December PV Newsletter


This Month: Granular Monitoring Decision Guide and new Virtual Device Feature


Find the Right Granular Monitoring Level for All Your Projects


As we all know, decisions you make today about the analytic powers of your monitoring system will directly affect the ability of the O&M provider to maintain optimum power generation throughout the lifetime of the system. Good system design choices are critical to ensure that performance guarantees can be met, allowing the project to achieve target ROI.

Granular monitoring is the most complex issue to consider during system planning. It is no secret that granular monitoring greatly strengthens your ability to quickly detect and fix problem areas in your solar power system, potentially saving thousands of dollars in lost production. But these savings must be weighed against the costs of granular monitoring and the associated service trips to the project site. Many integrators ask our staff: “where are the dollars in the granular monitoring equation?”

DECK Monitoring is pleased to provide a diagnostic tool that can bring some clarity to this financial calculation. Our new Granular Monitoring Decision Guide considers five independent variables to determine the most cost-effective granular option for each PV project we help to design. Your DECK account executive can use your data to make a granular monitoring recommendation for your project: string-level monitoring, sub-array monitoring, or basic level inverter monitoring only (no DC-side data).

Basic Math

One look at the diagram below (500 kW AC model) confirms the potential value of granular monitoring: in a system of this size, a smaller problem (such as loss of one string) will not impact overall production enough to be detected by basic level monitoring alone. If you only monitor at the inverter level, a small system failure could easily add up to thousands of dollars in lost production before a scheduled maintenance visit might detect the problem.

Our new Decision Guide works on a basic economic model.

First we calculate a range of values for potential loss in the system. This calculation involves four specific variables from each project:

  • Value of Electricity – The average electricity value for the site, in $/kWh. Includes FIT, PPA, REC’s, net-metering or any performance payments. This is the critical and dominant factor in determining the value of granular monitoring. The higher this number, the greater the value of detecting and fixing performance losses.
  • Annual Irradiance – This number represents a combination of system efficiency and the number of hours of sunlight at STC conditions (1000W/m^2) over an annual period. The unit of measurement is kWh/kWpeak/yr. An estimate of 1500 represents a well-designed, fixed-axis system in a location with average sunshine. Higher irradiance means more $ and higher sensitivity to losses.
  • System Size – Simply the peak AC power rating of the site. You can determine this number by summing the AC rating of the inverters on the site. Large system size creates more potential for small unseen losses.
  • Loss Risk – This is an estimate of the risk of production losses for the site. Primary consideration is soiling, module damage, loose/ohmic connections, shading, BoS factors, or even variation below modeled performance. For example, if the site is located in an agricultural or industrial area were dust is expected frequently, you are at higher risk of losses due to soiling. Higher loss risk increases the need for granular monitoring to detect losses between planned site visits.

Taken together, these factors produce a range of potential loss values for your system that will be used in our Decision Guide.

Second, we factor in the cost of granular monitoring and site visits: this calculation starts with the cost of monitoring, then adds values that you provide for cost of service trips to your project site. Higher cost of site visits weighs against granular monitoring because it may be more cost effective to allow some small problems to wait for scheduled maintenance visits rather than sending a repair technician as soon as the problem is detected. If the cost of monitoring exceeds the value of potential losses in your system, the Decision Guide returns a recommendation for basic (inverter) level monitoring only.

The final calculation will provide a range of scenarios to be considered by the Decision Guide. For example, the guide may find that you can schedule up to nine service trips each year before your costs would begin to outweigh the potential losses in your project: this scenario would be a strong candidate for granular monitoring because quickly detecting and repairing up to nine problem areas will be cost effective for your project. On the other hand, the guide may find that you can only schedule two service trips each year before costs will exceed potential losses. This project is a weaker candidate for granular monitoring because the costs to repair small problems outweighs the potential loss of revenue during periods between scheduled service visits.



Now it's Easier than Ever to Enter Your Own Performance Baseline Data



Here is another installment in our ongoing series “You Asked for It!”

Some of our customers have been requesting a way to see their own data in the DECK software interface. We have listened, and the result is our new Virtual Device feature.

The Virtual Device feature lets you input data sets into your DECK interface so the data can be viewed and manipulated with the analytic tools in your DECK software. Virtual Device data can be graphed alongside actual reporting data, allowing you to easily identify periodic anomalies and outlier data points.

Here are some of the things you can do with the Virtual Device feature:

  • Compare your modeled baseline performance projections against actual generation data
  • Download sets of historical generation data, modify that data with Excel macros or other programs, then re-load the modified data for comparison against reporting data
  • Upload historical system data from before DECK monitoring was activated at the project site

Uploading a data set to our Virtual Device feature is easy. First, access your DECK Admin Panel and navigate to the Overview page for the desired system. Look for the “upload data to create a virtual device” link just above the Device Reporting Hierarchy feature.

You will then access an upload interface where you will name your Virtual Device data set, identify the type of data, and answer a few questions to determine how our software will process the data. You will have the option to repeat your data on a daily, weekly, monthly, or yearly basis.


To upload data with our Virtual Device feature, you must format your data as a .csv file (this is a “Save as” option in Excel and most other spreadsheet programs). You will need to format your .csv file with two columns: the first column is for the time, the second column is for the numeric data points (each data point must be paired with a time value). Complete data formatting protocol can be read here:


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