There are various different ways of harnessing solar energy; here are the main principles.
Types of solar energy
A Solar Furnace in France, another form of solar concentrator. Photo courtesy of Joseph Giral
Solar photovoltaic cells (solar PV)
Solar photovoltaic cells are how we generate electricity directly from sunlight. The light shines on solar panels, which, via a lot of physics, turn the sunlight into a direct current.
Solar thermal
Solar thermal is the direct heating of a fluid, like water or air. Solar thermal is used to heat buildings through passive heating, as well as heat water for the hot water supply (or, for example, swimming pools).
Heat exchange
Heat engines can be used to take a supply of energy, and convert it into mechanical motion. An common example of this is a Stirling Engine, and many applications of solar energy involve this technology.
Another application of this is ground heat pumps which use the ground as a store of solar energy. The ground temperature stays relatively constant and so can be used as an energy reservoir.
Collecting solar energy
A solar concentrating tower in Andalusia. Photo courtesy of Energia solar - Solarweb.net
Solar panels
This is the way solar PV and solar thermal collect solar energy. The panels themselves differ, but they are the same in principle, and they share many of the same properties.
The energy collected by solar panels is proportional to their surface area, so the bigger the better.
In terms of appearance, they tend to be quite flat, though thermal panels are generally thicker than solar photovoltaic panels.
This is because there is less of a mechanical aspect to photovoltaic panels, as everything is electronic.
Solar photovoltaic panels are more expensive than solar thermal for this reason.
Photo courtesy of David Blaikie
Solar concentrators
Solar concentrators are large, curved mirrors which focus the sunlight to a specific point.
At the focus of the light, a method of converting this highly concentrated energy is placed (this is usually either a Stirling engine, solar photovoltaic cell or system of pipes for fluid to be heated).
Solar concentrators can be quite small (the size of a satellite dish) or immensely large, covering acres of land.
In this case, a solar tower is placed in the centre, and a large amount of electricity is produced.
A solar oven which can be used to cook food entirely by the sun. Photo courtesy of London Permaculture
Solar oven
This is another form of a solar concentrator, but without any other processes involved.
The curved reflective surface focusses the energy onto a point, and at this point is a placed a container filled with food. Solar energy is used to cook food directly.
This has proved to be an excellent way of sterilising water in Africa, as this technology is ideally suited to the intense sunlight and does not require power (or technical skills) to operate.
This concept could foreseeably be used in any sunny country to cook all meals - it is completely free, efficient and releases no emissions whatsoever. Pleasingly, it is also the most simple.
How does solar energy work domestically? - the applications
Domestic solar panels on a roof in Wisconsin. Photo courtesy of Matt Montagne
The best thing about solar power is that it is arguably the easiest to use for domestic purposes. If you have a south facing area of roof, can take advantage of residential solar energy.
Just imagine if every single house contributed to the national grid. We could use our own energy to power our own appliances, and when there is a surplus, we could sell it back to the grid.
I think solar energy has the potential to be one of the our main alternative sources of energy (I don't think it will ever be our primary energy source though.)
Return to alternative energy sources from how does solar energy work