By Kavita Vallabhaneni
From the December 2019 Issue
In today’s high-performance buildings and industrial facilities, managing energy and water costs associated with cooling is increasingly critical as facility executives seek to maximize process performance and profit per square foot while meeting sustainability goals. It is well established that water cooled systems are energy efficient and cost-effective, with potential savings of up to 50% in energy usage and cost over conventional air-cooled systems.
That said, based on a facility’s size, location, and load profile, a traditional water-cooled system with chiller or water source heat pump and cooling tower may not always be the best choice. This is especially true when ambient operating conditions vary from season to season and in locations where water is scarce and costly. All too often, facility managers have had to choose between energy savings and water savings and select a cooling system that meets the higher priority goal.
Innovation in HVAC systems has helped to eliminate this dilemma. New hybrid cooler technology supports both wet and dry cooling to achieve seasonally efficient heat rejection. The new hybrid coolers are modular and feature intelligent control systems that allow facilities managers to prioritize water and energy savings dynamically to achieve the right balance based on the facility’s daily operating environment.
If reducing energy use is important, either from a cost or sustainability perspective, hybrid coolers can use evaporative (wet) cooling to minimize the amount of energy used during periods of high ambient temperatures or building process loads. For facilities that need to conserve water, hybrid coolers can be configured to reduce water use by leveraging dry heat transfer and operating without spray water. Depending on the application, up to 50% water savings are achievable over conventional evaporative heat rejection.
Beyond energy and water savings, the newest hybrid systems offer features that reduce complexity, time and cost of installation and maintenance:
“Plug-and-play” modular configurations that enable expandable capacity: Hybrid coolers come in different cooling capacities, typically 20 and 30 tons, so it’s simple to determine the optimal number and capacity required for a facility. The modules can be combined and controlled to work most efficiently depending on daily and seasonal ambient temperature and load fluctuations. Increasing capacity is a matter of adding more modules.
Substantially smaller footprint: Depending on the system, hybrids can be as much as 40% smaller and eight feet shorter than traditional centrifugal fan fluid coolers. They also weigh up to 35% less. The small footprint and modular construction allow rigging and installation in tight spaces, and at lower cost, as individual modules can be moved with a pallet jack and fit in a freight elevator, eliminating the need for special rigging equipment.
Lower downtime through redundancy: If the facility uses multiple hybrid modules, there is always at least 50% redundancy in the system. Individual units can switch over to the dry cooling mode as back up to the evaporative mode.
Lower maintenance and repair costs: Direct drive systems available on hybrids eliminate moving parts, such as belts and gears. As such, the equipment life can be up to 50% longer than that of traditional coolers. Self-managing spray water systems and closed process fluid loop also help reduce cost and maintenance workload for facility managers and their teams.
Lower water management costs: Hybrid systems hold up to 60% less recirculating water volume in their basins than traditional systems, which reduces water treatment costs and chemical use.
Evaluating the best type of hybrid water-cooled system for any facility is driven by the facility’s operating profile. Facility size is the first consideration; this will determine how much capacity (and how many units) is required to cool the space effectively. Location is important because different climate conditions require different cooling strategies. Knowing the facility’s load profile is also essential as the system can be designed and configured based on loads that vary throughout the day, week to week, across the calendar cycle, or loads that are constant year-round, such as in data centers.
Other considerations are the facility’s energy use reduction goals, costs for energy, water and chemicals, space constraints for housing HVAC systems, and in-house capability to manage installation and management.
Today’s facility teams are constantly juggling multiple goals: improve HVAC performance, keep cooling costs in line, minimize both energy and water use, reduce maintenance time and costs, and achieve maximum sustainability. With lower energy consumption than straight air-cooled equipment and significantly lower water usage compared to conventional evaporative equipment, hybrid cooling systems provide the best of both worlds helping facility executives meet often conflicting operational goals.
Vallabhaneni is currently a technical director, global HVAC at Baltimore Aircoil Company. Over the last 25 years, she has held positions in technical applications, product management, and strategy development. Vallabhaneni earned a BS in Mechanical Engineering from UMBC and recently received her MBA (Finance/Management Concentrations) from Johns Hopkins University. She has authored various article and technical papers and delivered presentations.
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