How is Solar Energy Cost Determined?

The energy of solar energy is the energy from the celestial bodies outside the earth (mainly solar energy). It is the huge energy released by the fusion of hydrogen nuclei in the sun at very high temperatures. Most of the energy required by humans comes directly or indirectly from the sun. The fossil fuels such as coal, oil, and natural gas that we need for life are all formed by plants and animals buried in the ground after a long geological age after various plants convert solar energy into chemical energy through photosynthesis and store them in the plants. In addition, water energy, wind energy, wave energy, ocean current energy, etc. are also converted by solar energy.

The energy of solar energy is the energy from the celestial bodies outside the earth (mainly solar energy). It is the huge energy released by the fusion of hydrogen nuclei in the sun at very high temperatures. Most of the energy required by humans comes directly or indirectly from the sun. The fossil fuels such as coal, oil, and natural gas that we need for life are all formed by plants and animals buried in the ground after a long geological age after various plants convert solar energy into chemical energy through photosynthesis and store them in the plants. In addition, water energy, wind energy, wave energy, ocean current energy, etc. are also converted by solar energy.
Chinese name
solar energy generation
Foreign name
Solar power
Advantage
Renewable and clean
Types of
new energy
Energy production
Hydrogen fusion
Classification
Photoelectric and thermal power

Solar power background

Solar Power Energy Status

With the development of the economy and the progress of society, people have increasingly higher requirements for energy. Finding new energy has become an urgent issue facing human beings. There are four main sources of existing power energy, namely thermal power, hydropower, nuclear power and wind power.
Thermal power needs to burn fossil fuels such as coal and petroleum. On the one hand, fossil fuel reserves are limited, and they are becoming less and less burning, and they are facing the danger of depletion. On the other hand, combustion will emit carbon dioxide and sulfur oxides, which will lead to the greenhouse effect and acid rain, which will worsen the global environment.
If hydropower floods a large amount of land, it may lead to ecological damage, and once the large reservoirs collapse, the consequences will be disastrous. In addition, a country's hydropower resources are also limited and subject to seasonal influences.
Nuclear power is clean under normal circumstances, but in the event of a nuclear leak, the consequences are equally dire. The accident at the Chernobyl nuclear power plant in the former Soviet Union has caused 9 million people to various degrees of damage; at 13:46 on March 11, 2011, a magnitude 9.0 earthquake in Fukushima, Japan, triggered an international shock to the Fukushima nuclear power plant accident, causing Thirty kilometers near the nuclear power plant becomes an uninhabited area; marine resources with a radius of 5 kilometers will be affected to varying degrees or mutated by marine life.
As a clean renewable energy source, wind power generation has broad development prospects. Large wind energy reserves, and the widespread development of wind power is an effective way to solve China's insufficient energy supply; wind power is a clean energy application and an effective way to reduce greenhouse gas emissions.

Ideal energy for solar power

New energy must meet two conditions at the same time: first, it must be abundant and not exhausted; second, it must be safe and clean, and it will not threaten humans and damage the environment. There are two main types of new energy sources found: solar energy and fuel cells.
Solar roof power station (2 photos)
In the 21st century, solar energy will become one of the world's main energy sources, and it is the most primitive energy source. Almost all other energy sources on the planet come directly or indirectly from solar energy. Solar energy is the energy produced by the continuous nuclear fusion reaction process of sunspots inside or on the surface of the sun. Solar energy Solar energy has the advantages of sufficient resources, long life, widely distributed, safe, clean, and reliable technology. Because solar energy can be converted into many other forms of energy, it has a wide range of applications. In terms of heat utilization, there are solar greenhouses, drying of items and solar stoves, solar water heaters, etc. After years of development, solar power generation has also made considerable progress.
Obtaining electricity from solar energy requires photoelectric conversion through solar cells. It is completely different from other power generation principles in the past. To make solar power truly reach the practical level, one is to improve the efficiency of solar photovoltaic conversion and reduce its cost, and the other is to realize the interconnection of solar power with the power grid.

