Micro Inverters just suitable for small applications
Micro Inverters are no the be all end all solution but I feel they do make sense in some smaller applications. For example in small residential systems they do make sense. For a one or 2 module gird tied system micro inverters are likely the only solution. As system size increases above a few kW Micro inverters become too costly.
Another important consideration is the type of installation. In the residential space the roof is typically complex, has obstructions or may be exposed to shading from nearby objects. In these types of scenarios distributed MPPT solutions (micro inverters and DC power optimizers) do make sense. The ability to use different string lengths, different mounting orientations, different size modules, and shade tolerance are all valuable tools in rooftop PV system design. I must disagree with the conclusion that distributed solutions never add energy, and that shading rarely occurs. Shading is common in the residential space and there have been several independent studies that show that where shading occurs distributed technologies add substantial added energy. This makes perfect sense because with distributed MPPT solutions the current of the entire string is not reduced by shading one module in the string.
On the other end of the spectrum are ground mounted utility scale systems. In these types of systems many of the design advantages offered by distributed technologies are of less valuable. String length, module orientation, and module type are all simple inputs to the system design equation. In utility scale system shading is normally not an issue since nearby objects that would create shade are very uncommon. Without shading, the potential for increased energy yield typically comes from module mismatch. With a well matched array the lower efficiency of micros compared to larger inverters makes it difficult to produce additional energy. DC optimizers fare better here since their higher efficiency means that the lost energy recovered from mismatch can be larger than the losses incurred by inserting the optimizers into the system. Well matched is a key phrase since many systems installed during the many "PV booms" around the world are far from well matched.
One other important consideration is that modules do not age uniformly and mismatch losses increase over time. As we retrofit more older under-performing larger systems we are seeing significant increases in energy production. This is easily demonstrable by before and after comparisons. Performance gains of mid to high single digits are common and we have seen increases of over 15% in some more extreme cases. The cost of distributed MPPT technologies is ever decreasing and today we can demonstrate positive impacts on LCOE/ROI when recovering a couple percent of lost energy. This appears to be very achievable in arrays that are more than a few years old. Micro inverters are not typically a large scale viable retrofit solution since they would require a replacement of the entire inverter and reconfiguration of the AC collection wiring.
Another important consideration is the type of installation. In the residential space the roof is typically complex, has obstructions or may be exposed to shading from nearby objects. In these types of scenarios distributed MPPT solutions (micro inverters and DC power optimizers) do make sense. The ability to use different string lengths, different mounting orientations, different size modules, and shade tolerance are all valuable tools in rooftop PV system design. I must disagree with the conclusion that distributed solutions never add energy, and that shading rarely occurs. Shading is common in the residential space and there have been several independent studies that show that where shading occurs distributed technologies add substantial added energy. This makes perfect sense because with distributed MPPT solutions the current of the entire string is not reduced by shading one module in the string.
On the other end of the spectrum are ground mounted utility scale systems. In these types of systems many of the design advantages offered by distributed technologies are of less valuable. String length, module orientation, and module type are all simple inputs to the system design equation. In utility scale system shading is normally not an issue since nearby objects that would create shade are very uncommon. Without shading, the potential for increased energy yield typically comes from module mismatch. With a well matched array the lower efficiency of micros compared to larger inverters makes it difficult to produce additional energy. DC optimizers fare better here since their higher efficiency means that the lost energy recovered from mismatch can be larger than the losses incurred by inserting the optimizers into the system. Well matched is a key phrase since many systems installed during the many "PV booms" around the world are far from well matched.
One other important consideration is that modules do not age uniformly and mismatch losses increase over time. As we retrofit more older under-performing larger systems we are seeing significant increases in energy production. This is easily demonstrable by before and after comparisons. Performance gains of mid to high single digits are common and we have seen increases of over 15% in some more extreme cases. The cost of distributed MPPT technologies is ever decreasing and today we can demonstrate positive impacts on LCOE/ROI when recovering a couple percent of lost energy. This appears to be very achievable in arrays that are more than a few years old. Micro inverters are not typically a large scale viable retrofit solution since they would require a replacement of the entire inverter and reconfiguration of the AC collection wiring.
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