Energy recovery from fresh water supply pipelines at entrance of high-rise buildings in Hong Kong

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Energy recovery from fresh water supply pipelines at entrance of high-rise buildings in Hong Kong

 

Author: Liu, Yang
Title: Energy recovery from fresh water supply pipelines at entrance of high-rise buildings in Hong Kong
Degree: M.Eng.
Year: 2015
Subject: Water-supply -- China -- Hong Kong.
Renewable energy sources.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: ix, 62 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2826140
URI: http://theses.lib.polyu.edu.hk/handle/200/8231
Abstract: In Hong Kong, fresh water is distributed to customers by pumps from the service reservoirs through a network of water supply mains. Due to the hilly topography of Hong Kong, low-altitude parts of the water distribution networks will maintain a relatively higher water pressure than that in a high-altitude area. High water pressure has a great contribution to the leakage or rupture occurrence in the pipelines and in the buildings. Pressure Reducing Valves (PRVs) are often used as a measure for excessive pressure reducing devices in Hong Kong for the purpose of pressure management to control the water pressure in the pipelines, especially in buildings. The use of turbine systems to substitute the PRVs might be able to provide a better approach as a sustainable solution in terms of managing the system pressure as well as to provide a considerable profit by producing renewable hydropower. This project aims to find the feasibility of extracting energy from water supply system mains by using micro hydro water turbines to substitute the PRVs at entrance of a high-rise building from economical and energy efficiency aspects, respectively. A case study in Kam Shek San Tsuen was investigated first to simplify the research procedure. The water condition in Kam Shek San Tsuen was obtained and the useful water head was also determined based on required backpressure. According the turbine selection criteria introduced in this dissertation, the Micro Francis Turbine Generator System produced by Hitachi is the most suitable type for this project, and EBS-F80H was chosen as the energy generation system. The estimation equation of initial investment for micro hydropower systems calculated by Po-An Su was used. By using the calculation methods stated above, the payback period of the Kam Shek San Tsuen case study was estimated as about 7 years. Using the similar methods, the pay back periods of the energy recovery systems for different work conditions were also estimated. The results conclude that the available water head plays an important role in the economic evaluation of the system. Low rated power system with high available water head has a shorter payback period than that of a high rated power system with low available water head. Overall, the trend is indicates that in the pico-hydro range (<10kW), a higher rated power system has a shorter payback period. For further study, old buildings that are sensitive to the water pressure should be taken into consideration during the system installation. A hydraulic model of the water networks under peak demand conditions should be set up to predict the impact of the water pressure reduction. The final outlet pressure would be chosen through trial and error to make sure that there is no complaint from these old buildings.

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