IoT-Enabled Solar Powered Temperature and Relative Humidity Monitoring System for Cold Storages

Abstract

The manual oversight of environmental conditions within a cold storage facility proves laborious and prone to inaccuracies. In response, a cost-effective solution was developed and tested at the Pusa Farm Sun Fridge, aimed at providing real-time monitoring and recording of crucial parameters such as temperature and relative humidity (RH). The major components of the hardware are programmable microcontroller (Arduino UNO) with facility of data logging, DHT22 sensor (calibrated) to provide input to the datalogger/microcontroller; internet connectivity (using GSM mobile module SIM800A) to communicate the data to the web server ThingSpeak. The temperature and RH data of this IoT-based system was compared with data obtained from the Onset HOBO data logger (installed in the same cold storage) which is very expensive but widely recognized as the industry standard for indoor, outdoor, and underwater environmental monitoring. Validation against the industry-standard Onset HOBO data logger demonstrated strong correlation, with temperature and relative humidity achieving an R² value of 0.99 and 0.96, respectively, with data values closer to 1:1 line indicating very good performance of the developed system. The mean absolute error (MAE) was found to be 0.0033°C and 0.0004% for temperature and RH, respectively. The IoT based system was also experimented during the storage of potatoes. Notably, the system was powered by solar panels, ensuring uninterrupted operation even during power disruptions, with the added flexibility of adjusting data collection frequency through programming. Compact, portable, and notably cost-effective compared to traditional monitoring instruments, it holds promise for widespread adoption across various sectors. While the system currently focuses on monitoring, future iterations may incorporate control functionalities based on the gathered data.