SEVEN Self-Cleaning Irradiance Sensor (3S-SCIS): Clean Sensor and Correct Data

Any O&M service company would tell you that the main issue with irradiance sensors in dusty areas is neglect of the sensor on the mounting structure. People clean the modules regularly, but forget about the small sensor which is covered by dust after several weeks. As a result, the sensor measures less irradiance than it should and the performance ratio seems better than it is.

SEVEN Self-Cleaning Irradiance Sensor (3S-SCIS) is specifically designed to deal with this problem. It is an irradiance sensor based on PV reference cell with built-in self-cleaning mechanism, and, therefore, is always clean.

Why Is Important to Keep Irradiance Sensor Clean?

If the sensor is dirty, the measured irradiance will be lower than the irradiance at the site. As performance ratio measures the efficiency by dividing energy produced by energy available, the lower irradiance will result in inflated performance ratio.

And that is why in IEC 61724-1:2021 (8.2.5 and Table 7) the soiling of irradiance sensors must be prevented in the case of class A monitoring with at least weekly cleaning of the sensor for standard installations. Weekly cleaning on a remote large installation involves many trips and much work. The 3S-SCIS cleans automatically.

How Does 3S-SCIS Work?

There are three components of the system: irradiance sensor, water tank with pump, and electronic panel.

• Automatic cleaning: by default, the sensor is cleaned once a day at a scheduled time from the user interface (GUI). Additional up to three cleaning periods a day can be programmed, if required at your site.
• Water consumption: During regular cleaning of the device, its annual water consumption reaches around 36 litres per year. The 18-liter tank thus requires refilling only twice a year.
• Operation in winter: Pure water is used when temperatures exceed 0 °C. When temperature drops below 0 °C, pure water is mixed in a ratio of 65/35 with antifreeze.
• Flexibility of installation: The standard length of the water hose equals 5 meters and may be extended up to 20 meters, with a maximum water line height of 5 meters.

3S-SCIS Self Cleaning Irradiance Sensor

Key Technical Characteristics

Each sensor is calibrated under a Class AAA sun simulator according to IEC 60904-2 and IEC 60904-4, using a reference cell calibrated by the ISFH Institute in Germany. All specifications are available on the 3S-SCIS product page and in the 3S-SCIS datasheet.

Who is the 3S-SCIS for?

• Large-scale PV systems needing to conform to IEC 61724-1 Class A measurements
• Power stations located in dusty or desert areas where sensors get dirty in days
• Distant locations where each visit is expensive
• Asset owners and O&M providers looking for reliable PR calculations

If you want to calculate how much power is lost by dust on the modules, you will need to install SEVEN soiling sensors. And if you have doubts about rain being enough to keep panels clean, our article Do Solar Panels Need Cleaning, or Are Rain and Wind Enough? explains everything.

References

1. IEC 61724-1:2021, Photovoltaic system performance — Part 1: Monitoring, clause 8.2.5 and Table 7.
2. IEC 60904-2, Photovoltaic devices — Part 2: Requirements for photovoltaic reference devices.
3. IEC 60904-4, Photovoltaic devices — Part 4: Photovoltaic reference devices — Procedures for establishing calibration traceability.
4. SEVEN Sensor Solutions, Self Cleaning Irradiance Sensor – 3S-SCIS. https://www.sevensensor.com/self-cleaning-irradiance-sensor-3s-scis
5. SEVEN Sensor Solutions, 3S-SCIS Datasheet. https://www.sevensensor.com/files/d/en/3S-SCIS_Self-Cleaning-Irradiance-Sensor.pdf

Ouijdane BENAMAR Marketing Manager All Posts →