Solar energy systems are quickly rising as an alternative to electricity that is being generated by consuming depleting fossil fuels. It harnesses a renewable energy source – the sun – to generate electricity for homes and businesses. It produces less air pollution and lowers your carbon footprint.
More and more companies are offering varieties of solar kits and solar panel inverters aimed at consumers who are opting to install these systems at their homes or businesses. With all the options available, like monocrystalline and polycrystalline solar panels, string inverters or microinverters, even different watt solar panels, it is difficult to decide which solar panel kit is right for your needs.
Solar panel inverters are an integral part of any solar energy system, so it is essential to know which one best suits your needs.
What Is A Solar Panel Inverter?
Solar panel inverters are integral to solar panel systems. Photovoltaic solar panel systems, referred to as PV systems, generate voltage current that flows in one direction. This is called DC electricity (direct current). Most homes, businesses, and appliances are run off AC energy (or alternative current).
The solar panel inverter (or PV inverter) converts the DC electricity to AC electricity. This is also known as a pure sine wave inverter.
Inverters also monitor the PV array’s voltage and power output and offer diagnostic information if something doesn’t work quite right. It is responsible for the quality and safety of the electricity that comes out of your PV solar system.
How Do Inverters Work?
DC electricity travels in a direct line; it does not have a waveform. In contrast, AC electricity is in the form of a sine wave. If it is represented on an x-y graph, the wave will rise from 0 to a positive point, and then travel back down through the 0 to a negative point before going back to 0. This journey of “0-positive-0-negative-0” is seen as one cycle or one hertz. A regular sine wave has 60 repetitions of this cycle per second or 60 hertz per second.
AC electricity used by the grid uses actual sine waves, also called pure sine waves. High-end solar converters can provide these pure sine waves, while less expensive inverters produce something called modified sine waves. These waves do not have a slow flow and create smooth waves. They do still move “0-positive-0-negative-0,” but instead of waves, they more resemble steps.
The solar inverter mainly alternates the flow of electricity from 0 to positive, back through 0 to negative, and back to 0 again. Some mechanical inverters use electromagnetic switches to flick the current on and off at a very high speed, reversing the current direction and creating modified sine waves. This affects the inverter efficiency and could affect how well your appliances run. It could also mean that items with motors will use more electricity than if a pure sine wave was produced.
While most appliances could function on modified sine waves, different inverters and electricity load could also affect this.
Electronic inverters, also known as transformerless inverters, use inductors and capacitors to make the output current rise and fall gradually (instead of flicking it on and off), which results in a smoother wave.
Because you cannot create energy, only convert it from one form to another, inverters cannot produce a higher AC output than the DC that it receives. In reality, the AC output will be slightly lower as some energy gets lost to heat generation (the energy gets converted to heat energy).
What Are The Different Types Of Solar Inverters?
First, let’s become familiar with the different types of inverters available for solar systems.
Grid-Tie Inverters/Off-Grid Inverters:
Simply put, grid-tie solar systems have inverters that are connected to the primary electricity grid from a power utility, whereas off-grid inverters aren’t.
Off-grid solar inverters, used in off-grid solar systems, need batteries which are charged directly from the solar panels. From these batteries, the DC electricity is then inverted to AC electricity. The solar power system requires additional components like a charge controller, battery monitors, circuit breakers, and surge suppressors, among other things.
Off-grid inverters can produce pure sine waves or modified sine waves. Pure sinewave inverters are quieter than modified sine wave inverters and work best for modern appliances. Modified sine wave inverters are cheaper, but they also produce lower quality AC electricity, which could be problematic for some electrical equipment.
Grid-tie inverters convert DC to AC for the electricity to be used immediately or fed back into the electricity grid. These inverters are efficient and easy to install. A grid-tie inverter can be connected directly to the utility grid, so the AC electricity is sent straight to the network. Alternatively, the grid-tie solar power inverter can also send AC electricity to the building first from where any excess voltage will flow into the utility grid. Many areas credit independent electricity producers for this excess electricity through a net metering system.
Grid-tie inverters need to adhere to specific regulations. They must produce sinusoidal waves and have to stop working if there is a failure of grid power. This is to protect any technicians from getting electric shocks that could potentially happen if the transformer continued to send electricity into the grid. This means that if the grid electricity is down, these independent solar power producers will not have electricity.
Grid-tie inverter systems come in two types: string inverters (also known as central inverters) and microinverters.
