Easy Definition Of A Solar Inverter, And Its Working Principle

A technician fixing a solar inverter

A solar inverter is an indispensable part of a solar energy system. The system can’t work properly without a functioning inverter due to the necessity of changing the current from DC to AC. Most household appliances and office equipment use AC, so having all the power you have generated as DC may not be helpful. Your inverter is essential if you are using a net metering system.

The necessity of an inverter to convert all the power, in this case, is because you will have to transmit the power through the ordinary wiring system, so you have to invert all of it. The alternative would be to divert the energy and use it directly from the battery to power only the appliances that use the direct current while leaving electricity from the grid to power the rest.

Using power directly from the battery has its challenges because the inverter often works as a regulator, and not installing it might mean having unregulated power coursing through your wiring. There is no overemphasizing how much of an unmitigated disaster this can turn out to be.

The net metering system also requires you to transmit the additional power you get back to the grid. It will be impossible for you to send extra power back to the grid unless it is in AC, which is the same kind of power flowing through the powerlines.

A technician fixing a solar inverter
A technician fixing a solar inverter

How a Solar Inverter Works With Solar Panels

A solar inverter is also referred to as a PV inverter. Solar panels or PV panels are made up of layers of semiconductors. The semiconductors themselves are made up of gallium arsenide, also known as crystalline silicon. These semiconductor layers come in both positive and negative charges, which are connected with junctions. The semiconductors absorb energy from the sun and then send it to the PV cells.

The energy produced by the interaction between the sun’s rays and the semiconductors moves between the positive and negative layers of the semiconductors and produces a direct current that way.

Once generated, the energy is sent to a battery for future use and converted into 120V/240V current, which can be used to run most appliances or sent back to the grid. In some instances, the power goes directly from the PV to the inverter without being stored in a battery. Either way, the inverter makes it more widely useable around the home and makes net metering possible.

The technical details of how the inverter works, simplified, is that the energy goes through a transformer which causes the AC output. To get the power through the transformer, this inverter has to make the transformer ‘believe’ that the current is an alternate current because transformers work with the alternate current.

The inverter runs the direct current between two transistors at super-high speeds and then passes it through the transformer to achieve this end. Passing through the transformer converts the current into an alternate current.

Photo showing the inside of a solar power inverter
Photo showing the inside view of a solar inverter

What Does a Solar Inverter Do?

We have seen that the inverter converts power from direct current to alternating current, but it plays other roles such as;-

  • Maximizing power output
  • Acting as an interface with the grid
  • Makes report on power production
  • Keeps the system safe

A Solar Inverter Maximizes Power Output

One of the roles of inverters is to keep track of the array’s voltage and therefore keep track of the highest power at which the modules can function. The inverter thus identifies the wrong peaks that occur due to module degradation and shading due to environmental factors. Such shading reduces the production of power, but the inverter shows you where it occurs so that you can deal with it.

An Inverter Acts as an Interface With the Grid

The power you receive from the grid must come through the inverter. That’s how the connection works. Technology has given rise to smart inverters that communicate with the grid, keep an eye on the frequency, and control voltage in case of surges. The inverter smooths out minor disturbances in the power grid, but a smart one is programmed to sense if the disruption is too much or occurs for too long and switches off. Some go into standby mode to monitor the situation before they finally go off or go back online.

It Makes Reports on Power Production

All the power generated by your solar power system goes through the inverter, and it is an excellent device to monitor the system. The latest intelligent inverters have communication possibilities either by WiFi, Bluetooth, or Ethernet. Through these capabilities, the inverter can inform how the system functions. It can communicate to your smartphone on errors that may have occurred, reducing power and other diagnostic communications.

It Keeps the System Safe

The inverters are equipped to switch off when there is an electric arc. Electric arcs of this nature can occur due to the aging and natural attrition of the system. Different inverter brands play this role to varying levels of effectiveness.

What Information Does a Solar Inverter Show?

Inverters have different levels of sophistication. You should find out what the one you intend to buy can do. The following is some of the information you can get from the inverter.

  • How much power the system has produced since installation in KiloWatt Hours
  • KiloWatt Hours produced per day.
  • The number of KiloWatts the system is producing at the time of reading.
  • The number of hours the system has been working since installation.
Different types of inverters
Various types of inverters

Types of Solar Inverters

There are three primary inverters: micro-inverters, string inverters, and power optimizers. The following is more information on the three types.

  1. String inverters
  2. Microinverters
  3. Power optimizers

String Inverters

String inverters are the most commonly used the world over. Some people refer to them as standard centralized inverters. Each of the PVs in the system is connected and referred to as a string. You can have a number of strings (standing for panels) connected to the inverter.

