The Complete Guide to Solar Inverters - EcoFlow

It doesn’t matter whether you install an on-grid, off-grid, or hybrid residential solar power system.

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You need at least one solar inverter.

Depending on the size and type of solar panel array you choose, you may need more than one.

Inverters convert the solar power harvested by photovoltaic modules like solar panels into usable household electricity.

Some system topologies utilise storage inverters in addition to solar inverters.

But what exactly does a solar inverter do — and how does it work?

Read on to find out.

Solar inverters are an essential component in every residential photovoltaic system.

PV modules — like solar panels— produce direct current DC electricity using the photovoltaic effect.

However, virtually all home appliances and consumer electronic devices require alternating current (AC) electricity to start and run.

Similarly, utility grids worldwide primarily transmit and deliver AC electricity to homes and businesses. That’s why alternating current is commonly known as household electricity.

A solar inverter is built-in to compact off-grid electricity solutions like EcoFlow’s portable power stations. In larger residential and commercial solar balance of systems, the inverter may be a standalone component.

For example, EcoFlow DELTA Pro can provide up to 7.2 kilowatts (kW) of AC output (14.4kW surge power) and up to 3.2kW of solar charge input (12 x Ecoflow 400W rigid solar panels)

Photovoltaic modules capture photons from sunlight, convert them into DC electricity, and transmit them to a solar inverter through electrical cables. The inverter converts DC into AC electricity for use in your home or transmission back to the grid.

In off-grid or hybrid solar power systems, an additional component — the solar charge controller — directs DC current to a solar battery for storage or to the solar inverter for immediate use.

String inverters are the oldest and most common type of solar inverters for small systems in the 500-watt to 3kW range. They are often used in portable and residential applications.

The principle behind string inverters for photovoltaic arrays is the same regardless of the installation’s scale.

In grid-tied systems, solar panels connect directly to each other and transmit their combined DC electricity to the string inverter.

The string inverter converts DC to AC electricity, transmits it to your home for immediate consumption, or, through a bidirectional or smart meter, sends the electricity to the grid.

Net metering and Feed-in tariff schemes in South Africa are not currently viable (or available) for most consumers.

However, President Cyril Ramaphosa has promised that will change.

In the meantime, a hybrid or off-grid solar power system is the better choice.

In off-grid or hybrid solar systems, PV modules may send DC electricity to a solar charge controller first. However, the solar inverter is still an integral part of the balance of the system.

Off-grid solar power systems operate independently of the utility grid and rely on battery storage to function during hours when there’s little to no sunlight.

Solar energy is intermittent by nature. Electricity production diminishes on cloudy days, and solar panels don’t work at night.

Grid-tied systems don’t require storage because they toggle between utility and solar electricity automatically. However, on-grid systems without solar batteries don’t work during a blackout.

Off-grid systems of sufficient size offer complete energy security, and solar batteries are an essential component.

Unlike grid-tied systems without storage, the first stop for electricity after it’s produced by solar panels isn’t an inverter. Instead, a solar charge controller is first in the chain.

There are two types of solar charge controllers: Maximum Power Point Tracking (MPPT) and Pulse Width Modulation (PWM).  Both alternate between supplying DC electricity to a solar battery for storage or to an inverter for conversion to AC.

The term “hybrid” can refer to several different types of residential solar power systems, including installations that utilise wind power in addition to PV-generated electricity.

Here, we’ll focus on hybrid systems that offer solar power + storage.

A grid-tied solar power system without storage offers benefits like lower electricity bills and a reduced carbon footprint. However, on-grid PV systems that don’t have a solar battery will not provide electricity during a power outage.

Because a grid-tied system both transmits and consumes electricity from the power grid, it must shut down automatically during a blackout. Otherwise, electricity sent from a PV system could injure or kill workers trying to restore power or cause further damage to electricity infrastructure.

A correctly configured hybrid solar panel system will work during load-shedding and unscheduled blackouts.

