What is solar photovoltaic power generation?

1. the rise of photovoltaic power generation technology

At the end of 1990s, there appeared a "solar roof" craze in the world. The early development of photovoltaic power generation technology is mainly in Japan, Germany and the United States. These countries have successively put forward the plans of "1 10,000 roofs", "1 10,000 roofs" and "one million roofs". In recent years, developed countries have built "zero-energy-consumption houses", that is, all the energy needed by buildings is provided by solar photoelectric conversion devices, which is truly clean and pollution-free. Photovoltaic power generation technology represents the development trend of solar architecture in 2 1 century, and pushes the development of solar architecture to a new stage. Fribourg's famous "completely self-sufficient solar house" (Figure 7. 1) is a zero-energy building, which relies entirely on solar energy for heating and power generation instead of conventional energy.

2. Development of photovoltaic power generation technology in China.

Roughly estimated, the total roof area of existing buildings in China is about 400× 108m2. If 1% is equipped with photovoltaic system, the installed capacity of photovoltaic power generation can reach 3550×104 ~ 6620×104 kw, and the annual power generation is 287× 108 ~ 543. The area of desertified land in China is about 264× 104km2, of which the area of desertified land in arid area is more than 250× 104km2, mainly distributed in the northwest region with abundant light resources. According to the utilization ratio of 3% in Gobi desert area in China, the potential of solar power generation resources can reach 27× 108kW, and the annual power generation can reach 4.1×1kloc-0/2kw h.

Fig. 7. 1 "completely self-sufficient solar house" in Fribourg, Germany

The photovoltaic industry in China started in the 1970s and developed steadily in the 1990s, with the output of solar panels and their components increasing gradually. After 2000, in order to strengthen the management and control of power grid projects, State Grid Corporation of China issued many new management methods, requiring management to meet the unified standards of power grid project construction. In 2007, the output of photovoltaic cells in China surpassed Germany and Japan for the first time, and the solar energy utilization efficiency of photovoltaic cells gradually improved. 20 10 the cumulative installed capacity of solar photovoltaic in China is 450MW, and the compound growth rate of photovoltaic industry reaches 38%.

At present, China's photovoltaic power generation market has been involved in many fields, such as village-to-village communication project of the Ministry of Radio and Television, optical cable project of the Ministry of Industry, forest fire prevention communication project of the Ministry of Forestry, photovoltaic power generation project in desert areas and so on. China also put the development of solar photovoltaic power generation in an important position in major projects such as "973" and "863", and the preparations for the 2008 Beijing Green Olympics and the 20 10 Shanghai World Expo also greatly promoted the development of solar photovoltaic power generation.

3. Introduction of photovoltaic power generation system

Solar photovoltaic power generation system is a new type of power generation system, which uses the photovoltaic effect of semiconductor materials of solar cells to directly convert the radiant energy of sunlight into electric energy. According to different operation modes, solar photovoltaic power generation systems can be divided into independent photovoltaic power generation systems and grid-connected photovoltaic power generation systems. In order to maintain continuous power supply, the independent photovoltaic power generation system needs a storage battery as a storage device for electric energy, which is mainly used in remote areas and densely populated areas where the power grid cannot reach, and the whole system cost is relatively high; In areas with public power supply, photovoltaic power generation devices are connected to the power grid for grid-connected operation, which saves storage batteries, greatly reduces investment, and has better operating efficiency and environmental protection performance. A basic photovoltaic power generation system generally consists of solar panels, solar controllers, inverters and batteries (groups).

1) solar panels

Solar panel is the core part of solar photovoltaic power generation system, and its function is to directly convert solar energy into electric energy for load use or storage in storage battery for later use.

2) Solar controller

The basic function of the solar controller is to provide the best charging current and voltage for the battery, charge the battery quickly, stably and efficiently, reduce the loss in the charging process and prolong the service life of the battery as much as possible; At the same time, protect the battery from overcharge and overdischarge. If users use DC load, the solar controller can provide stable DC power for the load (the voltage and current of DC power generated by solar cell array are not very stable due to weather).

3) Inverter

The function of inverter is to convert the low-voltage DC provided by solar cell array and storage battery into 220V AC for AC load.

4) Battery (group)

The function of the storage battery (group) is to directly store the direct current generated by the solar array for the load. In the photovoltaic power generation system, the battery is in a state of floating charge and discharge. When the sunshine is heavy, the battery should be charged in addition to supplying power to the load. When there is little sunshine, this part of stored energy will be gradually released.

4. Application of photovoltaic power generation system

At present, the application of photovoltaic power generation system in China, on the one hand, mainly focuses on collecting photovoltaic power generation systems for users, building small photovoltaic power stations, solving the power supply problem of villages and families without electricity in remote areas, and providing the most basic living electricity for 2 million farmers and herdsmen in remote areas (that is, one-third of the population without electricity in China at present); On the other hand, by drawing lessons from the experience of developed countries in building rooftop photovoltaic power generation systems, in large and medium-sized cities with developed economy and high level of urban modernization, photovoltaic power supply will be promoted in public buildings and lighting systems of public facilities such as roads, parks and stations, and rooftop photovoltaic power generation systems will be built. In addition, a large-scale grid-connected photovoltaic system will be established to prepare for the application of large-scale grid-connected photovoltaic system when the cost of photovoltaic power generation drops to a certain level.

1) household photovoltaic power generation system and small photovoltaic power station

Household photovoltaic systems and small photovoltaic power plants belong to non-grid-connected photovoltaic power generation systems (independent systems), which are mostly used in poor mountainous areas and rural areas without electricity in China. Since it was put into use, it has reliable operation, normal power generation and excellent performance. For example, 353 sets of independent household solar photovoltaic power supply systems have been installed in poor mountainous areas of Jianchang County, Liaoning Province, and the total power of solar module can reach 22650W W.

