Designing for Efficiency: Best Practices in Energy-Efficient Data Center Design

In an age where digital services power everything from government operations to private enterprise, the energy-efficient data center is the beating heart of our connected world. However, these facilities are notorious for their immense high data center energy consumption. The July 2024 Best Practices Guide for Energy-Efficient Data Center Design, developed by FEMP and the National Renewable Energy Laboratory (NREL), is a blueprint for transforming data centers into models of efficiency, sustainability, and resilience.

This blog article explores the guide's comprehensive recommendations, categorized into key operational and infrastructural elements including IT systems, environmental conditions, air management, data center cooling systems, power distribution and UPS systems, and performance metrics.

Foundations of Sustainable Data Centers

The guide opens with a clear call to action: reducing energy-efficient data center energy use not only cuts costs but also reduces environmental impact. Efficiency in a data center isn't about a single improvement; it requires a holistic strategy:

• Minimize energy use with efficient IT, data center cooling systems, and power systems.
  
• Reuse waste heat reuse where possible.
  
• Reduce water use for cooling.
  
• Shift to renewable energy to improve the Carbon Usage Effectiveness (CUE).
  

This approach is centered around key metrics like Power Usage Effectiveness (PUE), Water Usage Effectiveness (WUE), Energy Reuse Effectiveness (ERE), and Carbon Usage Effectiveness (CUE).

Optimizing IT Systems for Performance and Efficiency

IT systems are the largest energy consumers in an energy-efficient data center. Optimizing them has a domino effect on data center cooling systems and power infrastructure. Key strategies include:

Cloud and Colocation Services

Organizations can save energy and reduce operating costs by leveraging cloud computing or colocation services instead of building on-premises infrastructure.

Efficient Servers

Modern servers offer:

• Variable speed fans
• ENERGY STAR® certified performance
• Better performance-per-watt
  

Using multi-core processors and right-sizing server usage improves utilization efficiency significantly.

Efficient Storage and Networking

• Thin provisioning ensures storage is not over-allocated.
• Idle-state logic and buffer optimization in network equipment reduce standby power.
  

High-Efficiency Power Supplies

Choosing 80 PLUS® Titanium-rated power supplies boosts efficiency to over 90%, minimizing conversion losses and easing the cooling load.

Environmental Conditions and ASHRAE Standards

The 2021 ASHRAE data center standards provide environmental envelopes for equipment operation:

• Recommended Range: Ensures reliability and efficiency (18–27°C or 64.4–80.6°F).
• Allowable Range: Safe functional limits, tested but not always efficient.

Raising server inlet temperatures within recommended ranges can reduce cooling loads but must be carefully managed to avoid excessive fan usage.

See Keentel Engineering MEP Engineering Services.

Advanced Air Management Strategies

Effective airflow management is essential for preventing hot spots, improving data center cooling efficiency, and reducing energy waste.

Cable Management

Removing abandoned cables and organizing wiring promotes unobstructed airflow, helping maintain consistent rack inlet temperatures and eliminating localized overheating.

Aisle Containment Systems

Implementing hot aisle/cold aisle containment—using sealed overhead plenums, floor grommets, and airflow baffles—prevents mixing of hot and cold air streams. This significantly improves cooling system performance and supports energy-efficient operation.

Supply and Return Optimization

Choosing between under-floor and overhead air distribution systems depends on facility design and thermal load zones. Pairing these with variable air volume (VAV) diffusers allows the system to dynamically adapt to real-time IT heat output.

Temperature Setpoint Adjustments

Raising supply and return air temperatures within ASHRAE-recommended thresholds can:

• Enhance economizer efficiency
• Enable standard HVAC units to operate more efficiently
• Allow for higher chilled water temperatures, improving chiller performance and reducing compressor energy consumption
  

Cooling Systems: From DX to Liquid Cooling

Cooling infrastructure represents a major share of data center energy usage. The FEMP guide recommends scalable, high-efficiency solutions to support sustainability and uptime.

Direct Expansion (DX) Units

Best suited for small and edge data centers, DX systems can be enhanced with evaporative cooling or air-side economizers to boost energy efficiency and reduce mechanical load.

Centralized Air Handlers

These systems offer superior part-load cooling performance and are well-suited for integration with economizers and hot aisle/cold aisle containment strategies to improve airflow efficiency.

High-Efficiency Chilled Water Systems

Optimized system design includes:

• VFD (Variable Frequency Drive) chillers
• Oversized cooling towers with low approach temperatures
• Variable flow pumping and optimized temperature differentials (ΔT values)
  

These strategies improve chilled water system efficiency while lowering overall PUE.

