The average solar power received by the Earth is 1,353 kilowatts per square meter, which is called the “solar constant”. In other words, the energy that the sun radiates to Earth every second is equivalent to about 5 million tons of coal equivalent.
The solar constant is measured outside the Earth's atmosphere, in a plane perpendicular to the incident light. The value measured by artificial satellites is approximately 1,367 watts per square meter [1,353 (± 21) W/m2 (1976, NASA)]. The cross section of the Earth is 127,400,000 square kilometers, hence the power received by the artificial satellite. the entire earth is 1,740 × 10^17 watts.
Since there are often sunspots and other solar activity on the surface of the sun, the solar constant is not fixed and varies by about 1% per year.
Advantages of solar energy
(1) Universal: The sun shines over the entire earth and has noca geographical restriction. It can be found everywhere, regardless of land or sea, mountains or islands. , and can be directly developed and the use is easy to collect and does not require mining and transportation.
(2) Harmless: The development and use of solar energy will not pollute the environment. It is one of the cleanest sources of energy, which is extremely valuable today as environmental pollution becomes more and more serious.
(3) Huge: The energy of solar radiation that reaches the Earth's surface each year is approximately equivalent to 130,000 billion tons of coal, and its total amount constitutes the greatest energy that can be developed in the world today.