What are Photovoltaic Cells?

Solar photovoltaic cells (photovoltaic cells for short) are used to directly convert the sun's light energy into electrical energy. At present, a large number of ground photovoltaic systems use silicon-based silicon solar cells, which can be divided into monocrystalline silicon, polycrystalline silicon, and amorphous silicon solar cells. In terms of comprehensive performance such as energy conversion efficiency and service life, monocrystalline silicon and polycrystalline silicon batteries are superior to amorphous silicon batteries. Polycrystalline silicon has lower conversion efficiency than monocrystalline silicon, but it is cheaper.

PV

Solar photovoltaic cells (photovoltaic cells for short) are used to directly convert the sun's light energy into electrical energy. Current ground

According to the application requirements, a group of photovoltaic cells, after a certain combination of solar cells reaches a certain rated output power and output voltage, is called

The term "Photovoltaics" comes from the Greek meaning light, volts, and electrical. It comes from the name of the Italian physicist Alessandro Volt. "Is used as a unit of voltage.

In the history of the development of solar energy, the "light from electricity" behavior caused by light shining on materials was discovered as early as the 19th century.

The term "photo-voltaic" only appeared in English in 1849, which means that electromotive force is generated by light, that is, light generates volts.

In 1839, the photovoltaic effect was first discovered by French physicist AEBecquerel.

In 1883, the first solar cell was successfully prepared by Charles Fritts. Charles uses a very thin layer of gold over a selenium semiconductor to form a semiconductor metal junction. The device has only 1% efficiency.

Solar cells are devices that directly convert light energy into electrical energy through the photoelectric effect or photochemical effect. Photoelectric

I. Equivalent Circuit Model

The equivalent circuit model of a PV cell (shown in Figure 1) can help us understand the working principle of this device. The model of an ideal PV cell can be expressed as a photocurrent source in parallel with a diode. The photons in the light source are absorbed by the solar cell material. If the energy of the photon is higher than the energy band of the battery material, the electrons are excited into the conduction band. If an external load is connected to the output of the PV cell, current will be generated.

Classified by structure

Homojunction

1.Advantages

No danger of depletion; Absolutely clean (no pollution, except for batteries); Not restricted by the geographical distribution of resources; Can generate electricity near the place where electricity is used; High energy quality; Emotionally acceptable to users; Short time to obtain energy; The power supply system works reliably.

2. Disadvantages

The energy distribution density of the irradiation is small; the energy obtained is related to the weather conditions such as the four seasons, day and night, and cloudy and sunny; the cost is relatively high.

First, user solar power

1. Small power supply ranging from 10-100W, used for military and civilian life power in remote areas without electricity, such as plateaus, islands, pastoral areas, border posts, etc., such as lighting, television, radio, etc .;

2. 3-5KW family roof grid-connected power generation system;

3. Photovoltaic water pump

Solve the problem of drinking and irrigating deep water wells in areas without electricity.

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.

Communication / communication field

Solar unattended microwave relay station, fiber optic 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 oil pipelines and reservoir gates, domestic and emergency power supplies for oil rigs, marine detection equipment, meteorological / hydrological observation equipment, etc.

Five, home lighting power

Such as garden lights, street lights, portable lights, camping lights, climbing lights, fishing lights, black light lights, tap lights, energy-saving lights, etc.

Sixth, photovoltaic power station

10KW-50MW independent photovoltaic power station, wind-solar (firewood) complementary power station, various large parking plant charging stations, etc.

The first generation of crystalline silicon solar cells has a conversion efficiency of about 18% in the mainstream market. Due to its early development, companies in the industry chain have mature production technologies, accounting for about 80% of the application market;

The second-generation thin-film solar cells, mainly industrialized thin-film silicon cells, CIGS cells, and CdTe cells, account for about 19% of the application market. Due to lower production costs, the market share is expected to exceed 20% by 2015 ;

The third generation of solar cells mainly includes concentrating and organic solar cells. The highest conversion efficiency of concentrated photovoltaic modules reaches 40%, but because the technology is not yet mature, concentrated photovoltaic cells account for about 1% of the application market and gain market share.

