I realize at a few points in this solar-power series, I have said a component is absolutely essential to the system. While this may seem hyperbolic, in actuality, it is because most parts of the system I outline are truly essential to its success. While this next component may not be technically essential to collect and store power, it does serve the purpose of making that power actually available to use in your home. Read on, for a general outline of solar power inverters.
What is it?
So what is an inverter, exactly? After all, while you’ve likely encountered a sizeable battery before, such as the one in your car, and at least heard of solar panels, chances are you’ve never stumbled across an inverter. Turns out, this is a crucial part of your system, as the power you collect from the sun is stored as DC, or Direct Current, power. Unfortunately, your household does not run off this style of current. Direct current only flows in one direction, hence its name. This is the sort of current your car’s electrical systems run on. Homes, however, are generally wired for AC, or alternating current. This is due to the fact that AC can be transported over long distances more easily, by converting it to a higher voltage (and thus lower current) using a transformer. At these higher voltages it will lose less energy in transmission, then will be converted back down to a low voltage when it reaches the house or neighborhood (by another transformer). Thus, to use your DC energy, you’ll need an inverter.
Unfortunately, the complexities don’t stop there. Inverters are also classified by whether your system is tied into the power grid, or completely removed from it, as you will need a different type of version depending upon the system. The good news is, if you are tied into the power grid, you can simplify your system immensely, and will not need a few of the things we have written about previously, such as batteries, charge controllers and the like.
Grid-Tie Solar Inverters
With this sort of system, your solar panels will connect directly to an inverter, which then ties into your main electrical panel, where the power grid is also connected. The reason this is important, is the inverter will not only run your devices through this panel, but when excess power is created, will actually turn your power meter back as it returns extra energy down the line. As mentioned, this sort of inverter does not require a battery bank or charge controller, since it utilizes the infrastructure already in place.
A low-cost grid-tie inverter, string inverters tie solar panels together through a series string designed for high voltage. This sort of system is best if your solar panels are all working or inactive at the same times, since everything runs together as a unit.
Easy and safe to install, optimizers can handle large string sizes, as they connect to each panel separately as DC-DC “converters,” though a central inverter still manages a final, DC-AC conversion. This former trait is similar to a microinverter
Also fairly easy to install, microinverters are modular and expandable. As mentioned above, they attach to each panel, which can be useful if part of your solar array is shaded for some of the day. A microinverter means each panel can operate independently, maximizing power production when a disparity in production between panels occurs. They are a more expensive option, however.
Off-Grid inverters connect solely to a battery bank, and change DC power stored there into AC power that can be used in your house. For those who want the convenience of remaining tied to the grid, while also benefiting from the security provided by a battery bank, some “off-grid” models even have an extra connection where they can tie into the grid, and sell excess power back into the system. These both are the sort of inverters that will require the variety of components outlined in previous articles (charge controllers, batteries, etc.) As the inverters work to convert regular direct current into alternating current that represents a sinewave (other forms of AC do exist, such as squarewave and trianglewave, but sinewave is the only commonly used for power), off-grid inverters are classified around this principle.
Pure sinewave inverters are expensive, but have a high quality power output (more on this in a moment) and are compatible with most appliances. Translation: for most buyers, they are the way to go. In fact, these things put out power of the same quality as the powergrid itself, and sometimes surpass it..
While these are lower cost, the sinewaves they produce are, as the name implies, a little different from a true sinewave. I don’t want to dig too deep into the electrical theory behind this, but what you need to know is this slightly wonky wave pattern can cause issues with appliances running motors, pumps or compressors (but I repeat myself). In essence, they cause them to run hotter, burning out quicker. Sensitive electronics such as computers and TVs are not immune either, as modified sinewave converters can cause static. Thus, unless you really know what you’re doing, and have thoroughly researched and selected the appliances in your home to work on a modified sinewave system, I would recommend sticking to the pure.
I hope this and the previous articles have been an informative primer on what to look for when selecting components for a solar system, and deepened your understanding of the science behind it. While this marks the end of our first large venture into the topic of solar energy, we will doubtless return to the topic in smaller, more detailed segments later on. Until then, may the sun shine on both you, and your panels!
A humble homesteader based in an undisclosed location, Lars Drecker splits his time between tending his little slice of self-sustaining heaven, and bothering his neighbors to do his work for him. This is mainly the fault of a debilitating predilection for fishing, hunting, camping and all other things outdoors. When not engaged in any of the above activities, you can normally find him broken down on the side of the road, in some piece of junk he just “fixed-up.”