Is Dry Cooler Needed When Build A Datacenter ?

What is a Dry Cooler?

A dry cooler is a heat rejection device that uses air (instead of water) to dissipate heat from a cooling system. It operates without water evaporation, making it suitable for water-scarce regions or environments where water usage must be minimized.

Key Factors in Deciding Whether to Use a Dry Cooler

1. Data Center Cooling Architecture

Data centers typically use one of two main cooling approaches:

Air-Based Cooling (e.g., CRAHs/CRACs, hot/cold aisle containment):

Heat is removed via air circulation, and a dry cooler may be used to dissipate heat from the air conditioning system’s condenser (e.g., in a split-system design where the condenser is outdoors).

Liquid Cooling (e.g., chilled water, direct-to-chip cooling):

Heat is carried by a liquid (water or dielectric fluid) to a heat exchanger. A dry cooler can be used here to reject heat from the liquid loop to the ambient air, eliminating the need for a traditional cooling tower (which uses water evaporation).

When needed: If the data center uses a liquid cooling system and aims to avoid water-intensive cooling towers, a dry cooler is a viable alternative.

2. Climate and Environmental Conditions

Water Availability:

In arid regions or areas with strict water regulations (e.g., water restrictions due to drought), dry coolers are preferable to water-cooled systems (which require cooling towers and constant water replenishment).

Temperature and Humidity:

Dry coolers are most efficient in cool climates (e.g., average annual temperatures <20°C/68°F). In hot climates, they may require larger surface areas or additional fans to achieve sufficient heat dissipation, increasing energy consumption.

In humid environments, dry coolers do not face scaling or corrosion issues like cooling towers, making them more maintenance-friendly.

3. Energy Efficiency and PUE Goals

Power Usage Effectiveness (PUE):

Dry coolers have higher energy consumption than cooling towers in hot climates (since fans must work harder to dissipate heat), which may raise PUE.

In cool climates, dry coolers can achieve low PUE by leveraging free cooling (e.g., using ambient air directly for cooling during cold seasons).

Hybrid Systems:

Some data centers use hybrid cooling systems (dry coolers + cooling towers) to optimize for both water efficiency and energy efficiency. For example:

Use dry coolers in cool seasons to save water.

Switch to cooling towers in hot seasons for better heat rejection efficiency.

4. Initial Cost vs. Long-Term Maintenance

Capital Expenditure (CAPEX):

Dry coolers have higher upfront costs than cooling towers due to their larger heat exchanger surfaces and more powerful fans.

Operational Expenditure (OPEX):

Lower water and chemical treatment costs compared to cooling towers.

Reduced risk of microbial growth (e.g., Legionella) in dry coolers, minimizing maintenance and compliance costs for water treatment.

Scenarios Where Dry Coolers Are Recommended

Water-Scarce Regions

Example: Data centers in deserts, drought-prone areas, or regions with high water costs (e.g., Middle East, parts of Australia).

Benefit: Eliminates water consumption entirely or reduces it significantly.

Liquid Cooling Systems

If the data center uses a chilled water loop or direct liquid cooling for servers, a dry cooler can replace a cooling tower to reject heat without water evaporation.

Example: High-density data centers (e.g., hyperscale facilities) using advanced cooling to manage heat loads >20 kW per rack.

Retrofitting Older Facilities

Existing data centers may add dry coolers to upgrade cooling capacity without modifying water infrastructure.

Sustainability Goals

Companies targeting zero-water cooling or LEED certification may prioritize dry coolers to meet environmental standards.

Scenarios Where Dry Coolers May Not Be Ideal

Hot Climates

In regions with high ambient temperatures (e.g., average summer temps >35°C/95°F), dry coolers require more energy to operate fans, leading to higher PUE and costs. Cooling towers (with water evaporation) are more efficient here.

Low-Cost Water Access

If water is abundant and cheap, a traditional water-cooled system (chiller + cooling tower) may be more cost-effective.

Space Constraints

Dry coolers require more physical space than cooling towers due to their larger heat exchanger arrays. This can be an issue in urban data centers with limited rooftop or outdoor space.

Alternatives to Dry Coolers

Cooling Towers: More efficient in hot/humid climates but require water and maintenance.

Free Cooling Systems: Use ambient air directly (e.g., air-side economizers) in cool climates to reduce reliance on mechanical cooling.

Hybrid Cooling Towers + Dry Coolers: Combine both for flexibility across seasons.

Conclusion

A dry cooler is a valuable component in data center cooling if:

You need to minimize water usage (e.g., due to environmental or regulatory constraints).

The data center uses liquid cooling and requires a waterless heat rejection solution.

The climate is cool or moderate, allowing efficient heat dissipation with reasonable energy use.

However, in hot climates or water-rich environments, other cooling methods (e.g., cooling towers, free cooling) may be more cost-effective and energy-efficient. A detailed thermal analysis and lifecycle cost assessment are recommended to determine the optimal solution for your specific needs.