The growing environmental footprint of data centers suggests the need for comprehensive models that enable designers and operators to optimize deployment configurations. In this paper, we discuss an exergy-based approach to the environmental design of one component of a data center, the computer room air conditioning (CRAC) unit. Previous work has examined the lifetime exergy consumption of the server technology portion of a data center. In this work we construct a lifetime exergy model for a direct expansion CRAC unit which when combined with the computer server model provides a more complete picture of the environmental impact of a data center. The lifetime model includes the material and energy consumption of the raw materials, transportation, manufacturing processes, operation and disposal. The application of the model is then explored under a variety of design configurations and utilization scenarios. Key parameters that affect the environmental footprint of the CRAC unit (as predicted by the lifetime exergy model) are identified. Case studies are performed to illustrate how variations in these key parameters can lead to significant differences in the lifetime exergy consumption of the CRAC unit. The paper concludes by recommending strategies to reduce the lifetime exergy consumption.

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