Fixed air change ventilation in a huge underground parking facility is a major energy consumption for a building. Variable and unidirectional flow and control by carbon monoxide (CO) sensors in a parking facility can help to reduce energy consumption. However, obstructions in the parking facility reduce the effectiveness of uni-directional flow. Also, siting of CO sensors at particular positions may not accurately reflect the CO level throughout the whole parking facility. This study proposes two energy-efficient approaches. The first approach is to reduce the ventilation rate based on the number of cars, which is determined by a parking guidance system. The second approach is a reversible zonal control system in relation to the human behaviour. Parking bays near access lobbies are always favoured. This behaviour is used to determine ventilation zoning. For commercial buildings, cars are parked for long periods of time, where CO and heat generated by cars can be removed within a certain period of time. All fan shafts are designed for zonal control and reversible mode, dynamically operated to effectively remove hot and contaminated air. This reversible zonal control system can remove the heat effectively within a shorter time, thus improving energy savings.
In hot and humid tropical countries, the air-conditioning system has a high energy usage in commercial buildings. This study introduces a static balance duct design method for a temperature dependent variable air volume system. Ducts are looped together, which cause the air to self-balance and minimize the pressure loss across the duct network. The static balance duct network can easily identify the critical zone of highest pressure loss. This zone appears at the longest duct length from the air source and is always consistent for different load conditions. The air supplied to this critical zone is controlled by the zone temperature sensor, which directs feedback to the variable frequency drive fan of the air-handling unit. The rest of the variable air volume terminal units are zone temperature controlled. The duct looping design mitigates the problems in pressure variations and complements the temperature dependent control strategy. An open office case study is carried out to demonstrate the merit of the static balance duct design method. An actual installation was completed in a shopping mall. The recorded temperature readings verified that the static balance duct network and temperature dependent variable air volume air-conditioning system is operational and functional. Approximately 27% energy savings is achieved compared to the constant air volume system. Practical application: The static balance duct design method is a combination of equal friction duct design method and a loop duct network. This static balance duct network can identify the critical zone of highest pressure loss and this zone is always consistent. In this temperature-dependent variable air volume (TDVAV), the variable air volume (VAV) terminal unit at the critical zone is eliminated. The zone temperature sensor at the critical zone provides direct feedback to the variable frequency drive fan. All other terminal units are temperature dependent. The static balance TDVAV system enhances energy savings, improves the performance of VAV system and reduces the faults for VAV systems.
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