Energy storage systems

In the analysis of energy storage processes, the part of the object or spatial area that is delineated in order to determine the object of study is called the energy storage system. It includes energy and matter input and output, energy conversion and storage devices. Energy storage systems often involve multiple energies, multiple devices, multiple substances, multiple processes and are complex energy systems that change over time and require several indicators to describe their performance. Commonly used evaluation indicators include energy storage density, energy storage power, energy storage efficiency as well as energy storage price and impact on the environment.

 

Energy storage methods

According to the energy storage method, energy storage can be divided into three categories: physical energy storage, chemical energy storage and electromagnetic energy storage, of which physical energy storage mainly includes pumped storage, compressed air energy storage, flywheel energy storage, etc. Chemical energy storage mainly includes lead-acid batteries, lithium-ion batteries, sodium-sulphur batteries, liquid flow batteries, etc. Electromagnetic energy storage mainly includes supercapacitor energy storage and superconducting energy storage.

Battery energy storage

Large power occasions generally use lead-acid batteries, mainly for emergency power, battery cars, power plants surplus energy storage. Dry batteries that can be recharged repeatedly can also be used in low power situations: e.g. NiMH batteries, Li-ion batteries, etc.

All-vanadium liquid flow battery, is a kind of vanadium ion valence change, to achieve the reciprocal conversion of chemical energy to electricity, so that the wind or solar energy generated by the force storage and release of large energy storage battery, the industry image called "power bank". The United States, Japan and other developed countries for power station peaking and wind energy storage of vanadium battery industry is developing rapidly, the technology has been basically mature. [7] Compared to lithium batteries, the biggest advantage of all-vanadium liquid flow batteries is that they do not burn and do not explode. [8] 

Inductor energy storage

The inductor itself is an energy storage element, storing electrical energy proportional to its own inductance and the square of the current flowing through itself: E = L*I*I/2. Since inductors are resistive at room temperature, and resistance consumes energy, many energy storage technologies use superconductors. Inductive energy storage is not yet mature, but there are examples of applications in the press.

Capacitor energy storage

Capacitors are also energy storage elements, where the amount of energy stored is proportional to their capacitance and the square of their terminal voltage: E = C*U*U/2. Capacitive energy storage is easy to maintain and does not require a superconductor. Another important aspect of capacitive energy storage is its ability to provide instantaneous high power, which is ideal for applications such as lasers and flash lamps.

Supercapacitors, also known as electrochemical capacitors, are a new type of energy storage device between traditional capacitors and rechargeable batteries. Their structure is similar to that of batteries, consisting of four main parts: double electrodes, electrolyte, collector and isolator, with the advantages of high power density, long cycle life, good low temperature performance, safety, reliability and environmental friendliness. However, the stored energy and retention time are limited due to the low dielectric withstand voltage and the presence of leakage current. Currently, supercapacitors are mainly based on double-layer capacitance at the porous carbon electrode/electrolyte interface, or quasi-capacitance generated by metal oxides or conducting polymers to achieve energy storage. [9] 

 

In addition, there are other ways of storing energy: for example, mechanical energy storage.

Energy storage is based on two main points:

1. the rapid development of the wind power photovoltaic industry will drive the development of the high-capacity energy storage industry. Energy storage technology has largely solved the problem of randomness and volatility of new energy generation, and can achieve smooth output of new energy generation, effectively regulating the changes in grid voltage, frequency and phase caused by new energy generation, so that large-scale wind power and photovoltaic generation can be easily and reliably integrated into the conventional grid. The future of energy storage batteries should be in the wind power and photovoltaic industries, especially in the wind power industry, which has been heavily laid out. Wind resources are unstable, in addition, wind resources are larger in the second half of the night and is the low valley of electricity, therefore, although the wind and photovoltaic industry has been developing rapidly in recent years, but has been plagued by the word "grid", the application of energy storage technology, can help wind farms output smoothing and 'peak to fill the valley The application of energy storage technology can help smooth the output of wind farms and 'fill in the valley with the peak'.

2. The good development of new energy vehicles, especially electric vehicles, is good for the development of power battery energy storage industry. Four ministries and commissions launched a pilot programme for a private purchase subsidy policy for new energy in five cities, which focuses on pure electric and plug-in hybrid power. Along with the development of electric vehicles, high-efficiency energy storage batteries are bound to gradually replace internal combustion engines. Along with the gradual decline in battery costs and increasing maturity, the ability to replace the internal combustion engine will gradually increase.

Energy storage technology can be said to be the core of the new energy industry revolution. The huge development potential of the energy storage industry will certainly lead to fierce competition in this market. If policies are put in place, China's energy storage industry can grow rapidly into an emerging strategic industry with significant global impact, and will also greatly promote the scale of domestic new energy development.