Solar Facts

Solar Basics

Sunday, 04 December 2005

When people talk about 'solar' they mean using the sun's energy to do things we need or want. This involves a range of tasks, including cooking, water heating, building heating and power generation. Solar is renewable - we don't use up the sun by utilising it's energy.

On this page we'll discuss solar power.

Solar power differs from conventional power generation in that:

it doesn't need big, pollution emitting power stations.
it can be generated at the home or industry (though large solar power plants do exist)
once installed it doesn't need supplying with raw materials

Solar works by converting energy from the sun, in the form of light, into electricity. There are various ways to do this:

Photovoltaic cells (Solar Panels)
Boiling a fluid and using it spin a turbine
Heating a heat powered engine

These are often referred to as solar converters.

Most systems can be setup to track the sun. This maximises efficiency and often means you need less of the expensive energy converters (ie Solar cells or Stirling engines).

Photovoltaic Cells (more commonly known as Solar Cells / Panels):
Solar cells are made up of semiconductors. Solar cells work via what is known as the photoelectric effect. In this light hits a conductor or semiconductor and transfers it's energy to that conductor. Light is actually a stream of energy particles called photons. When the photons hit the silicon atoms in the solar cells they transfer their energy and free the electrons from their orbit around the nucleus. Electricity has been generated. Photovoltaic cells are energy converters - converting the energy from sunlight into electricity.

Concentrators such as Fresnel lenses, mirrors, and mirrored dishes can be used to concentrate the sunlight on a small area of photovoltaic cells. This can substantially lower the cost, as the most expensive component in solar panels is the photovoltaic cells. Usually these devices are set up to track the sun to maximise efficiency.

Solar panels usually contain multiple solar cells encased in a durable casing. Glass is used to cover and protect the solar cells and a antireflective coating is used to minimise light 'lost'.

Solar Panels produce DC power, usually at 12V or 24V.

Fluid Boiling:
Usually involves mirrors or reflective surfaces to concentrate the sun's energy on a fluid reservoir. The fluid heats up and boils and the steam is used to turn a turbine, generating electricity. This is much the same as more conventional power generation (see Electricity Basics) except it doesn't require burning of raw materials.

Depending on turbine, can produce either DC or AC.

Heat Engine:
Usually involves concentrating using mirrors or reflective surfaces. These concentrate the light on the 'converter'. The converter is made up of the heat engine and the generator it runs. The most common engine used is a Stirling Engine. In Stirling engines, gas is enclosed in a sealed compartment - when heated, it moves, pushing a piston. This piston is used to power a generator. As the gas leaves the heat source it cools, and eventually returns to go through the cycle again. Stirling engines are very quiet, as no explosions are taking place.

Depending on generator, can produce either DC or AC

Last Updated ( Monday, 02 January 2006 )

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