New energy power generation generally refers to renewable energy that is developed and utilized on the basis of new technologies, including solar energy, biomass energy, wind energy, geothermal energy, wave energy, ocean current energy, and tidal energy. In addition, there are hydrogen energy, etc.; coal, oil, natural gas, water energy, nuclear fission energy and other energy sources that have been widely used are called conventional energy sources. New energy power generation is the process of using existing technologies to realize power generation through the above-mentioned new energy sources.
1. New energy power generation development and utilization
1.1 Energy resources
Energy resources include coal, oil, natural gas, hydropower, etc., as well as new energy sources such as solar energy, wind energy, biomass energy, geothermal energy, ocean energy, and nuclear energy. Throughout the history of social development, human beings have experienced firewood energy, coal energy, oil and natural gas energy, and are transitioning to a new energy era, and countless scholars are still unremittingly looking for and developing newer and safer energy for social progress. However, the energy available to people is still dominated by coal, oil, and natural gas. In the world's primary energy consumption structure, the sum of these three accounts for about 93%.
Energy can be divided into the following four categories according to its source:
The first category is from solar energy. In addition to direct solar radiation energy, fossil fuels such as coal, oil, and natural gas, and resources such as biomass energy, water energy, wind energy, and ocean energy all come indirectly from solar energy.
The second type is geothermal energy stored in the earth's interior in the form of thermal energy, such as underground hot water, underground steam, and dry hot rock mass.
The third category is nuclear fission energy such as uranium and thorium on the earth and nuclear fusion energy such as deuterium, tritium and lithium.
The fourth category is the gravitational force of stars such as the moon and the sun on the earth, and the energy generated mainly by the gravitational force of the moon, such as tidal energy.
Energy is classified according to its use, and the energy that can be directly obtained from nature without changing its basic form is called primary energy.
In a certain historical period and scientific and technological level, the energy that has been widely used by people is called conventional energy. Those energy sources that are ancient but require new and advanced science and technology to be widely used are called new energy sources. Any energy that can be continuously regenerated and replenished regularly in nature is called renewable energy. Energy that has been formed over hundreds of millions of years and cannot be recovered in a short period of time is called non-renewable energy.
1.2 Efficient use of resources
Among energy resources, non-renewable energy such as coal, oil, and natural gas can be used as both raw materials and fuels in many industries, agricultural sectors, and people's lives, and resources are in short supply. Therefore, how to optimize the allocation of resources and improve the effective utilization of energy is of great significance to the survival and reproduction of human beings and the economic development of the country. Human production and life are always faced with an unavoidable and unchangeable fact that resources are scarce. Even the infinite needs of human beings and the limitation of material resources will accompany the development of human society from beginning to end.
Electric energy is secondary energy converted from primary energy. Electric energy is not only suitable for mass production, centralized management, automatic control and long-distance transmission, but also easy to use, clean and economical. Replacing other energy sources with electric energy can improve energy utilization efficiency. With the development of the national economy, the proportion of direct consumption of primary energy in final consumption is decreasing day by day, the proportion of consumption of secondary energy is increasing, and the proportion of electric energy in primary energy consumption is increasing year by year. my country's electricity supply still cannot meet the growing demand for electricity from the development of the economy, the progress of science and technology, and the improvement of people's production and living standards.
my country's modernization drive is facing the great challenge of energy supply. In order to alleviate the tense situation of energy supply, we must advocate conservation in the whole society and build a conservation-oriented society. Saving electricity is not only saving primary energy, but also necessary to solve the current prominent contradiction between power supply and demand. Power saving is to obtain the maximum economic benefits with a certain amount of electric energy, that is, to use electric energy rationally and improve the utilization rate of electric energy. Even if the electricity is abundant and there is no shortage of electricity, it should be used reasonably and effectively and should not be squandered at will. According to sympathy, our country has formulated an energy policy to increase revenue and reduce expenditure, insist on equal emphasis on energy development and conservation, and put energy conservation and electricity conservation in the first place at present. In terms of source of income, we must vigorously develop coal, oil, and natural gas, and accelerate the pace of power construction, especially the development of hydropower. The development of the energy industry should focus on electric energy, actively develop thermal power, vigorously develop hydropower, build nuclear power in a focused and step-by-step manner, and actively develop new energy power generation. In terms of energy saving, we will vigorously carry out energy saving work such as coal saving, fuel saving, and electricity saving. The way out for saving electricity is to adhere to scientific management, rely on technological progress, take the road of rational and economical use of electricity, and improve the utilization rate of electric energy, so as to greatly reduce the power consumption of unit products and create the greatest wealth with the least amount of electric energy.
