Energy Efficiency
Can Be Improved
Because of the historical unimportance of energy efficiency
and the fact that energy expenses flow through the facilities
team, some data center managers don't yet grasp the
significance of data center energy costs. The 42U
Estimated Energy Expense calculator can be used
to determine the energy expense for a given data center.
The following information can then be used to create
an estimate of the range of savings that various energy
efficiency programs have the potential to yield.
Self-Funding Efficiency Program Model
A systematic, phased approach minimizes initial investment
requirements. This approach first establishes a baseline
consumption value. Efficiency gains are then measured
against the baseline resulting in measurable results.
A variety of low-cost/no-cost measures can be undertaken
in the initial phases that yield significant savings.
The resulting savings are then used to fund more sophisticated
efficiency programs.
42U efficiency solutions, backed by a team of efficiency
experts, establish the baseline for measuring ROI on
efficiency projects. By measuring ongoing efficiency
gains, efficiency programs can be cost-justified and
deliver documented savings.
Efficiency Messaging
The efficiency programs you institute can be used
to communicate a positive message both internally and
externally. Due to the substantial size of the savings,
the energy efficiency programs you undertake can have
a significant bottom line impact on your business. Internally,
the data center team can deliver excellent bottom line
results to the CIO who can deliver those results to
the executive team as well as the board.
Externally, efficiency initiatives can yield positive
press and satisfy larger corporate objectives. Green
initiatives are hot today and data center efficiency
programs are green. These efficiency efforts can be
positioned as green initiatives.
General Considerations
The dynamic nature of a data center makes maintaining
an efficient configuration a challenging effort. The
sheer volume of projects in play in the typical data
center can make the added effort of efficiency take
second billing to the core objective of availability.
Having established procedures and policies ensures any
project comprehends efficiency impacts and ensures data
center efficiency is maintained.
Another major consideration is longitudinal planning.
Investing the time and effort to improve visibility
of changes to computing needs will yield benefits in
the form of continued energy efficiency. This approach
allows rightsizing of the infrastructure, which has
the potential to reduce the energy expense by as much
as 50%. The use of modular component technologies enables
scaling the infrastructure in concert with application
growth.
Including the energy impacts in planning for new
applications was not cost effective, until recently.
The cost of power coupled with capacity limitations
has elevated the importance of energy efficiency planning.
This additional effort not only reduces energy costs,
it yields long term benefits in both reduced capital
and operational expenses.
The following sections describe specific areas to
examine for efficiency gains. Following these general
descriptions is a section that describes the potential
range of energy savings of ten efficiency strategies.
System Design
How the overall data center is designed has one of the
most significant impacts on data center efficiency.
Two data centers with the exact same set of equipment
can have very different energy bills based on how they
are configured. The assumption that focusing on individual
component efficiency results in an efficient system
is flawed. The interaction of the components must be
considered to achieve peak efficiency.
System Redesign
The reality is that most data centers are living
organisms that have grown over time. The original design
considerations have become obsolete as the core business
the data center supports has moved to meet market demands.
In this situation design and planning have to consider
existing conditions. These include the installed base
of technologies, their ages, and the ROI on upgrading
some or all subsystem components within the larger system.
Newer technologies are typically more
power efficient. This efficiency gain must be weighed
against the service life of the existing technology
as well as potential training requirements for new technology
operation and maintenance. For example, best-in-class
UPS systems have 70% less energy loss than legacy UPS
systems at typical loads.
Airflow Management
Airflow dynamics can be improved through a few simple
efforts. These improvements decrease server inlet temperatures
while increasing the CRAC return air temperature which
improves efficiency and reduces energy consumption.
Inside racks the open areas should be
covered so that air entering the rack passes through
the IT equipment rather than around it. Blanking panels
are an inexpensive solution that covers the vacant sections
inside of the rack.
Unstructured cabling can constrain exhaust
airflow from equipment in racks. The best practice is
to use a structured cabling system where excess cable
is eliminated. In addition to removing unused cabling,
cutting cables and power cords to the correct length
will provide more room for air to flow away from the
back of the rack.
Closing off gaps in other parts of air
plenums will also improve cooling efficiency. This can
be accomplished using devices such as floor grommets
to seal areas where cables enter and exit plenums. A
significant improvement in air pressure can be realized
by installing this type of simple equipment.
Sub-floor obstructions are another potential
area where airflow can be improved. Many data centers
use the sub-floor plenum for more than just airflow.
A physical examination of the entire plenum can reveal
blockage issues that if rectified will improve efficiency.
Taking fixed obstructions into account will also yield
a more efficient floor tile arrangement, discussed below.
Cooling Coordination
Most data centers have multiple air conditioning
systems. In some cases these systems have set points
that compete or conflict. One system may dehumidify
while another humidifies, or some systems may actually
be heating air. The various cooling technologies in
the data center need to be coordinated. Expert analysis
is often required to diagnose and remediate these types
of conditions.
Tile Management
This aspect of efficiency should be straight forward,
but this is not often the case. Determining the right
number, type and location of vented tiles in a data
center requires specific ASHRAE expertise, computational
fluid dynamics (CFD) software or some form of real-time
instrumentation. New technologies do provide substantial
help in this area.
