The Earth receives 174 petawatts (PW) of incoming solar
radiation (insolation) at the upper atmosphere. Approximately 30% is reflected
back to space while the rest is absorbed by clouds, oceans and land masses. The
spectrum of solar light at the Earth's surface is mostly spread across the visible
and near-infrared ranges with a small part in the near-ultraviolet.
Earth's land surface, oceans and atmosphere absorb solar
radiation, and this raises their temperature. Warm air containing evaporated
water from the oceans rises, causing atmospheric circulation or convection.
When the air reaches a high altitude, where the temperature is low, water vapor
condenses into clouds, which rain onto the Earth's surface, completing the
water cycle. The latent heat of water condensation amplifies convection,
producing atmospheric phenomena such as wind, cyclones and anti-cyclones.
Sunlight absorbed by the oceans and land masses keeps the surface at an average
temperature of 14 °C. By photosynthesis green plants convert solar energy into
chemical energy, which produces food, wood and the biomass from which fossil
fuels are derived.
The total solar energy absorbed by Earth's atmosphere,
oceans and land masses is approximately 3,850,000 exajoules (EJ) per year. In
2002, this was more energy in one hour than the world used in one year. Photosynthesis
captures approximately 3,000 EJ per year in biomass. The technical potential
available from biomass is from 100–300 EJ/year. The amount of solar energy
reaching the surface of the planet is so vast that in one year it is about
twice as much as will ever be obtained from all of the Earth's non-renewable
resources of coal, oil, natural gas, and mined uranium combined,
Solar energy can be harnessed at different levels around the
world, mostly depending on distance from the equator.
No comments:
Post a Comment