Personal comfort systems (PCS) maintain the occupant’s preferred thermal environment and expand his thermal comfort experience under varying environmental conditions. Among PCSs, radiant-based systems are popular due to their comfort and energy efficiency. A personal cooling radiant desk (PCRD) in conjunction with conventional heating, ventilation, and air conditioning (HVAC) has proven to reduce energy costs. A system’s energy and thermal performance, however, depends on various factors making it important to identify the optimal design parameters of a PCRD coupled with HVAC system in an office space. To optimize the energy and thermal performance of the PCRD-HVAC system, a numerical/mathematical model is developed simulating different design parameters. The model uses an artificial neural network (ANN), combined with a multi-objective genetic algorithm (MOGA) to identify the optimal design parameters. The decision variables include the supply temperature, the temperature, and the flow rate of chilled water flowing inside the desk. The study’s findings show that the optimal design parameters achieved a balance between thermal comfort and energy efficiency. The recommended design parameters result in an annual energy consumption of 3880 kWh and a predicted percentage of dissatisfied individuals (PPD) of 6 %. The experiment is carried out to validate the model showed a maximum relative error of only 12.54 %. The results of this study have important implications for designing sustainable cooling solutions for office spaces in hot climates. The successful optimization of the PCRD system highlights the importance of balancing energy efficiency and thermal comfort in designing sustainable cooling solutions.

Desiccant – dew point evaporative based cooling systems is known to be an effective system for the ventilation and cooling of poultry houses in hot and humid climates. However, they suffer from high water consumption that hinders their application in desert regions. In this work, it is proposed to integrate a water reclamation unit with the cooling system to produce water from the adsorbent’s humid regeneration stream. The performance of the hybrid cooling and water reclamation unit is evaluated for two desiccants: conventional (silica gel), which is cheap but has low water capacity, and novel (MIL-101-Cr, a type of metal organic framework), which is expensive but has high water capacity. The system was sized, and its operation was optimized using both adsorbents for a case study of a typical poultry house module located in the predominantly hot and humid climate of Qatar. This is achieved by developing numerical models for the different system’s subcomponents, which are then validated with the published data. An artificial neural network was trained using the numerical model of water adsorption to accelerate the computational time of the genetic algorithm used for the performance optimization. A lifecycle cost comparative analysis is conducted to determine the integrated system most cost-effective adsorbent.

Over the entire cooling season, it was found that the hybrid system using MIL-101-Cr resulted in 17% and 48% reduction in the thermal and electrical energy consumption compared to the one using silica gel. This has offered thus a 27% lower operating cost with a payback period of 11 years using the current market price of MIL-101-Cr.

Meeting hygrothermal and air quality requirements in livestock dwellings is crucial for upholding production quality standards. However, ventilation and air-conditioning in such enclosures is very energy-intensive, especially amidst climate change and intensifying summer conditions. This is due to large surface areas, livestock densities, and contaminants’ generation rates. Hence, striving for more efficient passive cooling techniques is always a desired goal to reduce the anthropogenic emissions of the agricultural sector without compromising production quality. In this study, the energy savings’ potential of two passive systems in a poultry house located in the semiarid climate of Beqaa Valley, Lebanon, was compared. The first system is the conventional stand-alone direct evaporative cooler (DEC), which evaporatively cools the outdoor clean air to temperatures close to its wet bulb. The second system combines with the DEC, an earth-to-air heat exchanger (EAHE) that sensibly precools the ambient air and reduces its wet-bulb temperature. This can increase the cooling capacity of the DEC, which can save substantial amounts of energy while achieving similar, if not better, indoor conditions. To conduct this study, simplified mathematical models were developed for the DEC, EAHE, and the poultry house space, assuming a well-mixed air volume. After sizing the systems, simulation results showed that the stand-alone DEC system was not able to meet relative humidity requirements at all times unlike the proposed hybrid EAHE/DEC system. Moreover, the hybrid EAHE/DEC system resulted in 40% reduction in air and water consumption rates compared with the DEC system during the summer season.

The building industry challenges have led researchers to develop a personalized conditioning system aiming to create a microclimate comfort zone around the occupant. Radiant cooling become prevalent due to their potential in affording both comfort and energy saving. Consequently, this study investigates the performance of a personalized cooling radiant cubicle (PCRC) combined with a conventional heating, ventilation, and air-conditioning (HVAC) system in an office room in hot climates. PCRC performance is assessed by introducing a novel model that combines computational fluid dynamics (CFD) and mathematical simulation based on two criteria: the ability in creating a thermal comfort zone near the occupant at high set-point temperatures and the economic feasibility in terms of energy savings and pay-back period. The results demonstrate that PCRC (i) maintains a comfortable personal thermal environment in the desired zone (ii) reduces the thermal asymmetry (iii) improves the corresponding predicted percentage of dissatisfied (PPD) index. When compared to published experiment, it is shown that the developed model is valid with a maximum relative error of 5% underlining its accuracy and eliminating the need of a full-physics based model. Moreover, implementing PCRC reduces cooling energy by 18% compared to conventional system with a payback period between 6 and 7 years.

