Jessica PirroMay 21, 20192060
A very vital part of a solar panel system is the inverters. Inverters convert direct current (DC) electricity that is produced by the solar panels, to electricity that your house can actually use. The inverters convert the DC electricity to alternating current (AC) electricity.
Like there are different kinds of panels, there are different kinds of inverters. There’s a string inverter, a microinverter and a power optimizer. The oldest inverter on the market today would be the stringer inverter.
What is a String inverter?
A string inverter system connects each group of solar panels by what is referred to as “strings”. Each string connects to a single inverter where the electricity is then converted from DC to AC electricity. You can usually find the single inverter is typically located in an electronics box that is typically placed on the side of the house on in the garage.
The panels are connected to the strings to the inverter, if there’s one or more panels that are under-producing energy (due to many factors, such as shading or dirt), the other panels that are on that string will also only be able to produce as much electricity that the affected panel is producing.
Usual string inverters are more than capable of handling more than one strings of panels attached to it. An example, if there is a three strings of five panels each, for a total of fifteen panels on a single string.
The size of the string inverter in kilowatt (kW) and the wattage of solar panels using is what determines how many panels that you can attach to one inverter without wasting too much energy.
When should you use string inverters?
String inverters can be effective for a lot of solar installation, but there are a few cases where string inverters aren’t the ideal for the situation. A string of panels can each only produce as much energy as the lowest-performing panel located on that string, this inverter technology isn’t the best if the panels are shading parts of the system during the day.
The module-level inverter system such as the optimizers or microinverter would better in the case that there are tall trees near the panels causing shading. If you really insist on getting a string inverter, removing trees or whatever object is causing the shading.
If your solar panels are going to be facing in all different directions, a string inverter isn’t going to be the best choice either. If the panels are going to be facing southward, they will be able to produce the optimal amount of energy, but if those panels are connected to panels that are facing the other direction, those southward facing panels are only going to only produce as much energy as the lower producing panels are. This will limit the overall production of the solar system.
How to evaluate string inverters?
When you are comparing the string inverter options, here are somethings that you should keep in the back of your mind:
Like most solar panels, string inverters each one has a different efficiency. The inverter’s efficiency is measured about how much energy is lost in the form if heat during the energy conversion from DC to AC electricity. The higher the efficiency of a string inverter leads to a higher overall system efficiency and there will be more overall energy produced.
The size of a solar inverter depends on a few different factors, which include the size of the solar array that they are connected to, your geographical location and other site-specific considerations. The string inverters that are larger are normally a bit more expensive but might be worth it to maximize the energy production.
Most string inverters come with a warranty that is typically between 5 and 15 years, that will cover certain problems such as manufacturer defects and environmental damages that are done to your inverter system.
Though they usually aren’t usually the most expensive component of a solar panel installation, it’s very important to compare and contrast the price that you’re going to pay for a string inverter. There are usually longer warranties for the larger, more efficient, string inverters. Usually these come with a higher price, but it depends on the roof setup and geography, you may be forced to send extra money.
A microinverter function in a parallel circuit. To simply put, a standard inverter will cap the electricity production of each panel by the lowest producing panel on your roof. A micro-inverter, on the other hand, will take full advantage of the production of each individual panel. It will convert the power generated by each panel to the grid voltage.
Micro inverters advantages
The core advantage of using microinverters is that theoretically, you can yield more solar electricity. The reason for this is that there are slight differences in voltages between solar panels. When solar panels are in a string the voltage is reduced to the voltage of the lowest voltage panel in the string. Optimizers are an option for standard inverters as well, which function very similarly to a micro-inverter. Micro-inverters and the add-on optimizers both offer an additional perk in system monitoring as well. With either of these devices, you have the ability to track the production of each individual panel, while with a standard inverter you only can track the production of the whole system.
If you were to expand your system in the future, micro-inverters are simple to add one at a time. However, with a standard inverter, it would be more costly to add another full unit. To sum it all up, micro-inverters definitely add value but are only recommended if you have panels facing multiple orientations or you have shading issues. Otherwise, the less expensive standard inverter is usually more cost effective.
The main disadvantage of microinverters is the price. They are typically a $1000 or so more expensive than a string inverter on a standard 5kW residential solar installation. The second disadvantage is that you have as many inverters on your roof as you have solar panels. Although microinverter manufacturers sell the ability to monitor each panel as a benefit of micro's (and it is) they then don't include the monitoring that allows the customer to do this. They only allow the installer to see the panel level data from your system and not you as a customer unless you agree to buy the higher level of monitoring as an upgrade. This means you as a customer only see system-wide monitoring information not what is going on with each panel. A skeptic would say that the reason they do this is to protect them and their installers from support calls related to broken inverters. It is very difficult with only system-wide monitoring data to determine if only one or two inverters out of 25 or so have failed.
So, which one is right for you?
Really, the main factor you should be looking at is your energy needs. The other factors tend to balance out, but if one is more appealing to you, like having multiple inverters as opposed to one big one you might have to replace, you should also take that into consideration.
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