Building sustainable data centers

1 Author : April 22, 2013 0

Located in Swindon, Wiltshire, the UK, Capgemini’s new data center, Merlin, is state-of-the-art, 3,000 sq. m Tier 3 facility. It has set a new global standard for energy efficiency, with an industry-leading Power Usage Effectiveness (PUE) rating and Merlin is vaunted as the world’s most sustainable data center. Capgemini explains how it built the Merlin center.

Capgemini took a 360-degree view of the efficiency and green imperatives for the new facility, including the desire to select a sustainable, brown-field site and avoid unnecessary construction activity that would in turn cause additional pollution and environmental damage. The Swindon site was selected from a large number of candidates based on a wide range of criteria including:

– Reuse of an existing building

– Renewable power provision

– Availability of appropriate telecommunications and other attributes

The new design uses innovative engineering solutions for some of the most power-hungry components of the data center, such as cooling, Uninterruptible Power Supply (UPS), lighting, and electrical infrastructure.

The highly flexible modules were configured to exactly match the needs of the client with implementation in as little as 22 weeks (the traditional construction approach can have lead times, which are typically over three times as long). According to Paul Feeney, technical design authority-global data centers at Capgemini, the resulting innovations deliver real efficiency and green benefits, while maintaining or improving on standards for data center security, power management and resilience.

What comprises the solution?

Merlin is an Uptime Institute certified Tier 3 data center, which is one of only three such sites in the UK. It is capable of delivering 3,000 sq. m of available technical floor space, comprising 12 modules each of 250 sq. m, containing 1,248 racks sized at 800mm x 1,000mm x 46U.

The modular data center comprises a climate control air optimizer module; a power delivery module housing A&B Bus Bar terminations at the distribution panel, BMS and CCTV services; fire extinguishing gas bottles and release mechanism; VESDA and fire alarm detection systems; and four sections making up the 250 sq.m technical floor for each module.


The site has been built to a security level compliant with a List X audit, for example, Ministry of Defence and Police Authorities. The modular computer halls can deliver Intrusion Level 3 (IL3) and Level 4 (IL4) rated security by applying different build options. Each module can also be upgraded to include a High Intensity Radiation Screening (HIRS) shell to meet the requirements of the UK government’s security equipment assessment panel for data security.

Flexible power options: Each module offers a minimum of 1,000 Watts per sq. m as standard. This can be upgraded to 2,000 Watts per sq. m through the addition of a second cooling unit either at the start or during operation, without any service disruption. Individual racks can be expanded beyond 10kW.

Power resilience: Two diversely routed 7MVA (Mega Volt Ampere) supplies are connected to the on-site substation, rising to 14MVA when required. One supply is always active and the other would be energized in the event of a primary sub-station failure. This power is backed up by continuous rated generators that can deliver power indefinitely. The containerized flywheel UPS system and fast-start generators ensure uninterrupted power supply in the event of grid failure. Each power unit contains three generators, in an N+1 configuration supporting 1,000 sq. m. When upgraded to 2,000 Watts per sq. m density, six generators in an N+2 configuration per 1,000 sq. m would support the load.

Innovative cooling system: Each module is equipped with an efficient dedicated Air Optimizer climate control cooling unit which cools air in three stages, with primary “fresh air” cooling, second-stage evaporative cooling and backup third-stage cooling through Direct Expansion R410a (DX). If upgraded to the higher 2,000 Watts per sq. m density, an additional Air Optimizer can be added without any service disruption. This represents a reduction in cooling energy of 92 percent compared with a conventional data center of nearly 50 percent.

Modular building management system and climate control: The Trend Building Management System (Trend BMS) is very sophisticated and designed for energy-efficiency. Fully managed hot and cold air flows enable constant peak operational efficiency. The use of Computational Fluid Dynamics (CFD) in the design of the modular data halls has enabled the designers to plan and control every aspect of air path. The entire air path from the air optimizer, through the cold corridors into the servers then out to the hot aisle, prevents recirculation of hot air and improves efficiency. The climate control system is claimed to be virtually maintenance-free. The Energy Reducing Cold Aisle containment system is used to ensure that the corridor is sealed and pressurized with a blanking panel system to stop cold air loss.

The cold aisles feature motorized louvered doors which adjust the air volume appropriately for the number of powered servers.

This sophisticated BMS features hundreds of sensors continuously monitoring the air temperature and quality, and able to make very fine adjustments. Thermal imaging is used to monitor constantly for any hot air leakage into cold aisles, while sensors in the hot aisles monitor for temperature, humidity and air pressure and velocity.

Power efficiency: Each 250 sq. m modular room with a full technical floor load at 1,000 Watts per sq. m will use 232 kW of energy for the IT equipment with only 10 kW of power used to cool the servers – a reduction in cooling energy of over 92 percent compared with a conventional data center using chilled water, and 75 percent compared with a high-efficiency modern data center with free cooling. The energy losses in the transformer and UPS are very low at only 60 kW per 1,000 sq. m. Bus Bars feed racks via 16 Amp and 32 Amp snap in commando boxes. No large scale Power Distribution Units (PDUs) or electrician is required.

Dedicated security and fire detection: Each unit has a dedicated CCTV network of cameras with audio links to enable contact between engineers and the control room. Fire detection systems include Very Early Smoke Detection Alarm (VESDA) which provides continuous air sampling for maximum early warning and detection and all fire and security panels are configured N+1 redundancy for resilience.

Clean build rooms: Four client build rooms are available for secure tech refresh activities. These rooms can be patched via fiber to any modular computer hall network. This facility can be booked by the client and Capgemini will provide varying levels of security depending on the nature of the client’s business, for example, Government IL3 security.

Capgemini was a winner of the Green Enterprise IT Awards in the Data Center Design category for Merlin.

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