By Wendy Torell
Part 1 of this article on prefabricated data centers outlined potential planning benefits that data center facility managers might find useful, as they consider a data center design based on prefabricated data center modules. This second half of the article explores the many variables associated with preparation of prefabricated data center sites. It also highlights logistical considerations for facility managers when procuring and installing these data center modules.
Site Preparation
Whether the data center project is a retrofit or new greenfield facility, some degree of work—possibly including applying for permits, readying the land, and installing pipes and wires—will generally be necessary. In cases where prefabricated architectures are used, the steps and the process tend to be simpler.
Permits and inspection. In general, the permitting process for prefabricated data center deployments is similar to that of traditional builds. However, because all necessary information is available directly from a single manufacturer, construction drawings for modular data centers can be more simply drawn, in turn enabling reviews and inspections to be completed more quickly.
Inspections by the authority having jurisdiction (AHJ) will generally only focus on the field constructed aspects of the prefabricated data center. From the standpoint of permitting costs, the value of the facility module is generally legitimately omitted from the schedule of values on which the cost of the permit is based. The theory is that the local inspector (while having every right to view and comment on the facility module) is not being tasked or responsible for its inspection, as the “inspection function” has been performed by recognized agencies and the cost of those approvals is incorporated into the purchase price of the modules.
Location: indoors vs. outdoors. Designed to be weathertight enclosures, most prefabricated data center modules are well-suited for outdoor installation. However, there are various reasons why a module may be installed indoors. These include:
- The module is skid-mounted
- The module is an enclosure that is intended for indoor use
- Protection of personnel from inclement weather during operation and maintenance activities
- Added security of critical systems
For leased data centers, outdoor placement can result in cost savings, as rental fees for outdoor space is often much less than indoor square footage. Parking lots, parking structures, warehouses, and open “green space” that have access to utilities, either from an existing building or directly from the utility, can be converted into a high-functioning data center site.
In addition to access to utilities, those responsible for a data center’s deployment should ensure that site layout is configured to provide easy module installation and removal, servicing, and housekeeping such as rain water management, snow removal, and lawn, sidewalk, and lot maintenance. Perimeter security and screening, in accordance with any terms and conditions of leases or zoning regulations, should also be considered.
Foundations for modules. Site planning documents usually include a “civil site plan,” “electrical site plan” and a “mechanical site plan.” Found within these are the foundations used to support the modules, of which there are three common types: continuous concrete slabs, multiple concrete slabs and piers (or a combination thereof). The site’s physical properties, such as soil conditions, surface water drainage, the presence of frost, and seismic and wind loading requirements for the geographical location, are typically used to identify the appropriate style and type of foundation:
- Continuous concrete slabs are the most common module foundation; provides a 360° walkable perimeter around the facility.
- Multiple independent slabs are most often used when a module is surrounded by impervious cover, and proper water drainage is difficult.
- Piers and concrete columns are smaller than slabs and used to provide support to the module’s load bearing contact points in areas where leaching is used for drainage.
Underground wire and piping interconnections. Utilities supplied to and received from data center modules are usually accomplished with less complexity and lower cost materials if these features are installed underground. Underground feeders and circuits, along with related communications raceways, and most mechanical connections install more simply and with lower cost installation materials when accomplished in this manner. With underground interconnections, the need for multiple support structures diminishes and lower cost to implement materials can be used. Many power modules can drop right over pre-installed underground electrical conduits, simplifying weather sealing and conductor terminations. Additionally, chilled water piping for cooling modules can be installed directly adjacent to the module, reducing or eliminating the need for support hardware.
Procurement
Because prefabricated modules are purchased from the vendor as a complete, integrated system, rather than a collection of individual parts, the procurement process can be expected to be simpler and quicker than that of a traditional data center. However, in order to ship and transport the modules, regulations outlining the dimensions and weight of the system must be met.
Transportation. The transport of data center modules to a site must adhere to prevailing local, state, and federal transportation rules that regulate cargo weight, dimensions, and the distribution of loads on a truck bed. These regulations are well-known to the broad and competitive transportation and logistics industry that is equipped to handle prefabricated data center modules.
Packaging. Because much of a prefabricated data center’s physical infrastructure is secure within the modules prior to delivery, the need for extensive amounts of packaging is reduced. In the case of the uninterruptible power supply, heavy batteries are removed after factory testing and prior to shipment to reduce potential damage.
Protection from the elements. Modules are readied for shipment at the factory, and protection from the elements and physical damage is a joint effort of the manufacturer and the manufacturer’s shipping company, removing the risk from the customer.
Site Installation
Well-designed prefabricated modules facilitate a simpler, quicker installation process. Since the delivery, placement, and connection can be executed quickly, key considerations during the installation process include the timely execution of the delivery plan, handling and placement plan, and integration plan that includes the physical attachment (for wind and seismic resistance), electrical, mechanical, and communications work.
Positioning and orientation. A module’s placement outdoors can have a significant impact on the delivery and operation of the module. To achieve optimal reliability, efficiency, accessibility, and maintainability, modules should be oriented so their shortest side faces the sun, minimizing heat gain. Modules should be placed away from trees, lamps, wires, or other objects that can pose a hazard during a natural event. The site layout should discourage potential vehicular collisions with the module. Beyond this, modules should be free from obstruction and located in an area that allows proper water drainage. In some cases, modules can be stacked.
Handling and placement. Data center modules should arrive at the installation site during the night prior to their placement on their foundations. Many common material handling machines can be used to properly move modules as needed. With truck cranes, several modules can be placed per hour, and modules built within ISO containers generally provide the greatest flexibility with attachment and placement.
Using an experienced crane company, minimizing contact between the crane’s lifting straps and the module, and balancing the module so it does not tilt or sway when lifted can help to prevent damage during the handling and placement process.
Securing the modules and seismic considerations. Once a module is placed in its intended location, it is important that it be fixed in place. This is often accomplished with anchor brackets which are fixed to the supporting structure by very secure fasteners, particularly in geographies where seismic or wind events have resulted in prescriptive requirements. Data center manufacturers generally offer a seismic planning guide to all prospective customers.
Implementation and deployment of prefabricated data center modules is substantially different than that of a traditional data center build. By recognizing and employing appropriate and usually simpler steps for planning and design, site preparation, and procurement and installation, facility managers can more fully realize the inherent benefits of such an architecture including speed of deployment, predictability, scalability, and lifecycle cost.
Torell is a senior research analyst at Schneider Electric’s Data Center Science Center. She researches best practices in data center design and operation and develops content and tools to help clients optimize their data center environments. Torell received her Bachelors of Mechanical Engineering degree from Union College in Schenectady, NY and her MBA from University of Rhode Island. She is an ASQ Certified Reliability Engineer.
A comprehensive two part series on modular data centers – Thanks for publishing and sharing your knowledge Wendy.
Best regards Gordon
http://www.datapod.com.au/