Automated PLC-Based Power Saving System for Classroom Electrical Loads Using Real Time Clock, Sensors, and Night-Time Cutoff Mechanism

The growing demand for electricity in educational institutions usually results in energy wastage by continuous use of electrical appliances such as lights and fans, even during idle time in classrooms. The remedy for this is through a smart and automatic system of managing power use effectively. In this paper, an effective solution by using a Siemens S7-200 Programmable Logic Controller (PLC) trainer kit with an embedded real-time clock (RTC) for scheduling is presented. The system is designed to regulate classroom electrical loads based on the institution's schedule, such that devices are utilized only when required. In order to further improve its decision-making, the system also includes a number of sensors like a Light Dependent Resistor (LDR) to track ambient light intensity, a temperature sensor to determine fan usage according to thermal condition, and an infrared (IR) sensor to determine occupancy. A contactor mechanism is also included to automatically switch off the power supply to classrooms or even blocks during nighttime hours, saving standby energy unnecessarily. The prototype was successfully designed and piloted in a real school setting, demonstrating efficacy in conserving electricity use by about 28%. The system is economical, scalable, and simple to maintain, providing an efficient and sustainable energy management solution for schools in the quest to improve efficiency and lower operational costs.