The solar AC power system is made up of

Tested under the condition that the air quality is AM1.5, the upper limit of the theoretical photoelectric conversion efficiency of silicon solar cells is about 33%: the light / electric conversion efficiency of commercial silicon solar cells is generally 12% to 15%; high-efficiency silicon solar cells The light / electric conversion efficiency of a battery is generally 18% to 20%. ^[2]

Solar cells are used in consumer goods, and most of them have charging problems. In the past, nickel-hydrogen or nickel-cadmium dry batteries were generally used as charging objects, but nickel-hydrogen dry batteries were not able to withstand high temperatures, and nickel-cadmium dry batteries had environmental pollution problems.

Super capacitors have developed rapidly, with large capacity, anti-reduction, and low prices. As a result, some solar products have begun to use super capacitors as charging objects, which has improved many problems of solar charging: photovoltaic cells have faster charging and longer life. 5 More than double the charging temperature range, reducing the use of solar cells (low-voltage charging).

Development of solar cell application market

Due to photovoltaic cell packaging technology, soldering materials and processing methods, and improvements on the chip, the life of solar systems in 1991 was about 5 to 10 years. In 1995, it increased to 10 to 20 years, and in 2000, it can be extended to more than 25 years. Solar cell sales in the US market alone were $ 3.5 billion in 1995. Due to the problems of oil and environmental protection (global greenhouse effect), and diplomatic assistance to backward areas, global solar cell sales have grown several times after 2000 AD.

After 2005, the demand for solar panels exploded due to new construction regulations in Germany and other environmentally-friendly advanced countries, and the market was severely out of stock instantly, resulting in the booming global solar cell industry. The stock prices of many solar cell factories overnight Rush to the highest point. At the same time, it also drives the transformation of traditional manufacturing industries that understand business opportunities and invests in the development and application of solar-related products.

Disadvantages and solutions

The inability to generate electricity at night is a major shortcoming of solar cells, but there are three ways to overcome this shortcoming.

Using solar cells as a supplementary power solution: Due to the high demand for electricity during the day, simply allowing solar cells to provide services during the day is just to make the power supply load such as power plants more even and reduce the peak load of the power grid; if Traditional approaches to peak loads can be more costly than using solar cells.

The solar energy during the day is converted into other energy forms for storage, such as batteries, flywheel devices, compressed air, pumped power plants, etc., and the stored energy is released at night.

The cost of solar cells is also very high: much higher than many green / renewable energy sources, unable to provide a lot of demand at a reasonable cost. In the future, we can expect scientists and engineers to continue to study, coupled with the advancement of semiconductor industry technology, the efficiency of solar cells has gradually increased, and the unit cost of power generation systems is decreasing year by year. Therefore, with the increase of solar cell efficiency, cost reduction and rising environmental awareness, the cost of solar cells is expected to be significantly reduced. You can also use cheap mirrors to reflect sunlight to expensive high-efficiency solar cells (pay attention to heat dissipation), which can reduce power generation costs.

Under the universal concept of energy conservation in the world, green technology for photovoltaic cells is already a rising star in the industry. And this wave of green technology trends, and the first to promote the solar energy market is most bullish, it may become the global star of tomorrow. Faced with the ever-rising international oil prices and the coming crisis of the third oil crisis, a reshuffle of energy cards around the world has sounded the drums and is ready to go.

When non-renewable energy sources such as electricity, coal, and petroleum have become urgent, and energy issues have increasingly become a bottleneck restricting international social and economic development, more and more countries have begun to implement the "sunshine plan" to develop solar energy resources and seek new impetus for economic development.

Some high-level nuclear research institutions in Europe have also begun to switch to renewable energy. Driven by the huge potential of the international photovoltaic market, the solar cell manufacturing industries in various countries are rushing to invest heavily in expanding production to compete for a place.

