ABSTRACT This research presents energy and exergy analyses of a new decentralized ventilation sys... more ABSTRACT This research presents energy and exergy analyses of a new decentralized ventilation system to adapt to the hot and humid climate compared to general centralized ventilation systems. A zone model of an office building was applied for a heat pump cooling system in Singapore. The cooling load capacity of the zone model was simulated using the building energy simulation software “TRNSYS” and energy and exergy analyses of the new ventilation system were carried out through numerical calculations based on the measured cooling load capacity. An effective energy solution for buildings was to increase cooling and ventilation efficiency. The energy and exergy analyses evaluated the performance of the various cooling systems. The research revealed that the new decentralized ventilation system adapted to the hot and humid climate had better performance compared to a centralized all-air system and to a chilled ceiling with centralized air handling unit system.
ABSTRACT This paper proposes a novel ventilation strategy for capturing CO2 with scheduled occupa... more ABSTRACT This paper proposes a novel ventilation strategy for capturing CO2 with scheduled occupancy diversity, and changes in recirculating ratio and infiltration rate. While many publications have described filters and a lamp that can efficiently capture and remove most pollutants (such as VOCs, dust, odors and viruses) to levels equivalent to those of conventional air dilution systems, no such system exists for CO2. This paper evaluates a strategy to recirculate air in the breathing zone through simulations with occupancy diversity factors from ASHRAE 90.1-2004 and Duarte et al.’s results for weekdays from 6 AM to 9 PM to evaluate a possibility of implementing a CO2 capture device. Using a lower indoor air recirculation ratio in spaces with high CO2 concentration is more effective at reducing CO2 concentration in the breathing zone. The results indicate that maximizing the air recirculation ratio by using the CO2 capturing unit could replace conventional air ventilation systems by sufficiently reducing the concentration of CO2 and supplying enough oxygen for occupational safety and health. Such a system could save air cooling or heating energy in buildings in hot or cold days or seasons, or when there are high outdoor pollution levels for a limited period of time.
The basic principle of low exergy building systems is the minimization of excess temperature grad... more The basic principle of low exergy building systems is the minimization of excess temperature gradients across building systems so that the quality of the energy supplied to the building better matches with the actual demand of the building. Several low exergy technologies which were developed at ETH, Switzerland were implemented in a small research laboratory (BubbleZERO) in Singapore to evaluate the performance of these systems for the tropics. In this paper, the indoor space conditioned by these technologies is analysed by computational fluid dynamics (CFD). Different sources of heat, water vapour and carbon dioxide have been modelled with suitable boundary conditions and emission sources., The CFD results have been verified with different numerical settings and the impact of different turbulence models and mesh densities on the accuracy of the CFD results has been studied. The results have shown that SST k-ω and Reynolds Stress turbulence models have close predictions while the s...
SUMMARY Typical infrastructure in office buildings does not facilitate the creation of a sustaina... more SUMMARY Typical infrastructure in office buildings does not facilitate the creation of a sustainable building, effectively using energy, materials, and space. One must recognize that sustainability doesn't only refer to the use of energy, but also to spatial quality, user comfort, and ease of facility management. Different from the commonplace hierarchical systems, our goal is to distribute infrastructure such that
We present the design, construction and operation of a novel building systems laboratory, the Bub... more We present the design, construction and operation of a novel building systems laboratory, the BubbleZERO—Zero Emission Research Operation. Our objective was to design a space to evaluate the performance of Swiss-developed low exergy building systems in the tropical climate of Singapore using an integrated design approach. The method we employed for evaluation in the tropics was to design and build a test bed out of the shipping containers that transported the prototype low exergy systems from Switzerland to Singapore. This approach resulted in a novel laboratory environment containing radiant cooling panels and decentralized air supply, along with a self-shading, inflated “bubble” skin, experimental low emissivity (LowE) glazing, LED lighting, wireless sensors and distributed control. The laboratory evaluates and demonstrates for the first time in Singapore an integrated high-temperature cooling system with separate demand-controlled ventilation adapted for the tropics. It is a functional lab testing system in real tropical conditions. As such, the results showing the ability to mitigate the risk of condensation by maintaining a dew point below 18 °C by the separate decentralized ventilation are significant and necessary for potential future implementation in buildings. In addition, the control system provides new proof of concept for distributed wireless sensors and control for reliable automation of the systems. These key results are presented along with the integrated design process and real-life tropical operation of the laboratory.
