How Solar Energy Works

Solar Panels

Solar panels are made up of individual cells that have layers of special semiconductor material arranged in positive and negative layers, similar to the setup of a battery. Light energy from the sun shines on the solar panel and photons which make up the light hit the layers of semiconductors and create a flow of electrical energy. The energy from the photons frees electrons within the semiconductor material, creating direct current (DC) electricity.Wiring connected to the positive and negative sides of the cell harness electrical current using wires connected to the panel to carry the electricity to an inverter where it can be converted into alternating current. Solar panels can linked together to provide either all or part of the power needed for a home or business.

Rooftop PV

A photovoltaic system is usually composed of several solar panels. For a typical home or small business, the solar panels are usually mounted on the roof. After sunlight creates electricity in the form of direct current (DC) it is sent to an inverter that changes the DC electricity into alternating current (AC) because our home appliances and lighting is designed for AC electricity. This electricity can be used in your home or business, sent to the electric grid and sold to the utility. In hybrid systems, electricity can be used in your home and the extra can be sold to the utility. The choice of using the electricity, selling it, or both options in the hybrid example depends on the policies available with your utility.

Utility-Scale, Ground Mount PV  

In NC, large utility-scale, ground mount PV systems have been installed to provide solar electricity for the electrical grid, similar to a traditional power plant. These systems are usually 35 acres or more and commonly generate at least 5 megawatts. (A home system may be 5 kilowatts or 1,000 times less powerful than a 5 megawatt utility-scale system). Once the DC electricity is generated, inverters convert the DC electricity into usable alternating current (AC) electricity, and then the electricity is sent into a transformer before it heads to a substation. At the substation, electricity is converted into a voltage that is able to meet the requirements of utility grid transmission lines and is either fed onto the electrical grid to serve the needs of local communities or travels to other regional locations or states.

Aerial view of Halifax 20 MW PV system

Typical ground mount, utility scale PV  

  Typical diagram of a utility-scale solar facility connection to the electrical grid

What is a solar panel made of?

Photovoltaic (PV) panels are manufactured as a solid panel and completely sealed so there is almost no risk of hazardous exposure toxic materials. PV panels are commonly installed in desert and arctic environments and are built to be completely weather tight under all environmental conditions. The top is typically tempered glass and a back plate is permanently sealed on the back side to sandwich in the solar cells which are between the glass and back plate.

As mentioned above, the PV panels themselves are made as a solid, sealed unit and water cannot wash any chemicals off them (there are no liquids in solar panels). In addition, the chemicals in PV panels do not vaporize off and panels have a very high melting point that exceeds most typical fires. Most of the PV panels used in NC use silicon in the solar cells. Silicon is a common material found in many soils, sands, and rocks. There is small amounts of solder containing some lead that is used to connect solar cell wires but as the cell is sealed in the panel, this small amount of solder cannot leave the panel.