The global solar cell market is fiercely competitive, and Europe and Japan's leading pattern has been broken. Although the main sales market is in Europe, the production of solar cells has moved to Asia. In 2011, driven by the photovoltaic market, global photovoltaic cell output continued to grow, reaching 29.5GW.

Driven by the world's photovoltaic market, China's solar cell manufacturing industry has achieved considerable development through introduction, digestion, absorption and re-innovation. The development of China's solar cell industry can be roughly divided into three stages. The first stage is the research and development period after 1984; the industry formation period after 2001 has ushered in. The second stage is also the period when solar cell manufacturers such as Suntech started their business; the third stage from 2005 to the present is the Chinese solar cell industry. Period of rapid development.

Photovoltaic cells benefited from national policies and financial support for solar and other new energy industries. In 2011, the solar cell industry grew rapidly. Six of the world's top ten solar cell manufacturers were Chinese companies.

China's research on solar cells started in 1958. In the late 1980s, China introduced a number of solar cell production lines, which increased the production capacity of solar cells in China from a few hundred kW in three small factories to four. The plant's 4.5MW, this capacity continued until 2002, and the output was only about 2MW. After 2002, the European market, especially the German market,

On November 26, 2013, the National Energy Administration issued the Interim Measures for the Supervision of Photovoltaic Power Generation Operations, which is valid for three years, stipulating that grid companies should fully purchase grid-connected photovoltaic power plant projects and distributed photovoltaic power generation projects connected to the grid within their grid coverage. The amount of electricity clarifies the various regulatory responsibilities of the energy authority and its dispatched organizations for photovoltaic power generation grid-connected operations, and the responsibilities of the photovoltaic power generation project operating entities and grid companies, so as to promote the orderly implementation of photovoltaic power generation grid-connection. The text is as follows:

"Interim Measures for the Supervision of Photovoltaic Power Generation Operations" ^[5]

Chapter I General Provisions

Article 1 In order to strengthen supervision, effectively ensure the effective operation of photovoltaic power generation systems, optimize the energy supply mode, and promote energy conservation and emission reduction, develop in accordance with laws and regulations such as the "Renewable Energy Law of the People's Republic of China" and "Regulations on Electricity Supervision" and relevant national regulations. This method.

Article 2. These measures apply to grid-connected photovoltaic power plant projects and distributed photovoltaic power generation projects.

Article 3 The State Council s energy authority and its dispatched agencies shall supervise the grid connection, operation, trading, and information disclosure of photovoltaic power generation projects in accordance with these Measures.

Any unit or individual who discovers violations of these Measures and relevant state regulations may lodge a complaint and report to the energy department in charge of the State Council and its dispatched agency. The energy department in charge of the State Council and its dispatched agency shall deal with it in accordance with law.

Article 4 The operating entities and grid companies of photovoltaic power generation projects shall abide by the electricity business permit system, carry out photovoltaic power generation related business in accordance with the law, and accept the supervision of the State Council s energy authority and its dispatched agencies.

Chapter II Supervision Contents

Article 5 The competent energy department of the State Council and its dispatched agencies shall supervise the implementation of the electricity license system of photovoltaic power generation project operators and power grid enterprises.

Except for photovoltaic power generation projects that are exempted from power business licenses in accordance with regulations, other operating entities of grid-connected photovoltaic power generation projects shall apply for power business licenses. The license holder shall maintain the permit conditions. If the permit items or registration items change, they shall go through the change formalities in accordance with regulations.

Article 6 The competent energy department of the State Council and its dispatched agencies shall supervise the quality of photovoltaic power generation in accordance with relevant regulations.

The power quality of the grid-connected points of photovoltaic power generation should comply with national standards to ensure the reliable operation of the power grid.

Article 7 The competent energy department of the State Council and its dispatched agencies shall supervise the construction of photovoltaic power grids.

