How to find out correct number of weather monitoring stations for a PV solar plant?

One of the most common questions that our clients ask us is what is the number of WMS that they need to install so as to satisfactorily monitor the complete plant. The number of WMS required to properly monitor a solar plant depends on the size of the plant. As a rule of thumb, for smaller plants of capacity in range of 5 MW to 10 MW, a single weather monitoring station is sufficient.

For larger plants, multiple WMS must be installed. If plants are of medium size, i.e. 25-50 MW, then 1 primary WMS with 2 pyranometers (to measure Global Horizontal Irradiance GHI and Global Tilt irradiance GTI) and all the weather sensors must be installed. These medium size plants must also have multiple secondary weather monitoring stations with 1 Data logger, 1 pyranometer (to measure Global Tilt Irradiance GTI) and 1 module temperature sensor.

One might wonder why more than one WMS are required for larger plants. If the plant size is large, spanning over hundreds of acres, the weather throughout the site will not be consistent; rather, individual sections will have their own micro-weather which will be different from the micro-weather of other portions of the same plant.

The number of WMS required does not depend solely on the plant capacity. Other factor which determines the number of WMS required is the geographical distribution of the solar panels. Some times, due to hilly terrain, solar panels are installed at geographically distinct locations and as a result, the micro weathers vary considerably. Considering this, the number of WMS required will depend on the number of such ‘micro regions’ in the given site.