Photovoltaic technology converts energy from the sun into usable
electricity. A solar cell generates direct current voltage when exposed to
sunlight. The power from a solar cell increases with brighter light and
lower ambient temperatures. A module of cells generates 200 to 300
watts of power, is about 3 feet by 6 feet and weighs about 50 pounds.
The module generates 30 to 50 volts Direct Current, or DC power.
The modules are grouped into an array, which may have multiple
strings or sub-arrays. The voltage generated by the array can be several
hundred volts DC. Power from the array is fed into an inverter. The
inverter changes the direct current to alternating current. The voltage is
changed as well to match the voltage in your home. This energy can
then be used on site, stored in batteries or sold back to the utility.
Another type of system integrates the inverter into the module. This a
micro-inverter system and the power coming from the array is already at
240 volts of alternating current. The array can be mounted on a roof or on the ground. All you need is an area with a clear view of the southern sky. There are basically three types of systems. An off- grid system generates and uses the energy on site with no connection to the utility grid. In a grid- tie system, all of the power generated is sold back to the utility. This is, by far, the simplest and most cost effective system. In between, we have grid-tied systems with battery storage. This system may provide limited power in the event of a power outage. If you're in the Tennessee Valley Authority service area, you may become a Green Power Partner and sell power to the utility. This is an attractive program from an investment standpoint. A grid-tied system will cost around three dollars per watt to install and an average system is 10,000 watts. That's an initial investment of $30,000. When you consider the 30% federal tax credit, it becomes a $21,000 investment. That system will pay for itself in less than ten years and should last more than 20 years.