An innovative approach to enhance sustainability of a district cooling system by adjusting cold thermal storage and chiller operation

Anderson, Austin; Rezaie, Behnaz; Rosen, Marc A.

doi:10.1016/j.energy.2020.118949

Cited by 22 publications

(11 citation statements)

References 31 publications

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“…This work forms part of broader research program by the author, including for example various studies involving exergy (Rosen 2011(Rosen , 2012(Rosen , 2013 and sustainability (Dincer and Rosen 2021). In particular, this article extends and updates earlier papers by the author that examined exergy consumption and entropy generation for the Earth (Rosen and Scott 2003a;Wright et al 2000) Wright and Rosen 2004) as well as for energy technologies in anthropogenic and natural systems (Rosen and Scott 2003b;Anderson et al 2021). This paper thereby constitutes a novel contribution to the literature on exergy and entropy budgets for the Earth, with new results.…”

Section: Introductionsupporting

confidence: 74%

Exergy consumption and entropy generation rates of earth: an assessment for the planet and its primary systems

Rosen

2021

Energ. Ecol. Environ.

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Although energy is conventionally examined when studying thermodynamic flows and balances for the Earth and its systems, the planet does not consume energy as its energy inflows and outflows are in balance. Similarly, energy is conserved for systems on the Earth. The Earth does, however, consume exergy and generate entropy, and it is insightful to examine the thermodynamics of the Earth in terms of exergy, or the related quantity entropy. These perspectives are considered here for the Earth and its main systems: the biosphere, people and civilization. The work provides an enhanced understanding of the type, location and causes of thermodynamic losses for the Earth as well as its main systems and subsystems, and of the connections and relations between the Earth and its biosphere, as well as civilization and people. It is observed for the year 2019 that civilization uses exergy to create many products and services and that the exergy consumption rate of the Earth's biosphere is approximately five times larger than that of civilization and 100 times larger than that of people as individuals. Also, the solar exergy rate provides the Earth with a very large exergy input rate, about 10,000 times greater than the needs.

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Section: Introductionsupporting

confidence: 74%

Exergy consumption and entropy generation rates of earth: an assessment for the planet and its primary systems

Rosen

2021

Energ. Ecol. Environ.

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“…Two typical periods from summer (Aug. [1][2][3][4][5][6][7][8][9][10][11][12][13][14]2018) and winter (Jan. 28-Feb. 11, 2018) seasons were selected for thermo-fluid validation. The results are summarized in Table 2 for the summer period and Table 3 for the winter period.…”

Section: Thermo-fluid Systemmentioning

confidence: 99%

“…Several tools have been adopted throughout literature for DC applications. Using TRNSYS, Anderson et al [2] adjusted the operating time of chillers (compressor and absorption), cooling towers, and thermal storages with a lumped campus thermal load to minimize exergy destruction. Chow et al [3] evaluated several water-cooled chiller plant configurations (including ther-mal storage, several heat rejection methods, and various pumping configurations) with TRNSYS for the plant/district simulation and HEVACOMP/DOE2 for the building thermal load models.…”

Section: Introductionmentioning

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 is currently more than any other country, but global installations are growing rapidly, particularly in the Middle East [2]. With buildings consuming 36% of global energy [3] and space cooling growing faster than any other end use [4], many are looking to DC for its energy efficiency and economic benefits [5,6,7]. Rather than individual buildings producing their cooling needs with individual air conditioning equipment, centralized plants produce chilled water (CHW) that can be distributed to multiple buildings connected to the district.…”

Section: Introductionmentioning

confidence: 99%

A Case Study on Condenser Water Supply Temperature Optimization with a District Cooling Plant

Hinkelman¹,

Wang²,

Fan³

et al. 2021

Preprint

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District cooling (DC) continues to proliferate due to increasing global cooling demands and economies of scale benefits; however, most district-scale modeling has focused on heating, and to the best of our knowledge, researchers have yet to model cooling plants featuring waterside economizers in DC settings. With the Modelica Buildings library expanding its capabilities to district scale, this study is one of the first to demonstrate how the open-source models can be used for detailed energy and control analysis of a DC plant. For a real-world case study, we developed and calibrated high-fidelity models for a DC system central plant at a college campus in Colorado, USA, and we optimized the condenser water supply temperature (CWST) setpoint for a DC plant across multiple time horizons using the Optimization library in Dymola. Results indicate that annual CWST optimization saves 4.7% annual plant energy, with less than 1% of additional energy savings gained through daily optimization. This confirms previous studies' findings that high frequency CWST optimizations are not necessary for the studied system.

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An innovative approach to enhance sustainability of a district cooling system by adjusting cold thermal storage and chiller operation

Cited by 22 publications

References 31 publications

Exergy consumption and entropy generation rates of earth: an assessment for the planet and its primary systems

Exergy consumption and entropy generation rates of earth: an assessment for the planet and its primary systems

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

A Case Study on Condenser Water Supply Temperature Optimization with a District Cooling Plant

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