Development and implementation of a virtual outside air wet-bulb temperature sensor for improving water-cooled chiller plant energy efficiency

Zheng, Keke; Watt, James; Wang, Chao; Cho, Yong

doi:10.1016/j.scs.2016.02.012

Cited by 8 publications

(4 citation statements)

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“…Future cases can use a hybrid approach to reduce the search space with a global optimization method, before selecting a local optimum. Second, the energy savings listed assume that the measurements are ideal, but physical T wb sensors can be inaccurate and prone to drift [63]. Thus, the energy savings from the Fixed and Adjusted T app cases may be overstated.…”

Section: Condenser Water Supply Temperature Optimizationmentioning

confidence: 99%

Modelica-based modeling and simulation of district cooling systems: A case study

et al. 2022

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Section: Condenser Water Supply Temperature Optimizationmentioning

confidence: 99%

Modelica-based modeling and simulation of district cooling systems: A case study

et al. 2022

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“…Future cases can use a hybrid approach to reduce the search space with a global optimization method, before selecting a local optimum. Second, the energy savings listed assume that the measurements are ideal, but physical T wb sensors can be inaccurate and prone to drift [55]. Thus, the energy savings from the Fixed and Adjusted T app cases may be overstated.…”

Section: Condenser Water Supply Temperature Optimizationmentioning

confidence: 99%

Modelica-Based Modeling and Simulation of District Cooling Systems: A Case Study

Hinkelman¹,

Wang²,

Gautier³

et al. 2021

Preprint

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While equation-based object-oriented modeling language Modelica can evaluate practical energy improvements for district cooling systems, few have adapted Modelica for this type of large-scale thermo-fluid system. Further, to our best knowledge, district cooling modeling studies have yet to include hydraulics in piping network nor waterside economizers. These are critical details to include when looking to make energy and control improvements in many physical system installations. To fi?ll these gaps, this study applies newly developed open-source models from the Modelica Buildings library. For a real-world case study, we modeled and simulated a district cooling system at a college campus in Colorado, United States, with six buildings connected to a central chiller plant featuring a waterside economizer. Several energy saving strategies are pursued based on the validated model, including control setpoint optimization, equipment modification, and pump setpoint adjustments. Results indicate that optimizing the condenser water supply temperature setpoint can save 2.5% to 4.4% energy; the nonintegrated waterside economizer saves 6.4% energy while cutting down the chillers' run times by 201 days/year, reducing maintenance costs, and extending chiller life; and adjusting the condenser water pump flow settings can save 10.2% energy. Through a combinationof the studied measures, the campus can annually save 84.6 MWh of energy, 8.9% of electricity costs, and 58.0 metric tons of carbon dioxide emissions. Further, the numerical results of simulating districts from tens to hundreds of buildings are presented.

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“…This results in the same class for T cwe , T db and T cwl with the highest COP class. The COP Market basket analysis could be further enhanced by resetting the cooling tower fan speed based on a control algorithm adjusting T cwe in response to the wet-bulb temperature of outdoor air (Zheng et al, 2016).…”

Section: Importance Of Variables In the Highest Coefficient Of Performance Classmentioning

confidence: 99%

Chiller system performance management with market basket analysis

2021

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Purpose This study aims to apply association rule mining (ARM) to uncover specific associations between operating components of a chiller system and improve its coefficient of performance (COP), hence reducing the electricity use of buildings with central air conditioning. Design/methodology/approach First, 13 operating variables were identified, comprising measures of temperatures and flow rates of system components and their switching statuses. The variables were grouped into four bins before carrying out ARM. Strong rules were produced to associate the variables and switching statuses with different COP classes. Findings The strong rules explain existing constraints on practising chiller sequencing and prioritise variables for optimisation. Based on strong rules for the highest COP class, the optimal operating strategy involves rescheduling chillers and their associated components in pairs during a high load operation. Resetting the chilled water supply temperature is the next best strategy, followed by resetting the condenser water entering temperature, subject to operating constraints. Research limitations/implications This study considers the even frequency method with four bins only. Replication work can be done with other discretisation methods and different numbers of classes to compare potential differences in the bin ranges of the optimised variables. Practical implications The strong rules identified by ARM highlight associations between variables and high or low COPs. This supports the selection of critical variables and the operating status of system components to maximise the COP. Tailor-made optimisation strategies and the associated electricity savings can be further evaluated. Originality/value Previous studies applied ARM for chiller fault detection but without considering system performance under the interaction of different components. The novelty of this study is its demonstration of ARM’s intelligence at discovering associations in past operating data. This enables the identification of tailor-made energy management opportunities, which are essential for all engineering systems. ARM is free from the prediction errors of typical regression and black-box models.

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Development and implementation of a virtual outside air wet-bulb temperature sensor for improving water-cooled chiller plant energy efficiency

Cited by 8 publications

References 1 publication

Modelica-based modeling and simulation of district cooling systems: A case study

Modelica-based modeling and simulation of district cooling systems: A case study

Modelica-Based Modeling and Simulation of District Cooling Systems: A Case Study

Chiller system performance management with market basket analysis

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