At present, the world is facing an increasingly serious energy crisis, and the main energy sources that human beings can use include traditional energy and new energy. The traditional energy used for power generation in China is mainly coal, while the new energy mainly refers to renewable energy such as solar energy, wind energy and tidal energy. New energy in our country has very rich resources, clean and environmental protection, the most important thing is that it can be renewable, and can replace many existing conventional energy, and has good application prospects. Solar energy is one of the most promising energy sources for human beings, and solar energy technology is also listed as an important research topic by most scientific research institutions and relevant departments. The photovoltaic technology of solar power generation is one of the hot spots in current research. At present, the photovoltaic industry is accelerating development, and it has begun to receive attention in the construction field and has been applied. Many countries and regions in the world have begun to use solar photovoltaic systems to provide electricity for buildings on a large scale.
1. Research status at home and abroad
In 1839, solar photovoltaic power generation kicked off the development of the prologue, thanks to the development of selenium photovoltaic effect of the first person – French scientist Becquerel. In the world, European countries attach the most importance to the research and development of solar photovoltaic technology, and its technical level is also in the forefront of the world. Various EU member States have made efforts and achieved great success in the research and development, application and promotion of solar energy technology. By November 2007, the total installed capacity of solar photovoltaic power generation in the European Union has reached 4.5GW, and the EU region has become the main region of photovoltaic power generation in the world, and its total installed capacity of photovoltaic power generation has been close to half of the world. In the United States, the electricity consumption of buildings accounts for 2/3 of the total electricity consumption of the country, the United States government has taken effective measures in the economy, invested a lot of costs to research solar photovoltaic technology, in order to encourage the promotion of this key project, Congress approved the solar photovoltaic system tax reduction bill, while developing a series of policies. In the solar photovoltaic building research, product development and application and materials have been rapid development, has been in the world’s leading level. The latitude across Asia is large, the development of the economic and technological level of various countries is unbalanced, and the regions with more mature solar photovoltaic technology are mainly concentrated in economically developed countries and regions such as Japan and South Korea, among which, Japan has the best development of photovoltaic technology. As a major energy consumer and importer, Japan relies on imports for 80% of its energy consumption, so it attaches great importance to the development of renewable energy technologies such as solar energy. As of 2004, the cumulative installed capacity of PV in Japan reached 1100MW. In short, solar photovoltaic technology has been widely developed and applied in the world’s major economically developed countries and regions, and some developed countries have formulated development plans for photovoltaic power generation from 2010 to 2030. In recent years, China’s energy construction and development has also made great achievements, especially in the 21st century, the state attaches great importance to the application of new energy and renewable energy in the field of construction, and strongly advocates. Building energy consumption is huge, in order to better save energy, in the research and development of solar photovoltaic products, China has become the world’s largest producer of solar photovoltaic products. However, it is still necessary to clearly see the problems existing in China’s solar photovoltaic industry, key technologies mainly rely on foreign introduction, independent research and development and innovation ability is relatively weak, the rapid development of industrial scale but the development of the industrial chain is not balanced, the domestic market has yet to be cultivated and developed. Solar energy resource distribution map (MJ/m2 • year) ≥9250 (High, High) 755058505000 < 4150 (Low, Low)
2. Issues related to solar photovoltaic technology