The photovoltaic power generation projects connected to the public power grid, the access system engineering, and the public grid transformation caused by the access are partly invested and constructed by the grid companies. Access to the photovoltaic power generation project on the user side, the access system project is invested and constructed by the project operating entity, and the public grid transformation caused by the access is invested and constructed by the grid company.

Article 8 The competent energy department of the State Council and its dispatched agencies shall supervise the grid-connected service of photovoltaic power generation.

Grid enterprises should establish and improve the grid connection service process of photovoltaic power plant projects in accordance with the principles of active service, simplicity and efficiency, and provide services such as grid connection process description, related policy interpretation, grid work progress inquiry, and grid connection commissioning and acceptance.

Grid companies should provide convenient conditions for the access of distributed photovoltaic power generation, and follow the principle of one mouthful of foreign in the entire process of application acceptance, connection system formulation, contract and agreement signing, grid acceptance, and grid debugging. To simplify the procedures.

Grid companies are exempt from distributed system capacity and related service fees for distributed photovoltaic power generation projects.

Article 9 The competent energy department of the State Council and its dispatched agencies shall supervise the time limit of the photovoltaic power generation grid connection.

The time limit for grid connection of photovoltaic power plant projects shall be implemented in accordance with relevant regulations of the National Energy Administration.

For distributed photovoltaic power generation projects, the grid company shall provide the project owner with an access system plan within 25 working days from the date of accepting the grid connection application; within 5 working days from the project owner confirming the access system plan, provide a letter of opinion on access to the grid , The project owner accordingly carries out follow-up work such as project filing and engineering design; completes the installation of the gate energy metering device within 10 working days from the acceptance of the grid acceptance and commissioning application, and signs the power purchase and sale contract with the project owner as required And grid connection agreement; organize the grid acceptance and grid debugging within 10 working days after the installation of the energy metering device at the gateway, provide the project owner with acceptance opinions, and directly transfer to the grid operation after the commissioning is passed. The acceptance standard shall be in accordance with relevant national regulations. carried out. If the acceptance fails, the grid company shall propose a solution to the project owner.

Article 10 The competent energy department of the State Council and its dispatched agencies supervise the signing, implementation and filing of contracts for the purchase and sale of photovoltaic power generation projects and grid connection agreements.

Grid enterprises should sign power purchase contract and grid connection scheduling agreement with the PV power plant project operating entity. The signing of the contract and agreement should comply with the relevant state regulations, and it should be filed with the State Council s energy agency within 10 working days after the contract and agreement is signed. The photovoltaic power plant purchase and sale contract and grid-connected dispatch agreement template will be formulated separately by the State Council s energy authority and the State Administration for Industry and Commerce.

Grid enterprises should timely sign grid connection agreements and purchase and sale contracts with the operating entities of distributed photovoltaic power generation projects in accordance with relevant regulations.

Article 11 The State Council s energy authority and its dispatched agencies shall supervise the dispatch of photovoltaic power generation by power dispatching agencies.

The power dispatching agency shall compile a power generation dispatching plan and organize its implementation in accordance with the state's regulations on grid connection of renewable energy generation. Except for force majeure or situations that endanger the security and stability of the power grid, power dispatching agencies shall not limit the output of photovoltaic power generation.

The situations that endanger the security and stability of the power grid referred to in these measures shall be identified by the State Council s energy authority and its dispatched organizations.

The operating entity of a photovoltaic power generation project shall abide by the relevant regulations on the operation and management of grid-connected power plants, obey the dispatch command and execute the dispatch order.

Article 12 The State Council s competent energy department and its dispatched agencies supervise the purchase of photovoltaic power generation by grid companies.

Grid companies should fully purchase the grid-connected power of photovoltaic power generation projects within the coverage of their power grids. In the event of force majeure or circumstances that endanger the security and stability of the power grid and fail to fully acquire the power grid, the grid company shall promptly notify the operating entity of the photovoltaic power generation project in writing of the time and reasons for the failure to go online in full, and report it to the State Council s energy agency Filing.

