As the third world develops its industry, led by China and India, the demand for energy rises, and the price of oil goes up. Add the need to lower the emission of greenhouse gases and protect the environment generally, and it’s not surprising that solar energy has become an increasingly important element in the global energy economy.
Rooftop solar is growing even faster than commercial solar power development. As the technology improves, the price of solar panels drops, and building your own solar panels cuts the cost even further. Given the importance of solar energy and solar panels, it’s a good idea to gain a basic understanding of what they are and how they work.
How Solar Energy Works
Solar energy makes use of the energy that reaches the Earth from the sun to generate electricity or heat. The amount of energy reaching the Earth from the sun is enormous: enough to meet all of humanity’s demand for energy about 8,000 times over.
The challenge is that it is also diffuse, with that energy spread out over the planet’s whole surface. For that reason, techniques of harnessing solar energy always consist of concentrating the sun’s energy over a sizable area and focusing. This is done in one of two ways.
Thermal solar power techniques use mirrors to focus the sunlight that falls onto an area so that it is concentrated on a single point. This generates a high temperature at the concentration point and heats a medium such as water, which is used to drive a generator to produce electricity. Solar thermal power is almost always a large-
How Solar Panels Work
The other way to use solar energy involves the photoelectric effect, solar cells, and solar panels. As with solar thermal power, the challenge is to concentrate solar energy into a usable quantity. A solar panel is made up of many solar cells. Each solar cell is made of purified, monocrystalline silicon with an electric lead attached.
When sunlight strikes the solar cell and is absorbed by it, the energy is added to the electrons of the silicon atoms, and when an electron is energized sufficiently it escapes the nucleus and is captured by the electrical lead to flow away as current.
Each solar cell produces only a very small amount of electricity, only a fraction of a volt, but the solar cells are connected in series to produce a combined current.
In a rootfop solar system, the combined output in full sunlight is roughly 18 volts. The current is in the form of direct current (DC). It is run through an inverter which changes it to alternating current (AC), the type of electricity produced by a generator and which electrical appliances are made to use.
How Solar Panels Are Made
The manufacture of solar panels starts with cutting monocrystalline silicon into small discs with a thickness less than a centimeter. The discs are polished to remove any irregularities, and then spread with charge-
covered with a protective layer of glass.
Finally, the solar cells are bonded to a heat-