Design and implementation of a low-cost datalogger for solar irradiance and PV module temperature

Photovoltaic module temperature and solar irradiance are two essential parameters that greatly affect the performance of solar plants. The measured information concerning these parameters is needed to size as well as predict future energy production of the plant. These data are often available at hourly intervals or more from meteorological stations and are expensive to acquire depending on the number of data points needed or from websites linked to satellites. Consequently, a method that can provide data at smaller time intervals is required to capture changes in irradiance and temperature. This paper presents a simple and cost-effective datalogger that measures the irradiance, relative humidity, module, and environmental temperatures. It used a 50 W photovoltaic module as an irradiance sensor. LM35 and DHT22 sensors were used for PV module and ambient temperature measurements, respectively. An interrupt service routine function implemented with the Arduino Mega microcontroller ensured a repetitive switching sequence of parallel resistance networks and the storage of desired current and voltage coordinates every 4s from 6 a.m. to 6 p.m. The irradiance computed was based on power at the maximum point with a load-switching network and in a short-circuit condition. The entire cost of the datalogger system was 153.12 euros, and major results show that the power at maximum power point method and ambient temperature give the best estimate of the photovoltaic module temperature. Consequently, the irradiance determined by the maximum power point method with ambient temperature can be used to evaluate the performance of photovoltaic modules using the single-diode model.