In the first November of 2021, my country's new energy power generation reached 1,035.57 billion kwh, breaking through 1 trillion kwh for the first time in the year, a year-on-year increase of 32.97%, accounting for 13.8% of the country's total electricity consumption, a year-on-year increase of 2.14 percentage points.
2. Classification of new energy power generation
Water energy is the potential energy and kinetic energy stored in rivers and ocean water bodies. It is a clean primary energy source and an inexhaustible renewable energy source. my country is rich in hydropower resources. According to the latest survey data, the theoretical reserves of my country's hydropower resources reach 689 million kW, of which the technically developable installed capacity is 493 million kW, and the economically developable installed capacity is 395 million kW, ranking first in the world. first place. As of the end of 2012, the total installed capacity of the country was 1.14 billion kW, of which the installed capacity of hydropower exceeded 249 million kW, accounting for 21.83% of the total installed capacity of the country.
A hydropower station is a factory that converts water energy into electrical energy. The basic process of energy conversion is: water energy-mechanical energy-electric energy.
Building dams in the upper reaches of the river concentrates the river water flow and the scattered river sections, so that the water in the reservoir 1 has a higher potential energy. When the water flows from the pressure water pipe 2 through the water turbine 4 installed in the hydropower plant 3 and is discharged to the downstream, The water turbine is driven to rotate, and the water energy is converted into the mechanical energy of the water turbine rotation; the rotating shaft of the water turbine drives the rotor of the generator 5 to rotate, and the mechanical energy is converted into electrical energy. This is the basic process of hydroelectric power generation.
Water flow and water head (the difference between upstream and downstream water levels, also called drop) are the two major factors that constitute water energy. According to the way of energy utilization, hydropower stations can be divided into: conventional hydropower stations that convert water energy in rivers into electrical energy, also known as hydropower stations. According to the method of concentrated drop, it has three basic forms, namely dam type, water diversion type and mixed pumped storage hydropower station that adjusts the peak and valley loads of the power system; hydropower stations that use the mechanical energy of water flow in ocean energy to generate electricity, namely tidal power stations, wave power stations, and ocean current power stations.
Hydropower mainly has the following characteristics:
2.1.1 Water energy is a renewable energy source, and the natural water flow generated by electricity is not lost, generally does not cause water pollution, and can still be used by downstream water departments.
2.1.2 Hydropower is a clean electricity production that does not emit harmful gases, soot and ash, and has no nuclear waste.
2.1.3 The efficiency of hydropower generation is high, and the power generation efficiency of conventional hydropower stations is above 80%.
2.1.4 Hydropower can simultaneously complete primary energy development and secondary energy conversion.
2.1.5 The production cost of hydroelectric power is low, no fuel is required, fewer operating personnel are required, the labor productivity is high, the management and operation are simple, and the operation reliability is high.
2.1.6 The hydroelectric generating set is flexible in starting and stopping, the output power increases and decreases quickly, and the variable range is large. It is an ideal peak-shaving, frequency-regulating and emergency backup power supply for the power system.
2.1.7 The one-time investment of hydropower development is large and the construction period is long. For example, the Three Gorges Project started construction in December 1994, and the first unit was connected to the grid for power generation in July 2003.
2.1.8 Affected by changes in the natural runoff of rivers, hydropower stations without reservoir regulation or with poor reservoir regulation capabilities have large changes in the annual and inter-annual power generation, which does not meet the needs of users for electricity. Therefore, general hydropower stations need to build reservoirs to regulate runoff to meet the needs of power system loads. Nowadays, the power system generally adopts the joint power supply mode of water, thermal and nuclear power plants, which can not only make up for the shortcomings of hydropower's natural runoff, but also make full use of hydroelectric power in wet seasons and save fuel consumed by thermal power plants. Tidal and wave energy also changes over time, and the power generated should also be matched with power generated by other types of energy sources.
