Adiabatic cooling for datacenters: best practices 2025

Adiabatique & datacenters: the 2025 best practices to cool more with less energy and water.

Adiabatic cooling leverages evaporation to reject heat at lower energy cost than traditional chillers, helping data centers drive down PUE while maintaining thermal compliance. This guide explains what adiabatic systems are, where they excel, how to manage water responsibly, and a step‑by‑step path to design, operate, and scale them safely in 2025.

In brief

• Cut cooling energy 20–40% versus compressor‑led systems; maintain resilience with hybrid dry/adiabatic designs.

• Choose the right topology (direct/indirect evaporative, adiabatic condensers, hybrid chillers) for your climate and uptime tier.

• Manage water with WUE targets, dual make‑up sources, treatment, and drought contingencies.

• Harden operations: filtration, Legionella control, N+1 pumps/fans, dry‑mode fallback, and smart controls.

• Monitor PUE, WUE, and thermal compliance; iterate with data and continuous commissioning.

Why adiabatic cooling belongs in modern data centers

Adiabatic systems reduce compressor lift by cooling intake air or condenser coils with evaporated water. In dry or temperate climates, they deliver long economizer hours and lower kWh/cooling ton. With 2023 industry surveys still citing a median PUE around 1.58, many facilities can move toward 1.2–1.35 by optimizing heat rejection and controls, especially at partial loads.

Water is the trade‑off. The right strategy balances electricity savings (lower scope 2 emissions) against water use and local scarcity, guided by WUE, make‑up source quality, and reuse options. For operators pursuing sustainability targets, adiabatic designs can materially reduce energy intensity while staying within responsible water budgets and regulatory expectations.

How adiabatic systems work

Direct vs. indirect evaporative cooling

• Direct evaporative cooling (DEC): Outdoor air passes through wetted media, cools adiabatically, then enters the white space. Highest energy savings but adds humidity and depends on outside air quality and psychrometrics.

• Indirect evaporative cooling (IEC): Separates airstreams with a heat exchanger; process air cools via wetted media without adding moisture to IT spaces. More controllable in humid or polluted environments.

• Hybrid: Combine IEC/DEC modes or adiabatic assist with DX/chilled water to extend operating envelopes and maintain SLAs during humidity peaks.

Adiabatic condensers and hybrid chillers

Retrofittable adiabatic pads or fogging systems pre‑cool condenser air on air‑cooled chillers/condensers, reducing head pressure and compressor work. Hybrid adiabatic chillers switch between dry, spray, and mechanical modes to meet load with minimal energy and water.

Controls, sensors, and water treatment

Performance hinges on smart sequencing: stage dry first, then adiabatic, then compressors. Key elements: - Differential pressure and wet‑bulb sensors - Variable‑speed fans/pumps - Conductivity‑based blowdown - Filtration (MERV/F7+), drift eliminators, and chemical or UV treatment - BAS/BMS integrations and fail‑safe interlocks

For thermal envelopes and allowable classes (A1–A4), align setpoints with the latest guidance from ASHRAE TC 9.9 to protect hardware and warranties. See ASHRAE’s datacom thermal guidelines for details: ASHRAE Datacom resources.

Best practices for 2025 deployments

1) Start with climate and site suitability

• Analyze 10‑year hourly weather data (dry‑bulb, wet‑bulb, humidity, PM2.5/PM10).

• Map economizer hours and maximum approach temperatures; assess heatwave and wildfire smoke risks.

• Check local water availability, tariffs, hardness/silica, and discharge permits.

2) Set dual KPIs: PUE and WUE

• PUE target: define seasonal targets and load‑dependent curves; benchmark against peers (industry median PUE remained ~1.58 in 2023 per Uptime Institute).

• WUE target: express in L/kWh IT, aligned with The Green Grid’s metric. Track monthly and seasonally. Reference: Water Usage Effectiveness (WUE) by The Green Grid.

