Popular Science | Professional terms and terms in the energy storage industry

Under the guidance of the national "dual carbon" policy, as an important support for promoting the transformation of traditional energy systems, the energy storage industry has grown rapidly. As practitioners and participants in the energy storage industry, we need to master some of the most basic professional knowledge. The following is a collection of some professional terms and terms about the energy storage industry and common professional terms, as follows.

1. Energy storage

Energy storage refers to the process of storing energy through medium or equipment and releasing it when needed. Through flexible charging and discharging control, it can match production capacity and energy consumption in time and space, which is a basis for flexibility.

From the perspective of the power system, energy storage can be divided into power generation side/power side, power grid side, and user side energy storage, among which power supply side and power grid side energy storage are also called premeter energy storage or large storage.

Energy storage before the meter refers to energy storage directly connected to the power grid and has independent power and power meter; otherwise, it is energy storage after the meter, and user-side energy storage is also called energy storage after the meter. User-side energy storage is divided into industrial and commercial energy storage and household energy storage.

From the perspective of business model, energy storage before the table should have the identity of an independent market entity, independently participate in market volume quotations, directly accept scheduling, and independent settlement, which can also be called independent energy storage.

2. New energy storage

New energy storage mainly refers to "energy storage projects that use electricity output as the main form except pumped storage and provide services to the outside world." Due to the short construction cycle, flexible site selection and strong regulation capabilities, it is more compatible with the development and consumption of new energy, and its advantages are gradually highlighted.

From the perspective of technological development route, new energy storage currently has a variety of technologies that are moving forward. From the current perspective, six new energy storage routes, including compressed air energy storage, liquid flow battery energy storage, sodium ion battery energy storage, molten salt energy storage, gravity energy storage, and flywheel energy storage, are the most worthy of attention.

As of the end of 2023, the cumulative installed capacity of new energy storage projects has been completed and put into operation across the country to reach 31.39 million kilowatts/66.87 million kilowatt-hours, with an average energy storage time of 2.1 hours. The new installed capacity in 2023 is about 22.6 million kilowatts/48.7 million kilowatt-hours, an increase of more than 260% from the end of 2022, nearly 10 times the installed capacity scale at the end of the 13th Five-Year Plan.

From the perspective of investment scale, since the 14th Five-Year Plan, the addition of new energy storage installed capacity has directly promoted economic investment of over 100 billion yuan, driving the further expansion of the upstream and downstream of the industrial chain, and becoming a "new driving force" for my country's economic development.

3. Long-term energy storage

It is generally believed that energy storage that can achieve charging and discharging cycles of more than 4 hours or days or months is collectively called long-term energy storage. Currently, long-term energy storage mainly includes: pumped energy storage, compressed air energy storage, photothermal energy storage, hydrogen energy storage and liquid flow batteries.

In order to alleviate the peak power supply pressure, among the policies issued in various parts of my country, the proportion of new energy allocation and storage is required to reach 10% to 20% (the proportion of installed capacity), and long-term energy storage demand with more than 4 hours and low-cost has gradually become a necessity.

Long-term energy storage has the advantages of improving the ability to absorb new energy, replacing traditional thermal power generation, providing flexible power resources for the power grid, reducing grid operating costs, and allowing enterprises to have stronger peak and valley arbitrage capabilities. At the same time, it can store electricity across days and months, meet the needs of stable operation of the power system, and help the construction of my country's new power system.

4. Household storage goes to sea

Household storage (i.e., household energy storage) refers to an energy storage system used for home users. It is usually installed in combination with household photovoltaic systems to provide electricity to home users. The working principle is to give priority to photovoltaic power generation during the day to use the load, and store excess energy in the battery, which can be optionally incorporated into the power grid when there is still surplus of electricity; when the photovoltaic system is not operating at night, it is discharged for local loads.

Driven by various factors such as favorable overseas policies, energy shortage, high electricity prices and cost reduction of photoelectric storage systems, the marketization of household energy storage has accelerated. The self-use power consumption model of "photovoltaic + energy storage" has been rapidly promoted, driving the increase in the demand for household storage in Europe and accelerating the overseas use of Chinese companies. However, since this track is still in the early stages of market development, if you want to gain a place in the household energy storage market, you still need to have core competitiveness.

5. Dynamic capacity enhancement

The transformer capacity of the user is fixed. Generally speaking, when the user needs the transformer to operate overload at a certain period of time, the transformer needs to be expanded.

Dynamic capacity increase is through the installation of energy storage systems. The energy storage system is used to store and discharge during the transformer's overload operation period to reduce the transformer load, thereby reducing the capacity increase and transformation costs of the transformer. Through energy storage systems, not only can the cost be greatly reduced, but it can also increase profits through peak and valley arbitrage.

6. Cyclic life

Cycle life refers to the service life of the battery during the charging and discharging cycle. Cycle life is usually measured by the number of charge and discharge times or cycle depth, and batteries with high cycle life can last longer, reducing the cost and time of replacing the battery.

7. Thermal loss

During the charging or discharging of the battery, the battery itself will generate strong heat and release high temperatures due to certain special reasons (such as internal short circuit and the battery itself heats up when it is charged and discharged by a large current).

If the normal operating temperature range is exceeded, the internal chemical components of the battery will undergo a chain reaction and release a large amount of heat and gas. These heat can easily spread rapidly to the adjacent battery through the heat dissipation route, resulting in heat loss and spreading rapidly. This situation may lead to serious consequences such as battery explosion or spontaneous combustion.

Therefore, energy storage batteries need to have a good thermal management system to ensure the safety of the batteries during use.

8. Microgrid

Microgrid is a concept relatively to traditional large power grids. Traditional large power grids mainly interact with one-way, and electricity reaches users layer by layer from power plants through transmission lines. Microgrid is a two-way interaction model. It is a small, autonomous power system that can operate independently or be interconnected with the main power grid.

Energy storage systems are often used in microgrids to balance energy supply and demand, improve energy utilization efficiency, etc. It can generate electricity on-site and balance on-site to maximize energy use efficiency.

9. Peak-to-valley electricity price difference

Peak and valley electricity refers to dividing the user's daily electricity consumption period (24 hours) into two parts: peak and valley period, where the electricity price is high during peak period and low during valley period.

The larger the price difference between peak and valley electricity prices, the more electricity bills it saves, thus bringing higher returns to energy storage users and shortening the cycle of recovery investment. This is what is often called peak and valley arbitrage.