVC functions are innate abilities for battery energy storage systems, and there is no suspense and pressure to use. And BESS has a modular design, flexible configuration, can be distributed to use the special points to make it possible to large-scale grid application. At the same time, BESS can also be conveniently used as a controllable load, that is to say, BESS has two role characteristics of power supply and load, and can instantly change identity according to the need. Therefore, the deployment of large-scale (independent or distributed) battery energy storage power stations on the grid side can completely or partially replace the existing thermal power peak regulating units, frequency regulating units, emergency standby units, reactive power generating units, controllable loads, etc., which has a very large economic value.

2.2 Energy storage on the power side

Energy storage technology is the core of achieving energy diversification. Renewable energy sources such as wind power and photovoltaics have the characteristics of instability and discontinuity, and large-scale grid integration of renewable energy will inevitably cause a certain impact on the original power system. Energy storage technology can suppress fluctuations in wind power output, thereby greatly reducing the pressure on the stable operation of the power grid (voltage stability, frequency stability, power flow controllable, and orderly dispatch). When there is a shortage of wind energy in the local area, electricity needs to be transmitted from the grid in other regions. If an energy storage system is equipped, it can be released according to demand to supplement the needs. When wind energy is sufficient, the battery can also absorb excess electricity, reducing the rate of wind abandonment and increasing wind energy Consumption, improve the transmission efficiency of the power system. At the same time, the energy storage system can also reduce voltage fluctuations, achieve voltage sags, stabilize power quality, and assist wind power to participate in peak shaving. The peak and frequency modulation capabilities of energy storage are mainly reflected in its extremely fast response speed, and the energy storage system can help realize automation, information, and intelligence, and facilitate power grid dispatch. On the whole, energy storage also reflects the economy of its optimized system, saving the construction cost of long-distance transmission lines of the power grid, and the construction and installation of energy storage power stations are simpler than power grid construction, shortening the construction period of the project. Besides, the participation of the battery energy storage system also meets the goals of energy saving and emission reduction, increasing the utilization rate of wind energy, reducing the number of standby units, reducing carbon emissions, and causing no pollution to the environment. In summary, energy storage technology has formed a greater market demand in new energy industries such as photovoltaics and wind power and will have broad development prospects in the future.

2.3 Energy storage on the user side

From the perspective of actual demand, energy storage can help users “cut peaks and fill valleys”, save electricity costs, help the power system to supply the electricity in a balanced manner, reduce production costs, and avoid problems such as huge losses caused by frequent startup and shutdown of some generator sets. To ensure the safety and stability of the power system. At present, industrial electricity in many regions of my country implements a peak-to-valley electricity price policy, and electricity prices are different at different times. Energy storage technology can store electricity during low electricity prices and release it when electricity prices are high. With the continuous development of energy storage technology and the continuous decline of battery costs, it has become possible for companies to use energy storage technology to achieve “peak-shaving and valley-filling” of electricity prices, which is also a “routine action” for energy storage on the user side. Besides, the energy storage system can also help users reduce the risk of power outages, improve power quality, reduce capacity and electricity bills, and participate in demand-side response, and play multiple values. From the perspective of the development trend of distributed photovoltaics, “photovoltaic + energy storage” will become the standard configuration. From a macro point of view, “PV + energy storage” can improve the stability of the power system and the integrity of power consumption; from an individual point of view, the “PV + energy storage” system can increase the spontaneous and self-use rate of users and bring greater benefits. With the continuous and efficient development of distributed photovoltaics, the construction of “source-network-load-storage” will achieve coordinated interaction, and it can be foreseen that the market space will expand to the user side at a geometric speed. Also, with the advancement of the power system reform, multiple values of user-side energy storage have emerged. Microgrids, incremental distribution networks, and users’ active participation in auxiliary services will all bring opportunities for energy storage, and user-side energy storage will surely become the most potential area for energy storage development.

3:Typical energy storage applications

3.1 Photovoltaic energy storage

The photovoltaic power generation is greatly affected by the weather and has a strong uncontrollability. For residential photovoltaic system users, electricity is usually generated only during the day or at noon, while the power consumption at night is greater. In this way, the electricity generated during the day needs to be stored by batteries to improve the use efficiency of their photovoltaic power generation. The main economic value of photovoltaic energy storage systems is that they can reduce the amount of electricity extracted from the public grid by increasing the number of cells, thus reducing power expenditure and dependence on the grid. Currently, in Europe, the average consumption rate of a single photovoltaic system is 35%, and the battery price accounts for more than 50% of the total energy storage system.

3.2 Household peak shaving and demand-side response

Household energy storage batteries can also be used to respond to the user’s demand side. Users can use batteries for charging when the grid load is small; when the grid load is large, using batteries for power supply can greatly reduce the grid load and save power at the same time Cost, optimize power supply reliability, and improve power quality. This type of battery is mainly used for household photovoltaic energy storage batteries and household electric vehicle batteries. According to research, the application prospects of electric vehicle batteries in this area are very impressive in the future. It is estimated that more than 70% of electric vehicle batteries can be used for household battery peak shaving.

3.3 Energy storage of electric vehicles

Each EV, which means “mobile battery on wheels” to the power industry, has a capacity of 40 to 100 kilowatt-hours, five to 10 times that of a typical home battery storage system. Like stationary household batteries, electric cars connected to the grid via charging piles can not only store electricity but also feed it into the grid on demand. For example, an electric-car owner returning home from work in the afternoon might set up the charging system in the hope that his car will be fully charged by the next morning. The system can then allocate the time needed to charge and use the rest to help regulate grid stability. Batteries can absorb and release large amounts of power in a short time, making them ideal for providing ancillary services to the grid. They stabilize the grid by keeping electricity flowing, improve reliability by acting as backup power, and can be recharged when electricity is plentiful and cheap.

4: Exploration and thinking of energy storage value

Scenarios application and value acquisition of energy storage technology should be explored from three levels.

4.1 The single income model only considers the investment income brought by the existing mechanism and system and does not consider other indirect benefits not covered by the mechanism and system. The method is simple, but it deviates greatly from the actual value of the energy storage price. For example, the scenario mode of TOU price management (peak-valley differential interest), power plant frequency modulation (frequency modulation service), etc.

4.2 The system value model considers all the benefits of energy storage in the power system and the system value of energy storage but does not consider the social benefits of energy storage, such as energy-saving and emission reduction, improvement of infrastructure utilization rate, etc. This method can better reflect the actual value of energy storage, such as the demand-side response of energy storage.

4.3 Comprehensive benefit model Taking the regional energy system as the research object, the benefits of energy storage are calculated by comparing the production and operation costs and social benefits of the system with and without energy storage. This method can reflect the actual value of energy storage more comprehensively, which is the inevitable trend of energy storage economic research. However, no economic benefit model is corresponding to the comprehensive benefit model of energy storage at present. The development of this level needs to be combined with the comprehensive social energy utilization and services, such as transportation, the interconnection model of power and gas networks, and the carbon exchange model under the future energy Internet model.