Solar power classification

Solar power

Solar photovoltaic power generation refers to a power generation method that directly converts light energy into electricity without using a thermal process. It includes photovoltaic power generation, photochemical power generation, light induction power generation and photobiological power generation. Photovoltaic power generation is a direct power generation method that uses solar-grade semiconductor electronic devices to effectively absorb solar radiation energy and convert it into electrical energy. It is the mainstream of solar power generation today. There are electrochemical photovoltaic cells, photoelectrolytic cells, and photocatalytic cells in photochemical power generation. Currently, photovoltaic cells have been used in practice. [1]
Photovoltaic power generation systems are mainly composed of solar cells, storage batteries, controllers and inverters. Among them, solar cells are a key part of photovoltaic power generation systems. The quality and cost of solar panels will directly determine the quality and cost of the entire system. Solar cells are mainly divided into crystalline silicon cells and thin-film cells. The former includes two types: monocrystalline silicon cells and polycrystalline silicon cells. The latter includes amorphous silicon solar cells, copper indium gallium selenium solar cells, and cadmium telluride solar cells.
The photoelectric conversion efficiency of the single crystal silicon solar cell is about 15%, up to 23%. Among the solar cells, the photoelectric conversion efficiency is the highest, but its manufacturing cost is high. The service life of monocrystalline silicon solar cells is generally up to 15 years, up to 25 years. Polycrystalline silicon solar cells have a photoelectric conversion efficiency of 14% to 16%, and their production cost is lower than that of monocrystalline silicon solar cells. Therefore, a large number of developments have been made.
Thin-film solar cells are solar cells using silicon, cadmium sulfide, gallium arsenide and other thin films as the base material. Thin-film solar cells can be manufactured using lightweight, low-cost substrate materials (such as glass, plastic, ceramics, etc.). The thickness of the thin-film solar cells that can generate voltage is less than 1 micron, which is convenient for transportation and installation. However, thin films deposited on heterogeneous substrates can cause some defects. Therefore, the mass production conversion efficiency of existing cadmium telluride and copper indium gallium selenium solar cells is only 12% to 14%, and the theoretical upper limit can reach 29 %. If the defects of cadmium telluride can be reduced during the production process, it will increase the battery life and improve its conversion efficiency. This requires studying the causes of defects and ways to reduce defects and control quality. The solar cell interface is also critical and requires significant investment in research and development.

Solar power

The method of generating electricity by converting solar radiant energy into electricity through water or other working substances and devices is called solar thermal power generation. First convert solar energy into thermal energy, and then convert thermal energy into electrical energy. It has two conversion methods: one is to directly convert the solar thermal energy into electrical energy, such as the temperature difference power generation of semiconductors or metal materials, thermionic and thermoelectric ions in vacuum devices Power generation, alkali metal thermoelectric conversion, and magnetic fluid power generation; another way is to use solar thermal energy to drive a generator through a heat engine (such as a steam turbine), similar to conventional thermal power generation, except that its thermal energy does not come from fuel, but from Solar energy. There are many types of solar thermal power generation, mainly including the following five types: tower system, trough system, disk system, solar pond and solar tower thermal airflow power generation. The first three are concentrating solar thermal power generation systems, and the latter two are non-concentrating. Some developed countries have taken solar thermal power generation technology as a national research and development focus, and have manufactured dozens of various types of solar thermal power generation demonstration power plants, which have reached the practical application level of grid-connected power generation. [1]
At present, the most promising solar thermal power generation systems in the world can be roughly divided into: a trough-shaped parabolic focusing system, a central receiver or a solar tower focusing system, and a disc-shaped parabolic focusing system. The three forms that are technically and economically feasible are: 30 ~ 80MW focused parabolic trough solar thermal power generation technology (referred to as parabolic trough type); 30 ~ 200MW spot focused central receiving solar thermal power generation technology (referred to as central receiving type); 7.5 25kW point focused parabolic disc solar thermal power generation technology (referred to as parabolic disc type).
The heat transfer medium of the focused solar thermal power generation system is mainly water, water vapor, and molten salt. These heat transfer mediums can be heated to 450 degrees Celsius in the receiver and then used for power generation. In addition, the thermal storage system of this power generation method can temporarily store thermal energy for several hours to reserve power during peak hours.
The parabolic trough focusing system uses a parabolic cylindrical trough launching mirror to collect sunlight on a tube-shaped receiver, and heats the heat transfer working medium in the tube to generate steam in the heat exchanger, which promotes conventional steam turbines to generate electricity. The tower solar thermal power system uses a set of heliostats that track the sun independently, and collects sunlight on a receiver on top of a fixed tower to generate high temperatures.
In addition to the above-mentioned traditional solar thermal power generation methods, research in new fields such as solar chimney power generation and solar pond power generation has also progressed.

Solar power generation device

Solar power is a device that uses solar cells to directly convert solar energy into electricity. Solar cells are solid devices that use the electronic properties of semiconductor materials to achieve PV conversion. In vast areas without power grids, this device can easily provide electricity for users to light and live. Some developed countries can also connect with regional power grids. Grid connection is complementary. From the point of view of civil use, the technology that has matured in foreign countries and is beginning to industrialize is the "photovoltaics-building (lighting) integration" technology, while domestic research and production of small solar power generation suitable for home lighting in areas without electricity system.
The solar power generation system mainly includes: solar cell modules (arrays), controllers, batteries, inverters, users, ie, lighting loads. Among them, solar cell modules and storage batteries are power supply systems, controllers and inverters are control protection systems, and loads are system terminals.
Solar cells and storage batteries constitute the power supply unit of the system, so the performance of the storage battery directly affects the operating characteristics of the system.

