CASE STUDY: 55MW Nevada Data Center
Conversion from Water-Cooled Plant to Air-Cooled Chillers Within a Fixed 65MW Utility Allocation
Executive Summary
A confidential 55MW Network Access Point (NAP) data center in Nevada sought to eliminate 170 million gallons per year of cooling tower water consumption by converting from a water-cooled central plant to air-cooled chillers.
However, the site operates under a strict 65MW utility power allocation. A fully dry air-cooled design, sized for the N=20 design ambient condition of 116.7°F, would have exceeded the available utility capacity and rendered the project infeasible.
By incorporating Peak+ adiabatic assist technology to suppress condenser entering air temperature (CEAT) during peak conditions, the mechanical plant was redesigned, peak chiller demand was reduced by approximately 9MW, and the project was delivered within the existing utility allocation.
The result:
• 94% reduction in consumptive cooling water use
• Elimination of cooling towers
• Viable air-cooled conversion without additional utility infrastructure
• Improved peak plant performance within a fixed power envelope
Site Conditions and Constraints
Critical IT Load: 55MW
Total Utility Allocation: 65MW
Annual Cooling Tower Water Use: 170,000,000 gallons
Design Criterion: N=20 Condenser Entering Air Temperature (CEAT) of 116.7°F
The owner’s objectives were clear:
- Eliminate evaporative cooling towers and associated water consumption.
- Maintain reliability and redundancy.
- Operate within the fixed 65MW utility allocation.
- Avoid costly and time-consuming utility upgrades.
The utility allocation was non-negotiable. Any solution exceeding 65MW during peak design conditions would not be viable.
Approach #1: Fully Dry Air-Cooled Conversion
The engineering team initially evaluated a completely dry air-cooled chiller plant sized for the 116.7°F design condition.
MECHANICAL CONFIGURATION
- Chillers: 30 units
- Nominal Capacity: 450 tons per unit
- Redundancy: 4+1 per electrical block (6 blocks)
- Input Power per Chiller @ 116.7°F: 674 kW
- Total Peak Chiller Plant Demand: 16.2 MW
- Cooling Water Consumption: Zero
UTILITY IMPACT
When combined with:
- 55MW IT load
- UPS losses
- Pumps and distribution
- Ancillary mechanical systems
The total site demand would have exceeded 72MW, oversubscribing the 65MW allocation by more than 7MW during peak conditions.
Because additional utility capacity was not available without major infrastructure upgrades, the fully dry conversion was infeasible.
Outcome: Electrically non-viable
Approach #2: Air-Cooled Chillers with Peak+ Adiabatic Assist
To explore alternatives, the owner and consulting engineer engaged Peak+ to evaluate targeted adiabatic precooling of condenser intake air.
Peak+ technology suppresses condenser entering air temperature (CEAT) during high ambient conditions using advanced controls to minimize water use while achieving a defined CEAT setpoint.
Instead of designing around 116.7°F ambient air, the plant could be designed around a controlled CEAT of 95°F during extreme conditions.
REDESIGNED MECHANICAL CONFIGURATION:
- Chillers: 18 units
- Nominal Capacity: 670 tons per unit
- Redundancy: 2+1 per electrical block (6 blocks)
- Max CEAT Setpoint: 95°F
- Input Power per Chiller @ 95°F: 383 kW
- Total Peak Chiller Plant Demand: 6.9 MW
- Annual Consumptive Water Use: <6,000,000 gallons
Why This Changed Everything
Suppressing CEAT during extreme temperature events fundamentally altered the mechanical design requirements:
- Chiller count reduced by 40% (30 → 18 units)
- Peak mechanical demand reduced by approximately 9MW
- Plant power reduced by 57% at design condition
- Total site power remained below 63MW
- Project delivered within 65MW allocation
This reduction did not create incremental IT yield beyond 55MW.
Instead, it made the conversion possible within a fixed utility envelope.
Without Peak+ adiabatic assist, the project would not have moved forward.
Outcome: Project Approved
Water and Environmental Impact
The hybrid air-cooled solution achieved:
- 94% reduction in consumptive cooling water use
- Reduction from 170 million gallons/year to less than 6 million gallons/year
- Elimination of cooling towers and associated drift, blowdown, and water treatment
This represents the elimination of approximately 164 million gallons per year of evaporative loss. The case study only considers onsite consumptive water use. Additional system-level benefits likely include:
- Reduced water consumption at power generation facilities due to lower peak grid demand
- Reduced seasonal strain on regional water infrastructure
- Lower operational variability in mechanical demand
Broader Implications
This project illustrates a critical point for high-density data center markets operating under power constraints:
When utility allocations are fixed, mechanical plant design becomes a capacity limiter.
Air-cooled conversions sized strictly to extreme dry-bulb conditions may be technically feasible but electrically non-viable.
Targeted suppression of condenser entering air temperature enables:
- Mechanical right-sizing / avoidance of overbuild
- Elimination of cooling towers
- Delivery of projects within constrained power envelopes
In constrained markets, peak plant performance — not average efficiency — determines project feasibility.
Key Results Summary
Conclusion
For this 55MW Nevada data center, the transition away from cooling towers was not limited by tonnage — it was limited by power.
By reducing peak mechanical demand approximately 9MW at the N=20 design condition, Peak+ adiabatic assist transformed an infeasible dry conversion into a viable hybrid air-cooled solution delivered within a fixed 65MW utility allocation.
The project demonstrates that in power-constrained markets, managing peak condenser entering air temperature can be the difference between overbuilding, utility upgrades, and project cancellation — or rapid deployment and successful execution.
