From what solar energy is to solar energy application related technology explanation, I believe that many people have a general understanding of solar energy, the following talk about solar energy application technology in photovoltaic power generation, the main two aspects: the principle and its advantages.

Ground-based concentrated solar power generation applications
1, solar photovoltaic power generation principle

Photovoltaic effect occurs in both liquid and solid substances, but only solid (especially semiconductor PN junction devices) in the sunlight irradiation photoelectric conversion efficiency is higher. The photovoltaic effect principle is used to make crystalline silicon solar cells, which can convert light energy from the sun directly into electricity. The energy converter of solar photovoltaic power generation is the solar cell, also known as photovoltaic cell, is the basis and core device of solar photovoltaic power generation system. The process of converting solar energy into electrical energy consists of 3 main steps.

(1) solar cells absorb a certain amount of energy photons, the semiconductor produces an electron-hole pair, called "photogenerated carriers", the electrical polarity of the two opposite, electrons are negatively charged, holes are positively charged.

(2) The photogenerated carriers with opposite electrical polarity are separated by the electrostatic field generated by the semiconductor PN junction.

(3) The photogenerated carrier electrons and holes are collected by the positive and negative poles of the solar cell, respectively, and generate current in the external circuit to obtain electrical energy.

The principle of solar photovoltaic power generation is shown in the figure below. When light shines on the surface of the solar cell, part of the photons are absorbed by the silicon material and the energy of the photons is transferred to the silicon atoms, causing the electrons to leap and become free electrons, which cluster on both sides of the PN junction to form a potential difference. When the external circuit is turned on, under the action of this voltage, there will be a current flow through the external circuit to produce a certain output power. The essence of this process is the conversion of photon energy into electrical energy.

In a solar power system, the total efficiency of the system η is determined by the photovoltaic conversion efficiency of the solar cell module, the controller efficiency, the battery efficiency, the inverter efficiency and the efficiency of the load. At present, the photoelectric conversion efficiency of solar cells is only about 17%. Therefore, to improve the photoelectric conversion efficiency of solar cell modules, reduce the cost per unit power of solar photovoltaic power generation system, is the focus and difficulty of the industrialization of solar photovoltaic power generation. Since the introduction of solar cells, crystalline silicon as the main material to maintain the dominant position. At present, the research on the conversion efficiency of silicon solar cells mainly revolves around increasing the energy absorption surface (such as the use of double-sided cells to reduce reflection), the use of absorption technology and passivation process to improve the conversion efficiency of silicon solar cells, cell ultra-thin type and other aspects.

At present, solar photovoltaic power generation systems are mainly used in the following 3 broad areas.

(1) To provide power for non-electricity occasions, mainly for the majority of non-electricity areas to provide power for the residents' living and production, microwave relay stations and cell phone base stations to provide power, etc.

(2) Solar energy daily electronic products, such as various types of solar chargers, solar street lamps and solar lawn lamps, etc.

(3) Grid-connected power generation, that is, access to the national grid. China's grid-connected photovoltaic power generation has been very mature, since 2013, the state has introduced a series of photovoltaic power generation promotion policies to encourage the construction of photovoltaic power generation facilities in areas with conditions for commercial and industrial and household use, public buildings, etc.

2、The advantages of solar power generation

Through the comparative analysis of several common new energy sources such as biomass, water, wind and solar energy, it is clear that solar power generation has the following unique advantages.

(1) Photovoltaic power generation has economic advantages

The economy of solar energy can be seen from two aspects: First, solar energy is inexhaustible, and no "tax" is levied when receiving solar energy, so it can be used anywhere; second, at the current level of technological development, some solar energy use already has economic. With the development of science and technology and human development and use of solar energy technology breakthroughs, the economic use of solar energy will be more obvious. If the 20th century is the century of oil, then the 21st century is the century of renewable energy (the century of solar energy).

From the point of view of solar photovoltaic power station construction cost, with the large-scale application and promotion of solar photovoltaic power generation, especially the upstream crystalline silicon industry and photovoltaic power generation technology is becoming more and more mature, building roofs, exterior walls and other platforms of composite development and utilization, the construction cost of solar photovoltaic power generation per kilowatt is getting lower and lower, compared to other renewable energy sources already have the same economic advantages, and with the implementation of the national policy of price parity Its popularity will become more and more widespread.

(2) Solar energy is an inexhaustible source of renewable energy

According to calculations, the total amount of solar energy reaching the earth's surface in a year is equivalent to a total of about 1.892x10^24 tons of standard coal, which is 10,000 times the current proven reserves of the world's major energy sources. The life span of the sun is at least 4 billion years, compared to the history of mankind, solar energy can be continuously supplied to the earth can be said to be infinite, which determines the development and utilization of solar energy will be the most effective way to solve the scarcity of conventional energy, depletion.

(3) No pollution to the environment

Solar energy, like wind power, tidal energy and other clean energy, its development and utilization of almost no pollution, coupled with its unlimited reserves, is the ideal alternative energy for mankind. As traditional fossil fuels (coal, oil and natural gas) emit a large amount of toxic and harmful substances in the process of use, which can cause serious pollution to water, soil and the atmosphere, forming the greenhouse effect and acid rain, seriously endangering the human living environment and health, there is an urgent need to develop new and relatively clean alternative energy sources, and solar energy as a relatively ideal clean energy, is receiving increasing attention from countries around the world.

From the current carbon emission rate (g/kW-h) of various power generation methods, not counting their upstream links: 275g/kW-h for coal, 204g/kW-h for oil, 181g/kW-h for natural gas, 20g/kW-h for wind power, while solar photovoltaic power generation is close to zero emission. Moreover, there is no waste material, waste water, waste gas, noise, or harmful substances in the process of power generation, and it does not pollute the environment.

No pollution from photovoltaic power generation
(4) Minimal energy conversion links

In terms of energy conversion, solar photovoltaic power generation directly converts solar radiation energy into electrical energy, and among all renewable energy sources, solar photovoltaic power generation has the least conversion links and the most direct utilization. Generally speaking, in the energy flow of the whole ecological environment, as the conversion link increases and the conversion chain lengthens, the energy loss will increase geometrically, and at the same time greatly increase the construction and operation costs and instability of the whole system. At present, the practical level of crystalline silicon solar cells photoelectric conversion efficiency of 15%-20%, the highest level of laboratory has reached 35%.

(5) The most economical and environmentally friendly

From the resource conditions, especially land occupation, biological energy, wind energy is more demanding, while the use of solar energy is very flexible. If solar photovoltaic power generation occupies an area of land 1,wind is 8-10 times more than solar energy, bioenergy is up to 100 times. In the case of hydropower, the construction of a large dam often requires the flooding of tens to hundreds of square kilometers of land. In contrast, solar power does not need to occupy more land, roofs, walls can become solar photovoltaic power generation using the site, but also the use of China's vast deserts, by building solar photovoltaic power generation base on the desert, directly reduce the desert zone direct solar radiation to the surface, effectively reduce the surface temperature, reduce evaporation, and thus make the survival and growth of plants in a considerable degree possible, and stabilize and reduce sand dunes, and in turn claim the clean renewable energy needed from nature.

(6) Free to use and no transportation

Human beings can convert solar energy into heat or electricity through specialized technology and equipment, and use it locally without transport for the benefit of mankind. Moreover, the use of this inexhaustible energy source is free of charge. Although the differences in latitude and climate conditions cause uneven solar radiation, solar energy is universal to most areas of the earth compared to other energy sources and can be used locally. This offers bright prospects for solving energy problems in countries and regions where conventional energy is scarce.