Post written by Kevin Smith, Division Manager for Energy Programs for the Office of Environmental and Energy Coordination
In the past decade or so, the climate change conversation has been shining a brighter light on solar energy. You may have a neighbor with solar panels on their roof, or maybe you own a rooftop solar system yourself. We understand that these panels convert sunlight into energy we can make use of, but how do they actually work?
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What’s in sunlight, exactly?
First, it’s important to understand that the sun gives off energy called electromagnetic radiation. This electromagnetic radiation contains light that we can see – visible; heat that we can feel – infrared; and “invisible light” at higher wavelengths called ultraviolet. All of this is energy and fortunately, we have the technology to convert it to other forms of energy that heat, cool, and light our buildings; and charge our electronics and electric vehicles.
What do solar panels do with that sunlight?
Solar power technology comes in different forms, but solar photovoltaics (PV) has emerged as the dominant technology for homeowners and commercial property owners. PV takes its name from the photovoltaic effect – the phenomenon where electrical current is produced when materials called semiconductors are exposed to light. When a semiconductor in a PV cell absorbs enough sunlight, its electrons are “excited” or ejected out of their atoms.
These electrons are then captured by a special coating on the front surface of the PV cell. Since electrons are negatively charged, a negative charge builds up on the front surface leaving a positive charge on the back surface. The electrons then flow through wires and eventually return to back surface of the PV cell, completing the circuit. This flow of electricity is driven by the charge difference between the front and back surfaces, which in turn is maintained by sunlight continuously striking the cell.
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Solar PV produces a type of current called direct current (DC), which is the same type of electricity used in our electronic devices. But the electricity used in our homes and buildings is called alternating current (AC). So, to take advantage of solar power, it must be converted from DC to AC. An inverter is a device that works much like the “power brick” or “block” that you plug into the wall to charge your phone. The inverter converts DC power from the solar PV system to AC power that the building or home can use.
What happens at night, or when it’s cloudy out?
It goes without saying that the sun needs to be shining for solar PV to work. But the beauty of installing solar at your home or business is that you won’t lose power, day or night, rain or shine. That’s because your home or building is still connected to the electric grid.
When the sun is shining, the building will first use any electricity generated by the solar PV system; any additional electricity needs will be made up from the grid. If the PV system is generating more electricity than the building needs, the excess electricity is pushed back to the grid, rolling back the electric meter (as an added bonus, in many states like Virginia, you get credit for that power from the electric company!).
If it’s cloudy or nighttime and the PV system is not generating electricity, the grid will supply all the electricity needs for the building. As it gets less cloudy, or the sun rises, the mix of electricity from the grid and the solar PV system changes automatically, instantaneously and seamlessly, so that inside your home, you never notice the difference.
Interested in going solar?
Now that you know how solar panels work, you may be wondering if solar power is right for you. The good news is that there has never been a better time to find out as there are group purchasing programs and federal tax credits and other incentives to help offset the costs.
Solarize Virginia and Capital Area Solar Switch are two programs that help take the guesswork out of solar by offering a free assessment from qualified solar installers, technical assistance to help answer all your questions, and a guaranteed discounted rate. Both programs are open for a limited time and you can sign up with no obligation to buy.
Fairfax County also offer other resources and benefits for homeowners looking to go solar, such as waived permit fees and tax exemptions.
Visit our Going Solar page to learn more!
Kevin Smith has been with OEEC since 2022 serving as the division manager for energy programs, leading the implementation of the county’s Operational Energy Strategy. He is a licensed mechanical engineer with over a decade of experience in building design & construction, and facilities optimization.
Climate Matters is the blog of Fairfax County’s Office of Environmental and Energy Coordination, where we share stories, insights and information related to climate change and environmental sustainability. Posts are written by knowledgeable and passionate OEEC staff members and guest authors. To read all blog posts, visit Climate Matters.