| At the present time, the concept of scientific development, the strategy of sustainable development, and the pressure from many aspects such as environment, economy and energy source, put forward higher request on building energy efficiency. Existing public buildings, which are of large quantity and broad range, have tremendous potential of energy saving. Especially their centralized air-conditioning systems, which are suffered some problems both in prevenient design and current operation, are in irreasonable situation of energy use presently, and need energy-efficient retrofit and optimization immediately. Besides, the goal of saving energy by 50% and corresponding prescripts in Design Standard for Energy Efficiency of Public Buildings (GB 50189-2005), also put forward request on energy-efficient retrofit and optimization to air-conditioning systems in existing public buildings.To make retrofit and optimization aimed, this thesis investigates and statistics air-conditioning systems and their energy consuming indices in existing public buildings. Firstly, based on design examples publicized by the journal of HV&AC, the investigation and statistics was implemented on the form of cold source and heat source, the form and the temperature difference between supply and return water of chilled water system, the mode of air handling and the form of airflow organization, and the form of automated control and measurement, in 94 public buildings. Then, with the emphasis on office buildings combined multi-function in hot summer and warm winter zone, some energy consuming indices were calculated and counted, such as installed chiller capacity per unit floor area of conditioned space, refrigerating coefficient of performance (COP) of chiller, efficiency ratio (ER) of axial power to transferred heat quantity in chilled water system, installed power of air-conditioning system and its main equipments, and the proportion of each main equipment taken in air-conditioning system. The investigation result was gathered and recorded in a database of centralized air-conditioning systems in existing public buildings, which had been built in this research. At the same time, linked with Design Standard for Energy Efficiency of Public Buildings, analysis and research on the distributing and change pattern of each form of air-conditioning system and each index of energy consumption in buildings with different types and scales in different zones, was implemented too. Both trumpet phenomena in installed chiller capacity per unit floor area of conditioned space, and spindle phenomena in installed electrical power per unit floor area of conditioned space or unit cooling capacity of air-conditioning system and its main equipments, were found during this research.This thesis also analyzes and explores the application of energy-efficient techniques in reforming and optimizing air-conditioning system, concerned on the analysis of cooling storage capability of fire protection pool, power calculation of pumps in variable primary flow chilled water system, influence on terminal unit performance of chilled water with big temperature difference and small flow capacity, and the approach of cooling tower and supply water temperature of free-cooling by cooling tower in transition season. Applicable situation and technical issues of these retrofit schemes are summarized and discussed too. Furthermore, this thesis analyzes and explores the notion of operation and the status and prospects of the development in our country of Energy Service Company (ESCO) under Energy Performance Contract (EPC) and Continuous Commissioning (CC) standing for commissioning, and compares their simple payback period and other characters. At last, it introduces both computer simulation and benchmarking involved in energy audit, by which it was considered both to form impetus and to evaluate schemes of energy-efficient retrofit and optimization. |
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