Investing time in this aspect of data
center management ensures overheated, or under-cooled,
areas of the data center are corrected. Comprehensive
tile analysis also allows CRAC location optimization.
Floor Layout
How equipment is arranged on the floor has a major
impact on energy efficiency in your data center. The
most important aspect of this is relates to cooling.
A best-practice layout will improve the efficiency of
air flow, which has a direct impact on the amount of
fan energy needed to direct cooled air to the equipment
that needs to be cooled.
The fundamental best-practice is hot/cold
aisle arrangement. This technique improves efficiency
in several ways. It allows you to arrange cooling equipment
in locations where it will establish the most efficient
airflow. Proper design establishes the cool air being
delivered to the IT equipment as directly as possible
as well as having the heated air returning to the cooling
equipment with a minimum of mixing of hot and cold airflows.
Air Containment
The next level of sophistication in data center
efficiency is to contain the airflow in the cold and
hot aisles to avoid mixing of air across or around aisles.
There are two primary types of containment models; hot-aisle
and cold-aisle containment. While both models ultimately
contain both types of aisles, as the names imply, each
technique optimizes for the physics of airflow for a
specific type of aisle.
In simple terms, hot aisle containment
is designed to evacuate heated air and direct it back
to the air conditioning equipment as efficiently as
possible. Cold aisle containment focuses on directing
the outlet air from the air conditioning equipment as
efficiently as possible to the front of the racks in
the cold aisle. Studies indicate that cold-aisle containment
is considerably more efficient than is hot-aisle containment.
Close Coupled Cooling
Historically, data center managers could use rack
load design points and assume this design point applied
to every rack. This allowed them to calculate cooling
and other infrastructure requirements using averages
and relatively simple math. The subsequent cooling system
design simply flooded the entire data center with cooled
air.
Today's reality is very different. Virtualization,
blade servers and other technologies have created a
situation where one rack can have a 3kW load and the
next rack a 30kW load. In a large data center these
high density racks can be distributed in an unpredictable
pattern across the floor.
Close-coupled cooling solves this challenge
by allowing high density racks to have supplemental
cooling that is dedicated to the rack or series of racks.
This type of solution improves efficiency because it
employs liquid cooling technology, shortens the air
paths and eliminates mixing of cold and hot air streams.
An area of concern related to liquid
cooling is delivery of liquid to the systems. Sound
engineering practices ensure this concern is addressed.
Insulation, accessibility, isolation and leak-detection
systems are some of the key design factors that ensure
a safe and reliable liquid cooling solution. Also, the
data center has already proven liquid cooling can be
managed when they deployed water-cooled mainframes.
Economizer Operation
In many geographic locations economizer technologies
can realize substantial energy savings. Many air conditioner
technologies offer economizer options, but this mode
is often disabled or the equipment is not correctly
configured to take advantage of this mode of operation.
Economizers leverage the outside ambient
air conditions to reduce or eliminate mechanical cooling.
There are two types of economizer technologies; air-side
and water-side. Air side economizer operations circulate
outside air through the cooling system when the ambient
air is at or below the CRAC outlet temperature setting.
The air must still be properly conditioned and filtered
to ensure proper humidity and particulate levels are
maintained. In areas near bodies of salt water, salinity
of the outside air must be reduced to avoid corrosion
issues.
Water side economizers use ambient external
air to chill water or coolant when the air temperature
is low enough to chill the water to the target temperature,
typically 45 degrees Fahrenheit. This type of technology
includes an appropriate heat exchanger as well as sensor
technologies that redirect the fluid flow through the
heat exchanger and turn off the mechanical chiller.
Server Replacement Policy
Some amount of server consolidation can be achieved
using an ongoing replacement policy. This can be particularly
effective in large data centers where there is a relatively
regular flow of equipment that is replaced due to failures
or support expiration. The policy identifies which energy
efficient systems should be used as replacements. For
example, a retired four-way server can be replaced with
a two-way dual-core server.
Consolidation
A formal consolidation effort will result in additional
savings. This effort is designed to identify underutilized,
idle or unused servers that can be decommissioned. Assessing
all servers in the datacenter and determining their
utilization rates will uncover servers that are doing
nothing as well as systems performing single, infrequent
or limited tasks. Consolidating these to a fewer number
of servers will eliminate systems.
Virtualization
Advances in software have abstracted operating systems
to a point where a direct physical relationship is no
longer required. Applications can run on a virtual server
using software that mimics operating system behaviors
for the given application. The virtualization software
manages the hardware requirements in a similar fashion,
placing an operational layer above the actual physical
servers. This allows more flexible management of the
hardware devices as well as more efficient utilization
rates.
Estimating Best Practice Energy Savings
The following information describes several efficiency
best practices to consider. 7 Each best practice indicates
the range of achievable energy savings. There are wide
ranges of savings due to the degree of variation in
specific technologies and data center designs.