Solar power battery unit

Due to technical and material reasons, the power generation of a single battery is very limited. A practical solar cell is a battery system consisting of a single battery connected in series and parallel, called a battery module (array). A single cell is a silicon crystal diode. According to the electronic characteristics of semiconductor materials, when sunlight shines on a PN junction composed of two types of homogeneous semiconductor materials, P-type and N-type, under certain conditions, The solar radiation is absorbed by the semiconductor material, and non-equilibrium carriers, namely electrons and holes, are generated in the conduction and valence bands. Similar to the PN junction barrier region, there is a strong built-in electrostatic field, so it can form current density J, short-circuit current Isc, and open-circuit voltage Uoc under light. If the electrodes on both sides of the built-in electric field are drawn out and connected to a load, in theory, a "photogenerated current" will flow through the circuit formed by the PN junction, the connection circuit and the load, and the solar cell module will realize the power P of the load. Output.
Theoretical research shows that the peak power Pk of a solar cell module is determined by the local average solar radiation intensity and the end-use power load (power demand).

Solar power storage unit

The direct current generated by the solar cell enters the storage battery first, and the characteristics of the storage battery affect the working efficiency and characteristics of the system. The battery technology is very mature, but its capacity is affected by the terminal power demand and the sunshine time (power generation time). Therefore, the battery watt-hour capacity and ampere-hour capacity are determined by the predetermined continuous non-sunlight time.

Solar power controller

The main function of the controller is to keep the solar power generation system near the maximum power point for power generation to obtain the highest efficiency. The charging control usually uses the pulse width modulation technology, that is, the PWM control method, so that the entire system always runs in the vicinity of the maximum power point Pm. Discharge control mainly refers to cutting off the switch when the battery is out of power or the system is faulty, such as when the battery is open or reversed. At present, Hitachi has developed a "sunflower" controller that can track both the control point Pm and the sun's movement parameters, which improves the efficiency of the fixed battery module by about 50%.

Solar power inverter

Inverter can be divided into self-excited oscillation inverter and other-excited oscillation inverter according to the excitation mode. The main function is to invert the direct current of the battery into alternating current. Through a full-bridge circuit, an SPWM processor is generally used to modulate, filter, boost, etc. to obtain a sinusoidal AC power matching the lighting load frequency f, rated voltage UN, etc., for use by the system end user.

Anti-reverse charge diode for solar power generation

The anti-reverse diode of the solar photovoltaic power generation system is also called blocking diode. Its role in solar cell modules is to prevent the solar cell array from discharging through the solar cell array when the solar cell array does not generate electricity in the rain and at night or a short circuit fault occurs. The anti-recharge diode is connected in series in the solar cell square-array circuit and plays a unidirectional conduction role. Therefore, it must ensure that there is a maximum current in the circuit, and it must withstand the impact of the maximum reverse voltage. Generally, a suitable rectifier diode can be selected as an anti-recharge diode. A board can be used without any diode, because the controller is inherently anti-backlash. If the boards are connected in series, a bypass diode needs to be installed. If they are connected in parallel, an anti-backlash diode must be installed to prevent the boards from charging directly. The anti-recharge diode is only for protection and will not affect the power generation effect.

Solar power efficiency

In a solar power generation system, the total efficiency ese of the system consists of the PV conversion rate of the battery module, the controller efficiency, the battery efficiency, the inverter efficiency, and the efficiency of the load. But compared to solar cell technology, it is much more mature than other controllers, inverters, lighting loads and other units in terms of technology and production level, and the system conversion rate is only about 17%. Therefore, increasing the conversion rate of battery modules and reducing the unit power cost are the focus and difficulty of industrialization of solar power generation. Since the advent of solar cells, crystalline silicon has maintained its dominant position as the leading material. The research on the conversion rate of silicon batteries is mainly focused on increasing the energy absorption surface, such as double-sided batteries, to reduce reflection; using the gettering technology to reduce the recombination of semiconductor materials; ultra-thin battery; improving the theory, establishing new models; Photocell, etc.

