Technical prospects are suitable for looking at the current and future comparison of PV

In general, solar power can be divided into solar thermal power generation and photovoltaic power generation. Generally speaking, solar power refers to solar photovoltaic power generation, referred to as "photovoltaic". Photovoltaic power generation is a technology that directly converts light energy into electrical energy by utilizing the photovoltaic effect of the semiconductor interface. The key component of this technology is the solar cell. The solar cells are packaged and protected in series to form a large-area solar cell module, and then combined with a power controller and other components to form a photovoltaic power generation device.

The solar photovoltaic system is mainly composed of a solar cell module (array), a controller, a battery , an inverter, and a user load. Among them, the solar cell module and the battery are power supply systems, the controller and the inverter are control protection systems, and the user load is a system terminal.

Since the commercialization of solar cells on the ground since the mid-1970s, crystalline silicon has dominated as a basic battery material. The solar cells prepared by crystalline silicon materials mainly include: single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, and thin film crystalline silicon cells. The single crystal silicon battery has high battery conversion efficiency and good stability, but the cost is high; the amorphous silicon solar cell has high production efficiency and low cost, but the conversion efficiency is low, and the efficiency decays relatively fast; the polycrystalline silicon solar cell has Stable conversion efficiency. And the performance price ratio is the highest; thin-film crystalline silicon solar cells have developed rapidly in recent years, but now still account for less than 6% of photovoltaic power generation. From the current point of view, although thin film batteries have good development potential, monocrystalline silicon and polycrystalline silicon batteries are still the mainstream products for a long time. Solar photovoltaic power generation technology is changing with each passing day. The enterprise conversion rate has reached 17%, the laboratory conversion rate has reached 24.7%, and the average annual growth rate has exceeded 0.2%.

Photovoltaic power generation products are mainly used in three aspects: one is to provide power for non-electrical occasions; the other is solar energy daily electronic products, such as various types of solar chargers, solar street lamps and solar lawns, etc.; This has been widely implemented in developed countries.

Because solar photovoltaic power generation is safe, reliable, noise-free, pollution-free, energy is available everywhere, no mechanical rotating parts, low failure rate, easy maintenance, unattended, short station construction period, random size and no need to set up transmission lines, convenient and Combined with buildings, it has become the most basic, most common and promising form of solar power generation.

In theory, photovoltaic power generation technology can be used in any occasion where power is required, from spacecraft, down to household power, to megawatt power stations, small to toys, and photovoltaic power everywhere. The most basic components of solar photovoltaic power generation are solar cells (sheets), such as monocrystalline silicon, polycrystalline silicon, amorphous silicon and thin film batteries. Among them, single crystal and polycrystalline batteries have the largest amount, and amorphous batteries are used for some small systems and calculator auxiliary power supplies. The efficiency of Chinese domestic crystalline silicon cells is about 15 to 19%, and the efficiency of similar products in the world is about 16 to 21%.

It is predicted that solar photovoltaic power generation will occupy an important seat in the world's energy consumption in the 21st century, not only to replace some of the conventional energy, but also to become the main body of the world's energy supply. It is estimated that by 2030, renewable energy will account for more than 30% of the total energy structure, and solar photovoltaic power generation will account for more than 10% of the world's total electricity supply; by 2040, renewable energy will account for the total More than 50% of energy consumption, solar photovoltaic power generation will account for more than 20% of total electricity; by the end of the 21st century, renewable energy will account for more than 80% of the energy structure, and solar power will account for more than 60%. These figures are sufficient to show the development prospects of the solar photovoltaic industry and its important strategic position in the energy field.

Photovoltaic power generation system

Taxonomy

Photovoltaic power generation systems are divided into independent photovoltaic systems and grid-connected photovoltaic systems. Independent photovoltaic power plants include village power supply systems in remote areas, solar household power systems, communication signal power supplies, cathodic protection, solar street lights, and other photovoltaic power generation systems with independent operation.

The grid-connected photovoltaic power generation system is a photovoltaic power generation system that is connected to the grid and delivers power to the grid. It can be divided into grid-connected power generation systems with and without batteries. The grid-connected power generation system with battery has schedulability, can be merged into or out of the grid as needed, and has the function of standby power supply, which can be powered urgently when the power grid is powered off. Photovoltaic grid-connected power generation systems with batteries are often installed in residential buildings; grid-connected power generation systems without batteries do not have the functions of schedulability and backup power, and are generally installed on larger systems.

