Title: Data Center Design Parameters and Considerations, Electrical Concerns
Course: 2016FA-MCO-110-401 > Section: Module 11: Data Centers

Click here for a downloadable version of this document:(EXTERNAL) Data Center Design Parameters and Considerations, Electrical Concerns

Backup Systems Scope

MCO back-up systems come in many varieties supporting all types of onsite services.  These discussions become very detailed and design-specific, but the major commonality is a need for emergency power.  System design can become very complex; however, there are a few factors most MCOs must take into consideration pertaining to how long these back-up systems need to operate and the level of site stability they need to support.

Power Quality and Availability

MCOs are becoming more power hungry everyday - often consuming as much power as a small town.  It should be no surprise, then, that power quality and availability always top the list of utility concerns during site planning and selection.  How stable are the local and regional grids?  What is the main source of supply to the grid?  Will the site have a dedicated utility feed, or is it shared with other commercial/industrial customer?

Power quality is a concept that deserves more detailed discussion in topics pertaining to equipment and system design, but for now, think of it as sags and swells in the power supply.  How consistent are the voltages or current being delivered?

Availability of utility power is the most prominent factor for analysis.  Availability is generally measured in number of outages during a given time period and average or cumulative minutes/hours of downtime during that period.  Most of this data is readily available from the utility supplier.

Utility Availability and Reliability

In industrial terms, Utilities refer to resources that require connection to public services such as power, water, sewage, and telecommunications.  Telecom is soon to be non-existent on this list as landline phones are rarely primary, critical resources anymore.  The rise of commercial high-speed fiber and copper data connections, frequently in markets with multiple competitive offerings, has commoditized voice and data transmission with high availability.  That said, even in locations with private/semi-private corporations providing power, water and sewage services, the strict regulatory governance and limited (if any) choice in connections allows these three resources to be considered "public" utilities for discussion's sake.

While some one-off programs might be negotiable, costs for connection and use of theses utilities are generally fixed based on scale.  These costs are similar in geographic regions, so if site selection is already narrowed down to a certain part of the country, this is a point only worthy of nominal consideration.  If the whole country is on the table, cost of power, for instance, does become a notable factor as the dominance of hyrdo-electric power in the Northern Rockies region may provide electricity costs less than half that of the nuclear-dominated Carolinas, which are in turn less than half that of the highly taxed grid in California.

At all phases of analysis, but certainly after the geography has been narrowed down, utility quality and availability quickly jump to the forefront.  For instance, one metropolitan area may boast incredible ease of connectivity and availability, but may have no history supplying a single customer at the volume of the MCO in planning.

Duration of Generator-Supplied Power (fuel stores)

With fossil-fuel powered generators being the most prevalent source of back-up power, there is plenty of MCO history to work from in designing the scale of these systems.  Modern diesel generators (most common type) have become very reliable and stable during operation.  It is then easy to calculate how much fuel will be required to support a given site load for a given period of time.

Next to consider is how available is re-fueling in the area.  Keeping in mind that not all MCOs are created equal, there are often regulations in place that require fuel suppliers to first service hospitals and emergency service centers during widespread utility outages.  Getting a feel for how long it would take to get a fuel supplier out to the site provides the basis for calculating the volume of onsite fuel storage, plus some safety factor assuming delays in the re-fueling.  It should also be noted that most tanker trucks hold somewhere between 5,000 and 8,000 gallons of fuel, so even if the supplier can get out to the site by day 2 or 3 of an event, it may take a long time, or long line of trucks to fill up tens of thousands of gallons on onsite storage.

Battery Life

Batteries are the most simple and traditional form of backup power.  Large scale systems can provide enormous amounts of backup power, but they consume a lot of space and are costly to install and maintain.  For planning purposes, designers must must first answer a simple question: Are the batteries intended to sustain operations during an outage, or merely provide a temporary buffer while permanent back-up systems (e.g. diesel generators) come online?

Given the level of energy used (voltage) and desired runtime, it is simple to calculate the number of batteries or size of system needed.  A particular system can either provide a small amount of power over a long period of time [think of an LED flashlight] or a large amount of power over a short time [digital cameras before lithium-ion batteries]. In the first scenario, a system might have days or weeks of battery runtime - perhaps just enough to keep the lights on.  In the second scenario, a system might have only a few minutes; like powering an entire data center just long enough for the generators to fire up and come online.

Objectives met:
- C11
- 11.3