Energy efficiency in electrical systems can be achieved through some measures to limit losses through devices among these components. Power parity (the amount of power put into a device equaling the amount of power provided to the device) provides for the most efficient use of power. Transformers and equipment which utilize transformers (such as UPS systems and PDU’s) tend to have some losses in efficiency due to the friction losses in the windings of these transformers. As equipment vendors apply more stringent manufacturing techniques to their products, improvements can be made to efficiencies of this type of equipment. UPS vendors now provide UPS systems which operate at a .95 or higher power factor. This means that there is only a 5% loss of power into the device compared to power supplied by the device. It should be noted that these power factors are generally based on a load limit on the device no lower than around 30% of the rated maximum for the device, although some of the newer UPS systems can maintain their power factor down to as low as 20% of the rated maximum. As equipment is replaced due to changes in a system, end of life, or equipment failure, higher efficiency equipment should be specified and provided to improve on energy efficiency for these systems.
Measurement and Recording Data
We mentioned in part 1 of this series that in order to understand the consumption of power related to the data center, metering of these systems needs to be provided. Further, trending of this information is invaluable to understanding a baseline of energy use as well as the outcome of changes implemented to improve efficiency. The Power Usage Effectiveness (PUE) of the systems is an indicator of how efficient the data center operates. It is very important to understand where your data center ranks for PUE in order to know what measures should be taken to improve efficiency. This means that recording power usage at the main switchgear supporting both the electrical and mechanical equipment supplying the data center, and at the distribution side of the UPS systems distribution (preferably at the 120/208 volt level at the PDU’s) is ideal to achieve the simplest means of calculating the PUE.
Lighting systems have been moving towards more energy efficient components in recent years. These systems have moved away from the use of incandescent and T12 luminaires to compact fluorescent and LED fixtures. ENERGY STAR has reported savings of 42% by switching from T12 fluorescent luminaires with magnetic ballasts to high efficiency T8 luminaires with electronic ballasts. It should be noted that oftentimes these higher efficiency luminaires actually produce higher lighting levels in addition to using less power. The more recent introduction of LED lighting luminaires, which can be retrofit into current fluorescent fixtures, is driving these efficiencies even higher.
Another energy savings measure which can be implemented in the data center is lighting controls. The notion of “lights out” data center operations refers to personnel not being normally stationed in the data center space. As operational controls of data processing applications become more network driven, and remotely accessed, less time is required in the data center to perform these activities. As a result of this reduced time spent in the data center, lighting becomes less necessary to operate under non-manned periods. Lighting controls utilizing occupancy sensors as a means of controlling lighting offers a reasonable solution to taking control of shutting off the lights out of the personnel entering and using the space. However, occupancy sensors do not allow for continued presence in the space when personnel are out of sensory contact with a motion or occupancy sensor due to working within or at the lower portions of equipment racks. In order to better accommodate these specialized circumstances in the data center, a combination of occupancy/motion sensors in conjunction with card access systems allows for a highly effective and efficient lighting controls strategy.
The Bottom Line
Once the proper metering components are in place and baselines are established, it’s relatively simple to determine which electrical infrastructure equipment will benefit from an upgrade and what the payback for the investment will be. Also, paying attention to lighting controls can improve energy efficiency in the data center. No matter what the situation is in your data center, a facility-wide energy audit from an experienced partner will help to identify the areas where the most immediate impact can be achieved.