Advantages and disadvantages of solar power

Solar photovoltaic power generation has many unique advantages:
1. Solar energy is an inexhaustible and inexhaustible source of clean energy, and solar photovoltaic power generation is safe and reliable, and will not be affected by the energy crisis and unstable factors in the fuel market;
2. The sun shines on the earth. Solar energy is available everywhere. Solar photovoltaic power generation is particularly suitable for remote areas without electricity, and it will reduce the construction of long-distance power grids and power loss on transmission lines.
3. No fuel is required for the generation of solar energy, which greatly reduces the operating costs;
4. In addition to tracking type, solar photovoltaic power generation has no moving parts, so it is not easy to be damaged, relatively easy to install, and simple to maintain;
5. Solar photovoltaic power generation does not generate any waste, and does not generate noise, greenhouses and toxic gases. It is an ideal clean energy. Install 1KW photovoltaic power generation system, which can reduce CO 2 600 2300kg, NOx16kg, SOx9kg and other particles 0.6kg each year;
6. The roof and walls of the building can be effectively used without occupying a lot of land, and the solar power generation board can directly absorb solar energy, thereby reducing the temperature of the wall and roof and reducing the load of indoor air conditioning;
7. The construction period of the solar photovoltaic power generation system is short, and the service life of the power generation components is long, the power generation method is more flexible, and the energy recovery period of the power generation system is short;
8. It is not limited by the geographical distribution of resources; it can generate electricity at the nearest place where electricity is used.
Everything has its two sides. Although solar photovoltaic power generation has many of the advantages mentioned above, it also has its disadvantages:
1. Geographical distribution, seasonal changes, and day-night alternation will seriously affect its power generation. When there is no sun, it cannot generate power or the power generation is very small, which will affect the normal use of power equipment;
2. The energy density is low. When it is used on a large scale, the occupied area will be relatively large, and it will be affected by the intensity of solar radiation;
3. The cost of photovoltaic system is relatively high, the system cost is 40,000 ~ 60,000 yuan / kW, and the high initial investment severely restricts its wide application;
4. The annual power generation hours are low, with an average of 1300 hours;
5. It is difficult to accurately predict the power generation of the system.

Status and Application of Solar Power

Solar power generation status

The use of solar energy is mainly divided into several aspects: small-scale solar power stations for households, large-scale grid-connected power stations, integrated photovoltaic glass curtain walls, solar street lights, wind-solar complementary street lights, and wind-solar complementary power supply systems, and wind-solar complementary systems.
The use of solar energy is not very popular. There are still problems of high cost and low conversion efficiency when using solar power, but solar cells have been used to provide energy for artificial satellites. Solar energy is the energy produced by the continuous nuclear fusion reaction process of sunspots inside or on the surface of the sun. The average solar radiation intensity in earth orbit is 1369w / . The circumference of the Earth's equator is 40,000km, so it can be calculated that the energy obtained by the Earth can reach 173,000TW. The standard peak intensity at sea level is 1kw / m2, and the annual average radiation intensity at a point on the earth's surface for 24h is 0.20kw / , which is equivalent to 102000TW of energy. Humans rely on this energy to survive, including all other forms of Renewable energy (except geothermal energy resources). Although the total amount of solar energy is equivalent to more than 10,000 times the energy used by human beings, the energy density of solar energy is low, and it varies from place to place and from time to time. This is development and utilization. The main problems facing solar energy. These characteristics of solar energy will limit its role in the overall integrated energy system to a certain extent. Although the energy that the sun radiates to the earth s atmosphere is only one-two billionths of its total radiant energy, it is already as high as 173,000TW, which means that the energy the sun irradiates to the earth every second is equivalent to 5 million tons of coal. Earth s wind, water, ocean temperature difference, wave and biomass energy, and some tidal energy are all derived from the sun; even fossil fuels (such as coal, oil, and natural gas) on the earth are fundamentally ancient. Since the stored solar energy, the broad range of solar energy includes a very large range, and the narrow solar energy is limited to the direct conversion of solar radiation's photothermal, photovoltaic, and photochemistry.
Although solar power generation is affected by day, night, rain, and season, it can be carried out in a decentralized manner, so it is suitable for each household to generate electricity separately, and it must be connected to the power supply network, so that each household can sell it to when power is rich Power companies can buy from power companies when they are insufficient. The technology to achieve this is not difficult to solve, the key is to have corresponding legal guarantees. At present, developed countries such as the United States and Japan have formulated corresponding laws to guarantee the interests of households that use solar power and encourage households to use solar power.
In Japan, in April 1992, the solar power generation system was connected to the power company's power grid, and some households have begun to install solar power generation equipment. Japan's Ministry of International Trade and Industry has implemented a two-thirds system of subsidizing the cost of purchasing solar power generation equipment for individual homes since 1994. It is required to have 1,000 households in the first year and 70,000 households to install solar power generation equipment in 2000. According to estimates by Japanese authorities, if 80% of Japan s 21 million individual dwellings are equipped with solar power generation equipment, it can meet 14% of the country s total power needs. If solar power is also used in units such as factories and office buildings, solar power It will account for 30% -40% of the national electricity. The most important factor currently hindering the popularity of solar power is its high cost. A 3 kW power generation system that meets the general household power needs requires 6 million to 7 million yen, not including installation labor. Relevant experts believe that solar power generation can really become widespread only if it falls to at least 1 million to 2 million yen. The key to reducing costs is to improve conversion efficiency and reduce costs of solar cells.
Texas Instruments Corporation and SCE Corporation announced that they have developed a new solar cell. Each unit is a bead with a diameter of less than 1 mm. They are densely and regularly distributed on soft aluminum foil, just like many silkworm eggs cling to each other. It's the same on paper. There are 1,700 such units distributed over an area of about 50 square centimeters. The characteristic of this new battery is that although the conversion efficiency is only 8% -10%, it is cheap. In addition, the aluminum foil backing is soft and sturdy, which can be folded freely like a cloth cloth and durable. It can generate electricity when hung in the sun, which is very convenient. It is said that using this new solar battery, the equipment with a generating capacity of only 1.5 to 2 US dollars per watt, and the cost per kilowatt-hour can be reduced to about 14 cents, which can compete with the electricity generated by ordinary power plants. Each family hangs this battery on the roof and wall of Xiangyang, and can get 2,000 kilowatt-hours of electricity every year.