This study investigates the application of the evaporatively-cooled window system in hot and humid climates and assesses its seasonal performance and benefits in terms of energy savings. The validated system is a hybrid combination of solar chimney, window and evaporative cooler that induces a natural buoyant flow originated by direct solar radiation application.

As proper solar radiation data is critical in applying solar-driven technologies, an on-site weather station was established in Qatar for the measurement of several meteorological parameters for the entire year of 2016. The measurements represent actual validated data recordings in the city of Doha, mimicking harshly hot and humid weather conditions. The simple application of the evaporatively-cooled window on a typical office space subjected to such driving weather conditions was found to save 8.8% of the space total annual energy demand. During the summer, the performance of the system was enhanced by saving 11.3% of the space total daily heat gain. However, the benefits of the system diminished and were sometimes unfavorable during the winter due to its limited cooling performance caused by high humidity.

Personal cooling vests that incorporate phase change material (PCM) have been utilized to improve thermal sensation of people working outdoors in different fields (firefighting, construction, military, police, etc.). In this study, an integrated fabric-PCM and bio-heat model was validated through human subject testing to determine the extent to which it could detect thermal and comfort responses when varying the arrangement of a fixed number of PCM packets in the cooling vest. The modeling approach was utilized for given PCM melting temperature to determine the number of packets needed and their optimal arrangement at moderate (35 °C) and hot (40 °C) environments for 45, 60 and 90 min working durations. The findings showed that when full coverage of the torso is not needed, optimal arrangements were those having full back coverage with the remaining packets on the upper front. Lower front cooling did not show significant improvement in comfort over upper front cooling. That effect was more evident when lower front PCM packets were used at the 40 °C hot environment. As the working duration increased, less differences were detected in skin temperatures and comfort between the optimal and worst cases since a higher PCM coverage area was necessary.

An evaporatively-cooled façade system, composed of a Photovoltaic thermal (PVT), evaporative cooler, and evaporatively-cooled façade, was previously developed. In this study, a control algorithm for the system parameters is implemented and applied on spaces with evaporatively-cooled façade to generate the least possible façade temperature, and consequently maximum possible energy savings. The optimization of the system parameters is expected to overcome the limitations of using evaporative coolers in humid countries. The application of the control algorithm managed to increase the reductions in the façade heat gain from 33.5% to 38.3%.

The system, integrated with the control algorithm, is then applied throughout the year on spaces located in Doha (Qatar) and Riyadh (Saudi Arabia), mimicking cities with harshly hot humid and dry weather conditions, respectively. The daily and monthly performances are further investigated in four different space orientations (i.e., north, east, south, and west). It was found that the application of the system can halve the highly glazed façade heat gain during the summer, in all orientations, and may have adverse, yet desirable effect during the winter. The integration of the control algorithm managed to reduce differences in system performance between dry and humid locations, thus generating total annual savings of up to 21.8% in any typical city of the Arabian Gulf.

Energy efficiency in buildings is crucial for the design of sustainable cities, especially in hot climates where demands are high. This study investigates the impact of the shading optical properties on the space energy demands when brise soleil is installed in offices with one fully-glazed façade in four different orientations. The criteria for the selection of best shading property are an office with minimal possible total energy demand and maximum outdoor view without any occupant sensation of visual discomfort caused by glare at any time of the year. In addition, this study examines the feasibility of integrating light dimming control to these offices.

A simulation model of an office space with external shading on a fully-glazed façade in one pre-selected orientation was developed and validated. Parametric studies on the shading reflectance and transmittance properties were conducted and their effects on spaces energy demands were observed for Qatar’s climate, mimicking a developing country with harshly hot weather conditions. In south-oriented offices, savings caused by the addition of brise soleil reach 36.3%; unreflective or barely transmissive slats are recommended and light dimming control is unjustified. Moreover, unreflective opaque shading without light dimming control is found to be optimal in east and west-oriented offices as it saves 37.2% of the space overall energy demand. In contrary, installing highly-transmissive shadings with light dimming control is justified in north-oriented offices as it keeps full outdoor visual sight and still saves energy of up to 11.6%.

A growing interest has been recently demonstrated in studying the thermal resilience of buildings that goes beyond minimum standard requirements to meet performance targets under extreme climate changes. However, there is currently no universally agreed-upon metric for measuring thermal resilience. Therefore, this study focuses on quantifying the thermal resilience of office buildings during a power outage disruption. This is achieved by developing a simplified straightforward model that is based on rational definition. The metric evaluates the number of safe and comfortable hours before loss of productivity for a typical hot office day based on two criteria: thermal habitability and passive survivability. When one of these conditions is jeopardized, the number of hours is recorded by performing energy simulations that account for different ranges of office building parameters. The simulation results are expressed in the form of a multi-variate linear regression equation. The minimum office thermal resilience (OTR) is found to occur at relatively large window to wall ratio (WWR), large solar heat gain coefficient (SHGC), and low external wall thermal capacity (kappa_w). To validate the developed simplified model, experiments are conducted in the Energy Efficiency and Building Design Laboratory located at Qatar University. Fair agreement is revealed between the energy simulations and the experiment, with a maximum relative error of 12%. Furthermore, the linear regression model developed in this study accurately predicts the office thermal resilience metric (OTR), with a mean relative error of 10% when compared to both the simulations and the experiments.