RSES Journal Winter 2025, RETA-RSES

most notably, evaporative cooling delivers considerable energy savings by removing more heat with significantly less airflow— up to four times less than conventional air-cooled systems—making it a highly effi cient and sustainable solution. Adiabatic Cooling Adiabatic cooling products also use evap oration, but as a means of cooling the entering air passing through a finned heat exchanger. In a properly designed and oper ated system, the finned heat exchanger stays dry, protecting the surfaces from scale and corrosion. The air can be cooled by either spraying water into the airstream or by using wet pads that provide a surface for water and air to interface. In the first case, the goal is that the water sprayed into the airstream evaporates before reaching the finned coil, avoiding scaling and corrosion on the coil, which can negatively impact system efficiency and equipment lifetime. In the second case, a wetted pad is used to cool the entering airstream. The pads are specially designed to retain water on the surface of the pads to ensure that it does not carry over to the finned coil, minimiz ing the potential for scale and corrosion. The water distribution system maximizes pad efficiency by effectively wetting the pad to minimize process fluid temperatures and prevent scale formation. Adiabatic cooling systems offer a highly efficient and water-conscious approach to thermal management by using a small amount of water to precool the air enter ing the heat exchanger. This process signifi cantly reduces the required airflow and fan power compared to traditional air-cooled systems, while also lowering the return fluid temperature. In the most efficient designs, the precooled air approaches the ambient wet-bulb temperature, resulting in a substan tial boost in cooling capacity and energy effi ciency. These systems are also adaptable to changing conditions; during periods of low thermal load or when ambient temperatures near freezing, they can operate in a dry-only mode to conserve water. Advanced control systems further enhance performance by enabling intel ligent switching between wet and dry modes based on user-defined parameters such as ambient temperature and heat load. Additional features like daily mainte nance cycles, energy saver modes, and water

conservation settings make adiabatic systems both flexible and user-friendly. Hybrid Cooling Hybrid products use a combination of dry and evaporative cooling technology. Combin ing the benefits of both, hybrid products can be ideal for water-sensitive applications while still offering high energy efficiency. Hybrid cooling systems offer a balanced approach to thermal energy management by enabling operation in both “wet” and “dry” modes. This flexibil ity allows the system to adapt based on site-specific water and energy requirements, as well as ambient conditions, optimiz ing resource conserva tion. When operating

Evaporative cooling system.

Ice storage unit. Photos courtesy Baltimore Air Coil Co.

in “wet” mode, hybrid systems can achieve lower process fluid temperatures, which contributes to reduced system operating costs. Additionally, their compact design offers notable footprint savings compared to traditional dry coolers or adiabatic units, making them easier to install and integrate into space-constrained environments. This adaptability makes hybrid cooling an effi cient and sustainable solution for a wide range of applications. Beyond heat rejection, thermal energy management also includes energy storage. Ice thermal storage is a powerful strategy that allows facilities to shift cooling loads from peak daytime hours to off-peak nighttime periods. By producing ice overnight and using it to provide cooling during the day, build ings can reduce peak electricity demand and lower energy costs. Ice storage can supplement or even replace mechanical cooling during high-demand periods, offering redundancy and operational flexibility. This strategy is especially effective in city grids and stadi ums, where cooling loads are predictable and substantial. It also aligns well with sustain

ability goals, as it enables facilities to take advantage of lower-carbon energy sources available during off-peak hours. Successful thermal energy manage ment requires smart equipment selec tion, thoughtful system design, responsive controls and a clear understanding of the building's thermal profile. Advanced controls and BMS systems can optimize fan speeds, water flow and operating modes in real time, ensuring that systems respond dynamically to changing conditions. Life cycle cost analysis is also essential, helping designers and operators evaluate the long term value of different cooling strategies, including installation, maintenance and utility costs. Whether prioritizing water conservation, energy savings, or system reliability, contrac tors and engineers must evaluate site-specific conditions and performance goals to select the most appropriate solution. Patrick Galliford is HVAC Applications Lead for Baltimore Air Coil Company, Inc. Find BAC at baltimoreaircoil.com.

WINTER 2025 RSES Journal 27

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