The sun is the closest star to the Earth and the only luminous object in the solar system. It brings light and heat to the earth and is the root of all life on Earth. The sun transmits energy to the surface of the earth in the form of light radiation. Solar energy is a renewable green energy source. It is an inexhaustible source of energy. When the power generation efficiency is 10% under standard solar lighting conditions during the day, the annual solar power generated on the entire surface of the earth is 114 & TImes; 1015 kWh. It is equivalent to 100 times the total energy consumption in the world today.
1. Universal
The sun shines on the earth, there are no geographical restrictions, no matter the land or the sea, whether it is a mountain or an island, it can be developed and utilized directly, and it is not necessary to mine and transport.
2, harmless
The development and utilization of solar energy does not pollute the environment. It is one of the cleanest energy sources. This is extremely valuable today as environmental pollution becomes more and more serious.
3, huge
The annual solar radiation energy reaching the surface of the earth is equivalent to about 130 trillion tons of standard coal, the total amount of which is the largest energy that can be developed in the world today. ?
4, long time
According to the current rate of nuclear energy generated by the sun, the storage of hydrogen is enough to last for tens of billions of years, and the life of the earth is also about several billion years. In this sense, it can be said that the energy of the sun is inexhaustible. Dispersibility
Although the total amount of solar radiation reaching the surface of the earth is large, the energy flow density is very low. On average, near the Tropic of Cancer, in the summer when the weather is relatively sunny, the irradiance of solar radiation is the largest at noon, and the average solar energy received in the area of ​​1 square meter perpendicular to the direction of sunlight has an average of about 1000W; The average day and night is only about 200W. In winter, it is only about half, and on cloudy days it is only about 1/5. This energy density is very low. Therefore, when using solar energy, in order to obtain a certain conversion power, a set of collection and conversion equipment having a relatively large area is often required, and the cost is high.
5, instability
Due to the limitations of natural conditions such as day and night, season, geographical latitude and altitude, and random factors such as sunny, cloudy, cloud, and rain, the solar irradiance reaching a certain ground is both intermittent and extremely unstable. This adds to the difficulty of large-scale application of solar energy. In order to make solar energy a continuous and stable energy source and eventually become an alternative energy source that can compete with conventional energy sources, it is necessary to solve the energy storage problem by storing solar radiation in clear daytime as much as possible for night or rain. Day use, energy storage is also one of the weaker links in solar energy utilization.
6, low efficiency and high cost
Some aspects of the development of solar energy utilization are theoretically feasible and technically mature. However, some solar energy utilization devices have low efficiency and high cost. In general, economics cannot compete with conventional energy sources. For a considerable period of time in the future, the further development of solar energy utilization is mainly constrained by economics.
(1) Photothermal utilization
Its basic principle is to collect solar radiant energy and convert it into heat energy through the interaction with matter. At present, the most used solar energy collection devices are mainly four types of flat type collectors, vacuum tube collectors, ceramic solar collectors and focusing collectors (slot type, dish type and tower type). Solar photothermal utilization is generally classified into low temperature utilization ("200 °C", medium temperature utilization (200 to 800 °C), and high temperature utilization ("800 °C) depending on the temperature and use that can be achieved. At present, low-temperature utilization mainly includes solar water heaters, solar water heaters, solar distillers, solar heating (solar rooms), solar greenhouses, solar air-conditioning refrigeration systems, etc. The medium-temperature utilization mainly includes solar cookers, solar thermal power generation concentrating collectors, etc. The use mainly includes high temperature solar furnaces.
(2) Power generation utilization
New energy The future use of solar energy is used to generate electricity. There are many ways to use solar power to generate electricity. There are two main types that have been put to practical use.
1. Light-heat-electric conversion. That is, using the thermal energy generated by solar radiation to generate electricity. Generally, a solar collector is used to convert the absorbed heat energy into steam of the working medium, and then the steam driven gas turbine drives the generator to generate electricity. The former process is light-to-heat conversion, and the latter process is heat-to-electric conversion. This method is simple and easy to implement, and the cost is low and the return is large, which is suitable for large-scale promotion in China.
2. Light-to-electricity conversion. The basic principle is to use the photovoltaic effect to convert solar radiant energy directly into electrical energy. Its basic device is a solar cell. Unfortunately, this type of power generation is only 10% efficient, and its cost is greater than its lifetime, without any economic value. In the process of manufacturing solar cells, secondary pollution is often generated.
(3) Solar cells
Material requirements: Radiation resistant to UV light, the light transmittance does not decrease. The tempered glass assembly can withstand a 25 mm diameter puck at 23 m/s.
Uses: Solar power is widely used in solar street lights, solar insecticidal lamps, solar portable systems, solar mobile power, solar applications, communications power, solar lighting, solar building and other fields.
Solar energy may become the main source of electricity by 2050, and the cost of power generation equipment has fallen sharply. According to the IEA report, solar photovoltaic (PV) systems will contribute up to 16% of the world's electricity by 2050, and solar thermal power (STE) from solar power plants will provide 11% of electricity.
(3) Photochemical utilization
This is a photo-chemical conversion method that uses solar radiation to directly decompose water to produce hydrogen. It includes photosynthesis, photoelectrochemistry, photochemical action, and photolysis.
Photochemical conversion is a process of converting into chemical energy by absorbing light radiation to cause a chemical reaction. The basic forms are photosynthesis of plants and the use of chemical changes in the storage of solar energy photochemical reactions.
Plants rely on chlorophyll to convert light energy into chemical energy, to achieve their own growth and reproduction. If you can reveal the mystery of photochemical conversion, artificial chlorophyll power generation can be realized. Solar photochemical conversion is actively exploring and researching.
The process of converting solar energy into biomass is achieved through photosynthesis of plants. Giant seaweed.
(4) Fuel utilization
Since June 2011, the European Union has devoted itself to the development and production of “solar†fuels by using the high-temperature energy provided by solar light and using water and carbon dioxide as raw materials. So far, the R&D team has successfully achieved the first full-scale production of laboratory-scale renewable fuels in the world. Its products are fully compliant with the EU's aircraft and automotive fuel standards, without any adjustments to the aircraft and car engines.
The “solar†fuel prototype developed and designed is mainly composed of two technical parts: the first part uses the high-temperature energy generated by concentrated solar light accumulation, supplemented by ETH Zürich's proprietary metal oxide material additive, which is designed and developed by itself. In the solar high-temperature reactor, water and carbon dioxide are converted into syngas, the main components of the syngas are hydrogen and carbon monoxide; the second part converts the superheated syngas into heat according to the Fischer-Tropsch Principe principle. A "solar" fuel product that can be commercialized in the market.
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