Why do solar power plants need weather monitoring station (WMS)?

Why is it necessary to install a weather monitoring station for your solar power plant?

Weather Monitoring Station (WMS) is one of the most crucial instruments installed in Solar PV Power plants. A weather monitoring station can be immensely helpful in monitoring the efficiency and performance of any solar power plant. The data from the WMS can be used to get many insights about the plant operation and possible avenues to increase the plant output. As we are aware, even a small decline in the plant efficiency can significantly affect the energy output and hence the ROI. This article tries to enlist all the possible benefits from a WMS to the plant owners.

What does a WMS do?

It is very important to understand that a WMS cannot help you change the weather parameters; but it helps you to analyze and predict them so as to get maximum output from your solar plant. Photovoltaic (PV) system performance depends on both the quality of the system and the weather. As the weather varies, the output of the PV system changes. Key factor affecting the PV system performance is the solar radiation data. But along with solar radiation data, the weather parameters like ambient temperature, relative humidity, wind speed, wind direction, atmospheric pressure and rain are the other important factors affecting the performance. The air temperature, relative humidity and module temperature have a significant influence on the efficiency of solar modules. The performance of solar modules is temperature-dependent. Module temperature gives an indication of change in efficiency of the modules. If the module surface temperature rises beyond the specified limit of the manufacturer, the efficiency of the panels will be reduced. This will give poor generation and will affect the plant performance. Data about amount and frequency of precipitation (rainfall) can help to explain low energy yields at high sun radiation. If we can accurately measure the total useable incident radiation under any environmental conditions then, we will be able to calculate if the PV system is generating electricity as per the expectations. The data of all these sensors can be used to schedule the maintenance of the plant.

Typically, a weather monitoring station monitors parameters such as solar radiation, other weather conditions such as wind velocity, wind direction, humidity, module temperature etc. Weather stations also calculate performance ratio (PR) of the solar power plant using all the captured data. The performance ratio (PR) for a solar power plant is defined in IEC 61724 [1] and is a metric commonly used to measure solar photovoltaic (PV) plant performance for acceptance and operations testing. The PR measures how effectively the plant converts sunlight collected by the PV panels into AC energy delivered to the load to what would be expected from the panel rating. This data can be accessed over cloud as well.

How does a WMS help improve the plant performance?

Data from the WMS helps in planning out the maintenance activities. For optimum operations, it is necessary that the solar panels are cleaned periodically. The decline in efficiency, observed in the WMS data can prompt the user to carryout these maintenance activities. Weather data and weather prediction can help in scheduling the maintenance and repairs. Doing maintenance and repairs at wrong time could prove to be a costly affair.

Wind velocity is important from the plant safety perspective. The heavy wind loads at site may cause damage to the PV modules. With accurate wind speed and direction data, user can take necessary steps to prevent damages and loss. Various types of sensors, like cup type mechanical sensors and ultrasonic type sensors are available and depending upon the requirements, one can choose the correct sensor.