Free Cooling Solutions

• Air-side economizers deliver full or partial cooling using ambient air in favorable climates.
• Water-side economizers excel in colder regions, enabling chilled water storage and thermal energy buffering for load shifting.
  

Direct Liquid Cooling

A next-gen approach for high-density computing environments, liquid cooling systems efficiently dissipate heat via:

• Rear-door heat exchangers
• Cold plates
• Single-phase and two-phase immersion cooling technologies
  

Aligned with higher ASHRAE W-classes (W32–W45), this method significantly improves free cooling potential and thermal transfer efficiency.

See Keentel Engineering Utility-Scale BESS Engineering Services.

Electrical Systems: Enhancing Distribution and Efficiency

Efficient electrical infrastructure design plays a crucial role in reducing total energy usage and improving system reliability in modern data centers.

Uninterruptible Power Supply (UPS)

Modern UPS systems now achieve greater than 95% efficiency.

• Enable eco-mode operation to reach up to 99% efficiency.
• Right-size UPS units to maintain optimal load factors and avoid energy waste from underutilized capacity.

Power Distribution Units (PDUs)

• Select dry-type transformers with a lower temperature rise to reduce core losses.
• Optimize voltage distribution strategy and physical PDU placement to minimize conductor resistance and heat loss.

DC Power Distribution

Although not yet widely adopted, DC power distribution is gaining traction in large-scale data centers as it significantly reduces AC-to-DC conversion losses. It also supports next-gen rack and server-level efficiencies.

Demand Response & Intelligent Lighting

• Enroll in utility demand response programs to take advantage of peak-time incentives and grid reliability.
• Deploy occupancy-based controls and energy-efficient LED lighting systems to lower base energy load and enhance automation.

Harnessing Waste Heat

Waste heat recovery is an increasingly valuable strategy for improving overall data center energy efficiency. Instead of venting heat as a byproduct, facilities can repurpose it to support nearby thermal needs, reducing carbon footprint and operating costs.

Waste Heat Can Be Reused In

• Preheating ventilation air for HVAC systems
• District heating networks serving adjacent buildings or campuses
• Domestic hot water systems for on-site or nearby facilities

Conditions Favorable for Waste Heat Utilization

• Proximity to a qualified heat host (e.g., commercial or residential load centers)
• Temperature compatibility between recovered heat and thermal demand
• Regulatory incentives or shared infrastructure ownership models that enable cost-effective implementation
  

Benchmarking Metrics for Continuous Improvement

To ensure ongoing data center performance optimization, the FEMP guide emphasizes tracking key operational metrics that directly impact efficiency, sustainability, and compliance.

Power Usage Effectiveness (PUE)

• A primary metric for measuring overall energy efficiency
• Industry average is 1.55, while top-tier data centers reach below 1.1

Energy Reuse Effectiveness (ERE)

• Promotes waste heat reuse strategies
• Values under 1.0 demonstrate successful heat recapture and reintegration

Water Usage Effectiveness (WUE) & Carbon Usage Effectiveness (CUE)

• Track data center water consumption and carbon emissions
• Support ESG targets and holistic sustainability reporting

Advanced Cooling & Airflow Metrics

• Rack Cooling Index (RCI): Measures compliance of IT intake air temperatures with ASHRAE standards
• Airflow Efficiency (Watts per CFM): Assesses how efficiently air is delivered to IT equipment
• Cooling System Efficiency (kW/ton): Evaluates HVAC energy intensity
• ISO/IEC 30134 KPIs: Provide standardized global benchmarks for energy, water, and reuse metrics

Conclusion: Roadmap to a Greener Digital Future

By adopting these best practices, energy-efficient data centers can drastically reduce their power consumption, carbon footprint, and O&M costs. The FEMP guide provides a strategic roadmap for building digital infrastructure that’s both resilient and future-ready.

Keentel Engineering is committed to helping organizations implement these standards through substation design, NERC compliance, and SCADA-integrated grid engineering services.

FAQs: Energy-Efficient Data Center Design

Ready to Build a Smarter, More Efficient Data Center?

Whether you're optimizing an existing facility or designing from the ground up, Keentel Engineering is here to support your energy efficiency goals. Our team specializes in:

• Data center electrical and cooling system design
• UPS and DC power distribution strategies
• ASHRAE-compliant airflow planning
• Energy benchmarking and regulatory alignment (PUE, ERE, WUE, CUE)
• NERC-compliant infrastructure engineering

Connect with our experts to schedule a consultation and discover how to reduce operational costs while improving resilience.

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