Building environmental performance model for variable air volume systems in air-conditioned high-rise buildings in sub-tropical climates.

摘要

As Hong Kong's economy prospered in the 1950s, air-conditioning became the norm as part of the building services designs for office buildings. Unfortunately, Cantonese speakers translated the term ‘air conditioning system’ into something which literally meant ‘cold air system’. The concept of indoor environmental quality (IEQ) was never properly rooted in the minds of users. Since the energy crisis of 1973, engineers have endeavoured to implement energy conservation in buildings. Unfortunately, the effort has often resulted in energy saving which ignores the fundamental delivery of indoor satisfaction. Hence, either energy is conserved sacrificing IEQ, or additional energy is consumed for cooling of occupant. These misconceptions prompt the development of an integrated design and operation protocol based on a so-called Building Environmental Performance Model (BEPM).; This project started with a concept of integrating the four basic indoor environmental qualities namely, thermal comfort, indoor air quality, visual and aural comfort. An overall indoor environmental quality index is derived to describe the state of the mind of a user in a balanced state with the indoor environment. A new portable instrument was designed for the purpose of assessment on site. This instrument was used to sample over 400 workstations in air-conditioned office premises. The results were validated by comparing with results obtained from a large scale IEQ study conducted in Hong Kong by the Department of Building Services Engineering prior to this project.; The Building Environmental Performance Model then links the IEQ and the building energy consumption together. It treats a building as a system. Energy consumption in the building services systems is the input to this system with the IEQ as the output. The BEP model incorporates two main modules: an adaptive comfort temperature control module (ACT), and a new CO₂ demand control module (nDCV). These two modules take an innovative approach to maintain satisfaction with the IEQ with optimum energy consumption. They provide a rational basis of effective control. The development of the model is based on extensive and intensive in-office study with reliable data, building calibration curves, and a new protocol to determine the most representative locations of controlling sensors.; The BEP model was built into an algorithm for implementation in a Direct Digital Control system. It was used in a longitudinal monitoring study in a typical Hong Kong office, so that the usefulness of the model could be verified.; Other than the development of a very useful portable IEQ logger, this project has developed a number of building calibration and monitoring protocols for real life application. In particular, a ventilation model was developed which is based on CO₂ profiles and occupant head count, and can estimate the various airflow quantities in a zone. This model can improve the operation and maintenance practices in building services engineering, because these flows have not previously been successfully quantified.