Achieving Japan's Highest Data-Centre Energy Efficiency (TTMD Turkish translation)

Overview

This article is the Turkish version of an ASHRAE Technology Award case study, published in TTMD Dergisi issue 145 (January-March 2025, p. 39). Its subject is the Shiroi Data Center Campus in Chiba, Japan, which reached PUE 1.2, described as the highest level for data centres in Japan. The server building is about 4,600 m2 with 900 racks; full build-out is planned at 50 MW receiving capacity and 6,000 racks at 6 kVA per rack.

The design combines architecture that prioritises equipment efficiency, consolidated high-efficiency air-cooled modular chillers, wall-discharge air conditioning for the server hall, AI control of supply air and water temperatures, and airflow control of ICT equipment. Supply air is 20-24 °C, and AI control holds rack inlet at 24 °C ±2 °C in operation. The campus stands out for bringing this architecture together in one facility, and each component's contribution is supported by separate quantified results.

The quantified results are as follows. In a temperate climate, outside-air cooling ran 55% of annual hours and met 39% of annual load. AI reset of chilled-water temperature gave an annual plant COP of 8.9, with air-transfer efficiency 1.7 times and plant COP 2 times those of a mixing-type data centre. ASHRAE 90.4-2022 MLC for climate zone 3A and over 300 kW of ITE must be below 0.21; the campus achieved 0.117, about 56% of the limit. AI control saves operators about 800 hours per year. The article provides good benchmark data for air-cooled designs in warm climates, but it reports the results of one campus (summary-level record, full text not read).

Key points

1. Server building about 4,600 m2 with 900 racks; full build-out planned at 50 MW receiving capacity and 6,000 racks at 6 kVA per rack.
2. Achieved PUE 1.2, described as the highest level for data centres in Japan.
3. Supply air 20-24 °C; AI control holds rack inlet at 24 °C ±2 °C in operation.
4. In a temperate climate, outside-air cooling ran 55% of annual hours and met 39% of annual load.
5. AI reset of chilled-water temperature gave an annual plant COP of 8.9; air-transfer efficiency 1.7 times and plant COP 2 times a mixing-type data centre.
6. ASHRAE 90.4-2022 MLC for zone 3A and over 300 kW ITE must be below 0.21; the campus achieved 0.117 (about 56% of the limit).
7. AI control saves operators about 800 hours per year.

Using it in design

• Use this case as a reference point for air-cooled, outside-air-assisted designs (PUE 1.2; MLC 0.117 in zone 3A).
• In the energy module, compute the ASHRAE 90.4 MLC and compare it with the climate-zone limit.
• In the airflow module, report the air-transfer factor (cooling kW per fan kW).
• Consider the AI-based reset strategy for supply air and chilled-water temperature as an option.

Who should read it

Mechanical engineers designing air-cooled data centres in warm climates and benchmarking energy performance.

Related standards

• ASHRAE 90.4-2022

Publication details

Authors

Masahiko Fujisaki; Ryozo Ooka

Publisher

Türk Tesisat Mühendisleri Derneği (TTMD) - TTMD Dergisi

Year

2025

Document number

TTMD Dergisi Sayı 145 (Ocak-Mart 2025), s. 39

Document language

English

Source type

Industry body

Access

Free to read

Licence

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

Citation