Solar Photovoltaic (PV)

Photovoltaic (PV) devices generate electricity directly from sunlight using a process that naturally occurs in some materials. Within a certain class of crystals, electrons are freed when tiny packets of light from the sun — called photons — are absorbed.

fig15eere-grid-connected

These electrons that are freed travel through a circuit as electricity. This process does not emit any harmful pollutants, making solar a clean, safe source of energy.

Solar PV systems are groupings, or “arrays,” of modules wired together along with an inverter and utility meter to produce electrical power. The panels are commonly protected with a 25-year warranty and are designed to withstand hail, lightening, and high winds.

The PV system is tied to the utility grid to ensure a steady supply of electricity. Any excess electricity the system produces will be fed back to the grid. To move “off-the-grid,” a battery backup system will be needed to supply electricity at night.

A PV system is typically installed on a roof, but can also be installed on the ground as a “ground-mount” system.
System Components
Racking

Residential solar systems are mounted to the roof with a racking system designed to secure the panels while not damaging your roof. They are generally not adjustable and designed to position the solar panels at a consistent elevation above the surface to which they are mounted. Residential systems can be mounted to all roof types including shingles, tiles, and metal roofs. Commercial systems can be mounted on a flat roof with a ballasted roof mount, which does not penetrate the surface. Systems can also be mounted on the ground if there is enough un-shaded area available.
Solar Panel or Solar Module

solar-module

Solar panels are comprised of many individual solar cells. Solar cells are made from layers of silicon, phosphorous (which gives the negative charge),and boron (which provides the positive charge). The solar cells are wired together in a circuit. When photons from the sun

strike the surface of the solar panel, electrons are knocked out of their atomic orbits and released into the electric field. The circuit of solar cells then pulls the free electrons into a directional current (also known as DC electricity). This entire process is known as the Photovoltaic Effect. Multiple panels are required to meet the electricity requirements of an average household. The DC electricity generated from the solar panels is then sent to the inverter.
Inverter

Solar inverters convert the electricity from solar panels, DC (direct current) into AC (alternating current), which is the type of power used in most homes. The inverter will allow the system owner to see exactly how much DC electricity is being generated by the solar system. Once the electricity has been converted from DC to AC, it is then sent to the utility meter.
Meter

When a building has a PV system installed, there is a PV meter installed to track the system’s energy generation (output) in kilowatt hours (kWh). The utility company replaces the existing building meter which tracks energy supplied to the home or business with a new dual-read billing meter (net meter). This dual-read meter captures two different readings: 1. The amount of energy supplied to the building by the utilities distribution grid and 2. Any excess energy generated by the solar PV system that was not used by the building at the time it was generated . This excess energy goes back into the distribution grid and is termed “push back.” This energy is “credited” to the customer’s bill.