Understanding the selection of three photovoltaic module temperature monitoring sensors – All in one diagram

For every 1°C increase in the temperature of photovoltaic modules, their power generation efficiency decreases by 0.3%–0.5%. During summer, the backsheet temperature of modules can exceed 65°C, leading to power losses of over 15%. However, many power plant operators focus solely on the ambient temperature while neglecting the actual module temperature – at an ambient temperature of 35°C, the module temperature may already reach 60°C, representing a difference of 25°C; the resulting power generation losses can be vastly different. Without proper monitoring of photovoltaic module temperatures, evaluating a power plant's efficiency is like the blind men describing an elephant – incomplete and misleading.

• 1 Sensor Types: How to choose between Pt1000, PT100, or NTC

  The core standard for photovoltaic module temperature monitoring is IEC 61724-1, which recommends the use of Pt1000A-grade platinum resistance Temperature Sensors. There are three reasons for this recommendation: the sensitivity of the PT1000 is four times that of the PT100, resulting in a smaller linear resistance error; the four-wire connection eliminates the influence of conductor resistance, achieving a measurement accuracy of ±0.15°C; and its long-term stability outperforms that of NTC thermistors, with an annual drift of <0.05°C. NTC thermistors (10K 3950) offer the advantages of fast response time and low cost, making them suitable for large-scale distributed deployments; however, their accuracy ranges from ±0.2°C to ±0.5°C, they exhibit strong nonlinearity, and require periodic calibration over extended periods of use. The PT100, as an entry-level option, features a three-wire connection with an accuracy of ±0.5°C, making it ideal for small and medium-sized power stations with limited budgets.

• 2 Output Signal: How to choose between 4–20 mA and RS485?

  The 4–20 mA current signal offers strong immunity to interference and a transmission range of over 500 meters, making it suitable for traditional PLC data acquisition systems and the most commonly used output method for temperature transmitters in photovoltaic power plants. The RS485 digital signal (Modbus-RTU protocol) supports multi-point networking; a single bus can connect up to 32 temperature sensors, making it ideal for IoT monitoring platforms in large-scale photovoltaic power plants. Recommendation: For distributed power stations with a capacity below 50 kW, the 4–20 mA signal is sufficient; for megawatt-scale ground-mounted power stations, RS485 networking is recommended to reduce wiring costs.

• 3 Installation Location and Method: The surface-mount backplane provides the most accurate central temperature measurement.

  The IEC 61724-1 standard specifies that the temperature sensor shall be attached to the cell closest to the center on the back side of the photovoltaic module, avoiding the cell boundaries. This is because the temperature distribution in the module's central region is the most uniform, thereby accurately representing the average operating temperature of the entire module. The sensor shall be mounted using a self-adhesive patching method, in conjunction with thermal conductive silicone grease to ensure optimal thermal conductivity. Note: The sensor's shading area shall not exceed 2% of the cell area (as required by the standard); otherwise, it may adversely affect power generation. The protection rating shall be no lower than IP67 to ensure long-term stable operation in outdoor environments.

Photovoltaic module temperature monitoring is not an optional feature – it is a mandatory requirement for improving power generation efficiency. Selecting the right temperature sensor enables precise calculation of the Power Plant Performance Ratio (PR), timely detection of hot-spot issues, and optimization of heat dissipation strategies. Weilian Fengran Sensing Technology offers a comprehensive range of PT1000/PT100/NTC photovoltaic module temperature sensors, supporting multiple output options including 4–20 mA and RS485; these sensors comply with the IEC 61724-1 standard. Please feel free to contact us for product selection and consultation.