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INDUSTRY I BALANCE OF SYSTEM


due to mechanical damage, such as blown bypass diodes, or excessive degradation, compared to warranted annual levels.


If precision panel-level data is coupled with a complete architectural model of the array, the Clarity system can build a comprehensive real-time picture of how the array is performing and use machine-based intelligence to recognize impairments, assess financial impact, understand the cost of remediation and recommend action. The O&M team can verify the action plan and have the components in-hand with a specific work plan, before they even visit the site.


An array Intelligence screenshot showing user interface and data collation ability


equipment manufacturers (OEM) against their 0.7 percent per annum degradation warranty when the monitoring tool has a plus or minus 5.0 percent measurement accuracy and is looking at panels in aggregates of tens of hundreds?


Large-scale solar array enhancement With the advent of distributed electronics in solar arrays, new solutions are emerging, which can help deal with these issues.


Panel-level monitoring offers insight into array performance with unprecedented granularity. Although this can come with increased upfront costs, the increased energy production significantly offsets these additional costs due to the identification and replacement of failed panels, implementation of a cleaning strategy driven by accurate soiling loss analysis and an efficient site O&M strategy driven by real-time insight, precise fault identification and quantification of the financial impact of each impairment.


In the Clarity system, panel-level monitoring is enabled by a small electronic module that can be connected to the J-Box of each panel in an array, or embedded within the J-Box by panel manufacturers. This module enables the monitoring of voltage, current and power at the individual panel-level to accuracies of 0.5 percent. This is 10 times more accurate and 10 times more granular than traditional string monitoring solutions on the market today.


Data acquisition and control of the distributed modules is facilitated through the Clarity mesh network, a self-organizing, self-healing wireless mesh network that scales to the largest utility arrays and is continually “re-architecting” itself as site conditions dictate. The network aggregates and time stamps all performance and environmental data which it then sends to the Cloud through a broadband backhaul (wired or wireless). Once in the Cloud, this data is fed to a suite of applications, which analyze the array for impairments and will recommend specific O&M action based on financial rules set by the owner. For instance, the system will monitor soiling levels, and create an alert to clean the array once the effect of soiling has exceeded the rules set for the site.


The other benefit of precision panel-level monitoring is the ability to identify all panel mismatch effects and very importantly, those that have triggered warranty claims, either in the first five years


Selective Optimization


The Clarity system also contains the option of DC optimizers that dynamically adjust for the effective mismatch between panels and across strings, recovering more than 50 percent of the otherwise lost power. This is especially useful when applied selectively to areas of an array that are known to suffer daily or seasonal shade, have high levels of soiling (array edges), or higher temperature gradients than usual. Across an entire array, DC optimization will yield a net energy output gain of five to eight percent across the array life, which can almost double the ROI on highly leveraged assets. When selectively applied to known problem areas, dynamic optimization can often double the performance of those sections of the array.


In new installs, optimizers enable site design features that reduce BOS costs to the extent that the optimization technology is virtually free, before accounting for any yield benefit. This comes through string stacking – the ability to stack more modules per string (up to double) while optimizers control the bus voltage to keep it below the upper threshold for the inverters. This has the effect of dramatically reducing wiring runs, labor costs and combiner box count, while also increasing the effective capacity of the inverter (by 66 percent or more) and slightly improving its efficiency.


Keeping safety in mind, the Clarity system comes equipped with electronic switch technology embedded within monitors and optimizers that can disconnect each panel from the string on command, reducing the maximum voltage within the DC array to no more than one panel open circuit voltage (Voc) within seconds. This feature is likely to be mandatory for any roof- mounted arrays in the NEC code for 2014. These switches can be activated individually, in defined groups (e.g. string or sub- array shutdown) or collectively (full array shutdown) from within


A dashboard screenshot showing the breadth of information covered and the useful overview ability.


Issue III 2012 I www.solar-international.net 27


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