INVERTERS Explained

Solar Micro-inverters Explained

How your meter can feed the grid as well as your home
Solar microinverters explained
Solar microinverters explained

An illustration showing the basic set-up for a household solar system with micro-inverters. The benefits brought by micro-inverters are making them increasingly popular. The reasons why are explained below.

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Solar Inverters

The heart and brains of your rooftop solar system

If you are new to rooftop solar or do not have a background in the electrical trades then you probably have never heard of an inverter.

This nifty and sophisticated box of electronics and switches Is not about turning things upside down – rather its main jobs are transforming the raw energy from the sun into a usable form, making sure your system is working to the max and letting you measure what’s happening.

To put it more formally, inverters are responsible for:

> Conversion

That’s conversion of DC (direct current) electricity produced by the solar panelsto appliance friendly 240V 50 Hz AC (alternating current), the form of power we are all familiar with and can use within our home or export to the grid.

> Controlling

Controlling the voltage of your system to extract the maximum power available (referred to as maximum power point tracking).

> Reporting

Reporting on your solar system’s performance – either on screen, via bluetooth or via the internet.

Inverters come in three categories – String inverters, Micro inverters or Central inverters. Each is designed for different situations and each has advantages and disadvantages.

 

FRONIUS string inverter 

String Inverters

The pros & cons

string inverter is connected to a series or “string” of solar panels and converts incoming DC power to outgoing AC power from ALL of the panels as a whole.

It is usually mounted on the wall a short distance away from your rooftop panels in a sheltered location between the solar array and your electricity meter/switchboard.

This is the most common type of solar inverter for residential and small to medium commercial systems in Australia and also the least costly.

For many commercial installations a series of string inverters typically will be used to cope with the higher number of panels.

String inverters are simple, proven and ideal if your roof is clear of any shading and your rooftop panels do not face in different directions – for example due to a gabled roof with different pitches and aspects.

The catch is that solar panels in an array feeding a string inverter will each produce only as much electricity as its least productive panel.

If ONE OR MORE of your solar panels is shaded during any part of the day or is degraded for any reason, the power output from all the PV panels in that entire string will be reduced to its level.

 

Equally if one part of your solar panels array has a different aspect and receives less sun then the output across all of your system will be degraded.

There also are limits on the maximum number of panels a string inverter can handle as well as compatibility issues between different types of solar panels, limiting expansion and panel replacement options.

These are reasons why micro solar inverters are becoming increasingly popular for household solar installations in Australia and elsewhere even though they cost more.

These issues are not so critical for commercial rooftop solar where a series of inverters will be linked to a string of panels. Any temporary point of failure is less significant as the power output of the rest of the system will not be degraded.

The Pros and Cons of Solar MICRO-INVERTERS

Micro inverters are installed near or under each individual PV panel in your solar energy array.

 

They convert the DC electricity from your solar panels into usable AC electricity BEFORE IT LEAVES YOUR ROOF, with no need for a separate string inverter located at your switchboard.

Some manufacturers are now integrating micro solar inverters into the solar panel itself. At Country Solar NT we typically mount them separately under the panels to protect them from the elements.

The big advantage of micro inverters is that they cancel out the impact of partial or complete shading or any other reduction in the output from a single panel due to a failure (or even the consequence of incontinence on the part of a large bird).

Because the DC-AC electricity conversion happens at each panel – there is no “bottleneck” when one panel’s output declines. If one panel is failing the others continue to function normally.

Micro inverters also allow you to readily monitor the performance of individual solar panels and makes future expansion of your system easier or the replacement of individual panels easier as different makes of solar panels can readily be interchanged.

Generally micro inverters also will increase the overall efficiency and power output of your system and offer some safety benefits.

A really critical benefit is that new-generation ENPHASE micro inverters recommended by Country Solar NT are designed to have a life of 20 years!

This is way more than the 10 to 12 year lifetime of most good quality string inverters. The catch is that micro solar inverters will cost you more up front.

However, the fact that more and more people are opting for the micro inverter solution for residential systems shows that solar customers see  the micro inverter benefits as good value, far outweighing the initial extra cost.

Central Inverters

central inverter is a high capacity inverter designed for use with a large commercial or utility-scale (solar farm) system and is not used for residential or smaller commercial installations.

It is like a very large string inverter but designed to handle much greater power  output and offer economies of scale. Central inverters can be very big, very heavy and very costly.

There are now many solar inverter manufacturers in the market but only a limited number stand out - at Country Solar NT we recommend only the world market leaders and innovators

To be brutally blunt, low end “el cheapo” inverters of any type or brand are a potential nightmare and to be avoided - below are brands we recommend

Austrian inverter manufacturer Fronius has  recognized expertise worldwide in controlling and monitoring energy for electric welding, battery charging, storage systems and solar electronics.

Fronius serves the Australian market through a Melbourne-based subsidiary which offers technical support and a repair center as back-up for its products.

SMA is unquestionably a world leader in string solar inverters in terms of both volume and quality.

Fully designed and manufactured in Germany, SMA has set the benchmark for solar inverters in the residential, commercial and utility solar markets.

VICTRON is a highly rated international supplier of sophisticated solar components headquartered in the Netherlands. A primary focus is meeting the needs of commercial-scale solar installations.

Victron maintains a presence in all Australian States and has a technical training centre in Adelaide.

 

California-based Enphase provides the world’s most advanced micro solar inverter technology.

It is the world’s leading micro inverter systems provider, continually pursuing unique, high-tech innovations to advance the performance and intelligence of residential and commercial solar energy systems.