(1) photothermal utilization
Its basic idea is to collect solar radiation energy and convert it into heat energy through interaction with matter for utilization. At present, there are three kinds of solar collectors that are used most, namely flat plate collectors, vacuum tube collectors and focusing collectors. Generally speaking, solar photothermal utilization can be divided into low-temperature utilization (< 200℃), medium-temperature utilization (200-800℃) and high-temperature utilization (> 800℃) according to the different temperatures and uses. At present, the low-temperature utilization mainly includes solar water heaters, solar dryers, solar distillers, solar houses, solar greenhouses, solar air conditioning and refrigeration systems, etc. Medium-temperature utilization mainly includes solar cookers and solar thermal power concentrating and heat collecting devices, while high-temperature utilization mainly includes high-temperature solar furnaces.
(2) Solar power generation
The large-scale utilization of solar energy in the future will be used for power generation. There are many ways to use solar energy to generate electricity. At present, there are two kinds of practical ones.
① Optical-thermal-electrical conversion. That is, using the heat energy generated by solar radiation to generate electricity. Generally, solar collectors are used to convert the absorbed heat energy into working medium steam, and then the steam drives the gas turbine to drive the generator to generate electricity. The former process is photothermal conversion, and the latter process is thermoelectric conversion.
② photoelectric conversion. Its basic principle is to directly convert solar radiation energy into electric energy through photovoltaic effect, and its basic device is solar cell.
(3) photochemical utilization
This is a photochemical conversion method that uses solar radiation energy to directly decompose water to produce hydrogen.
(4) Photobiological utilization
The process of converting solar energy into biomass is realized by photosynthesis of plants. At present, there are mainly fast-growing plants (such as firewood forests), oil crops and giant algae.