Safely Saving Energy in Today's Data Center

Managers of data centers are finding themselves increasingly under pressure to improve the energy efficiency of their facilities. Existing data centers present the greatest challenge because of their older infrastructure and restrictions on downtime to make changes. However, there are proven strategies that can enable a data center to increase energy efficiency without jeopardizing availability.

Before considering those options, it’s important to define the kind of data center that might benefit from those measures. These are data centers in which infrastructure availability meets the owner’s needs and reducing availability is not a viable option. What’s more, in these data centers the existing electrical and mechanical infrastructure will remain in service and will not be replaced. These data centers distribute cool air through a raised access floor. Finally, the discussion also assumes that the data center uses large double-conversion UPS systems.

If all of the above apply, facility executives have two options for saving electricity by turning things off: shutting down excess component redundancy or switching off lights.

Shutting down redundancies — This tactic applies if the facility has a single UPS system with more than one redundant module on line. In that case, all but one redundant module can be shut down. When using this practice, offline modules should be rotated to maintain storage battery charge.

Consider a facility that has a UPS output load of 500 kW with three 675 kW modules online. Each module operates at about 25 percent of rated capacity (500 kW/3 modules/675 kW per module); at this percent rated capacity, each module operates at 88 percent efficiency. If one module is shut down, the other two modules will operate at 37 percent of capacity and 91 percent efficiency. At $0.10/kWH for purchased electricity and 8,760 hours per year; this generates annual savings of $17,520. If the facility has redundant…