Article 13 The State Council s competent energy department and its dispatched agencies shall supervise the operation and maintenance of grid-connected photovoltaic power generation.

The grid-connected photovoltaic power plant project operator is responsible for the operation, maintenance, and management of the collector lines and booster stations in the photovoltaic power plant site, and the grid company is responsible for the photovoltaic power station's supporting power transmission project and the public grid's operation, maintenance, and management. Grid enterprises should arrange for the maintenance of grid equipment as far as possible without affecting the sending capacity of the grid-connected photovoltaic power plant, and notify the grid-connected photovoltaic power plant project operating entity in writing three months in advance.

The operating entities of distributed photovoltaic power generation projects can be responsible for the operation, maintenance and project management of photovoltaic power generation equipment under the guidance of grid companies.

Article 14 The State Council s competent energy department and its dispatched agencies shall supervise the measurement of photovoltaic power generation and grid-connected power in accordance with relevant regulations.

The grid-connected power metering point of a photovoltaic power plant project is set in principle at the demarcation point of property rights to measure the grid-connected power of the project. Grid companies are responsible for regular inspection and calibration, and device configuration and testing should meet national and industry related technical standards and regulations for electricity measurement.

Grid enterprises should install two sets of metering devices for distributed photovoltaic power generation projects, and measure the total power generation and grid-connected power separately.

Article 15 The State Council s competent energy department and its dispatched agencies shall supervise the settlement of photovoltaic power tariffs.

The settlement of electricity charges for photovoltaic power generation projects shall be implemented in accordance with relevant regulations. Where natural persons are the operating entities, power grid companies should try to simplify procedures and provide convenient settlement services.

Article 16 The competent energy department of the State Council and its dispatched agencies shall supervise the issuance of subsidies for photovoltaic power generation.

Grid enterprises shall transfer subsidy funds in a timely and full manner in accordance with the subsidy standards approved by the state.

Chapter III Supervision Measures

Article 17 The agencies of the State Council s energy authority and provincial energy authorities shall strengthen the management of photovoltaic power generation projects and the sharing of regulatory information to form a working mechanism of organic collaboration and division of responsibilities.

Article 18 Grid enterprises shall submit the following information to the State Council's energy authority agency in their region on a quarterly basis:

1. Grid-connected access of photovoltaic power generation projects, including access voltage level, access capacity, and grid-connected time.

2. Grid-connected transactions of photovoltaic power generation projects, including power generation, self-use power, online power, and online shopping power.

3 Important problems encountered during the grid-connected operation of photovoltaic power plant projects.

Grid-connected photovoltaic power plant operating entities shall regularly report operating information in accordance with relevant regulations such as industrial monitoring and quality supervision, and timely report accidents and important issues to the agency in charge of the State Council s energy department.

The energy department of the State Council and its dispatched agencies may require the photovoltaic power generation operation entity and the power grid enterprise to submit other documents and information related to the regulatory matters according to the needs of performing their regulatory duties.

Article 19 The competent energy department of the State Council and its dispatched agencies may take the following measures for on-site inspections:

1. Enter grid-connected photovoltaic power plants and grid companies for inspection;

2. Ask the staff of the photovoltaic power generation project and dispatching agency and ask them to explain the relevant inspection items;

3 Check and copy the documents and materials related to the inspection items, and seal the documents and materials that may be transferred, concealed and damaged;

4 Illegal acts discovered during the inspection have the right to correct them on the spot or request correction within a time limit.

Article 20 If the operating entity of a photovoltaic power generation project and the grid company fail to reach an agreement on grid connection, which affects the normal conduct of power transactions, the State Council s energy authority and its dispatched agencies shall coordinate; if coordination fails to reach an agreement, the State Council s energy director The department and its dispatched agency shall make a ruling in accordance with relevant regulations.

Grid companies and PV power project operating entities that have disputes over the performance of their contracts may apply to the State Council s energy authority and its agencies for mediation.

