How Solar Energy Works
Many of us have a general understanding of solar energy, but a large group don’t yet know exactly how the systems work to produce power from the sun. It’s important to understand the electricity grid, the functioning of the components that make up a solar power system, and the storage and usage options available for a broader understanding of how solar works and the options available.
The Electricity Grid and Solar Energy
One of the fundamental factors to understand is that the electricity as delivered to your home is AC, or alternating current. You don’t need to know much about the science of AC electricity, but it is important to know that most AC appliances cannot be run on DC, or direct current.
The electrical functioning of a photovoltaic cell is to receive sunlight and, within its materials, produce DC energy that flows along wires out of the cell. That means that in order to use this energy, you either need a piece of equipment called an inverter to convert that energy, or appliances that run directly on DC. The latter isn’t common, so an inverter does the important work in getting the DC solar energy from the array transformed into AC electricity:
1. The inverter converts the DC electricity into AC electricity so that it can supply power to the electrical outlets and appliances in your own home.
2. If grid-tied, the inverter also pushes excess electricity back to the wider electric utility grid for credit on your power bill.
Inside the PV Module
Fundamentally, a photo-voltaic module (often called a panel) is composed of multiple layers of functional materials. A glass lens layer protects the delicate silicon wafers which capture photons (light) and use them to conduct electrical charge into the embedded metal strips and out of the cells. An entire module may consists of 60, 72 or 96 of these cells connected together.
When you see a PV module, it may look like a simple panel of glass and metal, but it is a sophisticated machine that, despite not having moving parts, is designed to convert the most electricity possible from any amount of sunlight it receives. At any given time, engineers are innovating the materials and design of these modules for greater gains in efficiency, especially of the cells themselves.
After the Sun Goes Down
If you want your solar energy system to power your home in the evening, there is an obvious problem: there is no sun hitting the panels to convert into electricity. The choice between an off-grid solar power system, a grid-tied system or a hybrid system is an important consideration to make.
With a stand alone off-grid system, your solar panels are connected to a battery bank large enough to store all of the potential energy you might need. When you are not using all of the generated energy from the panels during the day, the excess goes into the batteries. That same energy discharges when you try to activate an appliance or turn on a light at a time when there is no sunlight. This kind of system, if sized correctly for your energy needs, can make it possible to have no connection to the power company at all – literally “off the grid.” Many of these systems also have an automatic backup fossil-fuel generator for periods where the array is obstructed by snow or other low-light conditions. However, the average American home uses too much power to economically take “off-grid”.
With a grid-tied system, your solar panel array is treated just like any other mini-power-plant in the wider network of electrical supply, referred to as distributed generation. Imagine that every time electricity passes through wires into or out of your home, that electricity is being “bought” or “sold.” When you are generating lots of solar energy but not using a lot of it, you are “selling” the extra energy to the power company for credit. When it is dark and you have no energy production, you “buy” energy in the traditional method from the power company. In this way, people with grid-tied systems use the utility company as their storage system rather than batteries, which is generally reliable and has “unlimited” energy available. This “net-metered” system directly results in lower electricity bills, and it’s also possible to “net-zero”, or cancel out your bill entirely over the course of a year. This is the least expensive way to utilize solar on your home.
Last, there is the hybrid solar power system, which is both grid-tied and has batteries. This type of system functions like a normal grid-tied system when the utility grid is operational, but if an outage occurs, the solar system automatically transitions to an off-grid system to self sufficiently run a number of important appliances in the home until utility power is restored. These are often referred to as “critical load” battery backup systems. This type of system falls in the middle of the cost spectrum.
How Solar Energy “Pays Back” the Building Owner
The initial investment in any solar power system can be steep, but the reason why many people are choosing solar is twofold: independence from outside forces and monetary benefits. Independence is fairly simple, since having a solar power array means that you can receive electricity from the sun at the same free rate even if prices for fossil fuels go up or if there is a loss of power elsewhere in your area.
The monetary benefits for solar energy come in a few ways. First, the electricity bill you typically groan about paying will go down, and if your system is large enough, may be eliminated altogether. Each month that you are saving money on your bill pushes you toward having received your initial investment back (referred to as the Return On Investment, or ROI). With proper maintenance, solar panels can last well over 25 years, so if you “pay yourself back” in less time than that, you actually earn money on your solar panels for any time after the initial payback. In this area, typical ROI is 10-12 years. It’s important to note that any size grid-tied system up to the maximum required to net-zero your home will have a similar payback period, with larger systems providing a greater reward after full payback is obtained.
To make solar energy even more attractive, a Federal tax credit, and in the case of Maryland, a state grant, make it possible to get a large chunk of your investment back within the first year. This effectively reduces the cost of your system, making it easier and faster to start seeing a return on investment for your solar energy system. Systems are generally maintenance free, and a well-installed solar panel array can last decades, eventually turning a profit in avoided cost of electricity after the initial ROI.
Interested in seeing lower electric bills and feeling the positive experience of generating your own personal power in WV, VA, MD or PA? Mountain View Solar is a credentialed and experienced local contractor with the expertise to help you find the custom solution that will work for you. Contact us to learn more about a professionally-installed solar array on your home or business building!
Additional Resources on Solar Energy:
Go Solar California: http://www.gosolarcalifornia.ca.gov/solar_basics/how.php