Solar Energy

Why do we need to develop solar energy vigorously

July 20, 2021
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8 mints to read

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

1. Principle of solar power photovoltaic generation.

The 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 is used to make crystalline silicon solar cells, which convert the sun's light energy directly into electricity. The energy converter of solar photovoltaic power generation is the solar cell, also known as the photovoltaic cell, which is the basis and core device of the 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, known as "photo-generated carriers", the electrical polarity of the two opposite, electrons with a negative charge, holes with a positive charge.

(2) The photo-generated carriers of opposite polarity are separated by the electrostatic field generated by the PN junction of the semiconductors.

(3) The photo-generated carrier electrons and holes are collected by the positive and negative poles of the solar cell respectively and generate a current in the external circuit, thus obtaining electrical energy.

When light strikes 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 switched on, a current will flow through the external circuit to produce a certain output power under the effect of this voltage. 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 efficiency of the controller, the efficiency of the storage battery, the efficiency of the inverter, and the efficiency of the load. At present, the photoelectric conversion efficiency of solar cells is only about 23%. Therefore, to improve the photoelectric conversion efficiency of solar cell modules and reduce the cost per unit power of solar photovoltaic power generation systems is the focus and difficulty of the industrialization of solar photovoltaic power generation. Since the introduction of solar cells, crystalline silicon has maintained its dominant position as the main material. The current research on the conversion efficiency of silicon solar cells mainly revolves around increasing the energy absorption surface (e.g. using double-sided cells to reduce reflection), the use of absorption technology, and the passivization process to improve the conversion efficiency of silicon solar cells, cell ultra-thin type and so on.

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

(1) To provide power for powerless occasions, mainly to provide power for residents' living and production in the vast areas without electricity, to provide power for microwave relay stations and mobile phone base stations, etc.

(2) Solar power for daily-use electronic products, such as various types of solar chargers, solar street lights, and solar lawn lamps, etc.

(3) Grid-connected power generation, i.e. access to the national grid. China's grid-connected photovoltaic power generation is already very mature. Since 2013, the state has introduced a series of policies to promote photovoltaic power generation, encouraging the construction of photovoltaic power generation facilities for commercial and industrial use, household use, and public buildings in areas where conditions exist.

120 watts solar powered LED street light (also called all in one solar street light) with an extra panel mounted on the pole.

2. Advantages of solar power generation

By comparing and analyzing 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: one is that solar energy is inexhaustible, and no "tax" is levied when receiving solar energy, so it can be used anywhere; the second is that at the current level of technological development, the use of some solar energy already has economic. With the development of science and technology and the breakthroughs in human development and the use of solar energy technology, the economics of solar energy use will become more obvious. If the 20th century was 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 costs, 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 per kilowatt of solar photovoltaic power generation is getting lower and lower, compared to other renewable energy sources already have the same economic advantages, and with the national policy of price parity, its popularity will be 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 about 1.892*10^24 tons of standard coal, which is 10,000 times the current proven reserves of the world's major energy sources. The sun's lifespan is still at least 4 billion years, compared to the history of mankind, solar energy can be continuously supplied to the earth for an unlimited period of time, which determines that the development and use of solar energy will be the most effective way for mankind to solve the lack of conventional energy depletion.

(3) No pollution to the environment.

Solar energy, like wind energy, tidal energy, and other clean energy, its development and use 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 during use, they can cause serious pollution to water, soil, and the atmosphere, forming the greenhouse effect and acid rain, seriously endangering the living environment and health of mankind, so there is an urgent need to develop new and relatively clean alternative energy sources, and solar energy, as a relatively ideal clean energy source, is receiving increasing attention from countries around the world.

The current carbon emission rates (g/kW-h) of various power generation methods, not counting their upstream links, are 275 g/kW-h for coal, 204 g/kW-h for oil, 181 g/kW-h for natural gas, and 20 g/kW-h for wind power, while solar photovoltaic power generation is close to zero emissions. In addition, there is no waste material, wastewater, waste gas, no noise, no substances harmful to the human body, and no pollution of the environment.

(4) Photovoltaic power generation is not only pollution-free but also has the lowest energy transformation process.

From the energy transformation process, solar photovoltaic power generation directly converts solar radiation into electrical energy, which is the most direct and least complicated of all renewable energy sources. Generally speaking, in the flow of energy in the whole ecological environment, as the number of transformation links increases and the transformation chain lengthens, the loss of energy 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 photovoltaic conversion efficiency of crystalline silicon solar cells is 15%-24%, the highest level of the laboratory has reached 35%.

(5) The most economical and environmentally friendly.

From the point of view of 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 of 1, the wind is 8-10 times more than solar energy, bio-energy is up to 100 times. In the case of hydro-power, the construction of a large dam often requires the flooding of dozens to hundreds of square kilometers of land. In contrast, solar power does not need to occupy more land, roofs and walls can become places for solar photovoltaic power generation, and can also be used to make use of our vast deserts, by building solar photovoltaic power generation bases on the deserts, directly reducing the solar radiation coming directly to the surface in the desert areas, effectively lowering the surface temperature and reducing evaporation, which in turn makes the survival and growth of plants possible to a considerable extent. stabilizing and reducing sand dunes, and in turn, asking nature for the clean renewable energy it needs.

(6) It is free to use and does not require transport.

Mankind can convert solar energy into heat or electricity by means of specialized technology and equipment and use it locally, without the need for transport, for the benefit of mankind. And the use of this inexhaustible source of energy is also free of charge.

Although solar radiation is uneven due to differences in latitude and climatic conditions, solar energy is universally available to the vast majority of the earth's regions and can be used locally compared to other energy sources. This offers bright prospects for solving energy problems in countries and regions where conventional energy is scarce. And these are the reasons that we need to develop solar energy vigorously.

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