Part III: The Data Center Forest Has Gotten Greener

In recent weeks I have examined the energy efficient improvements being made in the data center world. Great strides have been made in the last seven years, but how does this effect the end user’s bottom line? Let’s take a look.

UPS Data Center Case Study
The UPS Windward Data Center was designed and constructed in 1994 as the world’s very first Tier IV, both electrically and mechanically. The Uptime Institutes’ Tiers were developed in part from this design, which means it is fault tolerant and concurrently maintainable.

This design, although very robust from an availability standpoint, is inherently inefficient due to all systems having to be 2N. This means all electrical and mechanical systems have to be oversized by a minimum of 200%, which forces them by default to normally operate at only fractional loads. This often means they are not operating in their efficiency bands.

Once we began energy reduction quest, we began by measuring and then mapping our loads within the building. They were separated as follows:

  • Mechanical Cooling – Chiller, AHU, Pumps, Cooling Tower, Humidifiers
  • Electrical Losses – Substation Transformers, UPSs, Critical Power Distribution
  • CRAH Fan Energy
  • Office & Lighting
  • I.T. Loads

As mentioned earlier, the greatest energy reduction opportunities for an existing site lie within the Mechanical Systems. At UPS, there were numerous things we did to lower the proportional share of the mechanical load from around 20% to an annual average of 13%.

The two largest contributors were:

  1. Installation of a plate and frame heat exchanger for waterside economization in the winter
    • This, coupled with increasing the chilled water set point, allowed UPS to shut down a 400kW refrigerant chiller and operate on ‘Free Cooling’ upwards of 5-6 months each winter
    • This reduced energy consumption by approximately 1.5MMkWh’s annually
  2. Managing airflow on the Raised Floor enabled us to shut ‘OFF’ 30% of our CRAHs (these were the original constant-volume units which consumed 7kW of power each
    • This saved another 1.5MMkWh’s

By performing a retro-commissioning study on the other energy reduction activities, we could account for another 1.0MMkWh’s reduced annually.

In total, on an annual energy bill that would have been in the neighborhood of 27-28MMkWh’s, we reduced our consumption by 4.0MMkWh’s, around a 15% reduction. At Atlanta’s rate of around 5.0¢/kWh, this results in $200,000 annually. For the rest of the nation, in which the average is around 10.0¢/kWh, this annual savings doubles.

There’s another benefit…the air that we breathe!

Using the Department of Energy emissions data based on the fuel mix in Georgia, the resulting annual emissions reductions are as follows:

  • 5, 744, 000 lbs (2,872 tons) Carbon Dioxide
    • CO2 is a greenhouse gas considered to be the cause of Global Warming
  • 43,760 lbs (22 tons) of Sulfur Dioxide
    • SO2 has been shown to react with the weather and causes Acid Rain
  • 8,520 lbs (4.26 tons) of Nitrogen Oxide
    • NOx causes ground-level ozone on hot summer days
  • 108 lbs of Mercury

Saving money on energy certainly helps keep data center costs manageable. The unseen benefit is the reduction of emissions as a result of greater energy efficiencies, which ultimately improves the health of our planet.

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