Prototype energy models for data centers

Overview

This paper was published in Energy and Buildings (Elsevier) in 2021; its authors are Kaiyu Sun, Na Luo, Xuan Luo and Tianzhen Hong, and the work comes from Lawrence Berkeley National Laboratory. It builds two data centre prototype energy models in EnergyPlus and OpenStudio to complement the US Department of Energy's commercial building prototypes.

The small model is a computer room cooled by CRAC units. The large model is a stand-alone data centre with CRAH units and a central chiller plant. IT densities are 40 and 100 W/ft2 for the computer room and 100 and 500 W/ft2 for the stand-alone facility. The models follow ASHRAE 90.1 minimum requirements across vintages and cover all US climate zones.

The paper's methodological novelty is a new approach-temperature method implemented in EnergyPlus. It represents non-uniform air temperatures for different loads and containment conditions. The contribution is to bring the effect of airflow on temperature distribution into the models instead of assuming a single uniform room temperature. The approach temperatures are described as precomputed by CFD. This approach aims to show the energy effect of measures such as containment more realistically in simulation.

There are limits: the models are built for US climates and US standards, and the densities given are specific scenarios. Even so, these prototypes, linked to ASHRAE 90.1 and ASHRAE 90.4, give tools that want to calibrate an hourly cooling model and containment effectiveness a common reference point. They also provide a consistent set of models for energy code analyses.

Key points

1. The small model is a computer room with CRACs; the large model is a stand-alone data centre with CRAHs and a central chiller plant.
2. IT densities are 40 and 100 W/ft2 for the computer room and 100 and 500 W/ft2 for the stand-alone facility.
3. A new approach-temperature method in EnergyPlus represents non-uniform air temperatures for different loads and containment.
4. The approach temperatures are precomputed by CFD.
5. The models follow ASHRAE 90.1 minimum requirements across vintages.
6. The models cover all US climate zones.
7. The paper appeared in Energy and Buildings in 2021; the authors are from LBNL.

Using it in design

• Use the prototype densities and the approach-temperature concept to calibrate the tool's hourly cooling model and containment effectiveness.
• Design the EnergyPlus export to target these prototypes.
• In energy code comparisons, take these models, linked to ASHRAE 90.1 and 90.4, as the reference.
• Model the containment effect through a temperature distribution rather than a single room temperature.

Who should read it

Engineers doing data centre energy modelling, energy code compliance consultants and developers of simulation tools.

Related standards

• ASHRAE 90.1
• ASHRAE 90.4

Publication details

Authors

Kaiyu Sun; Na Luo; Xuan Luo; Tianzhen Hong

Publisher

Energy and Buildings (Elsevier)

Year

2021

Document language

English

Source type

Scientific

Access

Citation only

DOI

10.1016/j.enbuild.2020.110603

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation