1. Principle and characteristics of energy storage technology
The energy storage device composed of energy storage components and the power grid access device composed of power electronic devices become the two major parts of the energy storage system. Energy storage device is important to realize energy storage, release or fast power exchange. The power grid access device realizes the two-way energy transfer and conversion between the energy storage device and the power grid, and realizes the functions of power peak regulation, energy optimization, power supply reliability and power system stability.
The energy storage system has a wide range of capacity, from tens of kilowatts to hundreds of megawatts; The discharge time span is large, from millisecond to hour; Wide application range, throughout the entire power generation, transmission, distribution, electricity system; The research and application of large-scale power energy storage technology is just starting, which is a brand new topic and also a hot research field at home and abroad.
2. Common energy storage methods
At present, the important energy storage technologies include physical energy storage (such as pumped energy storage, compressed air energy storage, flywheel energy storage, etc.), chemical energy storage (such as all kinds of batteries, renewable fuel power batteries, liquid flow batteries, supercapacitors, etc.) and electromagnetic energy storage (such as superconducting electromagnetic energy storage, etc.).
1) The most mature and widely used physical energy storage is pumped storage, which is important for peak regulation, grain filling, frequency modulation, phase regulation and emergency reserve of power system. The release time of pumped storage can be from a few hours to a few days, and its energy conversion efficiency is in the range of 70% to 85%. The construction period of pumped storage power station is long and limited by terrain. When the power station is far away from the power consumption area, the transmission loss is large. Compressed air energy storage has been applied as early as 1978, but it has not been widely promoted due to the restriction of terrain and geological conditions. Flywheel energy storage uses a motor to drive the flywheel to rotate at high speed, which converts electrical energy into mechanical energy and stores it. When necessary, the flywheel drives the generator to generate electricity. Flywheel energy storage is characterized by long life, no pollution, little maintenance, but low energy density, which can be used as a supplement to battery system.
2) There are many types of chemical energy storage, with different technological development levels and application prospects:
(1) Battery energy storage is the most mature and reliable energy storage technology at present. According to the different chemical substances used, it can be divided into lead-acid battery, nickel-cadmium battery, nickel-metal hydride battery, lithium-ion battery, sodium sulfur battery, etc. Lead-acid battery has a mature technology, can be made into mass storage system, and unit energy cost and system cost is low, safe and reliable and reuse is good wait for a characteristic, is currently the most practical energy storage system, has been in a small wind power, photovoltaic power generation systems, as well as small and medium in the distributed generation system is widely used, but because lead is heavy metal pollution, Lead-acid batteries are not the future. Advanced batteries such as lithium-ion, sodium-sulfur and nickel-metal hydride batteries have high cost, and the large-capacity energy storage technology is not mature. The performance of the products cannot meet the requirements of energy storage at present, and the economy cannot be commercialized.
(2) Large-scale renewable fuel power battery has high investment, high price and low cycle conversion efficiency, so it is not suitable to be used as commercial energy storage system at present.
(3) Liquid flow energy storage battery has the advantages of high energy conversion efficiency, low operation and maintenance costs, and is one of the technologies for energy storage and regulation of efficient and large-scale grid-connected power generation. Liquid flow energy storage technology has been applied in demonstrative countries such as USA, Germany, Japan and UK, but it is still in the research and development stage in China.
Post time: Aug-17-2022