The type of inverter you need is dependent on whether you purchase a grid-tied system, go off-grid, or combine the two by opting for a hybrid.

In an on-grid system, solar panels transmit DC electricity directly to a solar inverter that converts the current into AC power for immediate consumption or transmission back to the grid.

In off-grid and hybrid systems, DC from photovoltaic modules is sent to a solar charge controller, which routes the power to a solar battery or to a solar inverter, depending on the parameters you specify.

Depending on your specific setup, multiple solar inverters and storage inverters may be required.

(Source: Alternative Energy  Tutorials)

Connecting Solar Panels of the Same Model and Rated Power in Series

To connect your solar panels in series, wire the positive terminal to the negative terminal of each panel in the array. At the end, you’ll have a single positive/negative connection that will plug into your balance of system.

By wiring your solar panels in series, the output voltage of the array accumulates. In the diagram above, the output voltage of each panel is 6 volts. At the end of the series, the cumulative output is 18V (3 panels x 6V = 18V).

What’s crucial to note is that while the voltage output increases with each panel added to the series, the amperage remains the same.

Series connections are typically used for grid-tied systems that require a voltage of 24V or more.

Voltage Accumulation: If your installation requires high voltage to operate — standard with on-grid systems — series or hybrid series/parallel wiring is probably essential. Even if it’s not, if your application is best served by higher voltage rather than amperage, a series connection is your best choice.

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Efficiency and Performance: Without considering other factors, series connections will output slightly more electricity from the PV panel array than other wiring methods. There is less power lost delivering electricity over distance to your balance system in a series connection.

Thinner Cables: A relatively minor consideration, but parallel connections require higher gauge wiring due to how the electricity is transmitted. Series connections may cost slightly less to wire the same number of panels.

Better for Distance: Depending on the total surface area of your installation and how long the cables must be to connect to your balance of system, series connections may deliver an additional benefit. Voltage travels more efficiently than amperage over long distances.

Obstruction and Shading: The most significant disadvantage of wiring solar panels in series is that the output of the entire array is dependent on the individual production of each module.

If you have 20 solar panels with a rated voltage of 6V each, the maximum potential output during peak sun hours is 120V. However, if just one module is in the shade (or damaged) and only produces 4V, the array’s output will be reduced to 4V per panel. Instead of 120V of production, your panels will output 80V. If part of your installation area suffers from significant shade during peak sun hours, you should consider parallel or hybrid connections instead.

Danger: High Voltage: There are many benefits to increasing the voltage output of your solar panel array. However, high voltage can be dangerous or deadly if improperly used. Working with high voltage also dramatically increases the risk for the person doing the installation. If you decide to proceed with a series connection, it’s best to hire a

professional installer.

(Source: Alternative Energy  Tutorials)

Connecting Solar Panels of the Same Model and Rated Power in Parallel

To wire solar panels in parallel, connect each panel’s positive terminals together. You also connect all the negative terminals to one another. Parallel wiring results in amperage accumulating and voltage remaining the same. The exact opposite effect of series wiring.

Again, using the same panels in the series example above, if the amperage per panel is 3V and you have 3 identical panels, your total output will be 9 amps (9A) and 6 volts (6V). The formula looks like this:

3A x 3 PV panels = 9A total output

Voltage doesn’t increase — the output remains 6V no matter how many solar panels you connect. If you have a 20-panel array connected in parallel with 6V/3A of rated power output, your maximum electricity production capacity is 6V/60A.

Cumulative Increase in Current: Each PV panel you add to an array connected in parallel adds its direct current output to the system’s total output.

Less Overall Vulnerability to Shade: Unlike the voltage produced by series connections, the increased amperage (current) produced by parallel connections is not dependent on the performance of individual panels. If one PV panel is covered in shade for part of the day, the performance of the entire array is not affected. Shaded panels will contribute less current to the total output, but the maximum output of the panels receiving direct sunlight remains the same.

