Illinois Data Centers: Advanced Cooling Techniques for Extreme Energy Savings

Illinois has emerged as a premier data center market, with the Chicago metropolitan area ranking among the top data center hubs in North America. The region's advantages—robust fiber connectivity, reliable power infrastructure, central geographic location, and a favorable climate for cooling—have attracted hyperscale operators, enterprise data centers, and colocation providers alike.

Yet data center operators in Illinois face the same fundamental challenge as their peers everywhere: energy costs. In an industry where electricity can represent 50-70% of operating expenses, efficiency optimization isn't just environmental responsibility—it's competitive necessity. And within the data center energy equation, cooling typically represents the largest opportunity for improvement.

This guide explores advanced cooling techniques for Illinois data centers, from proven economizer strategies that leverage the state's favorable climate to emerging technologies like liquid immersion that promise to revolutionize data center design. Whether you're optimizing an existing facility or planning new construction, these approaches can dramatically reduce your cooling energy consumption and improve your Power Usage Effectiveness (PUE).

Beyond the Server: Uncovering the #1 Energy Hog in Illinois Data Centers

The Data Center Energy Equation

Data centers consume energy in two primary categories:

IT Equipment Load

• Servers, storage, and networking equipment
• The productive computing work of the facility
• Measured in IT kW capacity utilized

Overhead Load

• Cooling systems (CRAC/CRAH units, chillers, cooling towers)
• Power distribution losses (UPS, PDU, transformers)
• Lighting, security, and building systems
• Support infrastructure

Power Usage Effectiveness (PUE) quantifies this relationship:

PUE = Total Facility Energy / IT Equipment Energy

A PUE of 2.0 means the facility consumes twice as much energy as the IT equipment itself—one watt of overhead for every watt of computing. A PUE of 1.5 means 50% overhead per watt of IT load.

Cooling: The Dominant Overhead Component

Within overhead load, cooling typically dominates:

Overhead Category	Typical Share
Cooling systems	40-60%
Power distribution losses	25-35%
Lighting and auxiliary	5-15%

For a facility with 1.6 PUE operating 1 MW of IT load:

• Total facility power: 1.6 MW
• Overhead power: 0.6 MW (600 kW)
• Cooling power estimate: 300-400 kW
• Annual cooling energy: 2.6-3.5 million kWh
• Annual cooling cost (at $0.08/kWh): $210,000-280,000

Even modest cooling efficiency improvements yield significant savings.

Understanding Cooling Load Sources

Data center cooling loads originate from multiple sources:

IT Equipment Heat Servers convert virtually all input power to heat:

• Modern servers: 250-1,000+ watts each
• High-performance computing: 1-5+ kW per server
• Storage arrays: 1-3 kW per unit
• Network equipment: 50-500 watts per switch/router

Power System Losses Electrical distribution generates heat:

• UPS systems: 5-15% of load as heat
• Transformers: 1-3% losses
• PDUs: 1-2% losses

Lighting and People Minor contributors:

• Lighting: Increasingly LED and low-impact
• Personnel: Minimal in modern facilities

Illinois Climate Advantage

Illinois' climate creates significant free cooling opportunity:

Chicago Area Climate Data

• Average annual temperature: 50°F
• Hours below 55°F (free cooling threshold): ~5,000
• Hours below 65°F: ~6,500
• Heating degree days: 6,200
• Cooling degree days: 850

This climate profile allows well-designed data centers to operate without mechanical refrigeration for 50-70% of annual hours—a substantial advantage over warmer climates.

Taming the Hot Aisle: Proven HVAC Optimization & Free Cooling Strategies

Airflow Management Fundamentals

Before pursuing advanced technologies, optimize basic airflow:

Hot Aisle/Cold Aisle Configuration Separate supply and return air paths:

• Equipment intakes face cold aisle (supply air)
• Equipment exhausts face hot aisle (return air)
• Prevents mixing that reduces cooling effectiveness

Containment Strategies Isolate hot and cold air streams:

Hot Aisle Containment

• Enclose hot aisle with doors, curtains, or rigid panels
• Return air drawn directly from contained space
• Allows higher return temperatures without equipment impact
• Typical cost: $500-2,000 per rack
• Energy savings: 15-30%

Cold Aisle Containment

• Enclose cold aisle to prevent warm air infiltration
• Supply air delivered only where needed
• Enables consistent inlet temperatures
• Typical cost: $500-1,500 per rack
• Energy savings: 10-25%

Blanking Panels and Sealing Eliminate bypass airflow:

• Install blanking panels in empty rack spaces
• Seal cable cutouts and floor penetrations
• Block gaps between racks and above/below equipment
• Cost: $100-500 per rack
• Impact: 5-15% efficiency improvement

Raised Temperature Operation

ASHRAE guidelines allow higher operating temperatures than many facilities use:

ASHRAE A1 Recommended Envelope

• Inlet temperature: 64.4-80.6°F (18-27°C)
• Inlet humidity: 5.5°C dew point to 60% RH

