The most important part of your residential solar system is your solar panels. The solar panels are the work horses of your system. These panels are designed to take the photons of light from the sun and turn them into moving electrons. How they do this is a bit technical but I will explain as best as I can. However, these electrons are moved by the suns light and travel, one after the other, down the copper pipeline that is your wire into your charge controller and on into your batteries.
Solar panels utilize on the suns energy by using the light rays from the sun and turning them directly into electricity. This is achieved by using the same material that is used in "semi-conductors". (Semi-Conductors are materials that are used to make the chips in your phone and computer). When the sun's light strikes this material, the top side becomes positively charged and the bottom side becomes negatively charged. This causes electrons to flow from the positive side to the negative side.
18 Volt Combo Kit
Solar Panels are made up of single units called Photovoltaic cells. A photovoltaic cell is a small piece of semi-conductor material that ranges in size from 1 to 15 centimeters in size. A single cell does not create a lot of electricity. This is the reason that cells are connected and arranged together in series and in parallel into what you normally see and that is a Solar Panel. The number of cells and the way the cells are connected determines how much electricity is produced. In order to increase the wattage of electricity produced, several modules can be connected in parallel. When this is done you have built a "solar array."
Since a single solar cell produces about half a volt, you would need about 36 cells in a panel in order to produce 18 volts. You need an 18 volt panel to keep a 12 volt battery charged. With an 18 volt solar panel you can power some small electrical appliances. With the right type of solar panel or combination of solar panels and a battery bank and a good inverter you can power just about any electrical device or devices you need.