The so-called "distributed energy resources" refers to the comprehensive energy utilization system distributed at the user end. The primary energy is mainly gaseous fuel, supplemented by renewable energy, using all available resources; the secondary energy is mainly distributed in the heat, electricity and cooling (value) cogeneration at the user end, supplemented by other central energy supply systems, to achieve direct Cascade utilization of energy to meet the various needs of users, and provide support and supplementation through the central energy supply system; in terms of environmental protection, part of the pollution will be dispersed and resourced, and strive to achieve the goal of moderate emissions; The sheet layout reduces the loss of long-distance energy transmission and effectively improves the safety and flexibility of energy utilization.
1. Introduction to distributed energy resources
Distributed energy resources is an energy supply method built on the user side, which can be operated independently or connected to the grid. It is a system that determines the mode and capacity of resources and environmental benefits by maximizing the user's various energy needs and resource allocation status. System integration and optimization, a new type of energy system that adopts demand-responsive design and modular configuration, is a decentralized energy supply method relative to centralized energy supply.
The International Distributed Energy Alliance WADE defines distributed energy resources as: a high-efficiency combined cooling/heating and power system installed at the user end, the system can generate electricity at (or near) the consumption location, and efficiently use the waste energy generated by power generation to produce heat and electricity; The on-site renewable energy system includes an energy recycling system that uses on-site waste gas, waste heat, and excess pressure difference to generate electricity. Since distributed energy resources is in the process of development in China, there are different expressions on the understanding of distributed energy resources. There are mainly two representative ones: the first refers to the small-scale, small-capacity, modularized, and decentralized way of directly installing the cooling/heating system on the user end, which can independently output cooling, heating, and electric energy. system. Energy includes various forms such as solar energy utilization, wind energy utilization, fuel cell and gas cooling, heating, and electricity tri-generation. The second type refers to the energy system installed at the user end. The primary energy is mainly gas fuel, supplemented by renewable energy. Secondary energy is mainly based on cogeneration of cold, heat, and electricity distributed at the user end, supplemented by other energy supply systems, combining electricity, heat, refrigeration, and energy storage technologies to directly meet various needs of users and realize energy cascade utilization. And provide support and supplement through the public energy supply system to maximize resource utilization.
2. Energy advantages of distributed energy resources
Distributed energy resources has the characteristics of reasonable energy efficiency, low loss, less pollution, flexible operation, and good system economy. The development mainly has issues such as grid connection, power supply quality, capacity reserve, and fuel supply.
The distributed energy resources system distributes the energy cascade utilization on the demand side, as well as the comprehensive utilization of resources and renewable energy facilities. According to the different needs of users for energy at the demand site, the energy supply is realized at the temperature corresponding point, and the loss in the transmission link is minimized, so as to maximize the efficiency of energy utilization.
Distributed energy resources is a system that maximizes resources and environmental benefits to determine the mode and capacity, and determines the scale according to the optimization of terminal energy utilization efficiency.
Distributed energy resources uses advanced energy conversion technology to try to reduce pollutant emissions and disperse emissions to facilitate the absorption of surrounding vegetation. At the same time, distributed energy resources takes advantage of its small emissions and low emission density to realize resource reuse of major emissions, such as fertilization of exhaust gas.
Distributed energy resources relies on the most advanced information technology, adopts intelligent monitoring, networked group control and remote control technology, and realizes unattended on-site. At the same time, it also relies on the energy social service system with energy service companies as the main body in the future to realize the professionalization of operation management and ensure the safe and reliable operation of various energy systems.
3. Technical basis of distributed energy resources
The basic science of distributed energy resources technology is mainly in the following aspects:
3.1 Power and energy conversion equipment: mainly refers to the improvement of some traditional technologies and the development of new technologies.
3.2 Primary and secondary energy-related technologies;
3.3 Intelligent control and group control optimization technology;
3.4 Comprehensive system optimization technology;
3.5 Deep resource utilization technology.
4. Development prospect of distributed energy resources
Distributed energy resources is developing rapidly in developed countries. The governments of developed countries have effectively promoted the development of distributed energy resources through planning guidance, technical support, preferential policies, and the establishment of reasonable price mechanisms and unified grid-connected standards. The proportion of distributed energy resources systems in the entire energy system has continued to increase. Distributed energy resources accounts for about 10%.