The household photovoltaic power supply system includes a DC system and an AC system. The DC system consists of three parts: solar cell module and bracket, controller and battery pack. The AC system has one more inverter than the DC system, and * * * consists of four parts.

During the day, the solar cell module receives the sunlight and outputs electric energy, and then charges the storage battery through the anti-reverse charging diode; At night, the DC system provides the DC output of the battery pack to the DC load through the controller, while the AC system converts the DC output of the battery pack into AC through the controller and provides it to the AC load through the inverter. In this system, the function of solar cell module is to convert solar radiation energy into electric energy; The function of the battery pack is to store the direct current output by the solar cell module; The function of anti-reverse charging diode is to prevent the battery pack from discharging through the solar cell module; The function of the controller is to protect the overcharge and overdischarge of the battery pack; The function of inverter is to convert the direct current output by battery pack into alternating current. Figure 7.2 shows the home photovoltaic power generation system.

Figure 7.2 Household Photovoltaic Power Generation System

In addition, China has also established some small photovoltaic power plants in remote areas of northwest China (such as Qinghai, Tibet, Xinjiang, Gansu and other places). Due to its special geographical location, photovoltaic power plants are particularly suitable for the special living environment in the west, especially in the Qinghai-Tibet Plateau. Vigorously developing and utilizing new solar energy and converting it into electric energy not only solved the power supply problem of some people without electricity, but also solved the communication problem in remote areas, promoted the western region to get rid of poverty and become rich, and coordinated the development of economy and ecological environment. Among them, Tibet has become the province with the largest installed capacity of photovoltaic power plants and photovoltaic cells in China, effectively improving the shortage of electricity for local herders. In terms of communication, the photovoltaic power supply used by microwave communication relay stations has reached more than 700kW, and there are 30,000 small photovoltaic power stations 1.3.

2) Roof photovoltaic power generation system

With the development of photovoltaic application technology, countries all over the world have launched corresponding rooftop photovoltaic plans. During the Ninth Five-Year Plan period, China State Science and Technology Commission also began to include solar roof system in the national scientific and technological research plan. Figure 7.3 shows the rooftop photovoltaic power generation system. The combination of solar photovoltaic power generation system and building has attracted worldwide attention because it has the following advantages:

(1) does not occupy land resources, which is especially important for cities with expensive land.

(2) It can generate electricity locally and use it locally to reduce the line loss of power transmission.

(3) The temperature rise of walls and roofs is reduced, the air conditioning load of buildings is lightened, and the energy consumption of air conditioning is reduced.

(4) Replacing and saving expensive exterior wall decoration materials (such as glass curtain wall). ), make the appearance of the building unified and harmonious, beautify the building environment.

(5) The peak demand for electricity is relieved, and the uninterrupted power supply requirements of safe power facilities are also met after installing storage batteries.

Figure 7.3 Roof photovoltaic power generation system

The success of bidding for the 2008 Olympic Games provides new opportunities for the utilization of solar energy. The state plans to incorporate solar photovoltaic power generation into Olympic buildings, and various Olympic buildings will adopt green energy utilization technologies such as solar energy on a large scale. The China Municipal Government has studied the combination of solar energy utilization and architectural design in the Olympic Village and Olympic venues, and applied it in the Olympic venues and the Olympic Village, which reduced building energy consumption and improved the overall image of the city.

Nowadays, many cities actively use small-scale solar photovoltaic power supply, and install solar garden lights, solar lawns, solar street lamps, municipal transportation and parking signs on roads, parks, stations and even homes. These lamps are novel in shape, elegant in appearance, varied in variety, durable, decorative and practical. They don't need to pull wires, occupy no space, and have the advantages of energy saving, environmental protection and convenient maintenance, and become a beautiful landscape of the city.

3) Large grid-connected photovoltaic power generation system

Grid-connected photovoltaic power generation system is an important symbol of photovoltaic technology progress, and it is also the development trend of solar photovoltaic power generation in the future. The photovoltaic system has entered the stage of large-scale power generation, which means that the current energy structure will undergo fundamental changes and is a revolution in energy utilization in human society. Figure 7.4 shows a solar photovoltaic power station.

Figure 7.4 Solar photovoltaic power station

At present, in the world, the United States, Germany and other developed countries have begun to build a number of kilowatt-level grid-connected photovoltaic power generation systems, and are building a number of megawatt-level grid-connected photovoltaic power generation systems. Even India, the Philippines and some African countries have begun to build large-scale grid-connected photovoltaic power generation systems.

China's grid-connected photovoltaic power generation system started late, and there is still a big gap compared with the above countries. However, China has built the largest grid-connected solar photovoltaic power station in Asia in Shenzhen International Garden and Flower Expo Park (Figure 7.5). Solar photovoltaic power plants have been installed in the comprehensive exhibition hall, flower exhibition hall, management center, tourist service center and the east slope of the north area, with a total capacity of 1mw and annual power generation of100×104 kW h, which is equivalent to saving more than 384t of standard coal, 48t of dust and10. After the completion of Ash 178 Shenzhen International Garden and Flower Expo Park 1MWp solar grid-connected photovoltaic power station, it has become the largest grid-connected photovoltaic power station in Asia and China at present, and it is also one of the few megawatt large-scale solar photovoltaic power stations in the world, which fills the gap in the design and construction of large-scale grid-connected photovoltaic power stations in China and will become a milestone in the history of grid-connected solar power generation in China.

Figure 7.5 Shenzhen International Garden and Flower Expo Park 1MWp Solar Grid-connected Photovoltaic Power Station