The solar panels are the most important part of the solar power system, they convert the solar energy into the electrical energy or to be more precise into dc energy.
The electrical appliances that we use in our homes and businesses are designed to operate in ac energy and we get ac energy from the grid to run appliances.
The output from the solar panels is to be converted into a.c. energy before feeding to the electrical appliances, otherwise they will not run. This function of energy conversion is effectively performed by the equipment called the inverter. It converts the d.c. energy into the a.c. energy and run the appliances.
There are basically 2 arrangements of connecting the output of the solar panels with the inverter. In the first arrangement, all the solar panels are connected together with a string and their collective d.c. output is fed to the single inverter and in return, this inverter converts the d.c. energy into a.c. energy and run the appliances. The inverter which supports this type of arrangement is called the string inverter of the central inverter. Please see the picture below:
The central inverter can be placed anywhere in the house or the office like under the stairs, in the basement, in the garage or in the storeroom. This technology is in practice for decades and is tried and tested technology.
This arrangement is very cost effective and is very easy to maintain because the inverter is placed at easily accessible locations.
It produces as much as the electricity as the least productive solar panel in the string. If any of the panels in the string is not working properly due to shading or any other reasons, the string inverter will convert and produce that much energy which the shaded panel is producing in that particular string, wasting the output of the other performing panels in the string. This technology is not suitable with panels facing multiple directions.
It is best for those owners who are looking for the cost-effective solar power systems and have shade free roofs receiving uniform solar radiations.
The concept of the micro-inverter technology is gaining popularity, especially in the residential solar power installations. In this arrangement, the micro-inverter is attached to the solar panel, you can say that there is one micro-inverter at the output of each solar panel which is converting d.c. energy to a.c. energy. Now, the output of each micro-inverter is combined and fed to the electrical appliances. Please see the picture below:
Advantages: They are more efficient than the string inverters in converting the dc energy into the ac energy. Even if any of the solar panels is under-performing, the output of other performing solar panels will not be affected as it is in the case of the central inverter. The micro-inverters let the owners observe the performance of the individual panels, making it very easy to point out the under-performing panel and fixing the problem more quickly.
These systems are costly and difficult to maintain as they are located on the roof below the solar panels.
It is suitable where panels are placed in the multiple directions and where there is less sunny space.
Choosing the right inverter:
Now you have understood the difference and the function of both the inverters. It is up to you whether you want a cost-effective system or a system which can produce extra energy and enhance the performance but at the cost of higher maintenance, the choice is yours.