System equipment

Photovoltaic power generation system is composed of solar cell array, battery pack, charge and discharge controller, inverter, AC power distribution cabinet, sun tracking control system and other equipment. The role of some of its equipment is:

Solar cell array

In the case of illumination (whether it is sunlight or the illumination produced by other illuminants), the battery absorbs light energy, and the accumulation of a different type of charge at both ends of the battery produces a "photogenerated voltage", which is the "photovoltaic effect". Under the effect of the photovoltaic effect, the two ends of the solar cell generate an electromotive force, which converts light energy into electrical energy, which is a device for energy conversion. Solar cells are generally silicon cells, which are classified into single crystal silicon solar cells, polycrystalline silicon solar cells, and amorphous silicon solar cells.

Battery pack

Its function is to store the energy emitted by the solar cell array when it is illuminated and to supply power to the load at any time. The basic requirements for solar cell power generation for the battery pack used are: a. low self-discharge rate; b. long service life; c. strong deep discharge capability; d. high charging efficiency; e. less maintenance or maintenance-free; Wide range; g. low price.

Charge and discharge controller

It is a device that can automatically prevent overcharging and overdischarging of the battery. Since the number of cycles of charging and discharging of the battery and the depth of discharge are important factors determining the service life of the battery, it is indispensable to control the charge and discharge controller of the battery pack for overcharging or overdischarging.

An inverter is a device that converts direct current into alternating current. Since the solar cell and the battery are DC power supplies, and the load is an AC load, the inverter is indispensable. Inverter can be divided into independent running inverter and grid-connected inverter according to the operation mode. The independently operated inverter is used in a stand-alone solar cell power generation system to supply independent loads. Grid-connected inverters are used in solar cell power generation systems that operate in parallel. The inverter can be divided into a square wave inverter and a sine wave inverter according to the output waveform. The square wave inverter circuit is simple, low in cost, but has a large harmonic component, and is generally used in systems below several hundred watts and with low harmonic requirements. Sinusoidal inverters are costly, but can be applied to a variety of loads.

Solar tracking control system

Because of the solar photovoltaic power generation system relative to a fixed location, the sun's illumination angle changes all the time in the four seasons of spring, summer, autumn and winter, and the solar light is always changing to the sun. At best. At present, the universal sun tracking control system in the world needs to calculate the angle of the sun at different times of each day of the year according to the latitude and longitude of the placement point, and store the sun position at each moment of the year to the PLC, MCU or computer. In software, it is also by calculating the position of the sun to achieve tracking. The computer data theory is used. It requires the data and settings of the Earth's latitude and longitude regions. Once installed, it is inconvenient to move or assemble and disassemble. After each move, it is necessary to reset the data and adjust each parameter; principle, circuit, technology, equipment Complex, non-professionals can't do anything. A solar photovoltaic power generation company in Hebei has developed an intelligent sun tracking system with world-leading, low-cost, easy-to-use, no need to calculate local sun position data, no software, and accurate tracking of the sun anytime and anywhere on mobile devices. The system is the first solar space position tracker in China that does not use computer software at all. It has the international leading level and can be used normally within the ambient temperature range of -50 ° C to 70 ° C without being restricted by geographical and external conditions. The tracking accuracy can be It achieves ±0.001°, maximizes solar tracking accuracy, and perfectly achieves timely tracking to maximize solar energy utilization. It can be widely used in places where all kinds of equipment need to use sun tracking. The automatic sun tracker is affordable, stable in performance, reasonable in structure, accurate in tracking, and easy to use. Install a solar power system with a smart sun tracker on a high-speed car, train, and communications emergency vehicle, special military vehicle, warship or ship, no matter where the system is going, how to turn around, turn, smart sun tracker Can ensure that the equipment is required to track the right part of the sun!

How photovoltaic power works

Photovoltaic power generation is a technology that directly converts light energy into electrical energy by utilizing the photovoltaic effect of the semiconductor interface. The key component of this technology is the solar cell. The solar cells are packaged and protected in series to form a large-area solar cell module, and then combined with a power controller and other components to form a photovoltaic power generation device. The advantage of photovoltaic power generation is that it is less restricted by geographical area, because the sun shines on the earth; the photovoltaic system also has the advantages of safe and reliable, no noise, low pollution, no need to consume fuel and erect transmission lines to generate electricity on site and short construction period.

Photovoltaic power generation uses solar cells to convert solar energy directly into electrical energy based on the principle of photovoltaic volts. Whether it is independent use or grid-connected power generation, photovoltaic power generation system is mainly composed of three parts: solar panels (components), controllers and inverters. They are mainly composed of electronic components and do not involve mechanical components. Therefore, photovoltaic power generation equipment Extremely refined, reliable, stable, long life, easy installation and maintenance. In theory, photovoltaic power generation technology can be used in any occasion where power is required, from spacecraft, down to household power, to megawatt power stations, small to toys, and photovoltaic power everywhere. The most basic components of solar photovoltaic power generation are solar cells (sheets), such as monocrystalline silicon, polycrystalline silicon, amorphous silicon and thin film batteries. At present, single crystal and polycrystalline batteries are used the most, and amorphous batteries are used in some small systems and calculator auxiliary power supplies.

