Solar Panel Systems 101: Understanding the basics
By Tom Tate
If a person had a Rip Van Winkle moment and fell asleep under a tree a decade ago, they would be amazed at how far solar photovoltaic (PV) systems have come. And they’d be right to feel that way as the technology continues to evolve at a rapid pace. Once the most expensive form of electricity generation, economies of scale in manufacturing and advances in technology are steadily driving prices down. In this guide, you'll learn everything you need to know to understand better how solar energy systems for your home really work.
How do solar panels for your home work?
The typical photovoltaic (PV) system has two main components, the solar panels and the inverter. Each part of the system helps to either generate electricity or convert that electricity into a usable form. Disconnect switches are also necessary so the system can be safely isolated for maintenance and other reasons.
How Do Solar Panels Generate Electricity?
Let’s take a look at the solar panels first. Each panel is composed of many smaller cells that are connected and together generate a certain amount of direct current (DC) electricity. When the system is designed, the number of panels used is determined by the amount of electricity required and the amount of space available to mount them. The collection of panels is called an array.
Scientists are constantly working with solar cell components to develop more efficient and powerful combinations. Today, the best commercially available panels have an average efficiency of around 17 percent with some high-efficiency panels exceeding 21 percent.
Many people are surprised to learn that heat has no part in the production of electricity. In fact, solar panels increase in efficiency as temperatures drop. This often strikes people as odd since many solar arrays are shown in deserts and other hot, arid locations. A solar array will produce at its best on a cold, clear winter day all things being equal.
What Is an Inverter?
An inverter is a piece of equipment that converts the DC electricity generated from a solar panel array into AC power, which flows into your home. Like the panels, the inverters are evolving and becoming more capable, with many now bearing the “smart” label indicating they can play an active role in the smart grid.
Do You Need an Inverter for Your Solar Panel System?
The short answer is yes. Solar cells generate DC power, but our homes and businesses use alternating current (AC) power. As a result, you need an inverter to make the power you’ve generated usable.
The Power Grid and Net Metering
Residential solar panel systems are usually installed in what is called a grid-tied configuration. This means that the system will only operate when electricity is present on your cooperative’s power lines. When a power outage occurs, the inverter automatically shuts down the flow of electricity from the solar array. Without this protective feature, the PV system could potentially back feed electricity into the co-op’s lines, becoming a life-threatening danger to line crews and anyone in the area. When the inverter shuts down, the solar power stops flowing, so members should not install a system with the expectation that it will power their home or business during an outage.
How Does Net Metering Work?
While solar panel systems are sized to come close to the expected electrical needs of the member, there is no way to continuously match the output of the array to the current need for electricity. At times, the amount of solar power will be more than needed. At other times, it will be less. Here is where net metering comes into play.
The co-op’s meter measures both the amount of electricity they supply when solar production is less than required and the amount of electricity sent into the co-op’s lines when solar output exceeds what is needed. On a regular basis, these flows are compared and credits or debits are applied to the member’s account. How this all works is determined by your co-op’s net metering rate.
Solar Power Terminology
- Solar panel: Combines individual photovoltaic cells into a larger, easier to install size.
- Solar array: A collection of solar panels that make up a solar energy system.
- Balance of the system: All other components of the solar energy system apart from the panels.
- Solar cell: The power-producing part of the panel, consisting of silicone and other chemicals. Cells can also be made from other materials like cadmium telluride.
- Inverter: The device that converts DC power into AC power.
- Racks: The structure on which the solar panels are mounted.
Solar PV has come a long way since first used on satellites in 1958. With this short overview, you now have a basic understanding of how these systems work.
Tom Tate writes on cooperative issues for the National Rural Electric Cooperative Association, the Arlington, Va.-based service arm of the nation’s 900-plus consumer-owned, not-for-profit electric cooperatives.
Other Solar Power Generation Information
How Much Electricity Can I Generate?
That depends on several factors:
- The size of your system. You can determine how much electricity you want to produce; then size your system accordingly. Note that you can start out small and add on. A system that will generate 100% of your energy needs is expensive, so most systems are sized to generate only a portion of your home’s needs.
- Your site. If you have a shade-free area from 9 a.m. to 3 p.m., you’ll be able to collect more sun and produce more energy than if your site is shaded.
- Your region. The more sunny days in your area, the more electricity you’ll be able to generate. For example, systems in the Southwest produce more electricity per year than in the northeast.
You can find online calculators to help answer this question in more detail, and installers can provide details about your situation, too.
How Long Is the Payback Period On a Solar System?
The payback period can range from fewer than 10 years to more than 20 years, depending on the system cost, available rebates and incentives, the amount of electricity produced, and the retail price of electricity you purchase from your cooperative. Check with your cooperative for more information.