Distributed energy resources in my country started relatively late, mainly concentrated in Beijing, Shanghai, Guangzhou and other big cities, where the installation sites are hospitals, hotels, office buildings and university towns. grid-connected" or "grid-connected without grid-connected" mode.
Distributed energy resources technology is an important development direction of the world's energy technology in the future. It has the characteristics of high energy utilization efficiency, small negative impact on the environment, improved energy supply reliability and good economic benefits.
Distributed energy resources is an energy development method that can best reflect multiple advantages such as energy saving, emission reduction, safety, and flexibility, and the "Twelfth Five-Year Plan" clearly proposes to promote the promotion and application of distributed energy resources systems. Therefore, domestic excellent companies in the distributed energy resources industry are paying more and more attention to the research of the industry market, especially the in-depth research on the company's development environment and demand trend changes.
Distributed energy resources technology is a must for China's sustainable development. China has a large population and its own resources are limited. According to the way of energy utilization, it is absolutely impossible to rely on its own energy to support the "all-round well-off" of 1.3 billion people. The use of international energy not only has serious constraints on energy security, but also poses a challenge to the development of the world. A new set of problems and contradictions. Based on the existing energy resources, China must make every effort to improve the efficiency of resource utilization and expand the scope of comprehensive utilization of resources. Distributed energy resources is undoubtedly the key technology to solve the problem.
Distributed energy resources is one of the effective ways to alleviate my country's severe power shortage and ensure the implementation of sustainable development strategies, with huge development potential. It meets the needs of energy strategy security, power security and my country's natural gas development strategy. It can alleviate the pressure of the environment and power grid peak regulation, and can improve energy utilization efficiency.
Since 2004, successive blackouts in the United States, Canada, the United Kingdom, Australia, Denmark, Sweden, Italy and other countries have profoundly demonstrated that there are serious technical defects in traditional energy supply forms. With the development of the times, especially in the information society It is no longer possible to continue to support the development of human civilization. It is necessary to accelerate the establishment of a new energy system in the information age. Distributed energy resources is the core technology of this system.
With the acceleration of my country's smart grid construction, it will effectively deal with the frequent and unstable voltage load of distributed energy resources and solve the technical problems of distributed energy resources grid connection. In addition, there are already a number of distributed energy resources professional service companies in my country, and most of the built projects are running well. Natural gas distributed energy resources has the conditions for large-scale development in my country.
5. Industry issues of distributed energy resources
As of June 2015, there are still many problems in the development of natural gas distributed energy resources in my country, including obstacles in technology, economy, market and operation management, such as user awareness, equipment localization, grid connection, and some Regional gas source issues, etc., but the core is still the price issue, which can be summarized into several aspects.
5.1 High Policy Risks and High Fuel Prices
Policies are not specific, resulting in poor implementation. At present, the national level and local governments have successively issued support policies to encourage the development of natural gas distributed energy resources, and put forward development goals and measures. Issues such as natural gas price discounts, on-grid electricity prices, and direct power supply cannot be implemented. Since national policies do not enforce standards, distributed energy resources strategic risks and market risks are high.
The power generation and transmission mode of distributed energy resources projects is in violation of the current "Electricity Law". At present, projects that have been invested or are under construction, the biggest obstacle is still the problem of "connecting to the grid" of electricity. At present, most of the power generated by natural gas distributed energy resources projects that have been built and operated are self-generated and used by the power grid company, and the electricity price is generally negotiated between the project company and the user.
Furthermore, natural gas distributed energy resources systems require a wide range of technical content, the core of which is power generation equipment. The current technical equipment of distributed energy resources stations mainly includes gas turbines, waste heat boilers, compression refrigeration, absorption refrigeration, cold storage and heat storage equipment, and control systems and equipment. Among all these hardware devices, there is still a large gap between China and foreign countries in terms of technology, and there is a lack of advanced technology with independent intellectual property rights.
5.2 The market environment needs to be cultivated
Natural gas distributed energy resources products have not yet entered the real market economy. The products produced by natural gas distributed energy resources - electricity, heat and cold energy, although widely recognized as commodities, have not implemented real market pricing, and their ex-factory prices are set by the government or guided by the government, so when the upstream When the cost of raw materials and labor rises, the price of downstream electricity, heating and cooling will not change, which will inevitably bring about greater contradictions.