The huge energy contained by the sun is the condition for the survival of all living things on the earth, including human beings, the sun radiates energy to the surrounding, and the main factors affecting the solar radiation include atmospheric conditions and obstacles near the earth’s position relative to the sun, etc. The earth’s surface is wrapped by air molecules, water droplets, dust, clouds and other components of the atmosphere. The distance from the Earth to the sun and the tilt of the Earth’s axis also affect the energy of solar radiation. From June to August every year, when the northern hemisphere is in summer, the inclined northern hemisphere of the Earth’s axis tilts toward the sun, while in winter, because the inclined northern hemisphere of the Earth’s axis is far away from the sun, there is a great difference in the energy of solar radiation in summer and winter. At the same time, topography, landforms and obstacles also have important effects on the solar radiation energy. According to the annual sunshine hours, the annual radiation amount, the amount of solar radiation received can be roughly divided into five categories of regions in China. Category 1: the annual sunshine duration is 3200h ~ 3300h, and the annual radiation amount is 670×104KL/cm2 ~ 837×104KL/cm2. It can be seen from the distribution map that Gansu, Ningxia, Xinjiang and other regions belong to this region; The second category: the annual sunshine hours are 3000h ~ 3200h, and the annual radiation amount is 586×104KL/cm2 ~ 670×104KL/cm2. It can be seen from the distribution map that northern Shanxi, northwestern Hebei, southern Ningxia and southern Inner Mongolia belong to this region; Three types of regions: the annual sunshine hours are 2200h ~ 3000h, the annual radiation amount is 502×104KL/cm2 ~ 586×104KL/cm2, from the distribution map can be seen that Shandong Province, Henan Province, Anhui Province, Liaoning, Jilin and other regions belong to this region; Four types of regions: the annual sunshine duration is 1400h ~ 2200h, the annual radiation amount is 419×104KL/cm2 ~ 502×104KL/cm2, and it can be seen from the distribution map that Fujian, Zhejiang and Guangdong belong to this region; Five categories of regions: the annual sunshine duration is 1000h ~ 1400h, the annual radiation amount is 335×104KL/cm2 ~ 419×104KL/cm2, Sichuan and Guizhou can be seen from the distribution map. It can be seen that the solar energy resources in our country are relatively rich in one to three types of areas, and relatively poor in four and five types of areas. The basic principle of solar photovoltaic power generation is as follows: when the sun is projected onto the battery, free electron-hole pairs are generated inside, the free electrons are swept to the n region by the P-N junction, and the holes are swept to the p region, forming a voltage at both ends of the P-N junction. When we use metal wires to connect the positive and negative terminals of the solar cell to the load, the external circuit forms a current. In the design process, in order to improve the photoelectric conversion efficiency and ensure a certain output power, the photovoltaic module composed of multiple cells in series is connected in series to form a photovoltaic array. Since the solar light intensity is unstable and changes significantly with time, the photovoltaic power generation system is not stable by the solar light intensity, changes significantly with time, the photovoltaic power generation system is changed by the change of solar light intensity, and the generated direct current, in order to carry out the conversion from DC to AC must be added to the inverter device, while adding the corresponding control device. After the photovoltaic array absorbs solar light, it can obtain a stable and reliable alternating current that can be used.
3. Application of solar photovoltaic power generation technology in the field of construction
In the building sector, many energy sources are limited and non-renewable; And it will produce a lot of waste, pollute the environment and destroy the ecological balance. If the solar photovoltaic technology is applied to the field of construction, it can replace or reduce limited, non-renewable energy consumption, reduce waste emissions, prevent air pollution, and then protect the ecological environment, but also in remote areas and energy-poor areas to solve the basic demand for electricity and reduce ecological environmental damage. Improve the comfort of residential housing, quality of life and the technological content of the building itself. At present, solar photovoltaic technology is also widely used in communications and industrial applications of microwave relay stations and satellite communications and satellite television systems; It is mainly used in photovoltaic lighting and other aspects in the construction field. According to relevant information, the application to the field of construction is more off-grid photovoltaic power generation system, the system is according to the solar photovoltaic power generation system and the public grid connection method is divided into one of the fields, this system can be independent power supply, and can be combined with wind power system, for building lighting and environmental lighting to provide electricity.
4. Concluding Remarks
Solar photovoltaic technology is used in many fields as a reliable, renewable and pollution-free clean energy. Especially in the field of construction applications, both energy saving and environmental protection. Solar photovoltaic power generation technology as the application of renewable energy, has a good application value, the study of solar photovoltaic power generation technology will also be a promising subject, the future building lighting technology to energy conservation and environmental protection direction plays an important role in promoting.
