Understanding the unique aspects of prefab vs traditional data centre deployments is vital to avoiding delay, cost and inefficiency, say Wendy Torell and Barry Rimmler of Schneider Electric’s Data Centre Science Centre
Implementing prefabricated data centres results in well understood benefits, such as speed of deployment, predictability, scalability and lifecycle cost. However, many of the practical considerations when deploying prefab infrastructure are less well known. Understanding the unique aspects of data centre projects is crucial to avoiding delays, unnecessary costs and, possibly, inefficient operations.
Planning and design considerations
Data centre project planning remains a major challenge for many companies, with poorly communicated plans, discussions at the wrong level of abstraction and a lack of stakeholder buy-in the main causes. Much of this can be resolved by adopting a four-stage approach laid out in “Data Center Projects: System Planning” a white paper authored by Neil Rasmussen, VP of Innovation at Schneider Electric.
But while steps are not eliminated through the adoption of prefabricated data centre modules, they can be simplified and shortened. Once the project parameters of criticality, capacity, growth plan, efficiency, density and budget are determined, the time complete planning is shortened largely because effective prefab designs are based around existing reference designs.
There are, however, two steps that are unique planning considerations for prefabricated data centres; how the equipment is classified financially, and the degree of component-level design engineering that is required.
Firstly, prefabricated modules that are assembled in a factory and packaged either as an assembly on a skid, or an assembly within an enclosure possess the unique attribute of being considered a “product”, rather than a basket of parts or subsystems. Therefore, modules are less likely to become part of the building, (to the same extent that components like panel boards, switchboards, pumps, drives, etc., might be), allowing them to be depreciated separately from the building.
Secondly, engineering a data centre from prefabricated modules involves more system-level design work when compared to engineering a data centre built from products and parts. Designing with prefabricated modules gives the team the ability to forego many of the purely “architectural” decisions associated with conventional designs, such as roof and side wall construction materials.
Prefabrication carries an implicit expectation that the components within the modules are well matched and thoroughly integrated. Importantly, all of the critical components and controls such as circuit breakers, transfer switches, VFDs, and chillers can be implemented and tested in the factory as a complete system, and carries a “listing” by one or more underwriting organizations (such as UL, ETL, or CSA). Communications and controls are ready to function when the module is delivered, with minimal on-site work. Data centre design therefore can occur at a system-level, which can shorten the overall design time from 24 to 12 weeks.
Site preparation considerations
Whether the project is a retrofit or a new “greenfield” data centre build, some degree of work is generally needed to ready the site for any new systems. Permits must be obtained, pipes and circuits must be laid, the land and/or building readied, and the site inspected. For a prefabricated modular data centre there are some unique considerations in completing these steps.
From a graphical point of view, data centres assembled using prefab modules can be more simply drawn, with systems represented much the way that a packaged generator set might be depicted with the focus upon the field connections required rather than the internal wiring and piping. All of the information will be available from the manufacturer in a format to allow the owner to develop detailed drawings according to the audience. Inspections will generally focus on the field constructed aspects of the prefabricated modules.
Many modules are designed to be weather-tight enclosures, making them well suited for outdoor installation as standalone structures. However, there are some reasons why a module may be installed inside a building, such as being skid mounted, not being in a weather-proof enclosure, for added security reasons or to protect personnel from inclement weather conditions during installation or maintenance.
While sites developed expressly for a modular data center provide the greatest number of options, space can usually be found on most campuses and office park locations. The site planning, in the case of retrofit sites, typically includes the repurposing of certain features of the site, such as parking lots, parking structures, warehouses, or “green space”. Among the most important site considerations regarding the location of the modules is the proximity and access to utilities – principally electricity, water, and in the case of IT space modules, the networks carriers.
Outdoor locations are uniquely suitable for utilizing medium voltage delivered from existing outdoor power distribution assets, or directly from the utility. In addition to access to utilities, should be configured with ease of module installation, servicing, and general housekeeping (such as rain water management, snow removal if applicable, and lawn, sidewalk, and lot maintenance) in mind. Additional consideration should be given to perimeter security or screening that may be required.
The procurement process for a prefabricated data center is simpler and quicker than that of a traditional data centre. The simplicity, in part, is the result of each module being purchased from a single vendor as a single complete system or set of systems, and not a collection of individual subsystems from various vendors. Delivery challenges from traditional data centre projects – such as receiving incomplete bill of materials, or missing delivery schedules for certain parts – are avoided when the entire system ships as one.
There are regulations that impact the dimensions and weight of prefabricated modules for delivery via roadways (and other forms of transportation), but prefab integrators/ vendors generally take this into account, since mobility is one of the common reasons for deploying prefabricated data centres.
One thing worth noting is that traditional data centre projects use significant volumes of packing materials resulting in added cost and complexity (i.e. for man-hours and machinery to dispose of the packaging). On the other hand, with prefabricated modules, the majority of the physical infrastructure (power, cooling, rack) subsystems are installed and secured within the modules prior to delivery, which reduces, by an order of magnitude, the amount of packaging necessary to transport the modules safely.
One exception is the UPS. When a module includes a UPS system, the batteries are generally removed after factory testing and prior to shipment, due to their heavy weight. Transporting the module with them installed may result in damage to the UPS frames during transit, as there is a great deal of variability in the performance of tractor trailer air ride systems. Therefore, the batteries are generally placed in cartons and ratcheted to the floor of the module.
Site installation considerations
Well-designed prefabricated modules facilitate a simpler, quicker installation process. Key considerations during the installation process include where to position the modules, how to handle and place the modules, and how to secure the modules to ensure a reliable, efficient operation.
Some prefabricated modules are designed to be stackable. When space is limited or at a cost premium, this may be an added benefit. It is important to include stackability in the design requirements when working with a vendor and project team to ensure site, structural, and environmental requirements are met.
Most prefabricated modules are within the common load ranges of industrial forklifts and drivable cranes. While seaport locations generally use ‘container handlers’ and overhead cranes to move the modules, mobile cranes are the economical lifting machine of choice for on-site installation. Truck cranes are able to travel the roads on conventional pneumatic tires, arrive on a site, and transform itself into a stable, heavy-duty lifting machine. The most time consuming aspect of on-site activity is the set-up and disassembly of the crane. However, once assembled a single crane can lift and place several data centre modules each hour.
Prefabricated data center modules change the nature of data centre planning, and to a large degree dramatically compress the schedule associated with bringing a data centre from concept to completion. For modules installed outdoors, the schedule is often a race between executing and completing the site plan, and the delivery date following the placement of an order. Understanding the unique aspects about these data centre projects is crucial to avoiding delays, unnecessary costs, damage, and/or inefficient operation. White Paper #166, “Practical Considerations for Implementing Prefabricated Data Centers” can be downloaded freely from the Schneider Electric website.