C052 -- Using Network Modeling to Test for ASHRAE 90.4 Standard Compliance

The ASHRAE 90.4 Standard provides important guidelines to justify data center design standards to meet energy efficiency criteria. As a building, a data center heat load due to the contained IT equipment far overshadows thermal gains and losses of traditional buildings that house people. In addition, one approach to being energy efficient is to evaporate water to achieve latent cooling, which can consume significant quantities of water, creating another potential environmental issue. Also, importantly, energy modelling tools assume mixing for thermal comfort, whereas data centers operate better with segregation of cold supply and warm return air. Thus, traditional energy modeling tools for general buildings are not ideally designed for evaluating data center performance. Designers therefore often resort to ad-hoc assessment approaches using the like of spreadsheets or other bespoke calculation approaches. The risk is that calculations are not very standardized and so methods and outcomes may not be very consistent, which is a disincentive for states to adopt the Standard. Therefore, general computational tools for design justification to the Standard are needed. The most useful tools contain a broad capability to model a variety of cooling and power systems and an underlying framework to calculate the corresponding MLC and ELC metrics associated with the Standard. One approach that accomplishes this task is to use network modeling to connect various cooling system component models into a system-wide framework, with a similar approach for the electrical system. Both systems are modeled under a single umbrella to account for system-system dependencies. This study describes an approach used to predict MLC and ELC metrics, and the associated compliance with the Standard, for one data center cooling (CRAC) and one power (non-redundant) configuration for a 1 MW data center. The study demonstrates that compliance checking predictions are both feasible and flexible when using a network modeling approach that connects various electrical and mechanical components in a systematic framework.