Energy Storage System (ESS for short) is a system that can store electrical energy and supply power, with functions such as smooth transition, peak shaving and valley filling, frequency regulation and voltage regulation. It can smooth the output of solar and wind power generation, and reduce the impact of its randomness, intermittency, and volatility on the grid and users; charge during valley price periods, and discharge during peak price periods can reduce users’ electricity bills; power outages in large power grids At this time, it can operate in an isolated manner to ensure uninterrupted power supply to users and the operation of the micro-grid.
The micro-grid system architecture includes energy storage, photovoltaics, wind turbines, etc. The energy storage system is the core component of the micro-grid and is often used together with photovoltaics and wind power. Because battery energy storage has the advantages of relatively mature technology, large capacity, safety and reliability, low noise, strong environmental adaptability, and easy installation, batteries are often used in energy storage systems to store electrical energy. At present, energy storage systems are mainly composed of energy storage units and monitoring and control systems. The dispatch management unit consists of the energy storage unit including the energy storage battery pack (BA), the battery management system (BMS), the energy storage converter (PCS), etc.; the monitoring and dispatch management unit includes the central control system (MGCC), the energy management system (EMS) etc.
Energy storage system includes energy and material input and output, energy conversion and storage equipment. An energy storage system often involves multiple energies, multiple devices, multiple substances, and multiple processes. It is a complex energy system that changes with time, and requires multiple indicators to describe its performance. Commonly used evaluation indicators include energy storage density, energy storage power, energy storage efficiency, energy storage price, and environmental impact.
The energy storage system can store excess thermal energy, kinetic energy, electrical energy, potential energy, chemical energy, etc., and change the energy output capacity, output location, output time, etc. At present, the research, development and application of energy storage technology are mainly based on the storage of thermal energy and electric energy, which are widely used in solar energy utilization, “peak shifting and valley filling” of electric power, waste heat and waste heat recovery, and energy saving of industrial and civil buildings and air conditioners, etc. field. Thermal energy storage is to store the excess heat that is not needed for a period of time in a certain way, and then extract it for use when needed. The technology of the energy storage system mainly includes the control of the energy storage converter, the management of the energy storage battery, and the reasonable scheduling of the system energy by the monitoring and scheduling management unit. Including sensible heat energy storage technology, latent heat energy storage technology, and chemical reaction heat energy storage technology.
In the solar heat utilization system, it is necessary to set up an energy storage device. The working principle of solar heat utilization is that the heat flow leaves the collector and enters the energy storage, and then supplies the heat engine through the heat energy converter. During the absence of sunlight, the cold fluid passes directly through the accumulator, extracts the stored heat and transfers it to the heat engine to work.
The basic task of energy storage systems is to overcome temporal or local differences between energy supply and demand. There are two situations for this difference. One is caused by sudden changes in energy demand, that is, there is a peak load problem. The energy storage method can play a role in regulating or buffering when the load change rate increases. Since the investment cost of an energy storage system is relatively lower than that of building a peak load plant, although the energy storage device will have storage losses, it can still reduce fuel costs because the stored energy comes from excess energy or new energy from the factory . The other is caused by reasons such as primary energy and energy conversion devices. The task of the energy storage system (device) is to balance the energy output, that is, not only to reduce the peak of the energy output, but also to fill the gap in the output. Trough (that is valley filling).
Common characteristics of energy storage systems:
The energy storage system can be connected to the power grid as an independent system, which can play the role of peak shaving and valley filling and reactive power compensation for the power grid; the energy storage system can also form a wind-solar storage system together with new energy power generation to smooth the new energy grid-connected power on the power generation side ; The energy storage system can also be built together with wind power generation, photovoltaic power generation and other new energy power generation systems in the load center to form a micro-grid system to improve energy utilization efficiency, improve power quality, improve power supply reliability, and reflect green environmental protection. According to the new energy access mode, the energy storage microgrid system can be divided into two control modes: common DC bus and common AC bus. The micro-grid power supply is realized through the multi-directional converter system to ensure the uninterrupted operation of the power load even in the state of grid power failure. Through the optimal configuration of batteries, inverters, bidirectional converters, and wind and solar equipment, Solar can realize engineering consulting, design, system integration, and station-level solutions for projects such as energy storage systems, wind and wind storage systems, and energy storage micro-grid systems. monitoring etc.