Solar power applications

1. User solar power supply: small power supply ranging from 10-100W, used for military and civilian life power in remote non-electric areas such as plateaus, islands, pastoral areas, border posts, etc., such as lighting, television, radio, etc .; Power generation system; photovoltaic water pump: solve deep water well drinking and irrigation in areas without electricity.
2. Transportation: such as beacon lights, traffic / railway signal lights, traffic warning / sign lights, street lights, high-altitude obstacle lights, highway / railway wireless telephone booths, unattended road shift power supply, etc.
3. Communication / communication field: solar unattended microwave relay station, optical cable maintenance station, broadcasting / communication / paging power system; rural carrier telephone photovoltaic system, small communication machine, soldier GPS power supply, etc.
4. Petroleum, marine, and meteorological fields: cathodic protection solar power systems for petroleum pipelines and reservoir gates, domestic and emergency power sources for oil rigs, marine detection equipment, and meteorological / hydrological observation equipment.
5. Power supply for home lamps: such as garden lights, street lights, portable lights, camping lights, climbing lights, fishing lights, black lights, tap lights, energy-saving lights, etc.
6. Photovoltaic power station: 10KW-50MW independent photovoltaic power station, wind-solar (firewood) complementary power station, various large parking plant charging stations, etc.
7. Solar buildings: Combining solar power with building materials to enable future large-scale buildings to achieve self-sufficiency is a major development direction in the future.
8. Other fields include: supporting with automobiles: solar cars / electric cars, battery charging equipment, car air conditioners, ventilation fans, cold drinks boxes, etc .; solar hydrogen fueling and fuel cell regeneration power generation systems; power supply of seawater desalination equipment; satellites, spacecraft, Space solar power station. ,

Design and Research of Solar Power

Successfully integrated solar modules and building components, such as solar roofs (roofs), walls, doors and windows, etc., to achieve "Photovoltaic-Architectural Lighting Integration (BIPV)". In June 1997, the United States announced the "Solar Million Roof Project", named after the president, to implement solar power systems for 1 million homes by 2010. Japan's "New Sunshine Project" has reduced the installation cost of photovoltaic building modules to 170-210 yen / W by 2000, the annual output of solar cells has reached 10MW, and the battery cost has been reduced to 25-30 yen / W. On May 14, 1999, Germany built the world's first zero-emission solar cell module plant in only one year and two months, using renewable energy to provide electricity, and CO2 is not emitted during production. The south wall of the factory is about 10m high PV array glass curtain wall, including roof PV modules. The entire factory building is equipped with 575m2 solar cell modules, which can provide more than one-third of the electricity for the building. The combination of the shape, color, architectural style of the PV modules on the roof and the building achieves perfect coordination with the surrounding natural environment. The building also has a capacity of about 45kW, which is provided by a thermal power plant using natural rapeseed oil as fuel. It is designed to basically balance the CO2 generated when rapeseed oil is burned with the CO2 required for rapeseed growth. It is a true zero-emission plant. BIPV also focuses on the study of architectural decoration arts. In the Czech Republic, the German company WIP and the Czech Republic cooperated to build the world's first color PV curtain wall. West Bengal, India installed 12.5kW BIPV for 117 villagers on a non-powered island. Domestic Changzhou Tianhe Aluminum Sheet Curtain Wall Manufacturing Co., Ltd. has successfully developed a "solar house", which combines power generation, energy saving, environmental protection and value-added into one room, and successfully combines photovoltaic technology with building technology. It is called solar building system (SPBS) , SPBS has passed expert demonstration on September 20, 2000. Shanghai Pudong has built the first solar-lighting public toilet in China, and all electricity is provided by rooftop solar cells. This will effectively promote the process of industrialization and marketization of energy-saving solar buildings.
The optimized design of the green lighting system requires high light output at low energy consumption and prolongs the service life of the lamp. Therefore, the design of the DC-AC inverter should obtain a reasonable filament warm-up time and the voltage and current waveforms of the exciting tube. There are four typical circuits for the excitation method of solar lighting sources in research and development: Self-excited push-pull oscillation circuit, which is preheated and started by filament series starter. The main parameters of the light source system are: input voltage DC = 12V, output light efficiency> 495Lm / piece, rated efficiency of the lamp 9W, effective life 3200h, continuous turn-on times> 1000 times. Self-excited push-pull oscillation (simple) circuit. The main parameters of this light source system are: input voltage DC = 12V, lamp power 9W, output light efficiency 315Lm / support, and the number of continuous starts> 1500 times. Self-excited single tube oscillation circuit, filament series relay preheating start mode. Self-excited single-tube oscillator (simple) circuit and other efficient energy-saving green light sources.