2.1.9 The reservoirs of hydropower stations can be used comprehensively to undertake tasks such as flood control, irrigation, shipping, water for urban and rural life, industrial and mining production, breeding, and tourism. If properly arranged, one reservoir can be used for multiple purposes, and one water can be used for multiple purposes, and the best comprehensive economic and social benefits can be obtained.
2.1.10 For hydropower stations with relatively large reservoirs, some reservoirs have greater inundation losses and more immigrants, which have changed people's production and living conditions; reservoir inundation affects the living environment of wild animals and plants; reservoirs regulate runoff and change the original environment. There are hydrological conditions, which have a certain impact on the ecological environment.
2.1.11 Hydropower resources are geographically distributed unevenly. Large-scale hydropower stations with better dam construction conditions and less reservoir inundation losses are often located in remote areas far away from the power load center. The construction conditions are difficult and long-term construction is required. Transmission lines increase the cost and transmission loss.
my country's river hydropower resources rank first in the world, but the installed capacity only accounts for about 25% of the exploitable resources. As a clean and renewable energy source, the development and utilization of hydropower has practical significance for changing my country's coal-based energy composition. However, about 70% of my country's river water energy resources are concentrated in the southwest region, and the economically developed eastern coastal areas have very little water energy resources, and the catastrophic impact of large-scale hydropower construction on the ecological environment is increasingly being affected by human beings. Attention; Southwest my country has extremely rich biological resources, spectacular natural landscape resources and long-standing ethnic cultural resources. It is believed that large-scale hydropower development will be carefully decided in the near future.
2.2 Solar power generation
According to the way of using solar energy, solar power generation mainly includes solar thermal power generation through thermal process (tower power generation, parabolic concentrating power generation, solar chimney power generation, thermal ion power generation, thermal photovoltaic power generation and temperature difference power generation, etc.) and photovoltaic power generation without thermal process , photoinduction power generation, photochemical power generation and photobiological power generation. The main applications are photovoltaic power generation (PV, Photovoltaic) that directly utilizes solar energy and solar thermal power generation (CSP, Concentrating Solar Power) that indirectly utilizes solar energy. Among them, the photovoltaic power generation that directly uses light energy to generate electricity is composed of photovoltaic (PV) cells and a balance system; the indirect use of light energy is the conversion of solar energy into heat energy, and solar thermal power generation (light=heat-electricity) that uses heat storage to generate electricity, CSP According to the arrangement of solar energy collection equipment, it can be divided into three types: trough type (Linear CSP), tower type (Power Tower CSP) and disc type (Dish/Engine CSP).
2.3 Photovoltaic power generation.
Photovoltaic (PV) power station [photovoltaic (PV) power station] is a power generation system that directly converts solar radiation energy into DC power through photovoltaic cell components, and connects it to the grid through a power conversion device, and transmits active power and reactive power to the grid. Generally, it includes a photovoltaic array (a large power supply device composed of several photovoltaic cell components connected in series or parallel according to the load capacity requirements), controller, inverter, energy storage controller, energy storage device, etc.
The grid-connected photovoltaic power generation system refers to the DC power output by photovoltaic cells, through the grid-connected photovoltaic inverter, the DC power is converted into a sine wave AC current with the same frequency and phase as the grid, and connected to the grid to realize the function of grid-connected power generation . The principle of photovoltaic power generation is determined by the photovoltaic cells that make up the photovoltaic array. The working principle of photovoltaic cells is to use the photovoltaic effect of photovoltaic cells (also known as photovoltaic effect) to convert energy. The photovoltaic effect is to use the photovoltaic effect of semiconductor p-n junctions. When light shines on the semiconductor, the photons of sunlight convert energy Provided to electrons, the electrons jump to a higher energy band and excite electron-hole pairs. The electrons, electrons and holes move to the two ends of the battery respectively. At this time, the photo-generated electric field not only cancels the barrier electric field, but also makes the p-zone Positively charged, the n region is negatively charged, and an electromotive force is formed between the n region and the p region, which means that the light causes a potential difference between different parts of the inhomogeneous semiconductor or the combination of the semiconductor and the metal. In this way, if the external path is formed, a current will be generated to form electric energy.
