SOLAR ELECTRICITY 101
Basics – How Light Generates Electricity
The Photoelectric Effect is the phenomena responsible for the operation of photovoltaic solar cells. This effect is what causes electrons to be emitted from silicon cells after the absorption of visible light photons. Basically, what is happening is that sunlight “particles” travel through space and the Earth’s atmosphere where they come into contact with the solar panel. The solar panel is made of a semiconductor, such as silicon. This semiconductor is bombarded by the sunlight “particles” and absorbs a portion of the sunlight’s energy. This energy absorption causes electrons in the semiconductor to be displaced, which allows them to flow freely. When metal contracts are added to the semiconductor cell, an electrical current is permitted to flow in the circuit (electrons are able to escape the cell). This current paired with the voltage of the semiconductor can be hooked up to electrical loads to provide power to do work.
The concept is simple and it works! The science behind it took some major research and development efforts from many people. It is time tested and proven though for over 50 years and we have learned that it is a very reliable source of energy.
The History & Basics of Solar
The U.S. Department of Energy, Energy Efficiency and Renewable Energy, provides a remarkable list of the use of solar energy from the beginnings of recorded history, to its present uses today. It is a very interesting document and can be found here.
Types of Solar Electric Systems
There are three basic types of solar-electric systems that are in common use in the United States residential and commercial sectors:
Grid-Interactive SolarElectric Systems
These systems are the most common types of systems and are the easiest to implement for your home or business. They also help to offset the peak loading on the grid because the most power is generated by these systems during the hottest and sunniest parts of the day. This time of day is when utility companies are producing the most electricity for powering air conditioning systems. The main components of the system are:
- Solar Panels to send DC power to the inverter
- DC disconnect switches to isolate the solar panels from the inverter
- Grid-Interactive Inverter to convert the DC electricity of the solar panels to usable AC electricity for your home or office
- AC disconnect switches to isolate the inverter output from the home or business electrical circuit
- A bi-directional meter to show what electricity is coming into the home or business versus what electricity is being “pushed” back to the utility grid
A simple operational description for this type of system would be:
- Your solar panels generate electricity during the day when the sun is shining
- Your grid-interactive inverter converts the DC electricity to AC electricity for use in your home or business
- If you are consuming more power than you are producing with your solar panels, the electricity from the solar panels goes directly to your home or business for usage
- If you are producing more power with your solar panels than you are consuming with your electrical loads in your home or business, any excess electricity is allowed to flow back into the utility grid.
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In net-metering situations, your utility provider would pay you for the excess electricity you put back into the grid
Isn’t that great?! Getting paid by the power company! That is a great feeling for many people that install grid-interactive solar-electric systems!
Here is a quick video of a meter spinning backwards after we turned on a 15 kW solar system:
METER SPINNING IN REVERSE SELLING POWER TO THE UTILITY COMPANY
