Solar power and solar panels are getting a lot of attention as part of the solution to our energy crisis. Solar energy, also called photovoltaic energy, is undergoing rapid changes thanks to massive investment in research and development. This article will discuss the basic makeup of photovoltaics in hopefully easy-to-understand terms.
Solar Cells
A solar panel is made of several photovoltaic cells. The cells are very thin, about 1/100th of an inch thick and usually 3 to 4 inches square. These cells convert sunlight to energy by the photovoltaic effect (we will discuss this effect in detail in a later article). These cells do not require fuel and have a standard lifetime of 20-30 years.
Solar Panels & Modules
Photovoltaic (PV) cells are assembled together to create a solar module. The module is what you are used to seeing as a panel. It has anywhere from 2 to 200 cells assembled together, encased in tempered glass and aluminum to make them weather resistant.
Tying Them Together
Like batteries, cells can be combined in series or in parallel to create larger and more specific voltages and amperages. For instance, four 1-volt/1-amp cells in series will combine for 4 volts, but the amperage will stay at 1 amp. By contrast, four 1-volt/1-amp cells in parallel will maintain 1 volt but have 4 amps of output. You can multiply the amperage by the wattage (in the example above 4 x 1) to get the watts generated. A watt is a measure of energy (think of a 40-watt light bulb).
Sizes and Shapes
Modules can be made in a many sizes and shapes to fit their application. Panels come in standard rectangular, triangular, foldable, and even thin-film rolls. This means they can be used in a wide variety of applications, from boats and rv's to electric cars and space stations.
The Solar Array
Modules are combined to create solar arrays. An array is a group of modules assembled together and designed to meet a certain electrical load. You've probably seen most arrays mounted on the rooftops of homes. These arrays are designed to generate a certain amount of electricity over the course of a year.
Efficiencies
Generally solar modules convert about 10-15% of the energy that strikes them into electricity. This means that for every 100 units of energy that actually hit the panel, only 15 of them actually enter the home as electricity. This is the biggest area of research now, as scientists recognize that significant advancements in solar efficiency will lead to cheaper solar energy.
AC vs DC
Panels generate direct current (DC) electricity. Think of a garden hose that is simply turned on produces water in a steady stream. Most household electronics and the electrical power grid are designed to take alternating current (AC) power. Now imagine that the water of coming out of the garden hose is being turned off and on so quickly that it has a "pulse". This is done because AC power travels over long distances much more efficiently.
This means however, that the electricity coming out of the solar array must be converted to AC if it is going into your home. This is done with an inverter, which takes the DC power and makes AC power. The power is then ready to service your home, an electrical grid, or a device. Some devices (certain lights, batteries, special devices) use DC power and therefore do not need an inverter.