Photovoltaic cells can be divided into silicon-based photovoltaic cells, compound-based photovoltaic cells, and organic semiconductor-based photovoltaic cells according to the materials used. Silicon-based photovoltaic cells can be divided into crystalline silicon-based and amorphous silicon-based photovoltaic cells. Among them, crystalline silicon-based photovoltaic cells can be divided into monocrystalline silicon and polycrystalline silicon photovoltaic cells.
The more mature and widely used is the crystalline silicon battery. The advantages of photovoltaic cells made of crystalline silicon materials are that they are very rich in raw materials, have high reliability, and relatively stable characteristics, and can generally be used for more than 20 years. In terms of comprehensive performance such as energy conversion efficiency and service life, monocrystalline silicon photovoltaic cells of crystalline silicon photovoltaic cells have the highest conversion efficiency among silicon photovoltaic cells, and the theoretical value of conversion efficiency is 24% to 26%, while the conversion efficiency of polycrystalline silicon is slightly lower. , The theoretical value of the conversion efficiency is 20%, but the price is cheaper; at the same time, monocrystalline silicon and polycrystalline silicon cells are better than amorphous silicon cells. Under large-scale industrial production conditions, the conversion efficiency of monocrystalline silicon cells has reached 16% to 18%, and the conversion efficiency of polycrystalline silicon cells is 12% to 14%. Thin-film cells with multi-thin layers and multi-p-n junction structure can achieve a photoelectric conversion efficiency of more than 40% to 50%. The basic principle is to lay a very thin layer of photoelectric material on a non-silicon material substrate, greatly Reduced consumption of silicon semiconductors for optoelectronic materials reduces the cost of photovoltaic cells. Silicon thin-film photovoltaic cells have more prospects for sustainable development due to their abundant raw material reserves, non-toxic and non-polluting.
2.4 Solar thermal power generation.
Solar thermal power generation, also called Concentrating Solar Power (CSP for short), is different from traditional power stations in that they use a large number of reflectors to gather direct solar light in a focused manner to heat the working fluid. Generate high-temperature and high-pressure steam, and convert heat energy into high-temperature steam to drive a steam turbine to generate electricity. Current solar thermal power generation can be divided into solar thermal power generation according to solar energy collection methods: trough solar thermal power generation, tower solar thermal power generation and dish solar thermal power generation.
2.5 Geothermal power generation
Geothermal power generation is the production process of converting underground thermal energy into mechanical energy, and then converting mechanical energy into electrical energy. According to the storage form of geothermal energy, geothermal energy can be divided into five categories: steam type, hot water type, dry hot rock type, ground pressure type and magma type. From the perspective of geothermal energy development and energy conversion, the above five types of geothermal resources can be used to generate electricity, but the steam and hot water resources are more developed and utilized.
The advantages of geothermal power generation are: generally no fuel is required, the cost of power generation is lower than that of hydropower, thermal power, and nuclear power in most cases, the utilization time of equipment is long, the investment in building plants is generally lower than that of hydropower stations, and it is not affected by rainfall and seasonal changes. Influence, stable power generation, can greatly reduce environmental pollution.
There are mainly two methods of using underground hot water to generate electricity: step-down expansion method and intermediate medium method.
2.5.1 Step-down expansion method. The decompression expansion method is designed based on the principle that the vaporization temperature of hot water is related to the pressure. For example, the vaporization temperature of water is 68.7°C at 0.3 absolute atmospheric pressure. By reducing the pressure, the hot water is boiled into steam to drive the turbine generator to generate electricity.
2.5.2 Intermediate medium method. The intermediate medium method adopts a double-cycle system, that is, uses underground hot water to indirectly heat some "low boiling point substances" to drive the steam turbine to generate power. For example, the boiling point of water under normal pressure is 100°C, while some substances such as ethyl chloride and freon have boiling points of 12.4°C and -29.8°C under normal pressure respectively. These substances are called "low boiling point substances". According to the characteristics of these substances boiling at low temperature, they can be used as an intermediate medium for underground hot water power generation. Using "intermediate medium" to generate electricity can use both underground hot water (steam) above 100°C and underground hot water below 100°C. For underground hot water with a lower temperature, the efficiency of "depressurization expansion method" is low, and there are certain technical difficulties, while the "intermediate medium method" is more appropriate.
