Evaporative Cooling for Lab Design: Balancing the Use of Energy and Water

Megan Gunther, Affiliated Engineers, Inc.

Evaporative cooling has proved to be very effective in dry climate zones for reducing mechanical cooling loads. When implemented in moderate dry climates, such as California, it can provide even greater savings by extending the available outside air economizing hours annually. For laboratories requiring 100% outside air and greater cooling demands than low-load spaces, evaporative cooling can have a significant impact on cooling energy and peak demand savings. In these same climates, however, water supply is often at threat. Are we able to balance the trade-offs between water consumption and energy reduction? While evaporative cooling increases water consumption directly at the source, there is an opportunity for both water and energy use reduction when we holistically evaluate our building systems, leveraging the energy:water nexus. This session explores the impact these systems can have on both cooling load requirements and water consumption, demonstrated through two different case studies. With each case, the analysis of evaporative cooling, including the tools used, will be presented.

The first case study explores an existing research facility in Silicon Valley where office and conference spaces were converted into BSL2 laboratories and high density lab equipment rooms. Energy reductions in existing facility fit-outs can prove to be sometimes challenging, especially when base building systems are already in place. The design team was challenged with designing around an existing chilled water plant that was near capacity and given the task of not increasing the plant size with the conversion of office/conference space into labs. Indirect evaporative cooling paired with the 100% outside air system led to a 25% cooling load reduction, minimizing the load on the chiller plant.

The second case study explores a new multi-story lab building in South San Francisco. A challenge often faced with improved energy performance is increased equipment capital cost, even when significant energy and operating savings can be demonstrated. The initial baseline system proposed was a water-cooled chiller plant pair with standard chilled water coil AHUs. Indirect evaporative cooling led to a 25% cooling load reduction, thus reducing the required installed chiller capacity. With this reduction, an air-cooled chiller plant was able to be proposed, eliminating cooling towers and reducing water consumption. The proposed system not only provided greater annual energy savings, but it also provided an 18% cost savings in equipment capital cost.

Learning Objectives

  • Develop an understanding of evaporative cooling and where it is best applied;
  • Realize the impact evaporative cooling can have on cooling load reduction;
  • Gain an understanding of the energy:water nexus and how to balance energy and water use for cooling; and
  • Learn how to use tools to predict energy savings and water consumption associated with these systems.

Biography:

Megan Gunther PE, LEED AP, WELL AP leads the Building Performance Practice group for AEI's San Francisco office and is a mechanical engineer with expertise in the analysis, engineering, and design of mechanical systems supporting laboratories, healthcare, and higher education spaces. Megan provides thought leadership through building performance simulation, leading to integrated design solutions with innovative energy and water conservation measures.

 

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