What is solar energy?

Word “solar” comes from Latin. It describes things and appearances produced by the action of the sun, (“sol” is sun in Latin).
Solar energy is the electromagnetic energy (solar radiation) transmitted by the sun. It is the basis of all terrestrial life on the planet, it is both light and heat.

What else can we say about solar energy?

That energy from the sun is free energy. It’s also clean energy, meaning it causes no pollution. We use it to heat houses, convert it to electricity, collect it in solar water heaters. The beauty of it is that there is no side effect like greenhouse gases, there is no carbon dioxide in the air nor burning fossil fuels.
Furthermore, the solar energy is renewable energy, since the sun gives off more energy than we would ever need. Total solar energy produced by the sun amounts to so many kilowatt-hours of energy that it could cover several thousand times larger energy consumption of all mankind. And only small amount of it is absorbed by atmosphere. As long as there is the sun, there will be enough solar power energy on Earth. It will never run out. It is sustainable energy.
Can you imagine the power of solar energy that comes to Earth in just one hour if you know that it is enough to meet world energy demand for an entire year?

Did you know?
“It takes only about 8 minutes for solar energy to travel from the sun to the earth.”
Along with basic solar energy, there is a secondary solar-powered resource such as wind and wave power or biomass. It is also renewable energy.
But what does it have to do with a solar energy? Let’s remember from biology class. When Earth’s atmosphere and surface (both land and oceans) absorb solar energy it raises their temperature. As we know, warm air rises, but this time it contains evaporated water from the oceans.

This causes atmospheric circulation. When the air reaches a high altitude with a low temperature, water vapour condenses back and forms clouds. With a rain from those clouds the water cycle is completed. The latent heat of water condensation amplifies circulation, producing all different kinds of wind in air and waves at sea. By photosynthesis green plants convert solar energy into chemical energy and when the plants die they decay in Earth resulting with the biomass from which fossil fuels are derived.

So, the majority of the renewable energy on Earth comes from primary and secondary solar energy as seen in Table 1.

Yearly Solar fluxes & Human Energy Consumption in EJ
solar 3.850.000
wind 2.250
biomass 3.000
Primary energy use (2005) 487
Electricity (2005) 57

Table 1: Yearly Solar fluxes & Human Energy Consumption in EJ (source Wikipedia)

It is quite obvious why solar power is called the Green Power, even though it is often taken for granted.

Yet, solar power energy and other kinds of renewable energies are still just an alternative energy.
In 2008 the mostly used world energy supply was fossil fuel with 81% and all the renewable (hydro, solar, wind, geothermal power and biofuels) just 12.9% as the graph 1 shows. Oil was the most popular single energy fuel, and combined with coal represented over 60% of the world energy supply in 2008.


Graph 1: World Energy Consumption in 2008 (source Wikipedia)

The Earth receives 174 petawatts (PW) of incoming solar radiation (insulation) 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.

Breakdown of the incoming solar energy

(source Wikipedia)

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