Solar cells produce direct current electricity from light, which can be used to power equipment or to recharge a battery. Solar panels convert sunlight into direct current (DC) electric power. DC power is then converted by inverter into alternating current (AC), to be compatible with power appliances and synchronized with utility power whenever the electrical grid is distributing electricity.
The amount of electricity consumed from the grid is measured by the utility meter. It also measures the amount of electricity we put back in the grid, depending on the direction of the flow of electricity. If more electricity is generated than consumed then the utility meter actually spins backward, sending unused power back to the electric supplier for credit.
Utility Power is automatically provided at night and also during the day when the demand exceeds the solar production.
PV technology generates electricity directly from electrons freed by the interaction of sunlight with a solar panel made of semiconductor material. The basic building block is known as a cell. PV cells have at least 2 layers of semiconductor, one is positively charged and one negatively. When the light shines on the semiconductor the electric field across the junction between these 2 layers causes electricity to flow. The greater intensity of light the greater the electricity. There are no moving parts, so this is a silent operation. Many cells put together are known as a module, and many modules assembled together form an array. A single module is enough to power an emergency telephone, but for a house or a power plant the modules must be arranged in multiples as arrays. PV system consists of an array of modules generating DC electricity, an inverter, and sometimes battery storage back up with charge controller.
The amount of electricity available depends on the geographic location. The amount of electricity generated is proportional to the number of panels and the type/efficiency of the panels. In California the average residential customer purchases 6,500 kWh per year. Economically the optimal solar system size is usually between 50% - 75% of the annual household needs. Typical residential solar PV systems range in size of 50 - 600 square feet. A system composed of the highest efficiency monocrystalline cells will produce 1kW per hour for every 60 square feet. Less efficient polycrystalline cells will require 90 - 130 square feet, while thin-film systems need the largest area, up to 300 square feet to generate 1 kW.
A significant market has emerged in off-grid locations for solar-power-charged storage-battery based solutions. There is a market for off-grid power for remote dwellings, boats, recreational vehicles, electric cars, roadside emergency telephones, remote sensing, and cathodic protection of pipelines.
