A hierarchical framework for holistic optimization of the operations of district cooling systems

The potential for greater energy efficiency gave rise to the popularity of implementing district cooling systems. In newer districts, however, the discrepancy between the designed capacity of the cooling system and actual cooling demand usually negates these benefits. In such scenarios, the optimiza...

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Main Authors: Chiam, Zhonglin, Easwaran, Arvind, Mouquet, David, Fazlollahi, Samira, Millás, Jaume V.
Other Authors: School of Computer Science and Engineering
Format: Article
Language:English
Published: 2021
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Online Access:https://hdl.handle.net/10356/151112
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1511122021-06-24T08:52:01Z A hierarchical framework for holistic optimization of the operations of district cooling systems Chiam, Zhonglin Easwaran, Arvind Mouquet, David Fazlollahi, Samira Millás, Jaume V. School of Computer Science and Engineering Veolia City Modeling Centre (VECMC) Engineering::Computer science and engineering District Cooling Systems Operation The potential for greater energy efficiency gave rise to the popularity of implementing district cooling systems. In newer districts, however, the discrepancy between the designed capacity of the cooling system and actual cooling demand usually negates these benefits. In such scenarios, the optimization of the system’s operations with respect to cooling demand could considerably improve the energy efficiency of the system, without incurring additional capital costs. Components of a district cooling system are usually operated at pre-defined setpoints or individually optimized, without regard of the impact on the overall system. Formulation of an optimization problem which adequately captures the thermal and physical interactions as well as the tight coupling between components, i.e., holistically, results in a mixed integer non-linear program which is large and difficult to solve. In this article, a hierarchical optimization framework for the hourly operation of district cooling systems is introduced to manage the problem. The initially complex model of the system was abstracted so that it could be solved effectively using the combination of a genetic algorithm and mixed integer linear program. The mixed integer linear program reduced the search space of the genetic algorithm, thereby increasing the likelihood of achieving global optimality. Finally, the methodology was applied to a case study based on an existing district cooling system in Europe for illustrative purposes. For the scenarios defined, the thermal and physical variables for each component were tuned such that the hourly cooling demand could be fulfilled with minimal electricity consumed. Results indicate potential electricity savings of up to 31%. At the optimum, some components operated less efficiently for the benefit of the overall system, further reinforcing the advantage of performing optimization holistically. The authors would like to acknowledge Veolia City Modeling Centre (VECMC) for the financial support. 2021-06-24T08:52:01Z 2021-06-24T08:52:01Z 2019 Journal Article Chiam, Z., Easwaran, A., Mouquet, D., Fazlollahi, S. & Millás, J. V. (2019). A hierarchical framework for holistic optimization of the operations of district cooling systems. Applied Energy, 239, 23-40. https://dx.doi.org/10.1016/j.apenergy.2019.01.134 0306-2619 https://hdl.handle.net/10356/151112 10.1016/j.apenergy.2019.01.134 2-s2.0-85060752895 239 23 40 en Applied Energy © 2019 Published by Elsevier Ltd. All rights reserved.
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Computer science and engineering
District Cooling Systems
Operation
spellingShingle Engineering::Computer science and engineering
District Cooling Systems
Operation
Chiam, Zhonglin
Easwaran, Arvind
Mouquet, David
Fazlollahi, Samira
Millás, Jaume V.
A hierarchical framework for holistic optimization of the operations of district cooling systems
description The potential for greater energy efficiency gave rise to the popularity of implementing district cooling systems. In newer districts, however, the discrepancy between the designed capacity of the cooling system and actual cooling demand usually negates these benefits. In such scenarios, the optimization of the system’s operations with respect to cooling demand could considerably improve the energy efficiency of the system, without incurring additional capital costs. Components of a district cooling system are usually operated at pre-defined setpoints or individually optimized, without regard of the impact on the overall system. Formulation of an optimization problem which adequately captures the thermal and physical interactions as well as the tight coupling between components, i.e., holistically, results in a mixed integer non-linear program which is large and difficult to solve. In this article, a hierarchical optimization framework for the hourly operation of district cooling systems is introduced to manage the problem. The initially complex model of the system was abstracted so that it could be solved effectively using the combination of a genetic algorithm and mixed integer linear program. The mixed integer linear program reduced the search space of the genetic algorithm, thereby increasing the likelihood of achieving global optimality. Finally, the methodology was applied to a case study based on an existing district cooling system in Europe for illustrative purposes. For the scenarios defined, the thermal and physical variables for each component were tuned such that the hourly cooling demand could be fulfilled with minimal electricity consumed. Results indicate potential electricity savings of up to 31%. At the optimum, some components operated less efficiently for the benefit of the overall system, further reinforcing the advantage of performing optimization holistically.
author2 School of Computer Science and Engineering
author_facet School of Computer Science and Engineering
Chiam, Zhonglin
Easwaran, Arvind
Mouquet, David
Fazlollahi, Samira
Millás, Jaume V.
format Article
author Chiam, Zhonglin
Easwaran, Arvind
Mouquet, David
Fazlollahi, Samira
Millás, Jaume V.
author_sort Chiam, Zhonglin
title A hierarchical framework for holistic optimization of the operations of district cooling systems
title_short A hierarchical framework for holistic optimization of the operations of district cooling systems
title_full A hierarchical framework for holistic optimization of the operations of district cooling systems
title_fullStr A hierarchical framework for holistic optimization of the operations of district cooling systems
title_full_unstemmed A hierarchical framework for holistic optimization of the operations of district cooling systems
title_sort hierarchical framework for holistic optimization of the operations of district cooling systems
publishDate 2021
url https://hdl.handle.net/10356/151112
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