Indirect Evaporative Cooling Technologies in the Data Centre: Using Hyperscale Technology for Retail Data Centres in Tropical Climates

Overview

An IEC unit is an air-to-air heat exchanger with water sprayed on the outdoor side, plus DX or chilled-water trim, and outdoor and indoor air never mix. The paper separates three operating modes: dry (heat exchanger only), wet (water sprayed on the outdoor air side) and DX/CW integration when ambient is too hot for 100% adiabatic cooling. The motivation is Singapore data: ambient is typically 27-32°C, mean annual humidity 83.9%, and cooling accounts for about 37% of data-centre energy there (NCCS). IEC is estimated to cut cooling energy by up to 50% against traditional approaches.

The conclusion is climate-specific: in Singapore the unit runs with DX trim about 99.5% of the time and evaporative-only 0.5%, and dry/winter mode is not applicable. In very humid climates the evaporative stage therefore nearly always runs alongside DX trim, so savings are smaller than at temperate sites but still meaningful. It follows that DX or chilled-water trim must be sized for close to full load.

Reported results come from Australian and Eastern European installations: NEXTDC M2 (Tier IV) targets annual PUE 1.28, and EvoBits reached PUE 1.15 at 35°C outdoors. At 100% load the IEC system is quoted at PUE 1.26 against 1.4 for a traditional chiller plant. These are temperate-climate installations rather than Singapore measurements, so the paper's tropical conclusion is an inference from its mode-hour distribution.

Key points

1. Singapore ambient is typically 27-32°C with mean annual humidity of 83.9%; cooling accounts for about 37% of data-centre energy there (NCCS).
2. IEC is estimated to cut cooling energy by up to 50% versus traditional approaches.
3. Operating modes: dry (heat exchanger only), wet (water sprayed on the outdoor air side) and DX/CW integration when ambient is too hot for 100% adiabatic cooling.
4. In Singapore the unit runs with DX trim about 99.5% of the time and evaporative-only 0.5%; dry/winter mode is not applicable.
5. Reported results: NEXTDC M2 (Tier IV) targets annual PUE 1.28; EvoBits reached PUE 1.15 at 35°C outdoor.
6. At 100% load the IEC system is quoted at PUE 1.26 versus 1.4 for a traditional chiller plant.

Using it in design

• Use hourly climate data (dry-bulb and wet-bulb) in cooling selection to estimate IEC mode hours.
• For humid tropical sites, require DX/CW trim sized for near-full load and warn that evaporative-only hours will be minimal.
• Give the catalogue IEC unit capacity per mode, water consumption and trim type.
• Report WUE together with PUE.

Who should read it

Mechanical designers evaluating evaporative cooling options for hot, humid climates.

Related standards

• ASHRAE TC 9.9 Thermal Guidelines
• SS 564 (Singapore Green Data Centres)
• ISO/IEC 30134-9

Publication details

Authors

Vertiv

Publisher

Vertiv

Year

2020

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation