Data center performance enhancement in desert environment of Dubai through air-cooled chiller plant optimization
Creators: name: Ong, Noriel
Publisher: name: figshare
Year: 2021
Subjects: subject: 120302 Design Innovation
subject: FOS: Arts (arts, history of arts, performing arts, music)
subject: 120402 Engineering Design Knowledge
subject: FOS: Other engineering and technologies
subject: 120404 Engineering Systems Design
subject: 129999 Built Environment and Design not elsewhere classified
subject: FOS: Civil engineering
subject: 120202 Building Science and Techniques
subject: 91505 Heat and Mass Transfer Operations
subject: Mechanical Engineering
subject: FOS: Mechanical engineering

description: Nowadays, a day without mobile devices and the internet is unimaginable. As humans take advantage of these technologies to improve the quality of life and businesses, data centers that support such technologies are rapidly growing globally.<br>The exponential growth of data center facilities, and their impacts on our environment, has become a major concern worldwide as these facilities consume 1% of the total electricity produced globally in 2019.<br>The mechanical cooling system is the second-largest energy consumer in a data center following the information and communication technology equipment. Many data center facilities around the world leverage free cooling to shed energy consumption and carbon emissions of the mechanical cooling system. However, the Middle East is an exemption for its extreme ambient conditions which makes free cooling almost impossible. Consequently, data centers in this region have the worst Power Usage Effectiveness (PUE) based on the latest survey of the Uptime Institute in 2020, with a regional average of 1.79 versus the global average of 1.59.<br>The United Arab Emirates (UAE) is one of the Gulf Cooperation Council (GCC) countries with the largest portion of internet users and its data center demand is expected to rise exponentially in the forthcoming years. Considering that the mechanical cooling system is second to the highest energy consumer in a data center facility, any reduction in its electrical consumption would have major impacts on the overall PUE of the data center which can contribute to lowering the Middle East’s regional PUE average.<br>This study has explored optimization strategies for an air-cooled chiller (ACC) plant of a data center building in Dubai, using a building case study, by implementing industry- leading and best practices and taking advantage of partial free cooling through adiabatic or evaporative cooling.<br>Energy simulations using Hourly Analysis Program (HAP) version 5.11 International Edition, and post-simulation calculations and data processing have been undertaken to establish the building energy scenarios. The simulation results for the Senario1 revealed an overall annual energy savings of 5%, which yields to a PUE of 1.70 and is reasonably less than but comparable with the Middle East’s regional average value. Whereas Scenario2 has demonstrated a 31% improvement on ACC plant’s energy consumption and carbon emissions after replacing the ACCs with the ones with variable speed drive (VSD) compressors, which makes up to an overall annual energy and carbon emissions improvement of 8.1%, that is resulting in a PUE of 1.56. Further reduction was realized after adding the adiabatic pre-cooling system (APS) to the ACCs with VSD compressors in Scenario3. The post-simulation calculations and data processing results show that the ambient air dry-bulb temperature (DBT) entering the condenser coils of the ACCs were reduced between 5 – 14°C, with saturation effectiveness up to 92%. Thus, improving the energy efficiency ratio (EER) by about 29% on average which further decreased the ACC plant’s energy consumption by 14.6%. As a result, the overall annual energy consumption and carbon emissions of the data center is further reduced to 11.9%, with a PUE of 1.50 that is reasonably lower than the global average PUE. Also, it was appreciated that the water consumption of the APS is only 0.0003 l/s per kW or 62.5% less than that of the water-cooled chiller (WCC) plant.<br>On the other hand, the financial analysis also proves that an annual operational utility cost savings of 8.1% and 10% can be realized with the ACCs with VSD compressors alone and that with APS respectively in comparison with Scenario1. These suggest a return on investment (ROI) of four and eight months respectively, and two years for the APS alone, which substantiate that these options are excellent investments not only for optimizing the performance of the ACC plant but also for reducing the PUE and carbon emissions of data centers in Dubai and in the Middle East region where ambient conditions are similar.