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String Inverters, Microinverters or Power Optimisers

Updated: Sep 5, 2019

If you are considering a solar power system for your home, one of the key decisions you make is the type of inverter to install. Inverters convert direct current (DC) energy generated by your solar panels into usable alternating current (AC) energy. Beside solar panels, inverters are the most important equipment in your solar power system.


3 Types of Solar Inverters

  1. String inverters (centralised inverter)

  2. Microinverters

  3. Power optimisers

Microinverters and power optimisers are often collectively referred to as “Module-Level Power Electronics” or MLPEs. String inverters are by far the most commonly deployed option globally and comprise the vast majority of the world’s inverter market. However, MLPE technologies are rapidly gaining popularity and market share as their costs have come down. Despite the global dominance of string inverters, several residential solar systems installed in Singapore used MLPE technologies.


String inverter, microinverter and string inverter with power optimisers

Inverters convert the DC electricity that your solar panels produce into appliance-friendly AC electricity.The 3 main inverter options available for homes residential and commercial solar installations are string inverters, microinverters and power optimisers. Microinverters and power optimisers are more expensive than string inverters. Microinverters and power optimisers are best for installations where one or more panels may be shaded, or where panels are facing different directions. Microinverters and power optimisers allow you to monitor the power production of each individual panel. A system that uses microinverters or power optimizers will produce slightly more power than a similar system with a string inverter.


1. String Inverters


String inverters are the most cost-effective inverter option available in the Singapore. Solar installation companies will generally offer you a system with a string inverter if your roof is not shaded at any point during the day and does not face in multiple directions such as a gabled roof.


How String Inverters Work


Your solar panels are arranged into groups connected by “strings.” Each string of panels is connected to a single inverter, which transforms the DC electricity produced by the panels into appliance-friendly AC electricity.


String inverter technology has been used for decades. It is a tried-and-true technology, but is not suitable for certain types of installations. A string of solar panels will only produce as much electricity as its least productive panel. For instance, if one or more of your solar panels is shaded during any part of the day, the power output from that entire string would be reduced to its level. For this reason, if your solar panels are installed facing different directions, a string inverter may not be a good choice.


One of the most common reasons for a panel to produce less power or stop producing power altogether is shading from nearby objects. If your roof is prone to shading any time during the day or in certain seasons, you could either remove the source of the shade or install the panels where they will not be shaded.


2. Microinverters


Microinverters are rapidly gaining popularity, particularly for residential solar systems. Microinverters tend to be more expensive than string inverters or power optimizers, but their costs are falling as they become more popular.


How Microinverters Work


Microinverters are installed on each individual panel in a solar energy system. They convert the DC electricity from your solar panels into AC electricity on your roof, with no need for a separate central inverter. In many cases, the microinverters are integrated into the solar panel itself, but they may also be mounted next to the panel on the mounting system.


One of the major advantages of microinverters is that they eliminate the negative impacts of partial or complete shading. When the DC-AC electricity conversion takes place at each panel, there is no “bottleneck” when one panel’s production decreases. Microinverters also allow you to monitor the performance of individual solar panels.


2. Power Optimisers


Power optimisers offer many of the same benefits as microinverters, but tend to be slightly less expensive. Power optimisers are often considered a compromise between the expensive microinverters and the standard string inverter.


How Power Optimisers Work


Like microinverters, power optimisers are located at each panel, usually integrated into the panels themselves. However, instead of converting the DC electricity to AC electricity at the panel site, they “condition” the DC electricity and send it to a string inverter. This approach results in higher system efficiency than a string inverter alone.


Similar to microinverters, power optimisers reduce the impact of panel shading on system performance, and also offer panel performance monitoring. Systems that use optimisers are typically more affordable than those that use microinverters.

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