For example, if you have 20 panels that output 3A of current in peak sunlight, but two are covered in shade, reducing their output to 2A, the cumulative output of your array will be reduced by 2A. The total (theoretical) output is 58A instead of 60A because each shaded panel produces 1A less.

For many rooftop installations, the advantage of parallel wiring is obvious. Depending on your location and roof structure, substantial portions of your solar panel array may be regularly shaded by obstructions like trees and neighbouring buildings for part of the day.

But they may produce their full rated power at regular intervals, depending on the earth’s rotation around the sun.

If the panel’s positioning means it never or rarely gets direct sunlight, you should move it.

Solar panels still produce electricity from ambient sunlight on overcast days. But PV panels do not always produce their full-rated power.

Why?

PV panel performance depends entirely on the amount of solar irradiance (sunlight) it receives.

That’s why solar panels don’t “work” at night.

Investing in a mounted solar panel you know will consistently be in the shade makes little sense.

Constant Voltage: Unlike series connections, you can add additional PV panels without increasing the voltage. This makes parallel connections invaluable in applications that require 12V power input, like many recreational vehicle systems.

Similarly, solar inverters have a maximum voltage capacity. You can add more PV panels to your array and continue using the same inverter. If you wired the same array in series and exceed the voltage capacity of your inverter, it will either shut down or permanently damage the component.

Connecting solar panels in series or parallel each has its pros and cons.

Can you have the best of both worlds?

Yes, many professional sizeable solar panel installations combine series and parallel wiring in one array to maximise the product of each group of panels.

It’s possible to strike the optimal balance between series and parallel wiring by carefully planning the wiring based on the location of the panels on the roof relative to the sun and obstacles that obstruct sunlight at certain times of day.

Typically, the goal is to achieve the right balance of producing volts and producing amps by wiring panels together in series and in parallel — not either/or.

If your residential solar installation will have more than 3 or 4 PV panels, it’s best to work with a professional installer. It will cost you more upfront but should substantially increase your return on investment and shorten your solar payback period.

For safety and performance reasons, we highly recommend that you DO NOT attempt hybrid series-parallel wiring of your solar panels on your own. Work with a reputable installer to achieve optimal results.

Some of the factors a solar power professional will consider when developing a wiring plan include.

Trying to choose an inverter and other components can become confusing. You can never be quite sure about compatibility between solar panels, batteries, inverters, and charge controllers. That’s why some companies have put together convenient all-in-one off-grid power solutions.

The EcoFlow Power Kits are an excellent example of a plug-and-play off-grid solar power system. They are perfect for cabins, tiny homes, and RVs.

The Power Hub includes all of the essential converters, outlets, and chargers for an off-grid system, including:

Do All Solar Systems Need an Inverter?

Yes, all photovoltaic solar power systems require at least one solar inverter. Solar panels harvest photons from sunlight to produce direct current (DC) electricity. Virtually all home appliances and personal devices — as well as the utility grid — require alternating current (AC or “household” electricity to function. A solar inverter converts DC to AC electricity.

What Is the Difference Between a Solar Panel and an Inverter?

Solar panels — or other photovoltaic modules — and at least one inverter are essential for residential solar power systems to operate. Solar panels harvest photons from sunlight using the photovoltaic effect and produce direct current (DC) electricity. However, your home operates using alternating current (AC or “household”) electricity. A solar inverter converts DC to AC electricity. Depending on your system, a storage inverter or power optimiser may also be required.

In short, you can’t have a residential or portable solar power system without at least one solar inverter.

The DC electricity produced by photovoltaic modules like solar panels won’t operate your home’s appliances and systems without the conversion to AC electricity a solar inverter performs.

If you’re looking for a whole home solar power system with no compatibility headaches that’s fully functional during load-shedding, check out the EcoFlow DELTA Pro and solar panels today.

Whether you’re shopping for portable power to-go or complete energy independence, EcoFlow has a solar power solution for you.

Are you interested in learning more about solar inverter manufacturer? Contact us today to secure an expert consultation!