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Data Centers

Schneider Electric Table of Contents

Build Energy Savings into Your Next Data Center

Table of Contents

Introduction .................................................................3

3. High-efficiency UPS ...........................................8

4. Converting to high voltage distribution ...............9

5. Variable-speed drives on pumps and chillers ...10

6. Capacity management tools ............................10

7. Room layout tools ...........................................11

Conclusion ................................................................12

5 Culprits of inefficiency ...............................................4

8 Characteristics of highly efficient data centers ...........5

7 Key elements of efficient data center design .............6

1. Scalable power and cooling ...............................7

2. Row-based cooling ...........................................8

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Data CentersIntroduction

When planning a new data center there’s no such thing as “too much” research, especially when it comes to energy efficiency. This e-book describes several advances in data center design that will

help achieve savings. It is interesting to note that, considered

separately, they are all effective approaches; however when you

combine them in an integrated approach, you achieve even greater

efficiencies than the sum of the parts.



Data Centers5 Culprits of inefficiency

To improve efficiency, you first have to know where inefficiencies are most commonly found in the physical infrastructure. There are five main inefficiency “culprits:”

1. Power equipment. UPS, transformers, transfer switches and wiring all waste power as a natural inefficiency of the equipment. This is significantly exaggerated when equip-ment is doubled for redundancy or operated below its rated power. Furthermore, the heat generated by this “wasted” energy has to be cooled by the air conditioning sys-tem, which uses even more power.

2. Cooling equipment. Much like power equipment, cooling equipment also wastes energy. In fact, it wastes far more energy, as much as the IT equipment consumes itself, in some cases.

3. Lighting. Lighting wastes power and generates heat unnecessarily when no one is in the data center.

4. Oversized equipment. Oversizing happens when the design value of the power and cooling system exceeds the needs of the actual IT load. It’s quite common, and typi-cally wastes more power than anything else.

5. Configuration. The physical layout of IT equipment has a significant impact on the efficiency of the cooling system. Poor configuration forces the cooling system to move much more air than is actually required and makes the air colder than necessary. It can also force various cooling units into conflict (i.e. where one is dehumidifying while another is humidifying).



Data Centers

To combat the “culprits” of inefficiency, the following 8 characteristics can be applied to dramatically improve data center efficiency (more details to come):

• Power and cooling equipment that’s not currently needed should be turned off.• Equipment should be scaled to meet the demand of the IT load as closely as possible,

not oversized for estimated “future” IT needs.• Power, cooling and lighting equipment should be energy efficient.• Subsystems should be optimized for fractional-load (not full-load) efficiency if you must

run them below their rated capacity (to support redundancy).• Capacity management tools should be used to minimize “stranded capacity.” (Stranded

capacity occurs whenever power, cooling and rack space are out of balance.)• Optimized, integrated physical configuration should be inherent within the system, and

not tied to the characteristics of the room where it resides. For example, row-based cooling should be integrated with the IT racks, independent of room-based cooling.

• The data center as a system should be instrumented to identify and warn about con-ditions that generate sub-optimal electrical consumption, so that they can be quickly corrected.

• The data center as a system should include management software and tools that maxi-mize operating efficiency and minimize or eliminate the possibility of sub-optimal con-

figuration or installation.

8 Characteristics of Highly Efficient Data Centers

When these principles come together in an integrated system, the efficiency gains can be dramatic. Next we’ll take a look at how these principles can be applied in real-world data center design.

>

For more about stranded capacity, see White Paper 150, Power and Cooling Capacity Management for Data Centers.

http://www.apc.com/whitepaper/?wp=150




Data Centers7 Key elements of efficient data center design

In order to achieve the 8 characteristics of highly efficient data centers, there are 7 design choices you can make now that aren’t always feasible after construction is complete:

1. Scalable power and cooling, to avoid over-sizing 2. Row-based cooling, to improve cooling efficiency 3. High-efficiency UPS, to improve power efficiency 4. Converting to high voltage distribution, to improve power efficiency5. Variable-speed drives on pumps and chillers, to improve efficiency at partial load and

on cool days 6. Capacity management tools, to improve utilization of power, cooling, and rack capacity 7. Room layout tools, to optimize room layout for cooling efficiency

$0 $200,000 $400,000 $600,000 $800,000 $1,000,000

UPS

PDU

Generator

Switchgear

Distribution Wiring

CRAC

Heat Rejection

Pumps

Chiller

Humidifier

Lights

Aux Devices

IT Load

$ per Year Electric Cost @ $.10/kwhr

Improved Architecture

Traditional Baseline

This figure illustrates the cost savings of this architecture for a 1 MW IT load and a typical electrical cost of $0.10 per kW-hr. Over a ten-year period, the sav-ings would be approxi-mately $9,000,000.

We’ll take a closer look at each of these elements on the following pages.

>



Data Centers

1. Scalable power and coolingMany data centers don’t run at a full IT load rating – especially smaller data centers or data centers early in their life cycle. In fact, while typical modern data centers are designed for 5-20 kW per cabinet, most operate around only 3 kW per cabinet. This difference means that data centers are physically much larger than needed, with longer airflow patterns, more air mixing, longer power distribution wiring runs, and more lighting than is actually required. Scalable power and cooling, such as modular design, can increase efficiency in these cases and allow you to save on capital and operating costs. Modular design inher-ently combats two of the main culprits of inefficiency. First, it eliminates oversizing and helps mitigate stranded capacity by providing an infrastructure that scales exactly with the IT infrastructure. Secondly, modular design can eliminate room configuration issues, such as with cooling, because optimized configuration is built into each modular pod, rack or row (see pictured example).

