Do you know what role microinverters play in solar installations and what advantages and disadvantages they have?
How do they differ from grid-tied inverters / inverters?
What are the main differences between string inverters and microinverters?
String inverters and microinverters are the two main types of inverters used in solar energy systems to convert direct current (DC) generated by solar panels into alternating current (AC) that can be used in homes and businesses.
A microphotovoltaic inverter functions on a similar principle to a traditional grid inverter. Its main purpose is to convert the direct current (DC) generated by photovoltaic panels into alternating current (AC). Only AC current is capable of powering electrical appliances used in the home.
Microinverter devices are more efficient for installations with varying sunlight conditions and are better suited for roofs with complex shading or multiple orientations. Chain inverters are more cost-effective and suitable for simple installations with constant sunlight.
Microinverters are also well suited for small PV installations with a small number of solar panels.
In contrast, traditional string inverters are optimized for larger systems and are not as flexible or scalable as microinverters.
Safety features make microinverters a safer choice for solar energy systems, both for the installer and the end user. They also help reduce the risk of fire and electrical hazards, making them a more reliable and safer option for solar energy applications.
Advantages and disadvantages when using microinverters in solar installations:
1. Location and installation.
Chain inverters are installed inside or outside the building, while microinverters are mounted directly under each solar panel. There are also solutions to which 2, 4 or even 6 photovoltaic panels can be connected.
Challenges in maintaining microinverters include issues related to adverse weather conditions such as storms and high temperatures, as well as the need for regular monitoring and maintenance of the system. For example, thunderstorms can make on-site maintenance difficult due to slippery ground and limited visibility, while high temperatures can lead to microinverters being de-rated or shut down, causing loss of power generation.
In addition, submerged PV modules can create insulation problems and there may be a risk of electrocution, requiring close monitoring and maintenance procedures.
To address these challenges, they are equipped with features such as module-level monitoring systems, remote fault diagnostics and analysis capabilities, as well as advanced levels of protection to ensure durability and safety
2. Panel-level conversion.
DC to AC conversion is done at the panel level, while daisy-chain inverters convert DC from multiple panels connected in series.
3. Maximizing the production of energii.
Microinverters can maximize energy production by ensuring that each panel operates at optimal efficiency, resulting in higher overall system performance.
Some specific ways to increase energy production include:
- Shade tolerance: they can continue to produce energy even when part of the panel is shaded, as they optimize the output of each panel independently
- Panel mismatch: they are able to compensate for differences in panel output, ensuring that each panel contributes to the overall energy production of the system.
- Dirt buildup: they are able to minimize the impact of dirt buildup on panel performance because they optimize the output power of each panel individually.
These features make them a more efficient and reliable choice for solar energy systems, allowing homeowners or businesses to maximize energy production and reduce their dependence on traditional energy sources.
The disadvantage of daisy-chain inverters is that they limit the power production of the lowest output panel in the chain.
4. Monitoring.
Microinverters provide panel-level monitoring, while string inverters provide system-level monitoring.
Module-level monitoring offered by microinverters, allows monitoring of the output of each individual solar panel. This feature enables accurate detection of faults and other performance issues, allowing remote troubleshooting and eliminating the need for time-consuming manual testing of each solar panel.
A potential single point of failure in a solar power system refers to the risk that the failure of a single component, such as a central or string inverter, could lead to a significant drop in overall system performance. This issue has been a concern in the solar industry, particularly in utility-scale solar installations. However, the use of microinverters and multi-module microinverters (MMMIs) can reduce this risk by eliminating a single point of failure. Unlike central or daisy-chain inverters, microinverters are connected directly to the output of each solar panel and operate independently. As a result, the failure of a single microinverter has a negligible impact on overall energy production, and there is no need for urgent repair or replacement of the failed unit. This approach, known as “operating systems resilience,” contributes to the longevity and economic viability of solar energy systems. In addition, the use of high granularity performance monitoring allows for informed maintenance and repair decisions, further enhancing system reliability. Overall, the use of microinverters helps to avoid a potential single point of failure, ensuring continuous energy production and protecting the solar investment and providing a faster return on investment.
5. Expanding the system or changing the configuration.
Microinverters make it easy to expand a solar system by attaching additional panels in any configuration to an existing installation, while daisy-chain inverters can be limited by their maximum power output or require additional changes when increasing the number of panels.
Increased design flexibility is their key advantage, offering the ability to install solar panels in different orientations or shaded areas, thus maximizing overall system efficiency.
This flexibility allows for a more customized system layout and facilitates expansion or modification of solar installations, providing scalability for future energy needs.
Scalability is their significant advantage over string inverters, as they are highly flexible in configuration and can be easily added or removed as needed, making it easy to expand or modify an existing solar system.
This feature provides flexibility for future energy needs and allows owners of solar PV systems to start producing their own renewable energy with even a few panels, and provides the opportunity to expand as needed without major modifications and with minimal cost.
6. Cost.
String inverters are generally less expensive than microinverters.
The higher initial cost is a significant disadvantage of microinverters compared to traditional string inverters.
However, a higher initial cost per watt-hour does not necessarily mean that microinverters will ultimately cost more, as several other factors must be considered, such as simpler and less time-consuming installation, better durability and longer life.
Therefore, the higher initial cost of microinverters can be offset by their long-term benefits and cost savings
7. Warranty on microinverters.
Microinverters typically have longer warranties than string inverters. Robust chain inverters have a basic warranty of 5 to 10 years while microinverters boast basic warranties of up to 12 years or more.
8. Enhanced safety.
Enhanced safety is an important advantage of microinverters over traditional string inverters. They offer several safety benefits namely:
- Lower DC voltage: they convert the DC current generated by solar panels into AC current at the panel level, resulting in a lower DC voltage (typically less than 60 V) compared to string inverters, which can have DC voltages of up to 600 V in residential systems and 1000 V in commercial systems.
- The lower DC voltage reduces the risk of electric shock and fire.
- Instant conversion to AC: They convert DC to AC at the panel level, which means there is no need to run high-voltage DC cables from the panels to the inverter. This eliminates the risk of arcing and fires caused by high-voltage DC cables.
- Rapid shutdown function (RSD): Many of these units are equipped with an RSD function that allows the system to be shut down quickly in the event of an emergency, such as a fire or grid failure. This function is required by law in the United States and is expected to be adopted in the European Union as well.
- The use of high-quality critical components and the implementation of the rapid shutdown function (RSD) contribute to the overall safety and reliability of microinverter systems.
- Safe installation: they are easier to install, reducing the risk of injury during installation. Since the current in a solar power system already accumulates during installation, even before connection, microinverters minimize the risk of electrocution.
- Fire safety: they are safer for firefighters because they stop generating power within 30 seconds in the event of a grid failure or shutdown. This reduces the risk of fire and electrocution.
- Quality and safety standards: Increasing attention to quality and safety in the solar industry, including training and certification of installers and inspection of solar installations, helps ensure that these devices are installed safely and correctly.
The choice between inverters and microinverters for photovoltaic systems depends on many factors. Microinverters have many advantages, such as providing high energy yields even under difficult installation conditions.
The final decision, microinverters or inverter, is best entrusted to a specialist who will select the appropriate solutions tailored to the customer’s specific needs.