The earth receives 174 Petawatts (10 to the power of 15 watts ie 174,000,000,000,000,000 watts) of incoming solar radiation at the upper atmosphere, of which around 30% is reflected back into space, the remaining 70% being absorbed by clouds, oceans and the land.
The 70% that is not reflected back into space keeps the surface of the Earth at an average temperature of 14 degrees celsius. In 2002 it was calculated that the total solar energy absorbed by the planet in one hour is more energy than all humans use in one year.
In fact, 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. In fact some countries could obtain all of their current power requirements via solar panels with arrays of existing technology panels (which are not yet that efficient at converting the sun’s rays into power) over relatively small areas. The US for example could satisfy their entire power demand by converting all of their roads (or the equivalent land area) to solar arrays, which would equate to 1.5% of the total land area of the US.
In the US one company has actually developed the technology and put together a plan to do just this – convert all the roads in the US into solar panels (see the YouTube video here – https://www.youtube.com/watch?v=qlTA3rnpgzU). Although it’s fair to say that the plan is not without controversy, if they could pull it off it would certainly have a big impact!
The sun also has a huge impact on the temperature inside your home, especially if you have a dark coloured roof and no insulation installed. A quick way to check how much heat is being transferred through your roof is to put your hand on the ceiling in the middle of a hot day. If this ceiling is warm (or maybe hot!), then heat from the sun is getting into your house. To minimise this, you can install insulation in your roof space, or replace your roof with a reflective metal roof, or you can treat your existing roof with a heat reflective coating, such as Dulux Infracool.
