Data Centres: Optimising existing estates in a world of diminishing returns

Overview

This white paper, published by AECOM in 2014, is a freely available consultancy document. It addresses whether to upgrade, consolidate or outsource legacy European data centres. It contrasts early-2000s design loads with current densities and outlines low-capex efficiency measures to apply before major investment. According to the key trends section, early-2000s halls were designed for 0.5-1.0 kW/m2 and a maximum of 4 kW per rack; by 2014, 2 kW/m2 and racks above 20 kW had become typical. The gap explains why legacy sites struggle on cooling and power, and it underpins the case for upgrading.

The case study shows the PUE improvement from airflow management, raised set points and chilled water changes, with a breakdown of losses by system. Audit measures include hot/cold aisles, blanking plates, cold-aisle curtains, supply air raised by 4 C, reduced CRAH airflow, raised chilled water temperature and a lowered pump set point. PUE fell from 1.56 to 1.42; the chiller share dropped from 0.26 to 0.22 and CRAC fans from 0.10 to 0.05 per unit of IT.

Annual saving per MW of IT is 140 kW, 1,277 MWh, GBP 147,000 and 518 t CO2. Upgrading chillers, UPS and controls could have reached PUE 1.32 with about a 3-year payback but was not funded. The conclusion notes that upgrading a legacy data centre can cost under 50% of a new build. The case is a single facility and should not be generalised.

Key points

1. Early-2000s halls were designed for 0.5-1.0 kW/m2 and max 4 kW/rack; 2 kW/m2 and >20 kW racks are typical in 2014.
2. Audit measures: hot/cold aisles, blanking plates, cold-aisle curtains, supply air +4 C, CRAH airflow reduced, chilled water temperature raised, pump set point lowered.
3. PUE fell from 1.56 to 1.42; chiller share 0.26 to 0.22 and CRAC fans 0.10 to 0.05 (per unit IT).
4. Annual saving per MW of IT: 140 kW, 1,277 MWh, GBP 147,000 and 518 t CO2.
5. Upgrading chillers, UPS and controls could reach PUE 1.32 with about 3-year payback but was not funded.
6. Upgrading a legacy data centre can cost under 50% of a new build.
7. Related references: ASHRAE Thermal Guidelines, EU Code of Conduct for Data Centres.

Using it in design

• Provide a PUE build-up chart by subsystem (chillers, fans, pumps, UPS, lighting, transformers) for existing-site audits.
• Offer a retrofit scenario that applies containment, set-point and chilled-water changes.
• Use the paper as a validation case for the PUE calculator.
• Rank low-cost measures before major investment and compare upgrade cost against a new build.

Who should read it

Managers deciding on upgrade, consolidation or outsourcing of existing data centers, and engineers carrying out energy audits.

Related standards

• ASHRAE Thermal Guidelines for Data Processing Environments
• EU Code of Conduct for Data Centres

Publication details

Authors

AECOM

Publisher

AECOM

Year

2014

Document language

English

Source type

Expert / community

Access

Free to read

Licence

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

Citation