Cooling Technologies for Internet Data Center in China: Principle, Energy Efficiency, and Applications

Overview

The energy consumption of internet data centres in China has become a pressing issue with the implementation of the Chinese dual-carbon strategic goals. The review covers air cooling, free cooling, liquid cooling, thermal energy storage cooling and building envelope. It first analyses the environmental requirements for the computer room and the main energy consumption items: cooling accounts for about 35-40% of total IDC energy consumption, the second largest consumer after IT equipment. GB 50174-2017 requires cold-aisle and rack-inlet temperature of 18-27 °C, dew point of 5.5-15 °C and RH not above 60%, and allows 15-32 °C when IT equipment requirements are relaxed.

An MIIT report found more than half of Chinese IDCs have PUE between 1.3 and 1.5, 37% above 1.5 and only a few below 1.2, with most having CLF of 0.15-0.25. Policy targets: large new IDCs below PUE 1.3 by end of 2023, below 1.25 in cold areas, and Guangdong requires new IDCs at no higher than 1.25 by 2025.

Four new cooling technologies are compared with traditional cooling. Free cooling is summarised as climate-dependent, with PUE of 1.4-1.6 and average energy saving of 35-40%; it can be combined with chillers or solar to improve stability. Thermal energy storage cooling can use natural cold sources by shaving peaks but must be coupled with other cooling technologies and needs an operating strategy. Liquid cooling offers higher energy efficiency and lower PUE than other technologies, especially for high-heat-density servers, but is not yet mature and engineering application is not widespread.

Conclusions: traditional cooling consumes a lot of energy and is inefficient because of cold and hot airflow mixing; most old IDCs use air cooling; free cooling is the most mature of the new technologies but strongly depends on geography and climate. Limits: a China-focused review, and figures come from studies under different conditions and cannot be compared directly on the same basis.

Key points

1. Cooling accounts for about 35-40% of total IDC energy consumption, the second largest consumer after IT equipment.
2. GB 50174-2017 requires cold-aisle and rack-inlet temperature of 18-27 °C, dew point of 5.5-15 °C and RH not above 60%, and allows 15-32 °C when IT equipment requirements are relaxed.
3. An MIIT report found more than half of Chinese IDCs have PUE between 1.3 and 1.5, 37% above 1.5 and only a few below 1.2; most have CLF of 0.15-0.25.
4. Policy targets: large new IDCs below PUE 1.3 by end of 2023, below 1.25 in cold areas; Guangdong requires new IDCs at no higher than 1.25 by 2025.
5. Free cooling is climate-dependent, with PUE of 1.4-1.6 and average energy saving of 35-40%; it can be combined with chillers or solar to improve stability.
6. Thermal energy storage cooling can use natural cold sources by shaving peaks but must be coupled with other cooling technologies and needs an operating strategy.

Using it in design

• In China, define project design targets from GB 50174-2017 temperature and humidity limits (18-27 °C, dew point 5.5-15 °C, RH at most 60%) and provincial PUE caps (for example Guangdong 1.25).
• Evaluate free cooling by climate (PUE 1.4-1.6, 35-40% saving) and compare liquid cooling as an option for high-heat-density loads.
• Treat thermal storage cooling as a peak-shaving tool, used with another cooling technology and an operating strategy.

Who should read it

Designers and policy specialists choosing data-centre cooling technology in China and similarly regulated markets.

Document contents

1. 1. Introduction
2. 2. Methodology (2.1 Requirement for Computer Room Environment, 2.2 Performance Criteria: energy efficiency assessment indicator, thermal environment assessment indicator)
3. 3. Status and Policies for Energy Conservation in China
4. 4. Traditional Air Cooling (4.2 Terminal of Air Cooling Technology: room-, row- and rack-level air cooling)
5. 5. New Cooling Technologies (5.1 Free Cooling: direct, indirect; 5.2 Liquid Cooling: cold plate, heat pipe, immersion, spray cooling; 5.3 Thermal Energy Storage; building envelope)
6. 6. Comparison of Different Cooling Technologies
7. 7. Conclusions

Related standards

• GB 50174-2017
• ASHRAE TC9.9 Thermal Guidelines

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Publication details

Authors

Xiaofei Huang; Junwei Yan; Xuan Zhou; Yixin Wu; Shichen Hu

Publisher

Energies (MDPI AG)

Year

2023

Volume

16

Issue

20

Pages

7158

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.3390/en16207158

Licence

CC BY 4.0 — share with attribution

Licence evidence

www.mdpi.com

Citation