Commercial PV System Data Monitoring, Part Two: Page 2 of 6
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Monitored data. The most basic inverter-level data acquisition system typically captures dc volts, amps and power on the input side of the inverter, and ac volts, amps, power and energy harvest on the ac side of the inverter. These data are frequently reported graphically via bar charts for various time periods (hour, day, month or year).
More advanced monitoring systems can capture environmental conditions or detailed data from subarrays, strings or even individual modules. It is also possible to monitor utility grid-power quality and stability by tracking grid voltage and frequency variations outside the IEEE 1547 windows and report the duration of any outages.
Monitoring instantaneous building demand and net energy consumption is another option. If the building load is monitored, it is possible to compare the ac energy consumption at the facility against the PV array production. This may have value both for PR purposes and as an educational tool. It may also allow facility managers to become aware of, investigate and monitor other energy-saving opportunities at the facility.
Note that if a building has a preexisting automation system, the PV data acquisition system may need to have network compatibility with that system. This depends on the level of functionality and integration desired by the customer.
Graphical interface. It is a good idea to “walk through” a vendor’s web portal before making purchasing decisions. If an interface is difficult to navigate, lacks detail or does not allow for managing work orders, the monitoring solution may not prove useful for O&M purposes. Once you have selected a provider, it may not be possible to overcome issues like this— short of finding another provider.
Another thing to consider is the degree of personalization possible for a web portal’s user interface and the relative effort involved. The ability to customize web portals merits consideration: If it is not possible to brand a portal with your logo, the monitoring system may not meet your marketing needs. Your customers may have similar branding needs. Some third-party data monitoring companies provide software customization free of charge. Some products, such as the SMA Sunny Portal, allow customers to modify the appearance of the website. Other solutions allow little to no customization.
“As the market continues to mature, costs are coming down and customizable energy monitoring is becoming available all the way down to the residential level,” notes Robert Schaefer, CEO at AlsoEnergy, a provider of renewable energy monitoring solutions. “All users want a direct relationship with their purchase,” he explains. “The user base is getting more sophisticated in its purchasing decisions.”
Consider whether the content being displayed can be varied easily, based on whether the viewer is the facility owner, system owner, financial backer or O&M provider. If the intended viewer is the general public, consider what kiosk or wallmounted displays are offered, as well as the cost and connectivity requirements.
If the web portal is primarily used for O&M purposes, you may want to select a system that allows for crosschecking performance at a variety of sites in the same general vicinity. Data acquisition systems themselves can and do fail, so this feature may provide additional insight into potential data acquisition problems or into other PV system problems. It may also be important to select a portal that includes performance ratio indicators or other quick indicators of general system health.
If the system is designed to generate error or alarm signals, consider how this feature operates. Faulty alarms and excessive email or text messages often prompt integrator complaints. To the extent that alarm triggers are configurable, it is possible to reduce or eliminate false alarms. If the source of the alarm requires corrective action, it may be possible to schedule service calls and keep maintenance logs from the O&M portal. Companies interested in managing a fleet of PV systems should consider a monitoring system with this functionality.
Contractual terms also vary. Some web portals are free with equipment purchase; others incur annual fees. Some vendors offer multiple levels of service and tiered fee structures. Be sure to determine the cost and terms of service before selecting a monitoring solution.