2.6 Ocean energy power generation
Ocean energy mainly includes tidal energy, wave energy, ocean current energy, seawater temperature difference energy and seawater salinity difference energy, etc. Tidal energy refers to the kinetic energy and potential energy of water formed by the rising and falling tides of seawater; wave energy refers to the kinetic energy and potential energy of waves on the ocean surface; current energy (tidal energy) refers to the kinetic energy of seawater flow, mainly referring to the water in submarine channels and straits. Relatively stable water flow, and regular seawater flow caused by tides; seawater temperature difference energy refers to the heat energy generated by the temperature difference between ocean surface seawater and deep seawater; seawater salinity difference energy refers to the difference between seawater and fresh water or two kinds of water Potential difference between seawater with different salinity.
Ocean energy power generation has the following characteristics.
2.6.1 Energy reserves are large and can be regenerated. The theoretical reserve of sea water temperature difference energy on the earth is about 50 billion kW, about 2 billion kW that can be developed and utilized; the reserve of wave energy is about 70 billion kW, about 3 billion kW that can be developed and utilized; the theoretical reserve of tidal energy is about 30 billion kW. The total power of ocean current energy (tidal current energy) is about 5 billion kW, of which about 50 million kW can be developed and utilized; the reserve of seawater temperature difference energy is about 30 billion kW, of which more than 2.6 billion kW can be developed and utilized.
2.6.2 Low energy density. Seawater temperature difference energy is low thermal head, the maximum temperature difference is 20-25°C; tidal energy is low water head, the maximum tidal range is 7-10m; ocean current energy and tidal current energy are low-velocity, the maximum flow velocity is generally only about 2m/s ; Wave energy, even for a sea surface with a wave height of 3m, its energy density is an order of magnitude lower than that of conventional coal power.
2.6.3 The stability is better than other natural energy sources. Seawater temperature difference energy and ocean current energy are relatively stable, and changes in tidal energy and tidal current energy follow a regular pattern.
2.6.4 The development is difficult and requires high technical requirements for materials and equipment.
2.7 Biomass power generation
Biomass energy resources are organic resources that can be converted into energy, mainly including firewood, crop straw, human and animal manure, food manufacturing industrial waste and wastewater, and organic waste. The most effective way to use biomass energy to generate electricity is to convert it into energy forms that can drive generators, such as gas, fuel oil and alcohol, etc., and then generate electricity according to general power generation technologies.
The main characteristics of biomass power generation technology are as follows:
2.7.1 There must be supporting biomass energy conversion technology, and the conversion equipment must be safe, reliable, and easy to maintain;
2.7.2 The raw materials for power generation using local biomass energy resources must have sufficient storage to ensure continuous supply;
2.7.3 The installed capacity of the power generation equipment used is generally small, and most of them operate independently;
2.7.4 Utilize local biomass energy resources to generate electricity and supply electricity locally, which is suitable for agricultural and animal husbandry areas and mountainous areas with scattered residence, sparse population, and small electricity load.
2.8 Key technologies that need to be solved when new energy power generation is connected to the grid
The intermittency and volatility of wind energy, solar energy and other new energy power generation requires coordination and cooperation after large-scale access to the grid, requiring the grid to continuously improve its adaptability, safety and stability control capabilities, and reduce the impact of wind and solar grid integration. Security and stability risks, and ultimately ensure the safe and stable operation of the power grid. According to statistics, in 2009, the installed wind power capacity of the State Grid Corporation of China system reached 17 million kW, of which the installed wind power capacity of the Three North Power Grid was 15.17 million kW, a year-on-year growth rate of 93.6%; the installed wind power capacity accounted for 2.70% of the total installed capacity of the company's system. Due to the lack of unified planning and hastily launching, many problems have been encountered in the transmission of wind power bases, and a large number of in-depth experimental research work is urgently needed in terms of grid connection technology. include:
2.8.1 Establish a complete wind power and photovoltaic power generation grid-connected technical standard system.
Due to the relatively late start of wind power and photovoltaic power generation in my country, there is still a large gap in the operation control technology of wind power and photovoltaic power generation. Therefore, it is necessary to learn from international advanced experience. On the other hand, it is necessary to speed up the formulation of national grid-connected technical guidelines to promote the improvement of equipment manufacturing technology and operating performance.