Solar power

Principle of solar power generation

A solar cell is a device that responds to light and converts light energy into electricity. There are many kinds of materials that can produce photovoltaic effect, such as: single crystal silicon, polysilicon, amorphous silicon, gallium arsenide, indium copper, selenium, and so on. The principle of their power generation is basically the same, and the crystalline silicon is used as an example to describe the photovoltaic power generation process. P-type crystalline silicon can be doped with phosphorus to obtain N-type silicon and form a P-N junction.
Jiguang Optoelectronics
When light hits the surface of a solar cell, part of the photons are absorbed by the silicon material; the energy of the photons is transferred to the silicon atoms, which causes the electrons to transition, and free electrons gather on both sides of the P-N junction to form a potential difference. In the circuit, under the action of this voltage, a current will flow through the external circuit to generate a certain output power.
The essence of this process is: the process of converting photon energy into electrical energy.

Solar power production

The production process can be roughly divided into five steps: a, purification process b, pulling rod process c, slicing process d, battery manufacturing process e, and packaging process. Taking single crystal silicon as an example, the production process can be divided into:
Process 1: silicon wafer cleaning and texturing
The purpose is to carry out surface treatment to remove the surface oil and metal impurities; to remove the cutting damage layer on the surface of the silicon wafer. Fabricate the surface of the silicon wafer to form an anti-reflection texture and reduce the surface reflectance. Anisotropic etching of Si in dilute NaOH solution forms a 3-6 micron pyramid structure on the surface of the silicon wafer, so that the light will be reflected and refracted multiple times on the surface of the silicon wafer, which increases the absorption of light.
Step 2: Diffusion
The single / double-sided liquid source phosphorus of the silicon wafer is diffused to make an N-type emitter region to form a basic structure of photoelectric conversion: a PN junction.
The liquid molecules of POCl3 enter the furnace tube with the carrier gas of N2, and the phosphorus atoms are replaced by a series of chemical reactions at high temperature, and diffuse into the surface of the silicon wafer, which is activated to form N-type doping and form a PN junction with the P-type substrate. The main chemical reaction formula is as follows: POCl3 + O2 P2O5 + Cl2 P2O5 + Si SiO2 + P.
Step 3: Plasma cutting
The short-circuit ring formed around the silicon wafer after the diffusion is removed.
Step 4: Remove the phosphosilicate glass
Phosphosilicate glass formed when silicon oxide surface oxide layer is removed and diffused (phosphosilicate glass refers to SiO2 layer doped with P2O5)
.
Step 5: PECVD
The purpose is to reduce reflection and passivation. PECVD is plasma enhanced chemical vapor deposition equipment, Plasma Enhanced Chemical Vapor Deposition; to produce SiN film (~ 80nm) to reduce reflection on the surface of silicon wafer; SiN film contains a large amount of hydrogen ions Injected into the silicon wafer, the purpose of surface passivation and bulk passivation is achieved, the carrier recombination is effectively reduced, and the short circuit current and open circuit voltage of the battery are improved. The silane reacts with ammonia to form SiN, which is deposited on the surface of the silicon wafer to form an antireflection film. Technology that uses high-frequency power glow discharge to generate plasma to influence the chemical vapor deposition process. The existence of plasma promotes the decomposition, combination, excitation and ionization of gas molecules, and promotes the formation of reactive groups, thereby reducing the deposition temperature. PECVD forms a film in the range of 200 ° C to 500 ° C, which is much smaller than other CVD films in the range of 700 ° C to 950 ° C. During the reaction, a large amount of hydrogen ions are implanted into the silicon wafer, which saturates the dangling bonds in the silicon wafer and deactivates the defects, thereby achieving the purpose of surface passivation and bulk passivation.
Process 6: Screen printing
The screen printing method is used to complete the fabrication of the back field, back electrode, and positive grid line electrode, and the generated photo-generated current has been extracted. Print a certain pattern of silver or aluminum paste on the surface of the silicon wafer to form an ohmic contact after sintering so that the current can be effectively output; Ag metal paste for the front electrode is usually printed in the shape of a grid line to achieve good contact while giving light High transmittance; the back surface is usually printed on the entire back surface with Al metal paste, one is to overcome the resistance caused by the battery in series, and the other is to reduce the recombination of the back surface.
Step 7: Drying and sintering
Dry the metal slurry and volatilize the additives in it (the first 3 zones); form aluminum-silicon alloy and silver aluminum alloy on the back to make good back contact (the middle 3 zones); the process of aluminum-silicon alloy is actually It is a process of P doping silicon, and it needs to be heated above the eutectic melting point of aluminum and silicon (577 ° C). After alloying, as the temperature decreases, the silicon in the liquid phase will re-solidify, forming a crystalline layer containing a small amount of aluminum, which compensates the donor impurities in the N layer, thereby obtaining a P layer with aluminum as the acceptor impurity. To achieve the purpose of eliminating back knots. A silver-silicon alloy is formed on the front side with good contact and light-shielding rate; the glass additive in the Ag paste burns through the SiN film at high temperature (~ 700 degrees), so that the Ag metal contacts the surface of the silicon wafer, and the silver-silicon eutectic point 760 degrees) or more.

