Performance Analysis of a Simplified Model of Cooling Load for a Typical Office Building

Abstract

Buildings are responsible for at least 40% of energy use in most countries of the world, and for up to 21% of greenhouse gas emissions globally. As this trend continues, real-time building load measurements are essential for dynamic load response control, understanding and improvement of load distributions and profiles, and for climate-responsive design, particularly in commercial buildings. The focus in this paper is the cooling load, which is the rate at which heat must be removed from the controlled zone to maintain the desired temperature. Estimation of maximum cooling load is necessary for sizing of cooling equipments. However, details needed for whole-building simulation are often unreliable or unavailable. As such, simplified models with reasonable accuracy and computational requirements are often used. A cyber-physical system, integration of physical sensors and mathematical model, is proposed in this paper for cooling load estimation. The physical sensor measurements are limited to outside air temperature, solar radiation, room air temperature, and building plug load. Meanwhile, resistance-capacitance (RC) concept was adopted to describe the physics and dynamics of the building envelope for its simplicity and reasonable computational requirements. The cyber-physical system was tested using a typical office having two thermal zones and compared with simulation results from EnergyPlus, a whole building simulation program. Phenomenon such as infiltration, inter-zone air mixing, and air moisture control were not taken into account for the model. Results are presented to determine the accuracy of the simplified model for cooling load estimation.