How Solar Energy Works

Summary: The history and science behind solar energy and how it works and the development of solar PV and thermal systems.

What is solar power?

Closeup image of the sunSolar power is energy that is radiated by the sun. The sun constantly radiates vast quantities of energy, mostly as visible or near visible light. More energy is radiated by the sun in a second than the total amount humans have used since time began!

The sun is essentially a large ball of gases, mainly helium and hydrogen. The sun’s energy comes from within the sun itself, via a process known as nuclear fusion. This is where the high pressure and temperature of the sun split hydrogen atoms apart. The nuclei of these hydrogen atoms then fuse to form a helium atom – four nuclei make one helium atom.

During this process matter is lost from the nuclei, and it is this matter that is radiated by the sun as energy. However, it takes many years for this energy to travel from the core to the sun’s surface. From this surface it then takes the energy a mere eight minutes for it to journey 93 million miles to Earth. The energy travels at the speed of light (186,000 miles per second).

Only one part in two billion of the energy that the Sun radiates reaches the surface of Earth. This volume of this energy is, however, still enormous.

Where does this energy go?

15% of this energy is reflected directly back into space. An additional 30% evaporates water as part of the water cycle. Some energy is also absorbed by the land and vegetation. The remaining energy could be used to supply our homes with electricity and hot water.

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Who invented the first technology used to capture solar energy?

An early example of some solar panelsHumans have been capturing and using solar energy since ancient times. Probably the earliest use of solar technology involved using magnifying glasses to focus a beam of sunlight onto wood to set fire to it.

Over 100 years ago, a French scientist used a solar collector system to drive a steam engine. Not long after that, people began researching mechanisms to truly capitalise on the potential of solar energy.

A milestone along this path was a solar boiler invented by American astrophysicist Charles Greeley in 1936. At this point the solar water heater became popular in Southwest America.

The industry continued to grow significantly until the mid-1950s, at which point cheap propane became the main fuel used to heat American homes.

International governments continued to be indifferent to the potential of solar energy until the oil shortages in the 1970’s. Today we use solar power to heat water and buildings and generate electricity.

How is solar energy harnessed now?

Solar panels installed onto roof of propertyToday solar energy is captured in two different ways – via solar thermal systems in a water or water/glycol mixture or via solar PV systems using photovoltaic cells.

The five most common ways that solar systems are used are:

  1. Very small portable solar PV systems. These devices are used in a variety of household products ranging from garden lights to calculators. Systems with a single large PV panel can be used on traffic signs and other isolated, power efficient installations.
  2. Using solar PV domestically to power your home or business. In many parts of the world solar PV is now truly feasible.
  3. Large solar PV systems. If you have a high enough sun exposure at your location, you may be able to use a large PV system to become energy independent from the grid. You could also complement your PV system with other renewable technologies to do this.
  4. Pool heating. You can heat water for use in your pool very easily by pumping it through a solar collector system sited nearby.
  5. Hot water heating using glycol. This mechanism is known as indirect circulation because the hot water is not heated directly by the collector. Instead, the collector heats a water/glycol mixture pumped around the system through pipes which are then exposed to the water in the hot water tank, heating the water.

Solar energy is an incredible resource we are only just beginning to truly capture. Why not check out our solar thermal and solar PV projects and see how much of a saving you could make?

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