ABSTRACT This research presents energy and exergy analyses of a new decentralized ventilation sys... more ABSTRACT This research presents energy and exergy analyses of a new decentralized ventilation system to adapt to the hot and humid climate compared to general centralized ventilation systems. A zone model of an office building was applied for a heat pump cooling system in Singapore. The cooling load capacity of the zone model was simulated using the building energy simulation software “TRNSYS” and energy and exergy analyses of the new ventilation system were carried out through numerical calculations based on the measured cooling load capacity. An effective energy solution for buildings was to increase cooling and ventilation efficiency. The energy and exergy analyses evaluated the performance of the various cooling systems. The research revealed that the new decentralized ventilation system adapted to the hot and humid climate had better performance compared to a centralized all-air system and to a chilled ceiling with centralized air handling unit system.
ABSTRACT This paper proposes a novel ventilation strategy for capturing CO2 with scheduled occupa... more ABSTRACT This paper proposes a novel ventilation strategy for capturing CO2 with scheduled occupancy diversity, and changes in recirculating ratio and infiltration rate. While many publications have described filters and a lamp that can efficiently capture and remove most pollutants (such as VOCs, dust, odors and viruses) to levels equivalent to those of conventional air dilution systems, no such system exists for CO2. This paper evaluates a strategy to recirculate air in the breathing zone through simulations with occupancy diversity factors from ASHRAE 90.1-2004 and Duarte et al.’s results for weekdays from 6 AM to 9 PM to evaluate a possibility of implementing a CO2 capture device. Using a lower indoor air recirculation ratio in spaces with high CO2 concentration is more effective at reducing CO2 concentration in the breathing zone. The results indicate that maximizing the air recirculation ratio by using the CO2 capturing unit could replace conventional air ventilation systems by sufficiently reducing the concentration of CO2 and supplying enough oxygen for occupational safety and health. Such a system could save air cooling or heating energy in buildings in hot or cold days or seasons, or when there are high outdoor pollution levels for a limited period of time.
The basic principle of low exergy building systems is the minimization of excess temperature grad... more The basic principle of low exergy building systems is the minimization of excess temperature gradients across building systems so that the quality of the energy supplied to the building better matches with the actual demand of the building. Several low exergy technologies which were developed at ETH, Switzerland were implemented in a small research laboratory (BubbleZERO) in Singapore to evaluate the performance of these systems for the tropics. In this paper, the indoor space conditioned by these technologies is analysed by computational fluid dynamics (CFD). Different sources of heat, water vapour and carbon dioxide have been modelled with suitable boundary conditions and emission sources., The CFD results have been verified with different numerical settings and the impact of different turbulence models and mesh densities on the accuracy of the CFD results has been studied. The results have shown that SST k-ω and Reynolds Stress turbulence models have close predictions while the s...
SUMMARY Typical infrastructure in office buildings does not facilitate the creation of a sustaina... more SUMMARY Typical infrastructure in office buildings does not facilitate the creation of a sustainable building, effectively using energy, materials, and space. One must recognize that sustainability doesn't only refer to the use of energy, but also to spatial quality, user comfort, and ease of facility management. Different from the commonplace hierarchical systems, our goal is to distribute infrastructure such that
We present the design, construction and operation of a novel building systems laboratory, the Bub... more We present the design, construction and operation of a novel building systems laboratory, the BubbleZERO—Zero Emission Research Operation. Our objective was to design a space to evaluate the performance of Swiss-developed low exergy building systems in the tropical climate of Singapore using an integrated design approach. The method we employed for evaluation in the tropics was to design and build a test bed out of the shipping containers that transported the prototype low exergy systems from Switzerland to Singapore. This approach resulted in a novel laboratory environment containing radiant cooling panels and decentralized air supply, along with a self-shading, inflated “bubble” skin, experimental low emissivity (LowE) glazing, LED lighting, wireless sensors and distributed control. The laboratory evaluates and demonstrates for the first time in Singapore an integrated high-temperature cooling system with separate demand-controlled ventilation adapted for the tropics. It is a functional lab testing system in real tropical conditions. As such, the results showing the ability to mitigate the risk of condensation by maintaining a dew point below 18 °C by the separate decentralized ventilation are significant and necessary for potential future implementation in buildings. In addition, the control system provides new proof of concept for distributed wireless sensors and control for reliable automation of the systems. These key results are presented along with the integrated design process and real-life tropical operation of the laboratory.
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Papers by Hansjürg Leibundgut