Benefits of Higher Setpoints

• Each 1°F increase reduces cooling energy 2-4%
• Higher chilled water temperatures improve chiller efficiency
• Extended economizer operation hours
• Reduced humidification/dehumidification load

Implementation Considerations

• Verify equipment warranties support higher temperatures
• Monitor inlet temperatures at rack level (not room average)
• Implement gradually with careful monitoring
• Address hot spots before raising average setpoints

Economizer Optimization

Economizers provide free cooling when outdoor conditions permit:

Air-Side Economizers Direct Air Economizer Brings outdoor air directly into data hall:

• Most efficient approach when conditions permit
• Requires filtration (Illinois agriculture, urban pollution)
• Humidity control can limit hours
• Best for: Lower-density facilities, locations with good air quality

Indirect Air Economizer Uses air-to-air heat exchanger:

• Outdoor air cools data center air without mixing
• No outdoor air quality concerns inside data hall
• Slightly lower efficiency than direct
• Best for: Higher-security facilities, locations with air quality concerns

Water-Side Economizers Uses cooling tower water directly for cooling:

• Plate-and-frame heat exchanger between tower and chilled water loop
• Available when wet bulb temperature permits
• Maintains closed chilled water system
• Illinois advantage: 5,000+ hours of water-side economizer operation annually

Economizer Control Optimization Many existing economizers underperform due to control issues:

• Verify economizer enables at proper temperature thresholds
• Check damper operation throughout range
• Ensure smooth transition between economizer and mechanical cooling
• Consider enthalpy-based controls vs. temperature-only
• Implement optimal economizer switchover strategies

For broader HVAC optimization guidance, see our resource on commercial HVAC system energy efficiency.

Chiller Plant Optimization

When mechanical cooling is required, plant optimization reduces energy:

Chilled Water Temperature Reset Higher chilled water temperatures improve chiller efficiency:

• Standard design: 42-45°F supply
• Optimized operation: 48-55°F when load permits
• 1-2% efficiency gain per degree of temperature rise
• Implementation: Variable setpoint based on cooling demand

Condenser Water Temperature Reset Lower condenser water improves efficiency:

• Standard design: Fixed 85°F condenser water
• Optimized: Variable based on wet bulb temperature
• Balance chiller efficiency vs. cooling tower energy
• Use optimization algorithms or manual schedules

Variable Speed Operation VSDs on cooling equipment reduce partial-load energy:

• Chilled water pumps: 30-50% savings at partial load
• Condenser water pumps: Similar potential
• Cooling tower fans: Major savings potential
• Typical payback: 2-4 years

Chiller Sequencing Optimize equipment staging:

• Avoid running multiple chillers at low load
• Stage based on efficiency curves, not simple capacity
• Consider environmental conditions in sequencing decisions

The Future is Fluid: Is Liquid Immersion Cooling Your Key to Extreme Savings?

Understanding Liquid Cooling Technologies

As chip power densities increase and air cooling approaches its limits, liquid cooling technologies are gaining adoption:

Direct-to-Chip (Cold Plate) Cooling Liquid circulates through cold plates attached to high-heat components:

• Targets specific high-power components (CPUs, GPUs)
• Maintains air cooling for lower-power components
• Retrofit possible for some server designs
• Reduces but doesn't eliminate air cooling requirements

Rear Door Heat Exchangers Liquid-cooled heat exchangers on rack doors:

• Captures heat from server exhausts
• Can eliminate or significantly reduce CRAC requirements
• Retrofit-friendly for existing facilities
• Cooling capacity: 20-50 kW per rack typically

Full Immersion Cooling Servers submerged in dielectric fluid:

• Single-phase immersion: Servers in non-conductive liquid bath
• Two-phase immersion: Liquid vaporizes and condenses on heat exchanger
• Highest efficiency possible (PUE 1.03-1.10)
• Enables extreme power densities (100+ kW per rack)

Immersion Cooling Deep Dive

How It Works Servers are submerged in thermally conductive, electrically insulating fluid:

1. Heat transfers directly from components to fluid
2. Fluid circulates (natural convection or pumped)
3. Heat exchanger removes heat from fluid
4. Warm water from heat exchanger rejects heat (cooling tower, dry cooler)

Benefits Energy Efficiency

• Eliminates server fans (5-15% of server power)
• Eliminates CRAC/CRAH units
• Enables high-temperature heat rejection (easier cooling)
• PUE improvement to 1.03-1.10 vs. 1.4-1.8 for air cooling

Compute Density

• 100+ kW per rack possible
• Enables higher chip power without throttling
• Reduces data center footprint per compute unit

Reliability

• No mechanical parts for airflow
• Consistent, stable temperatures
• No particulate contamination
• Potential for extended hardware life

Challenges Complexity

• Specialized containment and fluid handling
• Maintenance procedures differ from air-cooled systems
• Fluid compatibility considerations for all components
• Leak management and containment

Cost

• Higher capital cost per rack
• Dielectric fluid costs ($100-400 per gallon)
• Specialized training requirements
• Potential warranty implications

Operational Changes

• Hardware replacement procedures
• Fluid maintenance and replacement
• Fire suppression considerations
• Personnel safety protocols

Economic Analysis for Illinois

When does immersion cooling make sense?

