Energy-Saving in Air Conditioners Using PLC Control and the SCADA Monitoring System

The promotion of energy-saving air conditioners (ACs) continues to increase. Therefore, this research proposes the implementation of automatic control and monitoring for AC fan evaporator and compressor speeds using a programmable logic controller (PLC) along with supervisory control and data acquisition (SCADA). The proposed system uses a room-temperature sensor, connected to the PLC and programmed with a ladder diagram. It is connected to a SCADA installed computer for monitoring and data logging. The testing involves three methods: conventional, manual, and automatic PLC-based. Over a four-week period, the conventional method consumed 193.6 kW⋅h, 198.7 kW⋅h, and 206.6 kW⋅h in energy, while the manual method consumed 160.5 kW⋅h, 160.1 kW⋅h, and 161.9 kW⋅h, and the automatic method 150.8 kW⋅h, 152.6 kW⋅h, and 154.8 kW⋅h using the trapezoidal composite rule, Simpson's composite rule, and ordinary methods, respectively. The main research contribution is the provision of an energy-saving system for air conditioners over a long duration using PLC. The PLC-based automatic-to-manual energy savings equate to 6.0%, 5.8%, and 4.4%; whereas 22.0%, 24.0%, and 25.0% for the PLC-based automatic-to-conventional method. Therefore, the PLC-based automatic control is deemed appropriate for electrical energy-saving.