The development of solar photovoltaic power generation has become a trend. This chapter introduces the development status of solar photovoltaic power generation.
The sun is a star located in the center of the solar system with a surface temperature of about 5800K. Its energy comes from the internal hydrogen fusion reaction. The sun has existed for 5 billion years, and it consumes about 620 million tons of hydrogen per second. At this burning rate, the sun can continue to serve mankind for about 5 billion years.
The basic parameters of solar radiation can be estimated by the blackbody model. The radius of the sun Rs=6.96108m, the radius of the earth RE=6.38106m, and the distance between the sun and the earth d=1.4961011m. In the solar radiation spectrum, the wavelength corresponding to the maximum energy value is λm=490nm. If the sun is regarded as a black body, according to the Wien displacement law Tλm=b, the surface temperature of the sun is T=5900K (very close to the actual value T=5800K, where b is a constant, also known as the Wien constant, b=0.002897m ·K), and then according to Stepan Boltzmann’s law W0(T)=σT4, the transmit power per unit area can be obtained
W0=6.87107W/m2
In the formula, σ is the Stepan-Boltzmann constant, σ=5.6710-8W/(m2·K4).
Then the total power of solar radiation Ps = W04πRs2 = 4.21026W. Assuming that the solar radiation is distributed on a spherical surface with the distance from the sun to the earth as the radius, the power of solar radiation that the earth can receive per unit area is
P′E=PS/4πd2=1490W/m2
Since the distance from the earth to the sun is much greater than the radius of the earth, the earth can be regarded as a disk with a radius of RE, and the solar radiation power received by the earth is
PE=P′E*4πRE2=1.776 x1017W
From this, it can be calculated that the solar radiation energy received by the earth throughout the year is
WS=1.56*1018kWh
Someone has estimated that as long as the area of several hundred square kilometers in the African Sahara Desert is covered with photovoltaic modules, it can meet the electricity demand of the world.
Compared with fossil energy, wind energy, hydropower, etc., the global solar energy resources are more evenly distributed. The regions with richer solar energy resources in the world include North Africa, South Africa, the Middle East, Southern Europe, Australia, the southwestern United States, the east and west coasts of South America, and the western regions of China. The amount of solar radiation on China’s Qinghai-Tibet Plateau is close to that of the Sahara Desert in Africa, which has the richest solar resources in the world; the regions with poor solar resources in China are mainly located in parts of Guizhou and Sichuan, and most of the other areas can be better utilized PV. The western part of China has large deserts and Gobi areas, which are very suitable for the construction of large-scale ground photovoltaic power stations; while in the eastern coastal areas, there are a large number of factory buildings, which are suitable for the construction of large-scale rooftop photovoltaic power stations.
Taking 1000W photovoltaic modules as an example, in areas with medium solar resources, in China, such as Shanghai, the annual power generation is about 900kWh, and in Guangzhou, the annual power generation is about 1100kWh; in regions with rich solar resources, such as Kunming, the annual power generation can reach 1400kWh. It can reach 1500kWh in Hohhot, 1600kWh in Jiayuguan, Gansu, 1700kWh in Urumqi, Xinjiang, and more than 1800kWh in Xigaze, Tibet.
As a brand-new way of generating electricity, photovoltaic power generation is still in its infancy stage of As a brand-new way of generating electricity, solar photovoltaic power generation is still in its infancy stage of development worldwide.
According to statistics from the National Energy Administration, as of the end of 2017, China’s installed renewable energy power generation capacity reached
650 million kilowatts, accounting for 36.6% of the total installed power capacity, of which hydropower installed capacity reached 341 million kilowatts, wind power installed capacity reached 164 million kilowatts, photovoltaic power generation installed capacity reached 130 million kilowatts, and biomass power generation installed capacity reached 14.76 million kilowatts. China is not only the largest producer of photovoltaic power generation equipment, but also the largest application of photovoltaic power generation. The reason why photovoltaic power generation technology has gained worldwide attention and rapid development is mainly because it has the following advantages:
(1) Solar energy is inexhaustible and inexhaustible. It is widely distributed on the earth. Solar energy can be well developed and used regardless of whether it is on land or in the ocean, mountains and islands;
(2) Solar energy, like wind energy, ocean energy, and geothermal energy, is a renewable clean energy. It produces almost no pollution during its utilization, basically no CO2 emissions, and photovoltaic power generation is safe and reliable, with no noise and no pollutant emissions. Therefore, solar energy is a real green energy source;
(3) The main raw material used in solar cells is silicon. The content of silicon in the earth’s crust is very rich, accounting for about 26%, second only to oxygen, so there is no problem of resource depletion;
(4) Photovoltaic power generation equipment can be installed on the ground to build a large-scale ground power station, or installed on the roof or curtain wall, and even a power generation unit can be built on each building to serve thousands of households. This is other energy sources. Unattainable
(5) Compared with other forms of power generation, photovoltaic power plants are simple and quick to install, easy to expand and relocate, and will not cause environmental impact or damage;
(6) The operation mode of the photovoltaic power station is relatively simple, the replacement and maintenance of parts are convenient, it can be unattended, and the maintenance cost is low. As the core component of photovoltaic power generation, photovoltaic modules can normally work for at least 25 years under normal circumstances and have obvious economic advantages.
The energy radiated by the sun to the surface is greatly affected by the alternation of day and night in nature, seasonal changes, geographic latitude, altitude, meteorological conditions, and various random factors. It is in an intermittent and unstable state, which affects the effect of photovoltaic power generation. For example, if there is sunlight on a sunny day, it can generate power normally, and if there is no sunlight on a rainy day, the power generation effect is very poor; the sunshine time in summer and winter is different, and the amount of solar radiation is different, so the output of photovoltaic power generation is also different. Because of this, the current photovoltaic power generation mainly adopts the form of grid-connected power generation, so that it will not affect the normal power consumption of end users.
Due to the increasingly prominent environmental pollution caused by fossil energy consumption, the development of new energy sources has attracted the attention and attention of all countries in the world. At present, the three renewable energy technologies of wind energy, solar energy and biomass energy have developed rapidly. In the book “The Third Industrial Revolution”, American Jeremy Rifkin mentioned that the five pillars of the third industrial revolution are:
(1) Transition to renewable energy;
(2) Convert buildings on every continent into micro power plants to collect renewable energy on-site;
(3) Use hydrogen and other storage technologies in every building and infrastructure to store intermittent energy;
(4) Use Internet technology to transform the power grid on every continent into an energy sharing network. The working principle of this sharing network is similar to that of the Internet (thousands of buildings can produce a small amount of energy on-site, and the excess of these energy sources) It can be recycled by the power grid or shared across continents through networking);
(5) Shift the means of transportation to plug-in and fuel cell powered vehicles. The electric energy required by such electric vehicles can be bought and sold through the grid platform shared between continents.
It is foreseeable that solar photovoltaic power generation will continue to develop in the direction of integration with buildings, energy storage, and smart grids.Its production costs will continue to decline until it can fully compete with conventional energy generation and become the main power supply of human society. Way. At present, in many European countries, such as Denmark, Germany, Spain, Italy, etc., wind and solar power have occupied a large share. The development of renewable energy in the United States, Japan and my country has also shown that renewable energy can effectively change the energy structure.
According to statistics from many authoritative organizations, the current global solar energy application ratio is still very low, accounting for only 2% of the total global energy application, and by 2050, the global renewable new energy (including solar energy) application ratio can reach 70% about. From the spring of development trend, solar energy will gradually transition from supplementary energy to dominant energy, becoming the ultimate energy source for maintaining the sustainable and healthy development of human society.