3) Engineer for resilience, not just efficiency

• Design N+1 (or higher) on fans, pumps, and water make‑up; dual pipework where feasible.

• Provide dry‑mode fallback sized for critical load during water outages or air‑quality events.

• Use corrosion‑resistant materials (316L, epoxy‑coated coils), high‑efficiency drift eliminators, and enclosure designs that shed biofilm.

4) Water stewardship program

• Primary: municipal + secondary: harvested rainwater or treated greywater (where permitted).

• Closed‑loop or bleed‑minimized operation with conductivity setpoints, anti‑scaling chemistry, and side‑stream filtration.

• Reuse blowdown for landscaping or toilet flushing if quality allows; document permits and cross‑connection controls.

• Publish WUE and water sourcing in sustainability reports; align with EU Code of Conduct practices: EU Data Centres Code of Conduct.

5) Health, safety, and compliance

• Legionella risk management: risk assessments, biocide regime, temperature control, and regular microbiological testing; design to minimize aerosolization (high‑efficiency drift eliminators).

• Filtration strategy: F7–F9 prefilters, optional HEPA for DEC; wildfire smoke bypass modes.

• Document SOPs and emergency response for spills, chemical handling, and water restrictions.

6) Advanced controls and AI‑assisted optimization

• Model‑predictive control that forecasts wet‑bulb, load, and energy/water prices.

• Dynamic setpoints for supply air and approach temperatures, with fan/pump VFD coordination.

• Digital twins for scenario testing; anomaly detection on valves, nozzles, and media saturation.

• Integrate KPIs in the BMS and DCIM; alert on drift, fouling, or rising approach temperatures.

7) Commissioning and continuous improvement

• Seasonal commissioning (summer/winter), including smoke and drought simulations.

• Calibrate sensors, verify blowdown, and validate dry‑mode performance at critical load.

• Establish a cleaning cadence for media and coils based on airborne particulates and hardness.

• Review monthly PUE/WUE vs. weather normalization; refresh control sequences annually.

Performance, ROI, and typical ranges

Energy savings: Well‑tuned adiabatic systems commonly reduce cooling energy 20–40% versus all‑mechanical baselines, with higher gains in dry climates and at part load.

Water use: WUE varies widely by design and climate; operators report ranges from <0.1 to ~1.5 L/kWh IT for hybrid systems. Actuals depend on cycles of concentration, filtration, and local wet‑bulb.

PUE impact: Moving from 1.55 to 1.25 is feasible for many brownfield sites once economization is fully exploited and compressors are minimized in shoulder seasons. Independent research shows incremental PUE improvements continue year‑over‑year when controls are actively optimized; see industry surveys and guidance from Uptime Institute.

Payback: CAPEX often recoups in 2–5 years, driven by energy tariffs, available reuse water, and avoided chiller runtime. For robust business cases, combine energy price scenarios, drought constraints, and carbon intensity to reflect your locale.

Environmental and regulatory considerations

• Carbon: Lower compressor runtime reduces scope 2 emissions, especially in grids with higher kgCO₂e/kWh. Pair adiabatic systems with renewable PPAs or onsite PV+storage to compound gains.

• Water: In water‑stressed regions, prioritize IEC or hybrid designs, non‑potable sources, and dry‑fallback. Report WUE transparently.

• Air quality: Design for filtration upgrades and smoke bypass; pre‑filters prolong media life and sustain approach temperatures.

• Standards: Align with ASHRAE thermal envelopes and local public‑health codes. Participate in best‑practice communities like the Open Compute Project’s cooling workstreams: OCP Advanced Cooling Solutions.

Implementation roadmap you can follow

1) Strategy and baselining (2–4 weeks) - Audit cooling plant, PUE/WUE, controls, and water systems. - Climate/wet‑bulb study and economizer hour modeling.

2) Concept and design (4–8 weeks) - Select topology (IEC/DEC/adiabatic condenser/hybrid chiller). - Define redundancy, water sources, and control philosophy. - Lifecycle cost analysis across energy/water/maintenance.

