Types of Solar Electric Systems
There’s more than one way to generate renewable solar energy. It all depends on the type of solar electric system you choose. And for that, you need to understand the various classifications used for types of solar electric systems, which is determined by the functional requirements, the component parts, and how the solar electric system is connected to any other power sources.
Generally speaking, there are two main types of solar electric systems: those that are connected to the local energy grid, and those that stand-alone, but some systems function as hybrids of these two types. Each system type has its own advantages and disadvantages, though grid-tied solar electric is becoming much more common worldwide, making up close to 70% of the residential solar market today.
Grid-Connected Solar Electric Systems
A grid-connected solar electric system goes by several other names, including utility interactive, grid inter-tied, and grid-tie systems (GTS). The basic set-up of a grid-connected solar electric system involves solar panels that are linked to the local electric utility grid. But of course, the connection between the solar array and the utility grid is a bit more complex than that. The following are the required components for a grid-connected solar electric system:
AC breaker panel
Electrical wiring in your home
All of these components function together in an intricate design to collect and distribute clean, renewable energy. It starts with the solar panels that collect sunlight and convert it into an electrical current. The electricity that these panels produce is direct current (DC) energy, but since your home and the grid function on alternating current (AC) energy, the raw solar energy needs to be converted.
For that, the solar electric system relies on an inverter (sometimes called a power conditioning unit, or PCU), which is one of the most important components in your solar electric system. The inverter will convert the DC energy to AC energy which can then be used inside your home and or be safely sent to the local utility grid. From there, the electricity travels via your home’s normal wiring through the AC breaker panel.
A grid-tied solar electric system also requires an array DC disconnect, which is essentially a switch that allows you to stop the flow of electricity from your solar panels. This is used to shut the system down in emergencies or when maintenance needs to be performed. You will also have a utility disconnect which is used by the local utility to stop the flow of energy when they need to perform maintenance on the utility grid.
At this point, a kilowatt-hour meter provides a read-out of how much power your solar array has produced in order to calculate your monthly utility bill. This leads us to one of the biggest benefits of a grid-tied solar panel system. When connected to the existing power grid and producing energy, your solar panel will pump all excess clean energy you produce into the grid. Through a program called net metering, which many (but not all) communities now have, you will get credit from your local utility for all of the power fed into the grid. In essence, the meter will spin backwards during these times!
Conversely, at night and during times when your solar system doesn’t make enough energy for your home, you can draw power from the local utility grid. As a result, most grid-connected solar system do not include a battery since all of the energy is consumed as it is produced.
Stand-Alone, Off-Grid Solar Electric Systems
Unlike a grid-tied system, a stand-along solar electric array is usually sized to provide a minimum amount of energy in order to generate an entire home’s energy requirements (sometimes combined with geothermal, wind, or hydro power). Most grid-connected systems, on the other hand, normally provide only a portion of the energy needed by the home.
The components used in an off-grid solar electric system are very similar to those used in a grid-tied, but for a few additional components. Here’s the complete list:
AC breaker panel
Electrical wiring in your home
So how does an off-grid solar system differ from a grid-connected one? It collects solar energy in the same way and then converts it into an electrical (DC) current, but in this case, it can either funnel the electricity into your home or the battery system. It does not ever send electricity into the local electric utility grid.
In a stand-alone solar system, sometimes the DC energy is pumped straight into the DC battery, but it can also send the energy through an inverter to convert the DC energy into AC energy, just as before. Most often the electricity is then piped into your home or the batteries which can either store the energy for later use or be consumed immediately by your home, depending on the time of day and the amount of energy being produced and used. As with a grid-tied system, your off-grid solar array will also have a DC disconnect to allow you to shut the system down in an emergency and for maintenance, but it will also have a rectifier which is like a reverse inverter for changing AC to DC power for charging the batteries.
Batteries are finicky pieces of equipment, and as such they require some additional components to ensure they run well and last a long time. A system meter, for instance, will measure how full your battery is and how much energy is being produced by your panels versus how much you are using. This will give you a detailed look at how well your system is performing and whether or not you have any problems.
Another important component for battery health is the charge controller which also monitors and manages the charge coming from the panels into the batteries. For homes that are completely off the local electric grid, a back-up generator is usually part of the energy package as well. This gas or diesel-powered system provides electricity during periods of lesser sunlight and at night as needed. These can, however, be very noisy and produce a lot of fumes, so are often not preferred by solar owners.
Hybrid Solar Electric Systems
A hybrid solarelectric system combines some of the best characteristics of an off-grid and a grid-tied system. These systems are connected to the local utility grid, but also have a battery back-up system. The battery allows the homeowner to store energy for use during non-producing hours (at night or during black-outs). These systems are ideal for homes where the energy grid is unreliable because of inclement weather, an unstable utility generation system, and so on. This is of particular importance for those who rely on a constant source of energy for their home or business.
Choosing between a grid-tied, off-grid, or hybrid solar system does take a little expertise as you weigh the various options. This brief solar training guide should help you determine the right system for your home or inspire you to jump into a renewable energy career!
To learn more about solar electric systems sign up for a solar training course.