How Basic Solar Electric Systems Work

Solar electricity is the energy source for the new millennium, and engineers now have it down to a science. Someday soon, every home in America could be powered from this clean, renewable resource (with substantial help from other renewable energy sources).

Solar electricity is based on a natural phenomenon known as the photoelectric effect. Photoelectricity is simply the emission of electrons from a substance due to its interaction with light. The art of corralling those electrons into an electric current is called photovoltaics (PV). It is this process that drives the basic solar electric system.

Most solar electric systems are grid-tied, or connected to the electric grid, and work like this:

1. Sunlight strikes a solar PV panel. Inside that panel are one or more semiconductors that facilitate the creation of an electric current from sunlight.
2. That electricity is sent through wiring to an inverter, where the direct current (DC) is converted into alternating current (AC) compatible with your home appliances and the utility grid.
3. From the inverter, the AC voltage passes through the breaker panel, where it is sent one of two places – either into the home to power electrical devices or to the utility meter on the outside of the home (as excess energy).
4. The utility meter measures the amount of solar electricity as it is sent to the electric grid for use somewhere else. For homes with solar power systems, this meter counts in both directions. That is, when the solar panels are sending energy to the grid, the meter rolls backward, and at night when the grid is providing power to the home, it rolls forward.

So when the solar system is working at peak ability, producing more electricity than the home needs, that extra power is essentially being sold back to the utility, saving extra money on utility bills.

The other type of home solar electric system removes the electric grid from the equation. These off-grid systems store that excess electricity in batteries rather than rely on the utility for power at night. They work in a slightly different manner:

1. Solar radiation strikes the PV panels, creating electric current. That current must then pass through a charge controller.
2. The charge controller regulates the voltage running through it so that the batteries will not be damaged from overcharging. It acts sort of like a bottleneck, preventing too much electricity from “spilling” out at once.
3. From the charge controller, the current is sent to the battery bank (most residential solar electric systems require several batteries). Remember that this is still DC electricity.
4. It is from the batteries that power is drawn for use in the home. But first, it must pass through the inverter to become usable AC electricity.
5. Once converted to AC, the electricity is ready for use, passing through the breaker panel, where it is distributed around the house as appliances and light switches are turned on.

Solar electricity is a rather simple process. Most of the complex science goes into the solar panels, which are not yet as efficient as we’d like them to be. Scientific researchers are working tirelessly to improve the individual PV cells within the panels so that they can create more electricity in the same amount of space and time. Batteries too have room for improvement. But while solar cell and battery technology are continually under development, we can expect the basic solar electric system to continue working in much the same way it is shown in the diagrams above.

If there’s one piece of the puzzle missing from those diagrams, it is the solar contractor that installs the system. Their savvy and expertise is invaluable to a properly functioning solar electric system.

Posted on October 22nd in Solar Information by Dan.