Monitoring Batteryless PV Systems: Page 2 of 5

Intermediate

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A monitoring system can help assess PV system performance in real time or over a duration of time, and provide on-site and remotely accessible information for system owners and installers, and the general public.
Batteryless PV monitoring systems provide Web portals for remote, online access to the system through a computer, smartphone, or tablet.
The Fronius Datamanager is a wireless data logger that comes preinstalled in new inverters, and can be retrofitted to older models.
Solectria’s SolrenView DAS Gateway can monitor up to 16 inverters and owners can opt to share data publicly.
While net-energy meters and PV production meters both look like the ubiquitous kWh meter, it’s their position in the system that defines what they are monitoring: A net meter is placed between the AC service entrance and the utility grid connection.
While net-energy meters and PV production meters both look like the ubiquitous kWh meter, it’s their position in the system that defines what they are monitoring: A PV production meter is positioned between the inverter and the AC service entrance connection.
PV system data can be displayed via a wireless tabletop unit, like the SMA America Sunny Beam.
A current transducer snaps closed around a wire to measure current via induction.
Data can be conveyed from the data logger to the display or network connection via dedicated cable, wirelessly (as shown), or over power lines.
Most monitoring systems display very similar data, albeit in different visual interfaces. The biggest difference is that MLPE systems, like this Enphase Enlighten display, allow monitoring of individual PV modules.
Schneider Electric’s Conext Monitor 20 can monitor data from up to three Conext RL inverters.
PV monitoring options offered by inverter manufacturers, such as Solectria’s SolrenView (above), offer similar features and customizable views.
The Enphase Envoy collects data via the power lines from Enphase microinverters; besides an AC power supply, no additional wiring is necessary.
The SolarEdge mobile app allows monitoring system performance from almost anywhere. Most portals also provide email alerts.
ABB’s Aurora Vision Web portal displays data from each microinverter. The eight inverters in this system appear as overlapping lines on the graph—each inverter’s production has been nearly identical for the week shown, indicating that the system is performing well.

Network connections are required to send data from the acquisition system to the Internet. The Internet connection can be made wirelessly via a cell or satellite modem, or using a hard-wired connection, such as cable, DSL, or fiber-optic lines. The monitoring system’s data logger or gateway is connected to the router (and on to the Internet).

Data display options include local displays or Web portals. Local monitoring on an inverter or remote tabletop or wall-mounted display usually includes array and grid voltage, current, cumulative energy, and power.

A Web portal is the viewing platform for the PV system data, displayed via a computer, smartphone, or tablet. Multiple portals may be available for one PV system, with one a publicly available version offering a few details, and another (password-protected) providing enough information for maintenance and troubleshooting. Web portals can be branded with logos, and customized with site-specific information such as amount of carbon dioxide offset or the dollar value of energy generated. Reports on historic system production (for days, months, or years) can be created and downloaded from a Web portal as well.

Communications for monitoring can be entirely wireless, or rely on hardwired network cables (like CAT5 or CAT5E Ethernet cables) to move data from the inverter to the data logger or gateway, and on to the Internet via a router. Data from individual inverters can be transmitted over power lines (power-line communications; PLCs); Bluetooth; hard-wired Ethernet cables; or wirelessly.

Power supplies, like AC wall cubes, may be needed for an external data logger/gateway, cellular modem and energy meters. Per the National Electrical Code, the inverter AC output circuit must be dedicated to the PV system and cannot provide this 120 VAC power source.

Monitoring Capabilities & Different System Types

The data hosted by Web portals varies slightly by system topology (i.e. MLPEs vs. string inverters) and by equipment manufacturer, but the data displayed by monitoring portals is very similar across different platforms. For a string inverter system, at minimum, the portal displays kilowatt-hours of production for each inverter on a daily, weekly, monthly, yearly, and lifetime basis. Inverter power, reported at 15-minute or hourly intervals; DC and AC voltage; and current are also commonly measured parameters. The portal will also indicate if there is a potential problem with an individual inverter, for example, if the data is not being transmitted, or the power or energy levels are outside normal thresholds.

For MLPE systems, data provided by a manufacturer’s portal is more in-depth, as the module-mounted electronics allow easy access to each PV module’s power (current and voltage) and energy data, plus historical system energy data (daily, weekly, monthly, yearly, and cumulative kilowatt-hours). Portals can indicate module-level failures or performance issues, and graphically represent a “bird’s eye view” physical layout.

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