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What is a String Solar Inverter and How Does it Work?

The downside is that if one panel fails or produces less energy, it can lower the output of the whole string. DC optimizers can help reduce this but add extra cost. It’s important to design solar systems that work well with string solar inverter, and solar software can be very helpful for this.

The string solar inverter is widely utilized in solar projects due to its cost-effectiveness, quick installation process, and ease of use and maintenance. This article offers a comprehensive guide to string inverters, detailing their functionality, benefits, and drawbacks.

What is a String Solar Inverter?

string solar inverter

A string solar inverter is a type of device used in solar power systems. It converts the direct current (DC) electricity generated by solar panels into alternating current (AC) electricity that can be used to power your home or sent back to the grid. It’s called a “string” inverter because it typically connects multiple solar panels in series (or strings) to a single inverter. This setup is cost-effective and easy to install, making it popular for many solar projects.

How Does String Inverter Work?

Single phase string solar inverters convert the direct current (DC) power generated by your solar panel system  into alternating current (AC) electricity. The AC electricity can then be used to power your home or sent back to the grid, known as Net Energy Metering (NEM).

Solar panel inverters are responsible for converting DC electricity from your solar panels into usable AC electricity, which is then used to power homes and businesses. The vast majority of residential solar systems use string inverters.

The main disadvantage of using a string inverter is that the whole solar system will be affected if one or more panels are shaded throughout the day. This can reduce the energy production of your entire array.

However, this can be mitigated by incorporating microinverters into your solar panel installation. These module-level electronics track each solar panel’s peak output and maximize individual panel performance independent of the other panels on your roof, reducing the impact of shading. Also, as they are installed at the panel level, they are able to offer rapid shutdown capabilities that are required under Australian national electrical code.

Solar String Inverter Design

A solar power system’s inverter converts DC electricity from the solar panels into usable AC electricity for your home or business. The inverter is also a key component of your system that keeps energy generation regulated and running smoothly.

With a string inverter design, solar panels are wired into groups called strings. Each string is connected to a single inverter which then transforms the solar energy into usable AC electricity. The inverter is installed in the ground or mounted on the roof and connected to the panels via cables.

Because the panels are wired in groups and the inverter is centralized, the performance of one panel affects all other solar panels in the same circuit. Like in a relay race, when a team member trips, it slows down the whole group. This can happen to your solar array if one panel is shaded or has a malfunction.

Solar software that includes auto stringing functionality can ensure your panels are arranged correctly to maximize efficiency and performance. These tools evaluate the conditions of your roof, equipment and solar energy needs to create a best-fitting layout for your panels and inverter.

String Inverters Vs Micro inverters

String inverters are a great option for most solar panel systems. They’re standalone boxes ideally suited for unshaded solar panel arrays on roofs with uniform pitch. They’re also a cost-effective solution that allows for future expansion of the system.

The big downside to using a string inverter is that a problem with one of the panels in the array affects all the rest, eating into your solar savings. Adding DC optimizers does help reduce this effect, but they require additional equipment and don’t solve the issue completely.

Another major concern is that the design of a solar array using a string inverter needs to be careful about environmental conditions, particularly shade. If the conditions are mismatched in terms of azimuth/orientation or tilt, one panel will underperform the others and eat into your solar energy savings. This can be a challenge to work around when designing for your site. However, there are ways to overcome this, like using power optimizers or microinverters. These modules (also known as module-level power electronics, or MLPE) help improve performance and efficiency by reducing the impact of shading and offer panel-level monitoring.

String Inverter Vs Central Inverter

Compared to Central Inverters, string inverters are simpler and cheaper to install. They do not require DC combiner boxes and DC wiring harnesses, resulting in less overall component connections which can reduce installation costs. They are also less prone to failure if a single inverter fails as there is only one inverter rather than multiple.

On the other hand, Central inverters are more complex to operate and repair. They require a more costly DC to AC transformer and are often combined with DC wires for interconnection which increases system complexity. Also, if a single central inverter fails, all power from the entire block will be lost whereas only the faulty inverter will be turned off with a string inverter.

From a SCADA integrator standpoint, string inverters are more beneficial from a maintenance perspective as they can be turned off at the panel level if only one of them is malfunctioning. They do not, however, provide the same degree of monitoring granularity as microinverters. To ensure a PV system design that works best for your specific site conditions, work with an Solar Earth Inc’s Approved installer who can use design tools to configure your array and inverter appropriately.

String Inverter Vs Power Optimizer

In many cases, especially for homes with simple roofs that can’t support the additional complexity of a microinverter system, string inverters alone can still be a great solution. This is especially true if you pair your string inverter with power optimizers.

Solar power optimizers are small devices installed at the panel level that condition and route the DC energy to a central inverter. They mitigate shading losses that can negatively impact the output of a string of panels.

Another benefit of power optimizers is that they allow for panel-level monitoring. This means you can spot underperforming panels on your roof before they impact the performance of other panels.

One big drawback of both power optimizers and microinverters is their cost. They are often more expensive than standard string inverters. This is particularly true when you pair them with a backup battery system. Additionally, both will require periodic maintenance that requires someone to be on your roof. However, if your solar installation is properly sized and designed by an Solar Earth Inc’s Approved Installer you will be able to get the most value for your money with either option.