Seven Sensor Cloud Sensor 3S-CS-MB

Technical Specifications of Cloud Sensor

What is a cloud sensor used for?

When solar energy generation drops, the first question is: is the problem with the system or with the weather? Looking only at total irradiance, the effect of weather conditions can be confused with system losses. Cloud sensors clarify this distinction.

For example, if there is a sudden drop in production during the day, and cloud ratio and diffuse irradiance increase simultaneously, this drop is most likely due to a passing cloud. Since the sensor provides this information, it becomes easier to distinguish whether the performance drop is truly due to the system or to atmospheric conditions.

This allows for more accurate interpretation of performance indicators such as PR, and enables users to improve energy efficiency by taking necessary measures based on cloud cover levels.

Working Principle of the Cloud Sensor

The sensor consists of two irradiance sensors operating simultaneously and a shadow band. The task distribution is as follows:

• The open sensor measures the plane of array irradiance (POA) on the panel plane without any shadowing. This value is the sum of direct, diffuse, and reflected components.
• The shaded sensor is continuously shaded by a shade band. Therefore, it only measures diffuse irradiance (DPOA). The shade band provides shading in accordance with the IEC 61724 standard.

The system ratios diffuse irradiance to total irradiance. This ratio indicates how much of the sky is covered by clouds, i.e., the cloud ratio. As cloud cover increases, the share of diffuse irradiance increases, and the cloud ratio rises.

What data does the SEVEN cloud sensor measure?

The sensor is not limited to a single cloud ratio value. By breaking down the irradiance in the panel plane into its components, it presents four separate data points.

How to Express Cloudiness: Percentage and Okta

The sensor displays cloudiness in two different units.

• In percentage terms: 0% indicates a completely clear sky; 100% indicates a completely overcast and dark sky.
• In oktas: An okta is a meteorological unit that indicates what fraction of the sky is covered by clouds. The sky is divided into eight equal parts. 0 oktas mean a completely clear sky, while 8 oktas mean a completely cloudy sky.

Okta is widely used in meteorology. However, percentage representation is more practical in technical analysis, reporting, and automation systems. Since the sensor provides both values, it meets both needs.

Can Cloud Sensors be Used in Tracker and Fixed Systems?

SEVEN Cloud Sensor can be used in every power plant installation. In tracker systems, cloud ratio data helps to position panels optimally. Since diffuse irradiance is dominant in cloudy weather, turning the panel directly towards the sun may not always be the most efficient option. The cloud sensor ensures that this decision is data-driven.

In fixed systems, the sensor continuously monitors cloud cover and feeds into performance evaluation. Production reports become much more meaningful when read in conjunction with the actual state of the sky at that moment.