5.3 There are constraints on business operations
The restrictive factors in the operation of natural gas distributed energy resources enterprises are mainly reflected in the high investment cost, long payback period, equipment operation and high fuel cost.
The "China Distributed Energy resources Industry Market Prospect and Investment Strategic Planning Analysis Report" shows that in terms of fixed investment costs, it is still difficult for my country to achieve independent production of distributed energy resources complete sets of equipment, and key equipment and control systems still need to be imported. Although the price of imported equipment is decreasing year by year, it is still maintained at a relatively high level. High equipment cost is an important reason hindering the widespread promotion of distributed energy resources. At the same time, due to the scarcity of localized engineers and senior technicians, the installation cost of natural gas distributed energy resources projects also varies greatly, especially for some less mature technologies, the installation cost can account for 30% of the equipment cost.
Operation and maintenance costs. Because distributed energy resources is a new technology, there are few local engineers and senior technicians with management and maintenance experience, and the labor cost of operating and maintaining equipment cannot be underestimated. At the same time, since the host is imported equipment, regular inspection, replacement, and maintenance of system components and consumables The price is not cheap. Of course, operation and maintenance costs only account for a very low proportion of the entire electricity cost. For example, a micro gas turbine usually only needs to be maintained once or twice a year, and the average maintenance cost is 0.5-1.6 cents per kWh. According to research, the annual operation and maintenance cost of a domestic demonstration project reaches 22 million yuan.
6. Chinese application of distributed energy resources
According to the "2005 Statistical Annual Report on National Power Industry Power Generation" compiled by the China Electricity Council, by the end of 2005, China's coal-fired single-unit heating units of 6000KW and above reached 69.81 million KW. formula energy. We assume that in 2006, the national heating units will increase by 15 million KW. According to the "2010 Cogeneration Development Plan and 2020 Long-term Development Goals": by 2010, the total capacity of the country's cogeneration units will reach 120 million kilowatts, of which about 56 million kilowatts of urban building heating central heating power plants, industrial The thermal power plant for production is about 64 million kilowatts. It is estimated that by 2010, the installed capacity of power generation in the country will reach about 800 million kilowatts, and cogeneration will account for 15% of the total installed capacity of power generation in the country. According to the development situation, it was originally estimated that thermal power in 2010 will reach 120 million kilowatts, which may be too small. Because thermal power has reached 69.81 million kilowatts by the end of 2005, it is estimated that it can increase by 15 million kilowatts in 2006, and then it will increase by 10 million kilowatts every year, and it may reach 125 million kilowatts by the end of 2010.
At present, the situation of distributed energy resources fueled by natural gas in China is as follows: At present, a number of distributed heat, electricity and cold projects fueled by oil and gas have been put into operation in Beijing, Shanghai, Guangzhou and other places in my country, and have achieved obvious economic benefits and environmental protection. benefits and social benefits.
At the same time, the "New Energy Industry Development Plan" that has been revised several times has finally been tentatively finalized. On July 20, 2010, Jiang Bing, director of the Planning and Development Department of the National Energy Administration, disclosed the news: the planning period (2011-2020) will directly increase investment by as much as 5 trillion yuan. The plan puts forward policy guidance for the industrial application of technologies such as clean coal, smart grid, distributed energy resources, and new energy for vehicles, which will directly promote the investment boom of domestic distributed energy resources.
7. Incentive policies for distributed energy resources
Distributed energy resources has the advantages of protecting the environment, saving energy, reducing emissions, etc., but these advantages are external influences, and these advantages are difficult to reflect in the market, and the investment attraction of distributed energy resources is relatively weak, and the government needs to formulate relevant preferential policies Policy support.
7.1 Access conditions for distributed energy resources incentive policies
Distributed energy resources incentive policies should follow the principle of overall planning and consideration of resource development, energy demand, environmental protection and economic benefits, with the goal of energy conservation and emission reduction, the purpose of satisfying the reliability of power supply for users, and the focus on improving energy efficiency, adapting measures to local conditions, and standardizing development. in principle. Access conditions should include the following three aspects:
7.1.1 is to encourage the development of clean and environmentally friendly distributed energy resources, focusing on clean and efficient project types such as renewable energy, natural gas combined heat and power, combined cooling, heating and power, and fuel cells.