Many people position these inverters on the side of the house or in the garage from where they convert the power to AC for use in the home. These panels are affordable and highly durable; you can have one for years without ever doing maintenance work.

String inverters work best with simple solar system designs in locations exposed to prolonged durations of sunlight throughout the day.

String inverters have the disadvantage of having the performance of one panel affect the entire system. Thus if one panel is peeled or degraded by having a part of it shaded, the output of all panels in its string drops disproportionally. Also, these inverters don’t do very well when working with complex systems; they are meant for simple, basic systems.

Microinverters

Microinverters are the opposite of string inverters in terms of centrality and distribution. String inverters are centralized because you only have one unit at a central place in the system. On the other hand, microinverters are small inverters, one for each panel; thus, instead of sending DC to the central inverter using a cable, the microinverters convert it on the roof, right beside the PV that generated it.

Microinverters have several advantages, including protecting the generated power from being shaded as it is transmitted through power lines. They also make it possible for you to monitor the performance of individual panels by looking at the inverter.

You will need as many inverters as solar panels, which is more expensive than a single-string inverter. These inverters are located on the roof, making them more challenging to maintain. Sometimes you will need to troubleshoot all of them to determine which one is working and which one is faulty.

Microinverters are best suited for roofs whose designs make it difficult to use string inverters. These roofs are mostly the ones that face multiple directions. They are also helpful if you have located your panels in different places in the compound—some on the roof, others in the yard, etc. If your roof has obstacles to a neat PV arrangement, such as chimneys or dishes, you might also want to use microinverters.

Power Optimizers

Power optimizers were meant to be a compromise between microinverters and string inverters. Optimizers are located on the roof just like microinverters, and sometimes they are integrated into the solar panel. Each panel has an optimizer.

However, these power optimizers still send the power to a central inverter. Please note that power optimizers don’t convert the generated power into AC. They fix the electricity voltage before it is transmitted down to the inverter. The energy that has passed through the optimizer is said to have been conditioned, and it is in the best possible position to be converted by the time it gets to the inverter.

This system that uses optimizers is more effective than one that only uses string inverters for shading. This means that the power you eventually get to use will be closer to the energy you generated when you use an optimizer instead of when you use a string inverter.

The main advantage of using power optimizers is that they make it possible to generate and transmit power when you have a complex roof design or a diverse location solar panels. Like microinverters, these panels allow you to monitor each panel’s performance, but they cost much less than micro inverters.

Although they are cheaper than microinverters, a system with optimizers is more expensive. PVs with optimizers are also more costly to maintain, and they can prove unstable if one or more optimizers are faulty.

Characteristics of a Good Inverter

The information in the above section can help you determine which type of inverter is best for you. Whichever inverter applies in your case, you will find the following to be reasonable indications of whether an inverter is of good quality or not.

1. Relevant Standard Bodies Approve it

General standards bodies in different countries test the quality of products to ensure they meet acceptable quality thresholds. Find out the standard premium body in your jurisdiction and check if it has approved the inverter. It may be a general standards organization or a body that deals explicitly with energy products. It is advisable to research the manufacturing company to see if it has a track record for quality. You can find out more about the manufacturer by looking at customer reviews online. If they have overwhelmingly negative reviews, you are unlikely to enjoy the product.

2. It Should be of the Correct Size

Ensure the inverter you buy can comfortably handle the peak production of your solar panels. Your solar panels have a kilowatts rating, and your inverter has it too; ensure the two ratings match.

You probably know that solar panels rarely reach their peak performance, which may tempt you to go for a smaller inverter. Avoid this temptation because you don’t know when the panel will produce optimally, and you aren’t always sure how much less it will produce. This means that you can’t accurately how much capacity to reduce from the inverter. To avoid these problems, buy an inverter with the same rating as your solar panels’ output.

Technicians wiring a house
Technicians wiring a house

Installing the Inverter

There are many factors to consider when installing the inverter. Of course, you don’t have much choice in this matter if it is a microinverter. They will always be installed on the roof. Whether the inverter is weatherproof is essential to consider when installing it. Microinverters should either be weatherproof or located in a weatherproof box.

For string inverters, it is essential to shelter them from the elements and position them in a place where you can access them to read the data on your energy production. People often install them in the garage, but you can install them somewhere outside if they are weatherproof.

The inverter being one of the central elements of a solar system requires you to get it right. The information above will enable you to ask the right questions when you go looking for one.

Read More:

Solar System Sizing?

Solar Power, and how it Work?

What is a Solar Power System?

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