Advantages and Disadvantages of Photovoltaic Power Generation Compared with conventional thermal power generation systems, the advantages of photovoltaic power generation are mainly reflected in: 1 no exhaustion risk; 2 safe and reliable, no noise, no pollution, absolutely clean (no pollution); 3 not subject to resources The limitation of geographical distribution can take advantage of the roof of the building; 4 can generate electricity on the spot without fuel consumption and erection of transmission lines; 5 high energy quality; 6 users are emotionally acceptable; 7 short construction period, energy consumption short time.

Disadvantages: 1 The energy distribution density of the irradiation is small, that is, it takes up a huge area; 2 The energy obtained is related to meteorological conditions such as four seasons, day and night, and cloudy weather.

The origin and development of photovoltaic power generation

As early as 1839, the French scientist Becqurel discovered that light can create a potential difference between different parts of a semiconductor material. This phenomenon was later called the "photovoltaic effect", referred to as "photovoltaic effect."

In 1954, American scientists Chabine and Pilson first made practical monocrystalline silicon solar cells at Bell Labs in the United States, and created a practical photovoltaic power generation technology that converts solar energy into electrical energy.

After the 1970s, with the development of modern industry, the global energy crisis and air pollution problems have become increasingly prominent. Traditional fuel energy is decreasing day by day, and the harm to the environment is becoming increasingly prominent. At the same time, about 2 billion people in the world are not getting Normal energy supply. At this time, the whole world has turned its attention to renewable energy. It is hoped that renewable energy can change the human energy structure and maintain long-term sustainable development. Among them, solar energy has become the focus of attention with its unique advantages. Abundant solar radiant energy is an important energy source, an inexhaustible, inefficient, non-polluting, cheap, and freely usable energy source. The energy of solar energy reaching the ground every second is as high as 800,000 kilowatts. If 0.1% of the solar energy on the earth's surface is converted into electricity, the conversion rate is 5%, and the annual power generation can reach 5.6×1012 kilowatt hours, which is equivalent to 40 times of the world's energy consumption. . It is precisely because of these unique advantages of solar energy that after the 1980s, the types of solar cells have been increasing, the scope of application has become increasingly broad, and the market scale has gradually expanded.

After the 1990s, photovoltaic power generation developed rapidly. By 2006, more than 10 megawatt-scale photovoltaic power generation systems and 6 megawatt-scale connected photovoltaic power plants have been built in the world. The United States was the first country to develop a development plan for photovoltaic power generation. In 1997, the “Million Roof” project was proposed. Japan launched the new sunshine program in 1992. By 2003, Japan's PV module production accounted for 50% of the world's total, and four of the world's top 10 manufacturers were in Japan. The German New Renewable Energy Law stipulates the on-grid price of photovoltaic power generation, which has greatly promoted the development of the photovoltaic market and industry, making Germany the fastest growing country in the world after Japan. Switzerland, France, Italy, Spain, Finland and other countries have also formulated photovoltaic development plans, and invested heavily in technology development and accelerated industrialization.

The average annual growth rate of the world's PV modules in 1990-2005 was about 15%. In the late 1990s, development was even faster. In 1999, PV module production reached 200 MW. Commercial battery efficiency has increased from 10% to 13% to 13% to 15%, production scale has grown from 1 to 5 MW/year to 5 to 25 MW/year, and is expanding to 50 MW or even 100 MW. The production cost of photovoltaic modules has dropped below $3/W.

The 2006 PV industry survey shows that by 2010, the annual growth rate of the photovoltaic industry will remain above 30%. Annual sales will increase from $7 billion in 2004 to $30 billion in 2010. Many established PV manufacturing companies have also turned from a loss to a profit.
However, global PV installations reached their lowest point in V-shaped growth in 2009. In 2010, the global PV market installed capacity reached 18.2GW, an increase of 139% compared with last year. In terms of output value, the global revenue of the photovoltaic industry in 2010 reached 82 billion US dollars, compared with 10 billion in 2009 revenue of 40 billion US dollars. In terms of production, global solar cell production reached 20.5 GW in 2010, a significant increase from 9.86 GW in 2009, with thin film battery production accounting for 13.5% of total production.

