Onsite weather sensors provide valuable data points on parameters that impact solar plant performance. Parameters such as solar irradiance, wind speed, wind direction, air pressure, relative humidity, and module temperature can all be measured with the appropriate solar plant weather sensor. Each of these has the power to affect the amount of power produced. Knowing or predicting weather data can help maximize output of your solar plant. It helps to analyze performance deviations and avoid unnecessary site visits. It’s common knowledge that having a plant running free of errors, and producing the maximum amount of power, is vital to the return on the solar PV investment.

Many studies have been done on the importance of these parameters on solar PV arrays and provide an estimate of their effect on monthly energy production. Their significance has led to the development of several performance models and software tools to quantify the outcome of the performance of PV systems. One of the main differences between these PV system performance models is the extent to which these environmental factors are taken into account. Models also vary in the approach taken to calculate the operating temperature of the PV array and the incident irradiance falling on the surface of the array.

In order to illustrate how system performance works in terms of weather, let’s take a look at a couple of examples:

Example 1 – Module temperature and solar plant performance

Module temperature plays an important role in plant efficiency. Solar energy reduces as cell temperature rises, lowering the conversion efficiency of the cell. Analyzing the data provided by a module temperature sensor may help explain if an unexpected drop in power production is due to a rise in cell temperature.

In the example below we show a 650kW plant on a winter day. The chart on the right (below) shows the production was only 40kWp. To troubleshoot this deviation in solar power production, we can look at the weather sensor data in the chart on the left. The irradiance that day was healthy at 800W/m^2 peak but, when looking at the module temperature and ambient temperature we can conclude that it was snowing overnight. The melting snow can explain the low production during the day. If this solar PV plant did not have a weather sensor installed it, would be difficult to determine why the production was so low when all the inverters were working properly. It would also be impossible to prove what happened when viewing the low production in the monthly production summary report.

Solar Module Temp and Poduction Graph

Example 2 – Influence of soiling on solar plant performance

According to a recent study to predict energy loss in solar PV plants, dry climate photovoltaic system efficiency can decline by an average of 0.2% per day. Regularly cleaning solar panels is critical to optimum performance. Using an onsite weather sensor for solar irradiance, observing a slow decline in efficiency over time and analyzing this can help O&M providers to create the most cost-effective maintenance schedule.

The graphic below illustrates the impact of soiling on the solar plant production. The box in black outlines production after cleaning.

Using Solar Plant Weather Sensors with Solar-Log®

Solar-Log® products represent a key aspect for sustained profitability in the solar industry. The advanced data logging and energy management platform provides key metrics including bench-marking performance, advanced analytics, diagnostics and troubleshooting.

The Solar-Log® software enables you to connect over 1,000 components including inverters from all brands, and visualize it into one easy-to-use platform. The primary objective is to detect system failures, performance issues, and communication issues to the field service team immediately to ensure minimum downtime. High-quality solar plant weather sensors from manufacturers like Lufft and Rainwise can be connected to increase the accuracy of error detection.