Break-Even Analysis

Traditional Air Cooling (1.5 PUE)

• 1 MW IT load = 1.5 MW total power
• Annual energy: 13.1 million kWh
• Annual cost (at $0.08/kWh): $1,050,000

Immersion Cooling (1.05 PUE)

• 1 MW IT load = 1.05 MW total power
• Annual energy: 9.2 million kWh
• Annual cost: $736,000
• Annual savings: $314,000

Investment Recovery

• Immersion infrastructure premium: $1-3 million (varies significantly)
• Simple payback: 3-10 years
• Better economics at higher power densities

Illinois-Specific Considerations

• Excellent free cooling climate extends air cooling viability
• Lower electricity rates than coastal markets reduce absolute savings
• Water availability supports evaporative cooling alternatives
• Growing data center market provides service infrastructure

Best Fit Applications

• High-performance computing clusters
• AI/ML training facilities
• Cryptocurrency mining
• Edge computing in space-constrained locations
• New construction without legacy air infrastructure

From Audit to Action: Building Your Custom Energy Savings Roadmap in Illinois

Phase 1: Assessment and Baselining

Energy Data Collection Establish accurate baseline:

• Utility bills (12+ months)
• IT load metering
• Submetering by system (cooling, lighting, etc.)
• Environmental monitoring data
• PUE calculation and trending

Facility Assessment Evaluate current state:

• Cooling system inventory and condition
• Airflow patterns and containment status
• Economizer function and controls
• Temperature and humidity patterns
• Hot spots and bypass airflow

Benchmark Comparison Compare to industry standards:

• PUE vs. industry benchmarks
• Cooling system efficiency vs. design specs
• Operating parameters vs. ASHRAE recommendations
• Economizer utilization vs. climate potential

Phase 2: Opportunity Identification

Quick Wins (0-6 Month Payback)

• Blanking panels and sealing
• Setpoint optimization
• Economizer repair and tuning
• Decommission unused equipment
• Lighting controls

Medium-Term Projects (6-36 Month Payback)

• Hot/cold aisle containment
• VFD retrofits
• Chiller plant optimization
• Raised floor modifications
• Control system upgrades

Major Investments (3+ Year Payback)

• Cooling system replacement
• Liquid cooling deployment
• Free cooling system installation
• Building envelope improvements
• Major infrastructure upgrades

Phase 3: Project Development

Utility Incentive Integration Engage ComEd or Ameren early:

• Custom incentive pre-approval
• Baseline establishment requirements
• Documentation specifications
• Incentive timing coordination

Financial Modeling Develop comprehensive business case:

• Capital costs with incentive offsets
• Operating savings projections
• Risk factors and sensitivity analysis
• NPV, IRR, and payback calculations

Implementation Planning Sequence projects strategically:

• Address prerequisites (metering, controls)
• Prioritize by ROI and interdependencies
• Plan around maintenance windows
• Coordinate with capacity planning

Phase 4: Implementation and Verification

Project Execution Implement with attention to:

• Minimize operational disruption
• Maintain redundancy during transitions
• Commission systems thoroughly
• Document as-built conditions

Measurement and Verification Confirm savings achievement:

• Pre/post energy comparison
• Adjust for load and weather variations
• Calculate actual PUE improvement
• Document for incentive claims

Continuous Optimization Sustain improvements:

• Ongoing monitoring and trending
• Regular recommissioning
• Benchmark tracking
• Technology evolution monitoring

For related data center content, see our guide on data centers in Chicagoland grid and price impacts.

Conclusion: The Illinois Data Center Advantage

Illinois data centers operate in a uniquely favorable environment for cooling optimization. The state's climate provides thousands of free cooling hours annually—an advantage that well-designed facilities can leverage for industry-leading efficiency. Combined with robust utility incentive programs and competitive electricity rates, Illinois offers data center operators substantial opportunities for energy cost reduction.

The pathway to optimization combines proven strategies with emerging technologies:

1. Master the fundamentals: Airflow management, containment, and raised temperature operation deliver significant savings with modest investment

2. Maximize free cooling: Illinois' climate enables economizer operation for over half of annual hours—ensure systems capture this potential

3. Optimize mechanical systems: When free cooling isn't available, plant optimization reduces mechanical cooling energy

4. Evaluate advanced technologies: Liquid cooling may make sense for high-density applications, particularly new construction

5. Capture incentives: Illinois utility programs significantly improve project economics

For data center operators committed to operational excellence, cooling optimization represents one of the highest-value improvement opportunities available. The energy savings compound annually, the environmental benefits support sustainability goals, and the competitive advantage grows as energy costs increasingly differentiate market positions.

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Sources:

• ASHRAE Technical Committee 9.9 - Data Centers
• The Green Grid Resources
• U.S. Department of Energy Data Center Energy Practitioner Program
• Lawrence Berkeley National Laboratory Data Center Research
• Uptime Institute Data Center Research