E-Ref

The Entec Solar E-Ref is a reference module datalogger designed for permanent installation in operating PV plants. Where portable irradiance sensors like the E-Sens provide measurement support during testing campaigns, the E-Ref serves a different purpose: continuous, infrastructure-grade irradiance and temperature monitoring embedded into the plant's data acquisition chain.

The core principle is straightforward. The E-Ref connects to a calibrated reference PV module — a small module of the same technology as the plant's main array — and measures its Isc and Voc directly. From these two values it calculates plane-of-array irradiance and cell temperature, then outputs those values over Modbus to the plant's SCADA system at intervals as short as one minute. This approach has two important advantages over pyranometer-based monitoring: the reference module responds to the same spectral and angular effects as the plant modules, and the Isc/Voc method avoids permanent short-circuiting of the reference module (which would generate heat and degrade it), instead pulsing the measurement and protecting the module from hot spots.

The E-Ref/03 variant adds two additional measurement channels for bifacial reference modules — capturing front irradiance, rear irradiance, and cell temperature independently. This makes it the appropriate choice for bifacial arrays where rear-side contribution needs continuous monitoring for performance ratio calculations per IEC 61724-1.