Article 21 The competent energy department of the State Council and its dispatched agencies may disclose to the society the state of photovoltaic power generation operations across the country, and the implementation of relevant national renewable energy policies and regulations by power companies.

Article 22 Grid enterprises and operating entities of photovoltaic power generation projects violate the provisions of these Measures, and the competent department of energy of the State Council and its dispatched agencies may pursue related responsibilities in accordance with the Renewable Energy Law of the People's Republic of China and the Regulations on Electricity Supervision.

Grid enterprises that fail to complete the purchase of renewable energy power in accordance with regulations and cause economic losses to the operating entities of photovoltaic power generation projects shall be liable for compensation in accordance with the "Renewable Energy Law of the People's Republic of China".

Chapter IV Supplementary Provisions

Article 23 The interpretation of these measures is the responsibility of the National Energy Administration, and each dispatched agency may formulate detailed rules for supervision and implementation in accordance with local actual conditions.

Article 24 These Measures shall be implemented from the date of promulgation and shall be valid for 3 years.

Notice of the National Development and Reform Commission on the Price Policy of Photovoltaic Power Generation Projects in 2018 FAB Price Regulation [2017] No. 2196 ^[6]

Development and Reform Commissions, Price Bureaus, Energy Bureaus, Poverty Alleviation Offices, State Grid Corporation of China, China Southern Power Grid Corporation, Inner Mongolia Electric Power Corporation in each province, autonomous region, and municipality:

In order to implement the requirements of the Energy Development Strategy Action Plan (2014-2020) of the General Office of the State Council on the gradual decline of the benchmark on-grid electricity prices of new energy sources, reasonably guide the investment in new energy sources, and promote the healthy and orderly development of the photovoltaic power generation industry, it was decided to adjust the photovoltaic power generation in 2018 Benchmark feed-in tariff policy. Doing business with the National Energy Administration, the relevant matters are now notified as follows:

1. According to the current technological progress and cost reduction of the photovoltaic industry, reduce the benchmark on-grid tariffs of photovoltaic power plants that have been put into operation after January 1, 2018. The benchmark on-grid tariffs of Class I, II, and III resource areas have been adjusted to 0.55 per kWh Yuan, 0.65 yuan, 0.75 yuan (including tax). Beginning in 2019, all photovoltaic power generation projects included in the annual scale management of financial subsidies will implement the corresponding benchmark electricity prices according to the operation time.

2. For distributed photovoltaic power generation projects that have been put into operation after January 1, 2018, and adopt the "spontaneous self-use, surplus net" mode, the full electricity consumption subsidy standard is reduced by 0.05 yuan, that is, the subsidy standard is adjusted to 0.37 yuan per kilowatt hour (Tax included). The distributed photovoltaic power generation project adopting the "full-grid connection" model is executed at the price of the photovoltaic power station in its resource area. The distributed photovoltaic power generation project's own power consumption is exempt from various government funds and additional, system reserve capacity fees and other related grid-connected service fees that are collected along with the electricity price.

3. The benchmark electricity price of village-level photovoltaic poverty alleviation power stations (0.5 MW and below) and the electricity subsidy standards for household distributed photovoltaic poverty alleviation projects remain unchanged.

4. All new energy power generation enterprises and power grid enterprises must truthfully and completely record and save the relevant power generation projects' online trading power, prices, and subsidy amounts, accept the supervision and inspection of relevant departments, and submit relevant data to the National Renewable Energy Information Management Center. The price authorities at all levels shall strengthen the supervision of the implementation of on-grid tariffs for new energy and the settlement of additional subsidies for electricity prices, and urge the implementation of relevant on-grid tariff policies.

V. Encourage local governments to carry out pilot reforms of nearby PV power generation price reforms and market-based bidding and pricing in accordance with relevant state regulations, and gradually improve the mechanism for price discovery through the market.

6. The above provisions shall be implemented from January 1, 2018. ^[6-7]