What is Solar Power?

What is solar power? Directly or indirectly, our sun provides all the power we need to exist and supports all life forms. The sun drives our climate and our weather. Without it our world would be a frozen wasteland of ice-covered rock.

The power of the sun is quite amazing. On a clear day in the middle of summer, the solar energy we receive from the sun on just one square metre of the earth is equivalent to 1kW electrical power for lighting and heating. For a star that is 93 million miles away, that is quite some power!

What is Solar Power?

The photon - the Power of the Sun

The sun is 865,000 miles in diameter and the core temperature is estimated at 15,000,000°c. It is a huge mass of constant nuclear activity.

Deep in the centre of the sun, this nuclear activity is generating huge amounts of radiation, which in turn generates photons - quite literally bundles of light energy. These photons have no physical mass of their own, but carry huge amounts of energy and momentum.

Over time, these photons are pushed out from the centre of the sun. Once they reach the sun's surface, these photons are pushed out through space at a speed of 670 million miles per hour and reach earth in around eight minutes.

On their travel from the sun to earth, photons can collide with and be deflected by other particles, and are destroyed on contact with anything that can absorb radiation, generating heat. That is why you feel warm on a sunny day: your body is absorbing photons.

Our atmosphere absorbs a lot of these photons before they reach the surface of the earth. That is why the sun feels so much hotter in the middle of the day - when the sun is directly overhead and the photons have to travel through a lot less of the earths atmosphere to reach us - compared to the end of the day when the sun is setting and the photons have to travel through a much thicker layer of atmosphere to reach us.

Sun solar power diagram

In diagram 'A', above, the sun is shining directly overhead at midday and the photons are travelling through the thinnest layer of atmosphere on their journey to earth. At mid-day in the height of summer, solar power is much higher.

In diagram 'B', the sun is still shining on the same spot, but it is sunset rather than the middle of the day. The photons are therefore travelling through a much thicker layer of atmosphere on their journey to the same spot on the earths surface. As a result, the available solar power is much lower.

The atmospheric absorption of photons also explains why days in winter are colder than days in summer - as the earth is tilted away from the sun during winter, we get less sunlight and the atmospheric layer that the photons have to travel through to reach us is much thicker - meaning less solar power.

What is Solar Power?

Photons provide us with all the power we get from the sun. And it is in capturing the energy of the photons that we can harness this energy and use it in different ways.

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Did you know?

The largest solar power station is in Finsterwalde, Germany and produces 80.7 MW of electricity.

The largest private Solar aray in the UK has 1,116 panels installed on the roof of a cowshed and can provide electricity for the equalivant of 40 homes.

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Solar Book

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The Solar Electricity Handbook assumes no previous knowledge of solar power systems, it explains how panels work, how they can be used and explains the steps you need to take to successfully design and install a electric photovoltaic system from scratch.

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