3) Build and integrate (8–16 weeks) - Install equipment, media, treatment skid, and sensors. - Integrate BAS/DCIM, alarms, and cybersecurity hardening.

4) Commission and optimize (ongoing) - Seasonal commissioning and setpoint refinement. - KPI reviews, hygiene audits, and operator training.

How NOOR connects energy, digital, and new tech

NOOR’s tripartite approach aligns perfectly with adiabatic programs: - Energy: granular energy management, GTB/GTC integration, and renewable coupling to drive PUE down without sacrificing uptime. - Digital: resilient data center architectures, cybersecurity for BAS/DCIM, PRA/PCA planning, and cloud/hybrid strategies around the cooling stack. - New Tech: AI‑assisted controls, IoT sensorization, and custom applications for predictive maintenance and KPI visualization.

Discover how NOOR turns design into measurable performance: NOOR – score-grp.com.

There, where efficiency embraces innovation…

FAQ

Is adiabatic cooling viable in humid climates?

Yes, with the right topology. Indirect evaporative cooling or adiabatic‑assist condensers maintain benefits even when relative humidity is high, because they pre‑cool condenser air or isolate moisture from the IT airstream. Performance depends on wet‑bulb temperature, not just relative humidity, so analyze multi‑year hourly data. Hybrid systems that sequence dry → adiabatic → compressor modes deliver predictable cooling during humid peaks and can still reduce annual energy use materially compared to fully mechanical systems.

How much water will an adiabatic system consume?

It varies by climate, system type, and water treatment. A practical planning range for hybrid data center systems is often 0.1–1.0 L/kWh IT annually, but detailed modeling should use local wet‑bulb data, cycles of concentration, and expected economizer hours. Track WUE monthly, implement conductivity‑based blowdown, and consider non‑potable sources (rainwater, treated greywater where permitted). Always balance water savings against energy and carbon reductions to reflect local sustainability priorities.

Can adiabatic cooling meet ASHRAE TC 9.9 thermal guidelines?

Yes. Modern systems can hold supply and return temperatures within ASHRAE recommended or allowable ranges for classes A1–A4, provided controls and redundancy are properly engineered. Key enablers are variable‑speed fans/pumps, precise wet‑bulb sensing, high‑efficiency drift eliminators, and fallback dry mode during unfavorable conditions. Align alarm thresholds and sequences of operation with your hardware OEMs and consult the latest ASHRAE Datacom guidance for envelopes and humidity limits.

What about Legionella and hygiene risks?

Risk can be effectively managed by design and operations: minimize aerosol carryover with high‑efficiency drift eliminators, maintain biocide programs, monitor conductivity and pH, and schedule media/coils cleaning. Implement a formal water management plan, perform periodic microbiological testing, and train staff on chemical handling. Site selection matters too—position intakes away from contaminants and ensure easy access for maintenance. Follow local public‑health codes and document compliance.

How do adiabatic systems handle droughts or water restrictions?

Engineer resilience upfront. Provide dual make‑up sources (potable + stored rainwater or approved reuse), onsite storage for peak cooling, and a dry‑mode capacity sized for at least critical loads. Controls should auto‑switch to dry operation when make‑up is constrained. Communicate with utilities about restriction tiers, and model worst‑case scenarios during design. Monitoring WUE and reporting transparently also support stakeholder trust during water‑scarce periods.

Remember

• Adiabatic cooling can trim 20–40% of cooling energy and push PUE toward 1.2–1.35 in suitable climates.

• Water is manageable with WUE targets, treatment, non‑potable sources, and dry‑fallback.

• The right topology (IEC/DEC/hybrid) depends on weather, air quality, and uptime tier.

• Health, safety, and compliance require filtration, drift control, and documented water management.

• Smart controls, continuous commissioning, and clear KPIs sustain gains over time.

Ready to assess your site and build the business case? Start the conversation with NOOR: score-grp.com.