How Does a Grid-Tied Solar Photovoltaic System Work In Your High Performance Home?
Photovoltaic (PV) systems provide clean electricity that has
many benefits. Renewable energy is better for the environment, better
for your bottom line, and is long lasting. So while it is easy to
understand the benefits of clean energy, it is not always
easy to understand how it is produced. Certain components required by code have been left out of the following diagram in order to provide a simplified explanation of converting
sunlight to electricity and sending it out onto the grid.
Simply put, the photovoltaic effect is the process by which a PV cell converts light into electricity. In order to capture the sunlight and convert it to useable electricity that can be added to the grid there are a number of steps in the conversion process. Follow the diagram to learn how sun light is converted to electricity.
The array consists of one or more solar modules (panels) and each module is constructed of a series of PV cells. PV cells are made from a semiconductormaterial that produces a voltage or change in electrical conductivity when exposed to sunlight. Most PV cells are made from silicon and have been altered with other semiconductor materials that create loosely bound electrons that are easily moved when exposed to sunlight. When the loosely bound electrons moves they are conducted as an electrical current. PV cells are connected together to create the desired voltage and electrical output per module and then modulesare connected together to create the desired size for the array.
The array produces direct current (DC) electricity. This is a problem because buildingsare run on alternating current (AC) electricity. In order to overcome this problem the current is run through an inverter. Inverters produce AC Power from a DC power source that could be from the solar array or a battery bank. Once the power is inverted it canbe sold or net metered onto the utility grid as useable power.
AC Electric Panel:
In order to receive credit for the electricity produced by the solar array it must be connected to the utility grid. This is done in two ways. First, the power from the array is fed to the electrical distribution panel found in the building or second, it is connected between the electric panel and the meter. As a result, if the system is producing more energy than is being consumed the utility meter reads the difference before the electricity is added tothe grid.
On a sunny day the AC loads in the building are subsidized by the clean electricity the PV system is producing. On a cloudy day the AC loads are powered by the grid, but with credited energy the system has powered.
When a PV system is installed a meter that moves in two directions is also installed. On a building without a PV system the meter only moves in the direction that accounts for consumed electricity but on a building with a PV system the meter moves two ways. A meter that moves two ways accounts for electricity that is produced!
Once the electricity is metered the excess is added to the grid!