Data center cooling system designs of the past have used a great deal of water to achieve a low Power Usage Effectiveness (PUE) while at the same time fitting the client’s capital expense (CAPEX) and operating cost (OPEX) business goals.
By: Scott Wilson, PE Partner at EYP Mission Critical Facilities
Today, there is mounting pressure to reduce water consumption as well. We are starting to hear corporations pledging to be “water positive” which means restoring more water than what they use. In most climates (except for the most humid or most cold environments), the benefits of cooling using the evaporation of water is well established and beneficial from an energy consumption standpoint in all but the most humid or most cold environments. Unfortunately, what is also often true is that water can be expensive or have limited/ inconsistent availability in dry climates.
There are a number of options available. A business model approach yields a clear path to the best option. Here are a few:
A simple solution is to build the data center in a more favorable climate. A data center designed with a refrigerant-based cooling system augmented with evaporative cooling for Sterling, VA will use less cooling-related energy if built near Chicago, IL, and also use less water. From a business perspective based on location or latency, a favorable CAPEX and OPEX cooling climate may be quickly ruled out.
Another option is to use refrigerant-based cooling systems that do not consume water like air-cooled chillers. All things being equal, these systems will consume more energy than those that leverage evaporative cooling but may have a lower CAPEX. From a business perspective, the CAPEX vs. OPEX may be acceptable, possibly making it a preferred choice.
One of the fundamentals to understanding cooling energy consumption in data centers is the entering temperature of the heat transfer media (i.e., air or liquid) cooling the IT. The other is how the media is delivered to the IT (e.g., air handling units, cooling distribution units) and heat is rejected to the environment. Designers of water-cooled IT and immersion cooling systems have for many years recognized that given their system's ability to remove heat from the chips more efficiently than air-cooled IT, they can raise the coolant temperature high enough that in some climates no mechanical refrigeration is required. If the business goal is to eliminate water use, converting a data center to a liquid IT environment should reduce evaporative cooling needs.
These days it is not practical for most owners to convert to all liquid-cooled IT overnight. However, if the piping systems and associated cooling and heat rejection equipment are divided into separate systems, a strategy can be developed for long-term migration to liquid-cooled IT which will reduce the consumption of both water and cooling energy.
In conclusion, the balance of IT spending and the facility CAPEX and OPEX will drive the decision for any owner, but liquid-cooled IT offers a substantial opportunity to reduce a data center cooling system’s water and energy consumption. We should expect to see a steady growth in the use of liquid-cooled IT as we see more pressure to conserve water.
Scott Wilson is EYP MCF, Part of Ramboll CEO and leads the mechanical department on Government Projects.
Scott’s experience started in 1978 in mechanical systems design for institutional, government, commercial and industrial buildings, Scott Wilson is a Partner, and senior hands-on engineer for EYP MCF, Part of Ramboll.
Scott’s project experience includes data center projects in the health care, higher education, science research, colocation and Hyperscale industry. Scott’s tenure with EYP MCF, Part of Ramboll started in 2005, follows his long tenure with EYP Architecture and Engineering. Much of Team EYP MCF, Part of Ramboll’s continued collaborative data center work is often coordinated and performed under Scott’s leadership.
Scott’s project experience includes work across the United States and for the US State Department in more than 20 countries worldwide