Equation-based object-oriented modeling and simulation for data center cooling: A case study

Abstract

Data center cooling accounts for about 1% of electricity usage in the United States. Computer models are pivotal in designing and operating energy-efficient cooling systems. Compared to conventional building performance simulation programs, the equation-based object-oriented modeling language Modelica is an emerging approach that can enable fast prototyping and dynamic simulation of cooling systems. In this case study, we first modeled the cooling and control systems of an actual data center located in Massachusetts using the open-source Modelica Buildings library, and then calibrated a baseline model based on measurement data. The simulation of the baseline model identified several operation-related issues in the cooling and control systems, such as degraded cooling coils, improper dead band in control settings, and simultaneous cooling and heating in air handlers. Afterwards, we used a sequential search technique as well as an optimization scheme to investigate the energy saving potentials for different energy efficiency measures aiming to address the abovementioned issues. Simulation results show potential energy savings up to 24% by resolving identified control-related issues and optimizing the supply air temperature.

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

“…Due to uncertainties and gaps in measured data, validation of the entire DC plant for one year of measured data was not possible. This is consistent with many past DC and chiller plant modeling endeavors [6,23]. Thus, two time periods representing typical summer and winter conditions were selected to validate the model, encompassing both full and part load conditions.…”

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

“…Due to uncertainties and gaps in measured data, validation of the entire DC plant for one year of measured data was not possible. This is consistent with many past DC and chiller plant modeling endeavors (Oppelt et al 2016;Fu et al 2019). Thus, two time periods representing typical summer and winter conditions were selected to validate the model, encompassing both full and part load conditions.…”

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

“…Figure 12 shows the detailed analysis of the central plant operation for two sample windows during FC (Feb. [13][14][15][16][17][18]2018) and MC (Aug. [19][20][21][22][23][24]2018) modes. During FC mode, the plant's overall kW/ton was higher than that during MC mode.…”

“…It should be noted that there are many similarities between heating and cooling at districtscale [14]. In addition, Modelica-based modeling of other DHC types such as combined heat and power or ambient water networks [7,15,16] and chiller plants in non-DC applications [17,18,19,20,21] are also extensive. However, there is a general lack of publications on DC modeling and simulation [22].…”