String Microinverters And Central Microinverters:
A solar PV system consists of PV cells grouped into PV panels. A group of these panels forms a PV module. And one more time, group PV modules to make a solar array.
Most PV modules consist of many PV panels installed in a row. These rows are also referred to as strings. Each string carries DC electricity and is attached to a string inverter that will convert the DC electricity to AC electricity. This string inverter is a standalone box that can be mounted close to your fuse box and meter.
String inverters see the solar array as one solar panel instead of a collection of individual solar panels. This inverter works best with PV systems, where all the PV panels are installed on the same plane and facing the same direction. If one of the individual solar panels is not performing optimally (for example, if it is in the shade for part of the day), a string inverter will reduce the entire PV system’s output to that of the struggling panel. To get around this, solar system owners can install a power optimizer along with a string inverter.
A power optimizer can be used with a string inverter and is installed on each solar panel or can be integrated into a solar panel and sold as a Smart Module. The power optimizer conditions DC electricity before it goes to the inverter for higher efficacy than only using an inverter. Power optimizers offer the same benefits as microinverters (we will get to that in a moment), but at a slightly lower price.
Larger PV systems might require more than one string inverter, although technological advancements have made string inverters a viable option for solar systems up to about 1 MW. String inverters can work as a single-phase inverter, and they are also the best option if you require a three-phase inverter. These inverters take the DC electricity, convert it to AC electricity, and then distribute it to be shared across a three-phase supply.
Central inverters are best for larger solar system installations that produce a consistent energy output across the array. Here the strings of multiple modules are combined in a combiner box from which the DC electricity flows to the inverter to be turned into AC electricity. Central inverters generally have fewer components but do require a pad and combiner box.
Microinverters are installed on individual solar panels. This makes them excellent for solar panel systems where the panels are installed in different facing directions, or where some of the solar panels are in the shade for part of the day. This way, if a single solar panel is not functioning optimally, it does not affect the electricity output of the rest of the solar panel array.
Microinverters convert DC electricity to AC electricity at the panel, negating the need for a string inverter. Microinverters can maximize the energy output of each solar PV panel, leading to up to 25% more than string inverters. Because each inverter links to a single solar panel, it is easy to expand these kinds of solar systems, but access to the units is more difficult as they are usually installed on top of a roof.
While microinverters could be more expensive, some solar panels and inverter manufacturers integrate them into individual solar panels (and call them AC models), making them cheaper and easier to install.
Hybrid solar inverters provide some middle ground between off-grid and grid-tie options. It can function as an off-grid inverter but also give the possibility of falling back to the grid if needed.
These hybrid solar inverters blend energy to use the available energy sources most efficiently. If your solar system cannot produce the amount of electricity required, a hybrid inverter will register this and draw additional power either from batteries or from the primary power grid. These hybrid inverters, or inverter chargers, can also draw electricity from the grid to charge the system’s batteries if there is a disruption in the electricity supply.
What Is The Best Solar Panel Inverter For My Home?
The question about solar PV inverter sizing is entirely based on your electricity needs. You can get solar systems that provide most of the electrical requirements of your home or business, or you can get RV solar systems with small inverters that are good to generate the needs of an RV Home.
Keep in mind that there is a difference between the capacity of the inverter and its output. Capacity is the maximum amount of DC energy that can flow into the inverter while the output is how much AC electricity can be put out.
It is best to get an inverter that can handle a higher capacity than what your solar panel system can generate instead of the other way around. A 3kW inverter can handle and invert the electricity produced by a 1kW solar array. However, a 1kW inverter cannot use all the power produced by a 3kW solar array – leaving a lot to waste. If your inverter has a higher capacity, it will be easier to add more panels and increase the amount of energy produced and converted in the future.
Lifespan Of A Solar Panel Inverter
Solar panel systems generally have a lifespan of 25 years or more. Inverters do not last quite as long (although they do have a relatively long lifespan). String inverters have a lifespan of around 15 years, while solar micro inverters often come with a 25-year warranty.
The cost of a solar system plays a significant role in which solar kit you choose to purchase. While it might seem that some components make better financial sense at the moment, a more expensive option might be better in the long run. You must work out how much electricity you need, whether you will be linked to the primary electricity grid, and want to benefit from net metering and whether your energy requirements will change in the future. Taking your time to consider all your options, including which inverter type best suits your needs will ensure that you make the decision that best suits your present and future needs. This might mean that you need to invest a bit more right now to benefit even more from your solar panel in the future.