Solar energy is a kind of new energy and renewable energy. Therefore, this chapter first introduces the meaning, characteristics and types of new energy and renewable energy, and the great strategic significance of the development and utilization of new energy and renewable energy, and then introduces a brief history of solar energy utilization and solar energy. Use basic methods.
The basic meaning of new energy and renewable energy proposed by the New Energy and Renewable Energy Conference held by the United Nations in Nairobi, the capital of Kenya in 1981, is: based on new technologies and new materials, traditional renewable energy can be modernized and utilized. Use inexhaustible and recurring renewable energy to continuously replace fossil energy with limited resources and pollute the environment; it is different from conventional fossil energy, which can be developed continuously, is almost inexhaustible, and does not cause much damage to the environment. Conducive to a virtuous ecological cycle; the focus is on the development and utilization of solar energy, wind energy, biomass energy, ocean energy, geothermal energy and hydrogen energy.
The common characteristics of new energy and renewable energy include:
① The energy density is low and highly dispersed;
②Rich resources, renewable;
③Clean and clean, almost no pollutants that damage the ecological environment are discharged during use;
④ Solar energy, wind energy, tidal energy and other resources are intermittent and random;
⑤The technology of development and utilization is difficult, and the current production and utilization cost is high.
(1) The United Nations Development Program (UNDP) divides new energy and renewable energy into three categories:
① Large and medium-sized hydropower;
②New renewable energy, including small hydropower, solar energy, wind energy, modern biomass energy, geothermal energy and ocean energy, etc.;
③Traditional biomass energy.
(2) New renewable energy in my country currently refers to primary energy such as biomass energy, solar energy, wind energy, small hydropower, geothermal energy, ocean energy, and hydrogen energy in addition to conventional fossil energy, large and medium-sized hydropower and nuclear fission power generation. , Fuel cells and other secondary energy sources.
① Biomass energy. Green plants convert solar energy into chemical energy through chlorophyll and store energy inside biomass. Except for fossil fuels, all energy materials derived from animals and plants in organic matter belong to biomass energy, which usually include wood and forest wastes, agricultural wastes, aquatic plants, oil plants, urban and industrial organic wastes, animal manure, etc. The utilization of biomass energy mainly includes three ways: direct combustion, thermochemical conversion and biochemical conversion. The direct combustion of biomass will continue to be the main method of biomass energy utilization in rural areas in my country for a long time to come. At present, traditional wood-burning stoves with a thermal efficiency of only about 10% are renovated, and firewood-saving stoves with a thermal efficiency of 20% to 30% are promoted. This technology is simple, easy to promote, and has obvious benefits. This energy-saving measure has been listed as the focus of rural energy construction by the country. One of the tasks. The thermochemical conversion of biomass refers to the technology of vaporization, carbonization, pyrolysis and catalytic liquefaction of biomass under certain temperature and conditions to produce gaseous fuels, liquid fuels and chemical substances. Biochemical conversion of biomass includes biomass-biogas conversion and biomass-ethanol conversion. Biogas conversion is the production of a combustible mixed gas with methane as the main component, namely biogas, through microbial fermentation of organic substances in an anaerobic environment. Ethanol conversion uses raw materials such as sugar, starch and cellulose to produce ethanol through fermentation.
② Solar energy. The conversion and utilization of solar energy include photothermal conversion, photoelectric conversion and photochemical conversion. Receiving or gathering solar energy to convert it into thermal energy, and then using it in some aspects of production and life, is the basic way of light-to-heat conversion, that is, solar thermal utilization. Solar water heating system is currently the main form of solar thermal utilization in my country. It is a device that uses solar energy to heat water and store it in a water tank for use. The thermal energy produced by solar energy can be widely used in various fields such as heating, refrigeration, drying, distillation, greenhouse, cooking, industrial and agricultural production, and can be used for solar thermal power generation and thermal power. Solar cells made using the principle of photovoltaic effect can directly convert the sun’s light energy into electrical energy for use, which is called photoelectric conversion, that is, solar photovoltaic utilization. Photo-chemical conversion is still in the research and experimental stage. This conversion technology includes the generation of electricity from semiconductor electrodes and the electrolysis of water to produce hydrogen, and the use of calcium hydroxide or metal hydride to thermally decompose energy storage.