Sub-Array Monitoring for Commercial-Scale Systems: Cost-Effective Visibility into DC Array Performance

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Failures in individual solar modules and even entire strings of modules can go unnoticed for long periods of time, driving down system output and cutting into profitability. How can you identify those failures efficiently and cost effectively? Fat Spaniel offers owners of large commercial photovoltaic systems a range of monitoring options for tracking the performance of their solar arrays. These include:

- Low cost, low granularity: Measurement of DC current output at the inverter level, which provides a useful measure of overall system performance at no additional cost beyond inverter-direct monitoring.
- Highest cost, highest granularity: Smart combiner boxes combined with Fat Spaniel’s String Monitoring Service track the performance of every individual string of modules, to enable faster pin-pointing and repair of problems.

- Medium cost, medium granularity: Sub-array monitoring provides an appropriate compromise between system- and string-level performance visibility, at a reasonable cost.

Performance Visibility With Modest Cost: Sub-array Monitoring

Sub-array monitoring integrated into an inverter meshes perfectly with the standard large solar array made up of large numbers of modules. These modules are consolidated on the roof into sub-arrays by DC string combiner boxes. The output of these string combiner boxes is in turn consolidated at the inverter by an integrated DC sub-array combiner. Current sensors included with the sub-array combiner constantly measure the DC current produced by each sub-array. These current readings are sent to the Fat Spaniel data center, where they are processed and immediately made available through the Insight Manager multi-site management portal. Insight Manager provides the ability to see sub-array performance through a Web view.

Benefits

• Most cost-effective way to monitor solar electric sub-array performance
• The DC monitoring approach that is easiest to maintain over the life of the system
• Factory configuration of the sub-array combiner and monitoring hardware means no additional boxes to install or wires to run in the field
• Web-based display shows comparison of multiple sub-array’s performance to quickly spot problems