Distributed power supply devices refer to small modular, environment-compatible independent power supplies with a power of several thousand watts to 50 MW. These power sources are owned by utilities, power users or 3rd parties to meet power system and user-specific requirements. Such as peak shaving, power supply for remote users or commercial areas and residential areas, saving investment in power transmission and transformation, improving power supply reliability, etc.
Distributed at the user end, connected to the power grid with a voltage level of 35kV and below, and mainly consumed locally. Including solar energy, natural gas, biomass energy, wind energy, water energy, hydrogen energy, geothermal energy, ocean energy, comprehensive utilization of resources for power generation (including coal mine gas power generation) and energy storage.
1. The meaning of distributed power
The most concise definition of distributed power is: a power supply with a voltage level of 35kV and below that is not directly connected to the centralized power transmission system, mainly including power generation equipment and energy storage devices.
2. Advantages of distributed power
2.1 Economy: Since the distributed generation is located on the user side and close to the load center, the construction cost and loss of the transmission and distribution network are greatly reduced; at the same time, the planning and construction period of the distributed generation is short, the investment is quick, and the risk of investment is small .
2.2 Environmental protection: Distributed power generation can make extensive use of clean and renewable energy, reduce the consumption of fossil energy and the emission of harmful gases.
2.3 Flexibility: Distributed power generation systems mostly use small and medium-sized modular equipment with advanced performance, which are quick to start and stop, easy to maintain and manage, and flexible to adjust, and each power supply is relatively independent, which can meet different needs such as peak shaving and valley filling, power supply to important users, etc. need.
2.4 Security: Distributed power generation has a variety of forms, which can reduce the dependence on a single energy source and alleviate the expansion of the energy crisis to a certain extent; Potential for massive blackouts.
3. Characteristics of distributed power supply
Distributed energy systems do not simply adopt traditional power generation technology, but are based on new technologies such as automatic control systems, advanced material technology, and flexible manufacturing processes. They have low pollution emissions, flexibility, convenience, high reliability and High-efficiency new energy production system.
The power generation system that makes up the distributed energy system has the following characteristics:
3.1 Efficiently use the waste energy generated by power generation to generate heat and electricity;
3.2 On-site renewable energy system;
3.3 Including the energy recycling system that uses on-site waste gas, waste heat and excess pressure difference to generate electricity.
4. Classification of distributed power
Distributed Generation (DG) devices can be divided into heat, power and cooling combined power generation, internal combustion unit power generation, gas turbine power generation, small hydropower generation, wind power generation, solar photovoltaic power generation, fuel cell, etc. according to the different technologies used; DG can be divided into two forms: fossil energy (coal, oil, natural gas) power generation and renewable energy (wind, solar, tidal, biomass, small hydropower, etc.) power generation. Distributed Energy Storage (DES) device refers to a modular energy storage and conversion device that can be assembled quickly and connected to the distribution network. According to different energy storage forms, DES can be divided into electrochemical energy storage (such as battery energy storage device), electromagnetic energy storage (such as superconducting energy storage and supercapacitor energy storage, etc.), mechanical energy storage device (such as flywheel energy storage and compressed air energy storage, etc.), thermal energy storage devices, etc. In addition, electric vehicles, which are developing rapidly, can also send power to the distribution network when it is needed, so it is also a kind of DES.
5. Definition of Distributed Power
The definition of distributed power generation is that it is located near the user, the power generated can be used locally, connected to the power grid at a voltage level of 10 kV and below, and the total installed capacity of a single grid-connected point does not exceed 6 megawatts. Including solar energy, natural gas, biomass energy, wind energy, geothermal energy, ocean energy, comprehensive utilization of resources and other types of power generation.
6. The use of distributed power
Today's distributed power mainly refers to micro-grids composed of liquid or gas fueled internal combustion engines (IC), micro turbines (Micro turbines), various engineering fuel cells (Fuel Cell), solar power plants, and wind turbines. Because of its good environmental protection performance, distributed power supply and "small unit" are not the same concept.
7. The significance of distributed power
Distributed energy can use fuels such as natural gas and coalbed methane, waste gas resources such as biogas and coke oven gas, and even renewable resources such as wind energy, solar energy, and water energy. Since distributed energy projects are mostly built in cities, most distributed energy fuels are mostly natural gas or diesel. Specifically, the significance of developing distributed energy is as follows:
Since distributed energy can be used for heating and cooling with the waste heat of power generation, the energy can be used in a reasonable cascade, which can improve the efficiency of energy utilization (up to 70%-90%). Due to the grid connection of distributed power sources, the construction of large-scale power plants and high-voltage transmission networks is reduced or delayed, and the construction of power grids is delayed to save investment. At the same time, the power flow of the transmission and distribution network is reduced, and the network loss is correspondingly reduced.
7.2 Environmental protection
Because it uses natural gas as fuel or hydrogen, solar energy, and wind energy as energy sources, it can reduce the total emission of harmful substances and reduce the pressure on environmental protection: a large number of nearby power supply reduces the construction of large-capacity long-distance high-voltage transmission lines, thus It not only reduces the electromagnetic pollution of high-voltage transmission lines, but also reduces the land acquisition area and line corridors of high-voltage transmission lines, and reduces the felling of trees under the lines, which is conducive to environmental protection.
7.3 Diversity of energy use
Distributed power generation can utilize a variety of energy sources, such as clean energy (natural gas), new energy (hydrogen) and renewable energy (wind energy and solar energy, etc.), and at the same time provide users with multiple energy applications such as cold, heat, and electricity, so It is a very good way to solve the energy crisis, improve energy utilization efficiency and energy security issues.
7.4 Peak regulation effect
Summer and winter are often the peak load periods. At this time, if the combined cooling, heating and electricity supply system such as gas turbines fueled by natural gas is used, it can not only solve the cooling and heating needs in winter and summer, but also provide part of the Electricity, which can play a role in peak-shaving and valley-filling of the power grid. In addition, it also partially solves the problem of excessive peak-to-valley difference in natural gas supply, and plays a complementary role between natural gas and electricity.
7.5 Safety and reliability
When there is a large-scale power outage in the large power grid, the distributed power generation system with a special design can still maintain normal operation, thereby improving the safety and reliability of power supply.
7.6 Electricity Market Issues
Distributed power generation can adapt to the needs of the development of the power market, and a number of companies will raise funds to run power, and play a competitive role in the power construction market and power supply market.
7.7 Investment Risks
The installed capacity of distributed power generation is generally small and the construction period is short, so it can avoid the investment risks brought about by the construction period of similar large-scale power stations.
7.8 Power supply problems in remote areas
Many remote and rural areas in our country are far away from the large power grid, so it is difficult to supply power to them from the large power grid. Independent power generation systems using solar photovoltaic power generation, wind power generation and biomass power generation may well be a preferred method.