7.1.2 is to set up energy efficiency standards for distributed energy sources based on fossil fuels to promote the improvement of comprehensive utilization efficiency of energy. For example, the total thermal efficiency of a distributed energy resources system using fossil fuels should not be less than 70%, and the heat-to-power ratio should not be less than 75%.
7.1.3 is to encourage advanced energy utilization technologies. Encouragement should be given to micro gas turbines, fuel cells, and wind power generation, while small coal-fired power generation, diesel power generation, and other technologies with high pollution and backward technology should not be encouraged.
7.2 Incentive policies for distributed energy resources in my country
Taking into account the differences in the level of social and economic development in various regions, the relevant national departments can jointly formulate general principles and guidance for encouraging policy formulation, and each province can formulate specific incentive policies for distributed energy resources. Incentive policies can include the following three aspects:
7.2.1 is to provide incentives for distributed energy resources investment. Preferential policies include: financial subsidies according to the nameplate capacity of distributed energy resources equipment; in the case of immature technical conditions for domestic equipment, exemption of equipment import tax for projects that really need imported equipment, with the development of domestic distributed energy resources, to reduce the preferential intensity of equipment import tax year by year; banks and other financial institutions give priority loans to distributed energy resources projects and give preferential interest; provide financial subsidies for investment in distributed energy resources access systems.
7.2.2 is to subsidize the operation of distributed energy resources. The subsidy methods include: preferential policies for fuel prices used in distributed energy resources systems; for distributed energy resources companies, preferential policies such as tax reductions and exemptions are provided.
7.2.3 is to guide and encourage the research and development and promotion of distributed energy resources domestic equipment. Relevant measures include: establishing and improving the incentive and guarantee mechanism for scientific and technological innovation, increasing investment in distributed energy resources technology research and development, promoting technology transfer, improving the industrial innovation system, etc.; setting up special funds for distributed energy resources technology research, supporting and Encourage domestic enterprises to introduce, assimilate and absorb foreign advanced technologies, and make independent innovations on this basis.
8. The operation mode of distributed energy resources
my country's distributed energy resources is still in its infancy. Distributed energy resources has its own shortcomings such as large investment and complex operation and maintenance technology. The development of my country's distributed energy resources requires its operation mode to be crucial. In addition, there are still some legal obstacles in the aspect of distributed energy resources supplying power to other users, which is also a problem that needs to be solved in the development of distributed energy resources.
8.1 Analysis of the operation mode of distributed energy resources
There are three main modes of operation of distributed energy resources projects in my country:
Mode 1: The owner invests by himself and is responsible for daily maintenance. Distributed energy resources projects are invested and constructed by their owners, and the owners are responsible for organizing professionals to be responsible for daily equipment operation and maintenance.
Mode 2: adopt the energy service company mode. In this way, distributed energy resources projects are invested by the owner, and after the project is completed, energy services are hired or adopted, and professional institutions such as energy service companies are responsible for the operation and maintenance of the equipment.
Mode 3: Adopt the contract energy management mode. Energy-saving service companies sign energy-saving service contracts with customers, and can provide customers with energy efficiency and reduce energy consumption by using distributed energy resources equipment. The contract energy management provided by the energy-saving service company includes: project design, project financing, equipment procurement, construction, equipment installation and commissioning and other energy-saving services, and recovers investment and obtains profits from the energy-saving benefits obtained after energy-saving renovations by customers.
For distributed renewable energy, the initial investment is relatively small, the daily maintenance is relatively simple, and the surplus power is usually directly connected to the grid, and the mode 1 or mode 2 can be used.
For natural gas distributed energy resources, especially combined heat and power and trigeneration systems, since it involves knowledge of engine mechanics, grid connection and three-phase load management, thermal technology and computerized management of water circulation, multiple professional fields are required technicians are responsible for operation and maintenance. For this type of distributed energy resources system. Professional energy service companies can be introduced, and the energy service company is responsible for daily maintenance or contract energy management.
