1. The sun directly provides light and heat resources to the earth, and human life is inseparable from the sun.
2. Solar radiation maintains surface temperature and is the primary driving force for water, atmospheric movement, and human activities on Earth.
3. Fossil fuels such as coal and oil, which are the main sources of energy for industry, are solar energy accumulated after biological fixation during historical geological periods.
4. Solar radiation is the main energy used in solar cookers, solar water heaters, solar power plants, solar air conditioners, solar boilers, solar greenhouses and solar agriculture used in our daily life and source of production.