Solar energy offers one of the truly renewable alternatives to fossil fuels to meet the world’s energy needs. But how do you get electricity from the sun? How do you convert energy from the sun into a form – electricity – you can use, store, and transport?
There are actually two answers. One uses the sun’s energy to generate heat and produce electricity in a fairly conventional way. The other uses principals of atomic physics, first explained over one hundred years ago by Albert Einstein, to generate electricity in a very unique manor.
A Conventional Form of Solar Energy
Currently, almost all electricity is generated by producing high pressure steam to turn turbines which contain magnets surrounded by coils of wire. The spinning magnets cause electrons in the wires to move, which is electric current.
The only difference between a coal-fired power plant and a nuclear power plant is the source of heat for producing the steam. In a coal-fired power plant, coal is burned to produce the heat. In a nuclear power plant, the energy produced by nuclear fission provides the heat to get water to the super-heated state.
One form of solar power plant focuses sunlight from a vast array of reflectors on a single location, usually the top of a tower. Molten sand is passed through the tower, raising it to high temperatures (over 1000 degrees). This molten sand is then used to superheat water to produce high pressure steam.
The advantage of this type of system is energy can be stored in the sand in the form of heat, allowing electricity to be generated day and night. One disadvantage is the extreme danger associated with concentrating some much sunlight on one location.
Using Solar Panels
While solar thermal towers may represent a conventional way to convert solar energy to electricity, the form more familiar to most people is the solar panel. From calculators to roof tops to the International Space Station, solar panels have been a familiar part of modern life since the 1970’s. But how do they work?
The basic principle is simple. When a particle of light strikes an electron circling around an atom, it may give it enough energy to knock it free from the atom. This electron can then move through a wire producing an electric current. This same principle is used in the photocells found in light detecting circuits such as those in digital cameras.
The trick has been to produce enough of these free electrons to make a useful current. It doesn’t take much to run a calculator. It takes more to power a house. If you want to run a factory, you need either a large area of solar panels or solar panels which are very efficient.
Increasing the efficiency of solar panels is not easy, and requires careful manufacturing and complex techniques. This drives up the cost of more efficient solar panels, keeping them from being the economical alternative many would like to see them become.
One advantage of solar panels is their scalability. One small panel can power a calculator, while a large array on the roof can power a home or office building. One disadvantage lies in the fact they do night work when the sun is not shinning. This limitation can be overcome by storing power in batteries to be used overnight.
What does the future hold?
Currently, the best promise for large scale conversion of solar power to electricity comes from solar thermal power. These offer the possibility of replacing other forms of power plants without creating the pollution concern of their own. As solar panels become more efficient, the need for large power plants and power lines to transport the electricity they produce could diminish. In the future, you could see solar panels providing all the electrical needs on-site.
