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HOW SOLAR WORKS: STEP BY STEP

Sunlight and the Photoelectric Effect - Solar power cells use layers of semiconductors (usually silicon) to produce a scientific property known as the photoelectric effect. One layer of the cell produces negative ions, and the other positive ions. Direct photons of light striking these materials cause the release of electrons. When these free electrons are captured by the opposingly charged layer, an electric current has been is created.

Inside the Roof Mounted Array - The electricity created in each cell is a modest amount. Solar power cells are assembled in large groups to create solar modules or panels. Groups of modules wired and installed together are called arrays. Most arrays contain hundreds of solar cells working in unison. Solar arrays produce direct-current (DC) electricity that must be converted to alternating current (AC) to work in our house electrical systems.

These solar modules are tilted to maximize solar orientation and power production. In the Philadelphia area, power production is optimal at a 40 degree tilt, but arrays installed at as low as 15 degrees often do very well. Of course, at any tilt, the array must face the sun - typically a range of within 45 degrees of direct south can work fine.

Power Concentration and Conversion - DC current from the solar cells and modules is concentrated with combiners and then fed to a DC safety disconnect. Current from the disconnect then flows to a power inverter that converts the DC power to AC power, and also synchronizes it with the power being fed to the building from the utility grid.

Power Feeds into Existing House Circuit Breaker Panel - AC current from the inverter passes an AC disconnect and then connects directly to a backfeed breaker inside the house panel. Power loads from within the building can now directly draw clean, inexpensive, solar power. Electrons flow in the path of least resistance, so when the array is producing power and a power load exists inside the house, the power from the array flows directly to the load (lights, TV, appliances, etc.), bypassing the utility meter.

Net Metering - When the inverter produces more power than the loads of the building demand at any given time, the excess power feeds back through the meter to the utility power grid. Depending upon where the system is, the meter may actually spin backwards or a 2nd meter may measure and record the power surplus from the array. In all residential and small business systems in PA, the utility company must allow a net metering connection and must compensate the "producer" for excess power fed back into the grid.

Image by: Eos Energy Solutions www.eosss.com © 2008