Occupancy detection chair sensor: An energy conservation tool

Abstract

Occupants' behavior inside buildings is a vital parameter in determining the building energy consumption. Occupancy density distribution is a wide uncertain parameter due to the difficulty in predicting the attendants' behavior. Currently, occupancy detection tools and technologies have been insufficient of determining the exact number of occupants and, thus, the space ventilation requirements are not set at its optimized values. This capstone project was part of a bigger project conducted at Purdue Polytechnic Kokomo to better improve the energy consumption used for ventilation and AC in buildings. The objective of this capstone project was testing potential energy savings in an office space by using an occupancy seat sensor. An experimental and parametric approach were followed. The project was led by one MET student (Mechanical Engineering Technology). The project built and tested a seat occupancy chair sensor that detects a seated occupant of 40 lbf and above. The chair was tested inside a controlled office room. The transmitter of the sensor was connected to a programmable logic controller (PLC) unit that detected and recorded the chair status along with changes in temperature. To investigate potential savings due to the usage of occupancy detection sensors in an office, a parametric case study was conducted. The study compared the cooling load required based on actual number of occupants present versus the peak load when no chair sensors were used. It was found that the case with chair sensors that detects the variable occupancy level can save 15% every month (May through September) of the required cooling load and of the power consumed. This figure can significantly double to higher values when considering higher occupancy density spaces such as theaters, class rooms, and large meeting rooms. The project revealed high impact on the level of understanding for students. Students performance and project outcomes were assessed against ABET learning outcomes: (a) apply knowledge, techniques and skills to engineering technology activities, (b) apply knowledge of mathematics, science, and engineering to engineering technology programs, (c) Conduct tests, measurements, calibration and improve processes, (e) Problem Solving: ability to identify, formulate, and solve engineering problems, and (f) Effective Communication: ability to communicate effectively.