The prospect of solar power

The application of solar cells has entered the military, aerospace field into the industrial, commercial, agricultural, communications, household appliances, and public utilities sectors. It can be used in remote areas, mountains, deserts, islands, and rural areas, especially to save cost. Transmission line. But at the current stage, its cost is still very high, and it will cost tens of thousands of dollars to generate 1kW of electricity, so large-scale use is still subject to economic restrictions.
However, in the long run, with the improvement of solar cell manufacturing technology and the invention of new light-electric conversion devices, the protection of the environment and the huge demand for renewable clean energy in various countries, solar cells will still be more practical to use solar radiation energy. The feasible method can open up broad prospects for the large-scale use of solar energy in the future.

Distributed solar power

Solar power applications

Distributed photovoltaic power generation system, also known as decentralized power generation or distributed energy supply, refers to the deployment of a smaller photovoltaic power supply system at the user site or near the power site to meet the needs of specific users and support the economy of the existing distribution network. Operation, or both requirements.
The basic equipment of a distributed photovoltaic power generation system includes photovoltaic cell components, photovoltaic square array brackets, DC combiner boxes, DC power distribution cabinets, grid-connected inverters, AC power distribution cabinets and other equipment, as well as power plant monitoring devices and environmental monitoring devices. . Its operating mode is that under the condition of solar radiation, the solar cell module array of the photovoltaic power generation system converts the output power of solar energy into a DC distribution cabinet through a DC combiner box, and is converted into an AC power supply by a grid-connected inverter. The building's own load, excess or insufficient power is regulated by connecting to the grid.
System application scope: Small distributed power stations can be constructed in rural, pastoral, mountainous, developing medium and small cities or near commercial areas to solve local electricity demand. [2]

Features of solar power generation scheme

The systems are independent of each other and can be controlled by themselves to avoid large-scale power outages and high safety;
Make up for the lack of stability in large power grids, and continue to supply power in the event of an accident, becoming an indispensable important supplement for centralized power supply;
It can monitor the quality and performance of regional power in real time, which is very suitable for supplying electricity to residents in rural, pastoral, mountainous areas, developing small and medium cities or commercial areas, which greatly reduces the pressure on environmental protection;
Low transmission and distribution losses, even no, no need to build distribution stations, reduce or avoid additional transmission and distribution costs; low construction and installation costs;
The peak shaving performance is good, and the operation is simple; because there are fewer systems involved in the operation, the start and stop is fast, which is convenient to achieve full automation.

Solar Power Maintenance and Maintenance

1. Photovoltaic square array in solar photovoltaic power generation system: check and tighten the connecting bolts and wires, test the output, and adjust the tilt angle.
2. Tracker: Lubricate bearings, check bolts and damping.
3. Standby fuel system: The wiring is determined, and it has been checked and ready to use.
4. Charging controller: check the rectifier voltage setting and check that the voltmeter indicates normal. If the battery temperature is below 55 ° F, charging to a higher voltage should be allowed (at least 14.8 volts for a 12 volt system). If your charging controller has a temperature compensation function, it will be adjusted automatically. If there is an external temperature sensor, make sure it is attached to the battery. If there is no automatic adjustment function, you need to manually increase the voltage and adjust it back in spring (to 14.3 volts). If the charge controller is not adjustable, try to keep the battery in a warmer environment.
5. Storage battery (lead-acid): Check the voltage of each battery, eliminate the failure, and determine whether it needs balanced charging. If necessary, perform balanced charging maintenance (usually, 8 hours of medium overcharge after the battery is fully charged). Wash the liquid or dust from the battery (neutralize the acidic precipitate with dry soda powder). Clean or replace corroded terminals. Apply Vaseline oil to the terminals to prevent further corrosion. Check the battery fluid and refill with distilled or deionized water if necessary. Check the ventilation (if there are insects in the ventilation duct, etc.). Note: Check the wire size, connections, fuses and other safety measures. Ground lightning protection: Install or check the grounding post or ground wire.
6. Loads or electrical appliances: Check transformers for invisible loads or low-efficiency wall lamps and TVs with remote control that consume power as long as the power is on; check black incandescent lamps and consider replacing them with halogen or fluorescent lamps; replace black fluorescent lamps Tube; clean dust on the lamp and its mounting bracket.
7. Inverter: check the regulator, installation settings, wiring. Note: The charging voltage of the inverter with charging function should be set to 14.5 (29) volts. Refer to the manual. Add additional temperature probes if necessary.
8. Battery temperature The capacity of a lead-acid battery loses 25% at 30 ° F. When full, it freezes at 20 ° F and causes damage. Overheating in summer will also affect its life. Therefore, the battery should be avoided in extreme outdoor temperature environment. Batteries installed indoors can operate safely according to national standards. [3]

