The Sun produces an enormous amount of energy: approximately 1 x 1020 KiloWats hour per second (1 KiloWat per hour is the energy necessary to light a 100 watts light-bulb for 10 hours). The outer atmosphere intercepts approximately half of a billionth part of the energy generated by the Sun or approximately 1.5 trillions (1.500.000.000.000.000.000) of KiloWatts per hour a year.

However, due to the reflection, dispersion and absorption produced by the atmosphere gasses, just 47% of this energy, or roughly 0.7 trillions (700.000.000.000.000.000) KiloWatts per hour reach the surface of the Earth. This energy is the one that sets on the “machinery" of the Earth. It heats up the atmosphere, the oceans and the continents, generates the winds, moves the water cycles, makes plants grow, supplies food for animals and even (at the long run) produces fossil fuels.

  We depend on the energy of plants, water, wind and fossil fuels to make our industries operate, to heat up and cool down our homes and to move our transport systems. The amount of energy consumed globally every year is roughly 85 billion (85.000.000.000.000) KiloWatts per hour. This is what can be measured, that is to say, the energy that is bought, sold or commercialized. There is no way of exactly knowing what quantity of non-commercial energy is burnt out by every person (for example, how much wood is burnt, or how much water is used in minor waterfalls in order to produce electric energy). According to some experts, this non-commercial energy may be as much as a fifth of the total amount of consumed energy. Even if this were the case, the total energy consumed in the world would mean only 1/7.000 of the solar energy that comes into contact with the surface of the Earth every year.