Beginning in 2010, the Ministry of Finance, the Ministry of Science and Technology, the Ministry of Housing and Urban-Rural Development, and the National Energy Administration jointly issued a document to significantly adjust the relevant policies of the “Golden Sun Demonstration Project and Solar Photovoltaic Building Application Demonstration Project”, involving equipment bidding, project adjustment, Subsidy standards, project integration, and other key links. In 2010, a new 272MW project was added. In addition, it announced the establishment of 13 photovoltaic power generation centralized application demonstration parks throughout the country, as a basis for promoting the application of China's photovoltaic industry. And publicly stated that the domestic application scale should not be less than 1000MW per year after 2012. In August 2010, the National Energy Administration held a 238MW grid-connected photovoltaic power generation project concession bidding, and the final bid price was between 0.7288 yuan / kWh to 0.9907 yuan / kWh, far below industry expectations. The Chinese government's series of PV incentive policies have promoted the rapid growth of China's PV market. In 2009, China's annual PV installed capacity reached 160MW, exceeding the cumulative total installed by the end of 2008. In 2010, the actual installed capacity exceeded 500MW.

In 2010, China's photovoltaic cell production has exceeded 50% of global production. At present, dozens of PV companies have been listed at home and abroad. According to estimates, the annual output value of the industry exceeds 300 billion yuan, and the number of direct employees exceeds 300,000. China's photovoltaic industry has embarked on a rapid development path. It has mastered key process technologies including solar cell manufacturing and polysilicon production. The equipment and main raw materials have been gradually localized, the industrial scale has expanded rapidly, the industrial chain has been continuously improved, and manufacturing costs have continued to decline. Strong international competitiveness.

Prospects According to the 2007 Medium and Long-Term Development Plan for Renewable Energy, by 2020, China will strive to achieve an installed capacity of 1.8GW (million kilowatts) of solar power and 600GW (million kilowatts) by 2050. It is estimated that by 2050, China's renewable energy power installations will account for 25% of the country's installed power, of which photovoltaic power generation will account for 5%. It is expected that the compound growth rate of China's solar installed capacity will be as high as 25% before 2030.

By 2010, China has successively issued the “Interim Measures for the Management of Financial Subsidy Funds for Solar Photovoltaic Building Applications” and the “Notice on Implementing the Golden Sun Demonstration Project”, and has initiated two batches of 290MW photovoltaic power plant concession bidding projects. As of 2010, China's cumulative PV installed capacity reached 800MW, and the newly installed capacity reached 500MW in the same year, an increase of 166%.

The latest policy benchmark price

On August 1, 2011, the National Development and Reform Commission's website published the “Notice of the National Development and Reform Commission on Improving the On-grid Price Policy for Solar Photovoltaic Power Generation”, which stated that the photovoltaic projects that were approved for construction before the end of this year and that were completed and put into operation before the end of the year, The on-grid price is 1.15 yuan/kWh; the solar photovoltaic power generation projects approved in July and later, and approved before July but not yet completed by the end of the year, except for Tibet, still implement the on-grid price of 1.15 yuan per kWh, the rest The province's on-grid electricity price is implemented at 1 yuan per kWh. China's photovoltaic feed-in tariffs have been officially introduced. Although the benchmark electricity price is lower than local standards, it marks the real start of the domestic market and is conducive to the development of the photovoltaic industry.

Twelfth Five-Year Plan

In September 2011, according to the data in the draft of the “12th Five-Year Plan for Renewable Energy Development”, the solar PV “12th Five-Year” installation target was raised to 10GW, and by 2020, the solar PV installed capacity was significantly increased to 50GW. Last year, China's installed capacity was less than 500MW. This means that in the next few years, China's new PV installed capacity will reach 2GW per year. The domestic solar photovoltaic market is expected to be launched on a large scale during the “Twelfth Five-Year Plan” period, and the solar photovoltaic industry is also expected to usher in its golden development period.

"Planning" also proposed that the Chinese government will focus on supporting key photovoltaic enterprises, providing funding, loans and other aspects of support, will form 1 to 2 50,000-ton polysilicon enterprises, 2 to 4 10,000-ton polysilicon enterprises in 2015; 2 5G W-class solar cell companies, 8 to 10 GW-class solar cell companies; 3 to 4 PV-specific equipment companies with annual sales revenue of over 1 billion yuan; cultivate 1 to 2 PVs with annual sales revenue of over 100 billion yuan Enterprises, 3 to 5 PV companies with annual sales revenue of over 50 billion yuan.

In November 2011, according to relevant departments, the forthcoming “Twelfth Five-Year Plan for Renewable Energy Development” is expected to raise the target of solar power generation during the “Twelfth Five-Year Plan” period to 15 million kilowatts, of which the goal of photovoltaic power generation is 14 million. kilowatt. The price of renewable energy, which has received much attention from the industry before, is also expected to increase to 8%/kWh in the near future. A series of policy trends have played a strong voice that the domestic PV market is about to start on a large scale.