Photovoltaic Power Stations Key Data in Maintaince

A Comprehensive Guide to Sensor Systems in Solar Power Station Monitoring: From Irradiance to Insights

Solar power has become one of the fastest-growing renewable energy sources worldwide. As utility-scale solar plants expand, the need for accurate, real-time monitoring becomes critical. A solar plant monitoring system does far more than just track energy output—it ensures efficiency, predicts maintenance needs, and safeguards investments.

At the heart of these monitoring systems are sensors. From measuring sunlight with a pyranometer to detecting dust accumulation with a soiling monitoring device, sensors provide the data that operators need to optimize performance. According to IEC 61724-1, sensor systems even determine the official monitoring class of a PV plant, making them essential for both operational and financial reporting.

2. Why Do Solar Plants Need Sensors?

A solar farm is constantly exposed to changing environmental conditions. Without sensor systems, operators are essentially “flying blind.” Sensors provide:

• Performance benchmarking: By comparing solar radiation sensor data with actual output, operators can calculate the performance ratio (PR) of the plant.

• Fault detection: A drop in voltage, unexpected panel temperature, or sudden shading can be detected quickly.

• Predictive maintenance: Knowing when dust or heat is reducing efficiency helps schedule interventions before revenue loss occurs.

• Financial transparency: Investors and stakeholders rely on accurate PV monitoring systems to validate expected vs. actual production.

3. Key Types of Sensors in Solar Plant Monitoring

3.1 Irradiance Sensors

The most critical data for a solar plant is sunlight itself. Two main technologies are used:

• Pyranometer: A thermal or optical device that measures global solar radiation. High-accuracy thermopile pyranometers are required in Class A monitoring systems under IEC standards.

• Reference cell: A silicon-based solar radiation sensor built from the same material as PV modules, offering fast response but narrower spectral accuracy.

Both are often mounted in the plane of array (POA) to simulate the actual conditions of solar panels.

3.2 Temperature Sensors

Solar panel efficiency decreases as temperature rises. For example, a typical PV module loses ~0.4–0.5% efficiency per °C above its rated temperature.

• Module temperature sensors (e.g., PT100 or PT1000 probes) are attached to the back of panels to measure heat buildup.

• Ambient temperature sensors measure surrounding air temperature, usually housed in radiation shields.

Together, these sensors provide critical data for calculating the temperature-corrected performance ratio.

3.3 Weather Sensors

Environmental conditions beyond sunlight and temperature also affect plant performance:

• Wind speed and direction sensors: Protect plants from structural risks and assess cooling effects.

• Humidity sensors: Detect moisture levels that may contribute to module degradation.

• Rain gauges: Track precipitation, which can naturally clean panels or indicate potential flooding risks.

• Barometric pressure sensors: Useful for advanced meteorological modeling.

These sensors are usually grouped into a solar plant weather station, often installed near the center of the PV site.

3.4 Soiling & Dust Sensors

Dust, dirt, and bird droppings can reduce output by 5–20% in some regions. Relying on visual inspection alone often leads to unnecessary or delayed cleanings.

A soiling monitoring device measures the difference in output between a clean reference panel and an exposed test panel, or uses an optical dust sensor to quantify accumulation. This data allows operators to optimize cleaning schedules, balancing water and labor costs against energy losses.

3.5 Electrical Sensors

While environmental sensors measure external factors, electrical sensors measure what’s happening inside the system:

• Current sensors and voltage sensors at the string or inverter level detect mismatches or equipment failures.

• These feed into the PV monitoring system, helping detect inverter downtime, DC/AC conversion losses, and potential wiring faults.

3.6 Auxiliary Sensors

For specialized plants, auxiliary sensors provide deeper insights:

• Albedo sensors: Measure ground reflectance, crucial for bifacial PV plants.

• UV sensors: Monitor long-term module degradation.

• Tilt and orientation sensors: Ensure solar trackers are aligned correctly.

These sensors are not always mandatory but can unlock additional performance improvements.

4. Data Acquisition & Communication Systems

All sensors are only as useful as the system that collects and transmits their data.

• Data loggers record inputs from each sensor and feed them to a central monitoring platform.

• Communication protocols like RS-485 Modbus, LoRa, Zigbee, or Wi-Fi enable flexible integration.

• SCADA systems visualize, analyze, and trigger alerts for plant operators.

Reliability, redundancy, and cybersecurity are increasingly important as solar plants grow in scale.

5. Standards & Accuracy Classes (IEC 61724-1)

The IEC 61724-1 standard defines three monitoring classes for PV plants:

• Class A: Highest accuracy, requiring thermopile pyranometers, redundant sensors, and strict calibration. Used in utility-scale and investor-backed projects.

• Class B: Moderate accuracy, suitable for mid-size plants.

• Class C: Basic monitoring, often relying on silicon solar radiation sensors only.

Choosing the right class depends on project size, financial requirements, and operational needs.

6. Challenges in Sensor Systems

Despite their importance, sensors face several challenges:

• Calibration drift: Even the best sensors require regular calibration to maintain accuracy.

• Environmental exposure: Dust, UV radiation, and extreme heat shorten sensor lifespan.

• Maintenance costs: Cleaning pyranometer domes or replacing faulty modules adds O&M expenses.

• Integration issues: Different vendors may use different communication protocols, complicating data consolidation.

7. Best Practices for Reliable Monitoring

• Use at least two irradiance sensors (one POA, one GHI) for redundancy.

• Implement regular cleaning and calibration schedules.

• Choose rugged, weatherproof sensors designed for harsh outdoor conditions.

• Integrate all sensors into a centralized PV monitoring system with SCADA.

• Validate sensor data periodically against external benchmarks (satellite or drone data).

8. Future Trends in Solar Plant Monitoring

The future of solar plant monitoring will be defined by smarter, more connected systems:

• IoT-based wireless sensors for low-cost, wide-area deployment.

• AI-driven analytics for predicting faults before they occur.

• Drone and satellite integration to complement ground-based sensors.

• Digital twins of solar farms, combining sensor data with simulation models for real-time optimization.

These trends will reduce costs, improve accuracy, and help solar operators maximize profitability.

9. Conclusion

Sensor systems are the backbone of modern solar plant monitoring. From a simple pyranometer to a sophisticated soiling monitoring device, each sensor adds a critical layer of visibility.

By investing in accurate, reliable, and well-integrated sensor systems, operators can:

• Improve performance ratios,

• Reduce downtime,

• Optimize O&M costs, and

• Deliver higher ROI to stakeholders.

As solar power continues to scale globally, PV monitoring systems powered by advanced sensors will be the key to ensuring sustainable, reliable, and profitable operations.

Consider upgrading your sensor systems as a step toward smarter solar operations. Contact us for further details.