High efficiency integrated, scalable data center system

7 Key elements of efficient data center design



Data Centers

2. Row-based coolingIn row-based cooling, air conditioning sits within the rows of IT equipment, rather than at the perimeter of the room. This targets heat at its source, reduces mixing of hot and cold airstreams and results in better predictability of air distribution. Instead of wasting energy with constant speed fans that are common with perimeter units, row-based coolers have variable speed fans that spin only as fast as required to offset the heat. The chart on this page compares the efficiency curves of row-based vs. room-based cooling.

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3. High-efficiency UPSNew UPS systems are more energy efficient than ever, reducing wattage losses by up to 65%. While the efficiency of these UPS systems is significantly higher for any IT load, the efficiency gain is greatest at lighter loads. Remember that every UPS generates heat that must be cooled, and therefore adds to power consumption.

Be aware that some newer UPS systems offer an energy-saving setting known as “eco-mode” that allows the UPS manufacturer to achieve higher efficiency (on the order of 2%). However, because this mode does not offer protection from power quality problems, it is not recommended for data center use.

For more about the trade-offs with eco-mode, see White Paper 157, Eco-mode: Benefits and Risks of Energy-saving Modes of UPS Operation.





Data Centers

4. Converting to high voltage distribution Converting to high voltage distribution (the European standard of 415/240 V from the cur-rent North American standard of 208/120 V) offers significant efficiency improvements. Doing so eliminates power distribution unit (PDU) transformers and their associated energy losses. By eliminating PDUs, you’ll also save on copper costs, reduce floor loading and free up space for the IT equipment. PDUs typically cause an efficiency loss of 2% to 15%, with the larger percent losses occurring in data centers operating with redundant power paths and lighter IT loads.

DC vs. AC

Modern AC and DC distribution have nearly the same efficiency performance for the following reasons:

• Both systems eliminate the electrical waste of PDU transformers• New high-efficiency AC UPS systems achieve the same efficiency as DC

UPS systems• Both systems operate IT power supplies at a higher input voltage, which

improves efficiency

However, there is really no practical choice but to use AC power distribution, because of lack of safety regulations, and because power distribution devices and standard 380 V DC input IT products are not widely available.

For more about AC vs. DC power for data centers, see White Paper 127, A Quantitative Comparison of High Efficiency AC vs. DC Power Distribution for Data Centers.






Data Centers

5. Variable-speed drives on pumps and chillersPumps and chillers equipped with variable-speed drives (VSDs) and appropriate controls can reduce their speed and energy consumption to improve efficiency at partial load and on cool days. The energy savings varies depending on conditions, but can be 10% or more, especially for data centers that are not operating at full rated IT load, or for data centers with chiller or pump redundancy. Variable-speed drives on pumps and chillers can be considered a form of “automatic rightsizing.”

6. Capacity management toolsCapacity management is defined as the process for ensuring power, cooling, and space are available at the right time and in the right amount to support IT loads and processes. In other words, it helps you avoid stranded capacity. As discussed earlier, stranded capacity indicates a lack of one or more of the following:

• Floor and rack space • Power • Power distribution • Cooling • Cooling distribution

Nearly every data center today suffers from stranded capacity, and it seriously limits the performance of the data center. DCIM (data center infrastructure management) tools can help you manage this “stranded capacity” by giving you visibility into your systems and let-ting you simulate different configurations to find the optimal one.




Data Centers

7. Room layout toolsIn addition to capacity management, some DCIM tools can also assist with room layout. A room layout optimized for efficiency is one in which:

• Airflow path lengths are minimized to reduce fan power. • Airflow resistance is minimized to reduce fan power. • IT equipment exhaust air is returned directly at high temperature to the air conditioner

to maximize heat transfer. • Air conditioners are located so that airflow capacities are balanced to the nearby load

airflow requirements.

You probably realized that some of these objectives are automatically met by using row-based cooling. However, floor layout of both the IT equipment and the air conditioners has a major effect on the optimization. The optimum floor layout varies between data centers and depends on the shape and size of the room, target IT power densities within the room, and other site-dependent factors. It requires complex calculations that, fortunately, are available in some DCIM tools. As with capacity management tools, you can use room lay-out tools to simulate different scenarios to find the optimal layout.




Data CentersConclusion

When these 7 design elements are combined – scalable power and

cooling, row-based cooling, high efficiency UPS, converting to high

voltage distribution, variable speed fans and pumps, capacity man-

agement tools and room layout tools—you can save up to 40% more

energy over traditional data center design.

That said, it’s important to note that some of these elements, such as

high voltage distribution, aren’t feasible to implement after the data

center is built. Efficiency is rooted in the architecture and strategy of

your data center.

To see how different design choices will affect efficiency, check out our TradeOff Tool for data center efficiency.

http://www.apc.com/tool/?tt=6



Data Centers

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