Focusing on Water Usage Effectiveness for Cooling Systems to Boost Sustainability

Miles Auvil, Vertical Market Leader, Data Centers, Edge and High Tech Industrial, Trane Commercial HVAC

As the world continues to transition into learning, working and operating remotely, the data center industry is growing to match company and customer demands for high-performing IT equipment. However, with this increased demand for IT comes pressure for data center managers to meet sustainability goals to reduce their carbon footprints, save energy and reduce operating costs. However, there is another critical factor that improves sustainability in a data center: minimizing water usage.

The U.S. Environmental Protection Agency (EPA) predicts at least 40 states will have water shortages by 2024. Although water may not come to mind when thinking about a data center, the heating, ventilation and air conditioning (HVAC) systems data centers rely on to manage humidity and temperatures use water to generate cool, dry air. An April 2020 article from TIME reported the massive amounts of water required to cool some data centers, sometimes reaching up to 4 million gallons a day. To contribute to conservation efforts, data center managers can implement precision cooling strategies that improve water usage effectiveness (WUE).

Closed-Loop Cooling Design Improves Water Usage Effectiveness

Depending on the location of a data center and the amount of space it has, there are cooling strategies that can help save water. Cooling experts can use naturally closed-loop cooling systems and pair them with air condensers to improve WUE. A closed-loop system removes heat without letting outside air into the enclosure.

If a data center has a lot of building space, a closed-loop design is simple to achieve. These facilities can use an air-cooled chiller as their primary cooling solution. An air-cooled chiller system includes a compressor, evaporator, expansion valve and condenser and connects to multiple Computer Room Air Handlers (CRAHs) to cool a facility. Air-cooled chillers are naturally closed-loop, meaning that with this design, there is no water loss whatsoever.

While air-cooled chillers are ideal for increasing WUE, they typically require more space due to large condenser coils. Additionally, this kind of chiller is generally located outside, on the roof or in an adjacent mechanical yard. Therefore, a data center must have the available land or roof space to use an air-cooled design.

For data centers that can incorporate air-cooled chillers, there can be an added cost savings due to the way the system recirculates water. In areas where water scarcity is an issue or where water bills are costly, an air-cooled system virtually avoids water consumption. Closed-loop cooling systems can also help data center managers potentially eliminate the need for a water permit and avoid burdening the local water utility and the surrounding community. Water permits can be cost prohibitive or might not be available in a given region due to drought conditions or natural resources that have been depleted over time.

When A Closed-Loop System is Unachievable, Create One

An air-cooled system design is the best option to conserve water when cooling, but not all data centers have the environment to execute it. For example, data centers in urban-dense environments, perhaps housed in multi-story buildings, need cooling solutions that maximize footprint for IT equipment, do not require unavailable adjacent real estate, have infeasible piping distances or available rooftop real estate for air-cooled chillers. These facilities need water-cooled chillers. A water-cooled chiller works in tandem with CRAHs to cool a facility. When trying to maximize space, water-cooled chillers are ideal because they are located within a building, provide greater tonnage density and connect to shared or dedicated condenser water loops feasible for multi-story applications.

Water-cooled chillers utilize a cooling tower that evaporates water, has drift and blow-down and requires a continuous supply of water to replace what has evaporated. Due to the constant need for water supply, experts refer to a water-cooled system as an open-loop design.

Historically, an open-loop system could not help a data center owner contribute to sustainability efforts via WUE. However, in recent years, cooling experts have developed a solution to this problem. Many HVAC experts will recommend that water-cooled chiller plants be paired with adiabatic dry coolers. An adiabatic dry cooler is a closed-loop, air-cooled system, that sprays water on the HVAC system’s condenser coils to quickly drop air temperature during peak temperature days. It’s not completely water-less, but it provides a measurable WUE savings when compared to an open-loop design.

Combining a water-cooled chiller with an adiabatic solution effectively “closes” the open-loop design and improves WUE. This strategy is not only wise for new data centers; it’s great for existing open-loop water-cooled chiller plants.

Improve WUE, Improve Sustainability

As the “data center race” persists in order for companies to keep up with IT demands, data center managers must consider sustainability. Regardless of how and where a facility is built, there are cooling solutions to help save water and improve sustainability efforts.

Miles Auvil is the Vertical Market Leader, Data Centers, Edge and High Tech Industrial at Trane Commercial HVAC. Trane – by Trane Technologies – a global climate innovator, creates comfortable, energy-efficient indoor environments for commercial and residential applications.