More than 100 years ago, people started the research on solar power generation. Practical solar power generation has a history of nearly half a century. Solar power generation will be the main development direction of large-scale utilization of solar energy in the future.
Solar power generation mainly includes two methods: solar thermal power generation and solar light power generation.
① Solar thermal power generation
Solar thermal power generation is the use of thermal energy generated by solar radiation to generate electricity, which is realized on the basis of solar thermal utilization. Generally, it is necessary to convert solar radiant energy into heat energy first, and then convert heat energy into electric energy, which is actually a conversion process of “light-heat-electricity”.
There are two types of solar thermal power generation: one is steam thermal power generation, and the other is direct conversion of thermoelectric power.
Steam thermodynamic power generation is to first use the heat provided by solar energy to generate steam, and then use the thermal power of high temperature and high pressure steam to drive a generator to generate electricity. At present, the solar thermal power generation technology in practical application is mainly in this form, the technology is relatively mature, and the scale is also relatively large.
Thermoelectric direct conversion, that is, direct power generation using the heat provided by solar energy (mostly relying on special physical phenomena or chemical reactions). Possible realization forms include thermoelectric power generation of semiconductors or metal materials, thermal electron and thermionic power generation in vacuum devices, and alkali Metal thermal power conversion and magnetic fluid power generation, etc. The advantage of this type of power generation method is that the power generation device itself has no moving parts, but the general power generation is very small, and some methods are still in the stage of principle testing. The more mature ones are mainly solar semiconductor thermoelectric power generation.
The story of discovery: Seebeck effect and thermoelectric power generation
In 1821, the German chemist Seebeck discovered that when two different metal conductors are connected into a closed circuit, if its two contacts are placed in environments with different temperatures, current will be generated in the circuit. This phenomenon is called the Seebeck effect, and such a circuit is called a thermocouple. In this case, the electromotive force that generates current is called thermoelectromotive force. For example, if the cold joint of iron and copper is 1°C and the hot joint is 100°C, a thermoelectromotive force of 5.2mV is generated.
The thermoelectromotive force generated by the metal thermocouple is small, and it is often used to measure the temperature difference. But when the thermocouple is connected in series to form a thermopile, it can also be used as a low-power power source, which is called a thermoelectric battery. Thermoelectric batteries made of semiconductor materials have a strong thermoelectric effect. If the temperature difference between the hot end and the cold end is greater than 800°C, the power generation efficiency of the N-P type semiconductor (such as telluride) thermoelectric battery can reach 15% to 20%, which can be used as a small power source in many fields.
②Solar light power generation
Solar photovoltaic power generation refers to a power generation method that directly converts light energy into electrical energy without a thermal process. In a broad sense, photovoltaic power generation includes photovoltaic power generation, photochemical power generation, photobiological power generation, and light induction power generation.
Photochemical power generation and photobiological conversion are mainly realized through the process of photochemical conversion.
Light induction power generation is a phenomenon in which certain organic polymer groups absorb the light energy of the sun and become photopolarized dipoles. The positive and negative charges accumulated at the two ends of the induced photopolarized dipoles are respectively drawn out, namely Get the photocurrent. Since it is very difficult to find suitable light-sensitive polymer materials, make their molecular clusters orderly arranged, and install extremely fine electrodes on the polymer clusters, these steps are very difficult, so this technology is still in principle. Sexual experimentation stage.
Photovoltaic power generation uses the photoelectric effect of certain substances (photovoltaic effect) to directly convert solar radiation energy into electrical energy. At present, the high-end products (photovoltaic cells) of this application method have matured and become the mainstream of solar power generation at present and in the future.
The practical methods of solar power generation today are basically solar thermal power generation and photovoltaic power generation.
The energy conversion process used by solar energy is in addition to the use of solar power. There are also solar photochemical conversion power generation and other forms of utilization. If you want to know more, this site has more knowledge about solar energy and its utilization.