8.2 The problem of supplying power to other users
The development and utilization of distributed energy resources should first be based on meeting the energy needs of users themselves, reducing energy transmission losses, and improving the comprehensive energy utilization efficiency of users. On the basis of meeting its own power demand, there may be a surplus of power during the low power consumption period of users.
According to the provisions of my country's "Electricity Law", "power supply enterprises supply power to users in the approved power supply business area", "only one power supply business organization is established in a power supply business area", "power supply business organizations hold the "power supply business license" The administrative department must apply for a business license before it can operate." Distributed energy resources owners sell excess power to other users, which does not comply with the relevant provisions of the Electricity Law.
In addition, since my country has not launched competition on the electricity retail side, independent transmission and distribution prices have not yet been formed, and the policy conditions do not yet meet the conditions for selling the surplus electricity of distributed energy resources to other users. It is suggested that at this stage, the surplus electricity of distributed energy resources is only sold to grid companies, and the on-grid electricity price shall be implemented according to the on-grid electricity price of distributed energy resources approved by the government. With the development of my country's electricity market construction and the establishment of the transmission and distribution price mechanism, when the policy and legal conditions are met, the electricity sales transaction between distributed energy resources and other users will be carried out.
9. The development significance of distributed energy resources
Specifically, the significance of developing distributed energy resources is as follows:
Since distributed energy resources 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.
9.2 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.
9.3 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.
9.4 Peak regulation effect
Summer and winter are often the peak load periods. At this time, if a combined cooling, heating and electricity system such as a gas turbine fueled by natural gas is used, it can not only meet the cooling and heating needs in summer and winter, 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.
9.5 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.
9.6 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.
9.7 Investment Risk The installed capacity of distributed power generation is generally small and the construction period is short, so the investment risk brought by the construction period of similar large-scale power stations can be avoided.
9.8 Power supply problems in remote areas Many remote and rural areas in my country are far away from the large power grid, so it is difficult to supply power to them from the large power grid. Self-contained power generation systems using solar photovoltaic power, wind power and biomass power generation may well be a preferred method.
As far as the world is concerned, countries with higher energy utilization rates and better environmental protection are more enthusiastic about the promotion and application of distributed energy resources technology, and the support policies are clearer. For example, Denmark, the Netherlands, and Japan have adopted a series of incentive policies for distributed power; after the "911 Incident", out of consideration for power supply security, developed countries have accelerated the pace of distributed power construction. So far, Britain has There are more than 1,000 distributed power stations; there are more than 6,000 distributed power stations in the United States, and there are more than 200 distributed power stations on university campuses alone. Among many countries, Denmark is recognized in the world as a model of the organic combination of economic development, resource consumption and environmental protection, and a country that has achieved sustainable development. Over the past 20 years, Denmark's GNP has doubled, but energy consumption has not increased, and environmental pollution has not intensified. The secret is that Denmark actively develops combined cooling, heating and electricity, promotes scientific energy use, and supports distributed energy resources. Support the development of the national economy by improving energy efficiency. Before 2013, there was not a single thermal power plant in Denmark that did not provide heat, and there was not a single heating boiler room that did not generate electricity. The separate generation of cold, heat, and electricity products was transformed into a high-tech cogeneration of cold, heat, and electricity, which made technological progress change. into real productivity.
According to literature reports, before 2010, 25% to 30% of the cumulative new power generation capacity in the world was distributed power generation. The United States is the country that develops the most new energy and renewable distributed energy resources generation in the world, and is also the main provider of most commercial distributed power equipment in the world. In 2004, the total capacity of distributed power generation in the United States was 67 GW, accounting for about 7% of the total domestic power generation in the United States, reaching the world average level. Distributed power, while the National Natural Gas Foundation estimates that it is as high as 30%. By 2020, more than half of new commercial or office buildings will use distributed power. At the same time, by 2020, 15% of existing buildings will switch to distributed power. The development of distributed power in Europe is at the leading level in the world; in 2000, the installed capacity of distributed power in the European Union was 74 GW, and in 2004 the total power generation of distributed power in Denmark, the Netherlands and Finland accounted for 52% of the total domestic power generation. , 38% and 36%, the EU predicts that it will reach 195 GW in 2020, and the power generation will reach 22% of the total power generation.