Photovoltaic panels convert solar energy into electricity that can be used to power homes, businesses and other buildings. However, for this to be possible, it is necessary to effectively convert the direct current generated by the panels into alternating current that is compatible with the power grid. For this purpose, grid inverters and microinverters are used. In this article we will discuss both inverters and microinverters, their use, advantages and disadvantages.
Grid inverters are among the most popular devices used in photovoltaic systems. Their main task is to convert direct current from solar panels to alternating current, maximize power, optimize voltage and current, and ensure safe connection to the power grid.
In traditional photovoltaic installations, panels are usually connected in series, with all power going to a central inverter. This arrangement forces all modules to operate at the same power. This means that the units operating more efficiently match the efficiency of the weakest link in the chain, leading to a reduction in overall system efficiency. The solution to this problem is to use power optimizers, but this involves additional investment costs.
In the case of mains inverters, it is important to ensure adequate protection, as they operate at high DC voltages of up to 1,000 V, which can lead to arcing.
Inverters are usually mounted in electrical rooms or near photovoltaic panels to allow for adequate cooling and protection from the weather. It is worth noting that, compared to microinverters, they tend to have a shorter lifespan of about 10 years. However, they come in different variants, allowing investors to select the ideal model for their particular installation.
Advantages of grid-tied inverters:
- higher efficiency for larger installations where multiple modules are connected to a single inverter,
- lower initial cost,
- installation in an easily accessible location for trouble-free service or replacement,
- simplified installation, as only one inverter is used to connect the entire system,
- widely used and popular in the market, which means easier access to different models and spare parts.
Disadvantages of network inverters:
- shading of one module negatively affects the performance of the entire system,
- require more protection due to their design,
- high DC voltage of up to 1000 V,
- when expanding the system, the need to replace the inverter with a larger one or build an additional independent installation using another inverter.
Microinverters are a relatively new technology in the field of photovoltaics, which differs from traditional grid-tied inverters. Microinverters are mounted directly to each photovoltaic panel and convert the direct current generated by that panel into alternating current.
With the use of microinverters, each solar panel operates independently, meaning that any shaded panels or failure of one panel does not affect the efficiency of the others, allowing them to operate at maximum efficiency.
In addition, in installations based on microinverters, where current is not converted from all modules in the chain, the maximum DC voltage does not exceed 65 V, which means greater safety for the entire system.
It is worth noting that the service life of microinverters, compared to grid inverters, is longer due to their individual design and distributed load, and can be up to 25 years.
Advantages of microinverters:
- each module operates independently at maximum efficiency,
- safer solution, due to operation at lower voltages,
- easy identification of problems because each module is individually monitored,
- possibility to expand the system in the future by adding more microinverters,
- cost comparable to traditional installations,
- possibility to create very small installations (e.g., balconies).
Disadvantages of microinverters:
- higher initial cost associated with the larger number of microinverters needed,
- difficult accessibility to the microinverter in case of failure,
- the need to install and maintain more units, which can be more time-consuming and costly,
- less availability of different sizes and wattages of microinverters, which can be limiting when designing more extensive installations.
Comparison of advantages and disadvantages of microinverters and grid inverters
Below we will compare the two devices. We will look at several categories that will be helpful in understanding the difference between the two solutions.
Table 3: Comparison of advantages and disadvantages of microinverters and grid-tied inverters.
|System performance||Depends on the performance of the least efficient panel||The highest possible, as each module operates at maximum power|
|Scalability||Limited by inverter power||Ease of adding new panels to the installation|
|Costs||Lower initial costs||Higher initial costs|
|Monitoring||Monitoring of the entire installation||Individual monitoring for each panel|
|Safety||Requires more security||Safe, lower voltage in PV module|
|Error detection||Error detection for the entire module chain||Error detection at the individual module level|
|Service||Easy access to the device||Impeded access to the device|
|Location||Installed in one central location||Mounted under each photovoltaic panel|
|Optimization||Works at most efficient levels under optimal conditions||Works at most efficient levels even under suboptimal conditions|
|Complexity of the system||Simplicity and fewer points of failure||More devices, more complex systems|
Grid inverters and microinverters are key components of photovoltaic systems, enabling efficient conversion of solar energy to AC power. The choice between the two solutions depends on a number of factors, such as the size of the installation, budget, expected efficiency and investor preference.
Grid inverters are often used in larger installations, offering efficiency, advanced features and an attractive price, however they are more susceptible to the effects of shading.
Microinverters, on the other hand, are ideal for smaller installations, providing maximum panel efficiency, greater security and ease of expansion.
In conclusion, the choice between grid-tied inverters and microinverters should be made on the basis of individual preferences, installation characteristics and available financial resources. For larger PV systems, where simplicity and lower costs are important, grid-tied inverters are the optimal solution. In contrast, for smaller and more complex installations that require panel-level optimization and higher flexibility, microinverters may be more appropriate. It is worth remembering that before making a choice, consulting a professional can help you make the optimal decision that will ensure excellent performance and long-term profitability of your photovoltaic installation.
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