User satisfaction and energy use behavior in offices in Qatar

The occupant behavior significantly contributes to the total energy use in buildings and its understanding is greatly needed in energy analysis/simulation studies. Uncertainties about the occupant behavior adversely affect the building performance predictability of the simulation models. As field data in Qatar on occupant energy use and behavior was unavailable, we conducted an environmental satisfaction and energy use survey in the city of Doha, Qatar in seven office buildings. Building occupants were highly satisfied with their work environments with respect to most of the environmental parameters excepting acoustics. Access to operable controls such as windows, thermostats improved their satisfaction. Subjects in private offices were more satisfied with their work environments. We noted the self-declared productivity of respondents to be high in general. It was significantly higher in offices with better occupant access to temperature controls. Noise level dissatisfaction was the highest in high partitioned cubicle offices and satisfaction was high in open plan offices. These findings provide vital design direction for new offices and environmental systems design and for managerial motivational campaigns. Practical application: Using field study data, we analyzed the occupant behavior and environmental satisfaction in offices in Doha, Qatar. The Middle East in general and Qatar in particular are known to consume enormous energy for buildings leaving a large ecological footprint. The finding of this study informs the designers of air-conditioning systems about the user behavioral patterns. Further, these findings help the building managers in designing targeted energy awareness/saving campaigns, as user motivation is vital in energy saving. ? 2018, The Chartered Institution of Building Services Engineers 2018.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Qatar Foundation funded this research through grant number NPRP 7-143-2-070

Building energy model calibration using automated optimization-based algorithm

Multiple numbers of Building Energy Simulation (BES) programs have been improved and implemented during the last decades. BES models play a crucial role in understanding building energy demands and accelerating the malfunction diagnosis. However, due to the very high number of interacting parameters, most of the developed energy simulation programs do not accurately predict building energy performance under a known condition. Even the energy models which are developed with the very precise assignment of parameters, there is always significant discrepancies between the simulation results and the real-time data measurements. Current study develops an optimization-based framework to calibrate the whole building energy model. The optimization algorithm attempts to set the identified parameters to minimize the error between the simulation results and the real-time measurements. Due to the high number of parameters, the developed optimization algorithm utilizes a Harmony Search algorithm as its search engine coupled with the energy simulation model to accelerate the calibration process. Moreover, to illustrate the efficiency of using the developed framework, a case study of the office building is modeled and calibrated and the statistical analysis was conducted to assess the accuracy of the results. The results of the calibration process show the reliability of the framework. - 2019This work was supported by the Qatar National Research Foundation (QNRF)/National Priorities Research Program (NPRP 7 - 143 - 2 - 070). Authors would like to acknowledge their supports through this research.Scopu

Evaluation of self-healing mechanisms in concrete with double-walled sodium silicate microcapsules

The objective of this study is to evaluate a new generation of self-healing materials that hold promise for better durability and performance. The in situ polymerization method was used to develop double-walled microcapsules. The microcapsules were prepared in a single batch process containing sodium silicate as the healing agent encapsulated in double-walled polyurethane/urea-formaldehyde (PU/UF) microcapsules. Double-walled microcapsules provide enhanced durability at high temperatures compared with single-walled microcapsules while preserving adequate interfacial bonding of microcapsules. A parametric study was carried out to investigate the effect of different parameters such as agitation rate, pH, and temperature on the performance of the microcapsules and to determine the optimum microencapsulation procedure. The prepared microcapsules were then incorporated into self-healing concrete beams. To monitor the healing process of the cracks, microcracks were created by imposing a certain magnitude of displacement in the middle of the beams. The healing process of concrete specimens was monitored and quantified using portable ultrasonic nondestructive digital indicating tester (PUNDIT). Results showed that lower pH and higher agitation rate and curing temperature improve the formation of microcapsule shells. Measurements of ultrasonic wave transmission time through the concrete specimens containing different contents of microcapsules were analyzed to quantify the healing rate. It was found that the healing rate in concrete beams with 5% microcapsules was higher in the first week in comparison with specimen containing 2.5% of microcapsules