2.8.2 Establish wind power and photovoltaic power generation forecasting system and network access certification system.
my country's wind power and photovoltaic power generation laboratory and certification system construction is still in its infancy, and a lot of basic work needs to be carried out, including: in-depth research on wind power and photovoltaic power generation forecasting theory and methods, improving the development of forecasting systems, and studying the application principles of the system and methods; test technology research, test standard formulation and test equipment development, etc. At the same time, it is necessary to speed up the construction of wind power and photovoltaic power generation research and testing centers and test bases, and establish a network access certification system as soon as possible on this basis.
2.8.3 Strengthen system technology research on wind farms and photovoltaic power stations connected to the grid.
188.8.131.52 New energy power generation simulation technology. Further improve the development of power system calculation and analysis software including various wind turbines/wind farms and photovoltaic power generation simulation models; realize the simulation modeling of various types of new energy power generation processes; the simulation function has leaped from offline to online and real-time simulation functions.
184.108.40.206 Analysis technology for new energy power generation. Carry out technical and economic analysis on issues such as large-scale wind power, photovoltaic power generation and other conventional power bundled long-distance transmission schemes, wind-solar-storage integrated operation, and system peak-shaving power supply construction; Conduct comprehensive research on regulation performance, system active power reserve, reactive power reserve, frequency control, voltage control, system safety and stability, etc., to ensure the safety and stability of the system; break through the online real-time and recursive operation characteristics of distributed access to new energy power generation , Intelligent analysis technology.
220.127.116.11 Energy storage technology for connecting new energy power generation to the grid. In-depth research and comparative analysis of various energy storage technologies: pumped hydro storage, chemical battery storage, compressed air storage, etc. Improving energy conversion efficiency and reducing costs are important directions for energy storage technology research in the future; the State Grid Corporation Zhangbei Wind-Storage-Storage Joint Demonstration Project is under construction, which is a domestic test project for large-scale energy storage for new energy access to the grid.
18.104.22.168 New energy power generation dispatching support technology. Realize and improve wind power and photovoltaic power generation forecasting systems suitable for large-scale centralized access, as well as distributed wind power and photovoltaic power generation forecasting systems; establish an intelligent dispatching system suitable for large-scale centralized access of intermittent power sources, and grasp the power of various energy sources Optimal dispatching technology; establish an optimal dispatching system adapted to distributed new energy power, realize the energy optimization management system of distribution network with multiple energy sources, and master the theory and technology of micro-grid economic operation.
22.214.171.124 Operation control technology for new energy power generation connection. Master the wide-area self-coordination technology for large-scale system frequency modulation and peak regulation under the large and frequent fluctuations in the transmission power of large-scale intermittent power sources; optimize the allocation of large-scale system reserve capacity and auxiliary decision-making technology; master the active power control strategy for large-scale intermittent power sources connected to large power grids and reactive power and voltage control technology; master the optimization control technology of energy storage system and control device; master the safety control technology suitable for distributed access of new energy power generation, including the countermeasures of changing the grid-connected power generation mode to independent power generation mode through regulation "island" technology.
126.96.36.199 Power quality assessment and control technology for new energy power generation. Study the power quality evaluation system and indicators of new energy power generation access, and put forward corresponding control requirements; study the analysis method, detection method and treatment technology of the impact of new energy power generation access on power quality of the grid; master the use of a variety of new components, comprehensive The key technology to control the power quality pollution of new energy power generation access.
188.8.131.52 Large-scale new energy power transmission technology. Master the technical/economic comparative analysis technology of large-scale new energy power transmission using EHV AC, conventional DC and flexible DC (VSC); master the independent research and development, production, engineering integration and operation control technology of flexible DC (VSC) transmission equipment ; Propose a DC transmission scheme and control strategy suitable for large-scale intermittent power; Propose a large-scale offshore wind power access method and control strategy.
3. Data of new energy power generation
According to news in December 2021, in the first 11 months of 2021, China's new energy power generation capacity reached 1,035.57 billion kwh, breaking through the 1 trillion kwh mark for the first time this year, a year-on-year increase of 32.97%, accounting for the proportion of electricity consumption of the whole society in the country. 13.8%, an increase of 2.14 percentage points year-on-year.