Prospects for solar power

Genesis plan proposed by Japan. Prepare to use the desert and ocean areas on the ground for power generation, and connect global solar power stations into a unified grid with superconducting cables to supply power to the world. According to estimates, by 2000, 2050, and 2100, even if all solar power is used to supply global energy, it will occupy only 651,100 square kilometers, 1,867,900 square kilometers, and 8.919 million square kilometers. Only 829.19 million square kilometers account for 2.3% of the total ocean area or 51.4% of the total desert, and even only 91.5% of the Sahara Desert. So this solution is possible.
Sky Power Generation Program. As early as 1980, NASA and the Department of Energy proposed the idea of constructing a solar power station in space, preparing to place a large flat plate of 10 kilometers long and 5 kilometers wide on a synchronous orbit, covered with solar cells, which could provide 5 million Kilowatts of electricity. But this needs to solve the problem of wireless power transmission to the ground. Various schemes such as microbeams and laser beams have been proposed. Although a short-range, short-time, low-power microwave wireless power transmission has been achieved with a model aircraft, it is still a long way from being practical.
From the energy saving and emission reduction targets of various countries and the UN's "Renewable Energy Special Report", it is seen that achieving a high proportion of renewable energy replacement by 2050 is a worldwide trend, which will promote the development of China's solar photovoltaic power generation industry. . On October 26, 2012, the State Grid Corporation issued the "Opinions on Doing a Good Job in Distributed Photovoltaic Power Generation Grid Connected Services", which greatly reduced the threshold for photovoltaic power generation to enter the grid; the National Energy Administration clearly stated that the installed target by 2020 is 100 million KW In the next few years, the domestic installed capacity will exceed 10 GW. The total energy demand will reach 5 billion tons of standard coal by 2030, and 5.2 billion tons by 2050. Renewable energy will account for 40% of the total energy demand in 2050, and renewable energy will account for 60% of the electricity demand. Photovoltaic Power generation may reach 1 billion KW. The strong support of national policies will promote the rapid and healthy development of China's solar photovoltaic power generation industry. [4]
The National Energy Administration issued the "Notice on the Comprehensive Development of the 13th Five-Year Plan" for solar energy development on December 24. Among them, solar thermal power is mentioned as an important content, which means that Power generation will become an important industry in China during the "13th Five-Year Plan" period. The main types of solar energy use include solar photovoltaic power generation and solar thermal utilization, and areas with solar thermal power generation project construction conditions should also include solar thermal power generation. The planning period is 2016-2020, and the development goals look forward to 2030. Among them, the planning and research contents of solar thermal power generation include: the key areas and scales of solar thermal power generation, the location and construction conditions of key projects, technical routes, and technical and economic research. The research contents of solar thermal utilization planning include: solar thermal utilization goals, key regions, development models, urban and rural building application promotion methods and measures, etc.
The thematic planning of solar thermal utilization includes research and put forward the overall goals and tasks of solar thermal utilization during the "Thirteenth Five-Year Plan" period, and put forward the classified development goals and regional layout of such fields as building hot water heating, industrial hot water, air conditioning and refrigeration; Roadmap for the development of technology used; for the key links of medium and high temperature technology research and development, key equipment manufacturing, system integration technology, integration with conventional energy systems, etc., the development goals, implementation plans and safeguard measures for technological innovation are proposed; analysis and comparison of Chinese and foreign products and systems Competitive advantages and disadvantages, compare the advantages and disadvantages of domestic and foreign manufacturing industries, research and propose goals, tasks and safeguard measures to enhance industrial competitiveness during the "Thirteenth Five-Year Plan" period; The tasks, objectives and implementation steps of the certification system, and put forward policies and measures to strengthen product quality control, operation and maintenance system construction.
China's CSP industry has basically completed the construction of the industrial chain and accumulated technology after experiencing the accumulation of the 12th Five-Year Plan period. Some enterprises have also acquired certain project development experience. 2015 is the last year of the Twelfth Five-Year Plan. Although we have been unable to complete the original 1GW installed target, with the increasing emphasis on the CSP industry at the government level, the substantive support policy is issued, relying on the existing industrial foundation. China's CSP industry will also usher in an outbreak during the 13th Five-Year Plan period. [5]
There is no doubt that photovoltaic power generation technology using solar power has a bright future. Solar energy resources are almost unlimited, and photovoltaic power generation does not cause any environmental pollution. It is an ideal energy source to meet future social needs. With the in-depth development of photovoltaic power generation technology, the gradual improvement of conversion efficiency, the increasingly reasonable system costs, and the improvement of related distributed power generation technologies and smart grids, the green energy of photovoltaic power generation will become an important energy in the future society. [6]

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