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Future Microgrid and Multi-Energy Complementary Technology Trends

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2020-11-26

For a long time, the microgrid has emphasized the distributed characteristics more, whether it is connected to the large power grid or not, self-management and self-control are its typical characteristics. No matter how it is defined, microgrids are still inseparable from the properties of their power grids, and must also comply with some golden rules in power grid design. Among them, security and stability are undoubtedly the most important criteria. In order to ensure security while accessing a high proportion of distributed renewable energy, the most critical thing is the flexibility of the system.
Under the framework of flexibility, countries have slightly different definitions and development trends for microgrids. In July, my country issued the "Trial Measures for Promoting the Construction of Grid-connected Microgrids", which gave the official definition of microgrids. . Today, we are introducing a series of development trends in the construction of microgrids in the United States. The core of which is the cogeneration equipment system. The coupling of thermoelectricity at the consumer end and the decoupling of the production end will easily solve a series of flexible and flexible microgrids. Sexual issues.

In many microgrid construction practices in the United States, the following trends and standards for future microgrid construction are summarized:

1. Put energy efficiency first and refuse to waste
What is the cheapest and cleanest electricity? A lot of people would say renewable electricity. But in fact, the electricity that is wasted in the process of energy production, transportation and consumption is the part we should be most concerned about. A recent report by the ACEEE organization pointed out that the average cost of generating one kilowatt-hour of electricity through energy-saving measures and energy-efficient equipment is around 2.8 cents, or 17 cents. Compared with the coal power generation cost of about 35 cents in my country, the power brought by energy upgrade is very competitive.

2. Cogeneration, multi-energy complementary Cogeneration, as the name suggests, is an energy production method that produces heat and electricity at the same time. The waste heat in the power generation process is reused and converted into cold energy for heating, domestic hot water, industrial heating and even through absorption refrigeration equipment. This coupled energy production method can increase the energy efficiency utilization rate to 80%, and the efficiency of the same fuel used to produce electricity and heat energy respectively does not exceed 45%. At present, with the maturity of gas turbine miniaturization technology, efficient cogeneration equipment can also become the core component of distributed energy supply.

There are also several important reasons why cogeneration equipment is gradually becoming one of the indispensable elements in microgrid design:
If the simultaneous production of heat is not considered, the cost of generating electricity from a small gas turbine is usually higher than the cost of purchasing electricity from the grid. Only the comprehensive energy cost after coupling thermal energy is more competitive;
Combined heat and power plants are more reliable and flexible than renewable energy sources;
The CHP plant can also be used as an emergency power source for many elevators and water pumps, which would not be sufficiently safe to be provided by batteries alone.
Another important reason is that the storage of thermal energy is much easier than the storage of electrical energy, and the fluctuation of thermal load is smaller than that of electrical load. The additional installation of thermal storage equipment in the cogeneration equipment can realize the decoupling of thermal and power production, providing more flexibility. The storage capacity of the heat grid itself also provides some resilience to the system. Among the various microgrid design models at present, the thermoelectric multi-energy complementary mode is the most cost-effective, none of which is available.
3. Wind-solar complementarity, clean power Under the current technical level, cogeneration equipment will become the core of the micro-grid system, and in areas where conditions permit, wind power and photovoltaics will also become an important part of the micro-grid power generation. In the practice of many microgrid projects in the United States, cogeneration usually accounts for 80% of the power generation capacity, and wind power and photovoltaics account for the remaining 20%. In the future, as the cost of renewable energy power generation continues to decrease and new technologies develop, the proportion of renewable energy power generation will continue to increase.
The advantage of renewable energy power is naturally clean power with zero emissions, and there is no need to build additional fuel transportation channels. The disadvantages are also very obvious. In the absence of sufficient energy storage equipment, the stability of energy supply has been greatly affected. challenge.
4. Necessary energy storage to ensure safety In order to alleviate the intermittent power generation and load side fluctuations of wind power and photovoltaics in the microgrid system, energy storage equipment has become the standard configuration of most microgrids. The energy storage device here refers not only to batteries, but also to the storage of different types of energy media such as heat storage and gas storage. In the case that the cost of batteries as a large-scale energy storage device is still high, other types of energy storage devices can be more applied in multi-energy complementary microgrid projects.

At present, the energy storage equipment of most microgrid projects is still used to smooth the user load curve and make up for the electricity generation and consumption gap within the day and week. There is no better integration plan for long-term seasonal energy storage equipment.
In general, the design and planning of microgrids must fully consider the local resource endowment and the needs of users, take the safety and reliability of system energy supply as the first standard, and then consider economy and environmental friendliness on this basis. The design should consider not only the balance of energy supply and demand, but also the balance between equipment that can provide flexibility and equipment that consumes flexibility.