Pros and cons of using string inverters vs microinverters vs DC optimizers in grid-tied solar systems?
Grid-tied solar power systems are popularly configured with string inverters, or, microinverters, or, string inverters with DC optimizers.
Grid-tied solar power systems with String inverters:
In case of a design using string inverters, each string inverter is connected to a number of solar panels. The inverter collects the accumulated DC current from the solar panels and converts it into AC power that it feeds into the distribution board.
Advantages of Design with String inverters
- Lower initial cost
- Easy access to the inverter and troubleshooting in case of a problem with the inverter
Disadvantages of Design with String inverters
- A drop in generation from one panel (due to either shading/ageing/defects) effects the output of the entire string of panels
- The solar energy harness from individual panels is not maximized all times
- There is no panel level monitoring hence identification or troubleshooting a problem related to solar panels takes longer
Grid-tied solar power systems with Microinverters:
In case of a design using microinverters, each solar panel is connected to an individual microinverter that converts the DC power of each solar panel into AC output.
You can read in detail about the pros & cons of using microinverters here.
Grid-tied solar power systems with DC Optimizers:
In case of a design using DC power optimizers, solar panels are connected to several DC power optimizers that then provide the accumulated DC current to a string inverter that converts it into AC power. While the architecture is similar to Microinverters there are certain differences as mentioned below:
Advantages of Design with DC Power Optimizers:
- Lower initial cost compared to microinverters as one optimizer can be shared between one or more solar panels along with the cost savings of using a single string inverter
- Similar to microinverters, DC power optimizers isolate each panel form the rest of the system maximizing generation and minimizing shading/mismatch issues.
Disadvantages of Design with DC Power Optimizers:
- High voltage DC is not eliminated on the roof when compared to microinverters
- Less flexible compared to microinverters as DC optimizers need to be designed to match the maximum panels per string on string inverters
- Less robust when compared to microinverters as if any individual optimizer fails then the entire string will fail. Also, the number of points of failure are higher compared to mircroinverters or string inverters.
In summary, if there exist shading issues on your roof or individual solar panels need to be installed in different directions or at different tilts and you would like to expand your solar capacity in future then a solution with microinverters would be the preferred option. However, in case you have budget considerations then a string inverter based architecture or a solution using DC power optimizers at a slightly higher cost would suit you better.
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