This information can be used in conjunction
with the Estimated Energy Expense calculation <hyperlink
to E3 page> to estimate the potential savings for a
specific data center. This data is intended to be used
to begin the discussion of energy efficiency programs.
The 42U team can mature this estimated
data into a reliable baseline that can be used to document
measurable ROI. 42U solutions can reduce energy expenses
by between 20-50%6 for low-cost/no-cost improvements
and up to 80% for systematic efficiency efforts.
Blanking Panel Installation - 1-2%
This is a low-cost program that can reduce energy
expense by 1-2%. This can be done in any data center.
Blanking panels are a fundamental airflow control strategy
that improves airflow through equipment and avoids inefficient
airflow around the equipment needing cooling. This practice
decreases server inlet temperatures as well as increases
the CRAC return air temperature, both of which improve
operational efficiency.
Floor Plenum Management - 1-6%
This is another low-cost program for raised floor
data centers that can reduce energy expense by 1-6%.
Vented tiles are incorrectly located or sized in many
data centers. Due to the complexity of airflow behavior,
the correct configurations are not readily obvious.
A professional assessment will ensure optimal results.
Open spaces around cable feeds in the
floor plenum should also be sealed with grommets. This
improves plenum air pressure and further reduces bypass
airflow.
Floor Layout Planning - 5-15%
With correct cabling this can be a no-cost effort
that can reduce energy expense by 5-15%. This best practice
is to arrange racks in alternating hot and cold aisles
with rack fronts and backs facing one another, coupled
with efficient air conditioner locations.
Without structured cabling, and possibly
for other reasons, this may be a difficult or impossible
retrofit. It is best applied to expansions and new designs.
Aisle Containment Systems - 5-10%
In data centers with hot/cold aisle arrangements
containment systems can reduce energy expense by 5-10%.
This is a lower-cost solution that contains the airflow
and directs it directly to the equipment in an efficient
manner. Containment can focus on either the hot aisle
or the cold aisle, but cold aisle containment has been
proven to be more efficient.
Air Conditioner Coordination - 0-10%
An assessment of the settings and interaction of
multiple CRACs in a data center can reduce energy expense
by 0-10%. The sole expense for this program is a professional
assessment. Ensuring that units are not working against
one another eliminates gross energy waste.
Power Equipment Efficiency - 4-10%
Refreshing older UPS systems with new best-in-class
technology can reduce energy expense by 4-10%. Newer
technologies have 70% less losses than legacy systems
at typical load levels. A focus on light load efficiency,
not peak load efficiency, is the key parameter because
this is the typical operating state for the UPS.
Economizer Systems - 4-15%
In some geographic locations economizers can reduce
energy expense by 4-15%. This type of solution is difficult
to retrofit and requires a professional assessment to
determine how cost-effective this solution is for a
given data center.
Air Conditioner Architecture - 7-15%
For higher-density environments this approach can
reduce energy expense by 7-15%. This approach reduces
the air paths requiring less fan power and eliminating
mixing of air. This can be implemented as row-oriented
cooling or close-coupled cooling depending on the number
of high density rack involved.
Virtualization - 10-40%
This solution has a very significant impact that
can reduce energy expense by 10-40%. While not technically
a physical infrastructure solution, it involves consolidation
of application onto fewer servers.
Infrastructure Right-Sizing - 10-30%
This solution can result in energy savings of 10-30%.
This deploys a modular approach to power and cooling
architecture that allows scaling these aspects of the
infrastructure to the specific needs of the data center.
The savings comes in the form of eliminating over-provisioning.
Planning For Efficiency
Due to the complex interactions of best practices, estimating
the net impact of multiple programs is difficult. From
a business best practice perspective, 42U advises clients
to begin by establishing an energy expense baseline
and then implementing each program in an orderly, measurable
process. The low-cost/no-cost efforts should be performed
first to build momentum for the more complex and sophisticated
programs. The savings realized can be used to fund the
more advanced solutions.
Energy Program Cost Justification
While a formalized and measurable program should
ultimately be defined, early discussions can be facilitated
by applying the projected savings above to the Estimated
Energy Expense <hyperlink to E3 page> to have a working
number for the savings potential. This provides insight
into the potential of energy efficiency programs.
Summary
The importance of energy efficiency in the data center
is a relatively recent realization that is only now
dawning across the data center landscape. Costs as well
as environmental concerns are forcing the data center
management community to give more consideration to energy
efficiency programs. The information above helps data
center managers to quantify the value of various efficiency
programs.
42U helps data center managers to identify the efficiency
programs that are most appropriate for a specific data
center and define a phased plan for implementing those
programs. For clients interested in cost-justifying
efficiency programs, 42U establishes an energy expense
baseline and assists clients in instrumenting data centers
to allow linear tracking of energy consumption, enabling
computation of a reliable ROI as each efficiency best
practice is implemented.
Supporting Studies
This section identifies the specific references used
to create this material.
- The $0.40kWh figure comes from a specific engagement
with a client who pays this rate for a data center
located in mid-Manhattan.
- Murphy J., "Building a Green Data Center," Robert
Frances Group, 2007 - Page three displays a graph
showing average cost/kWh at $0.10 in 2006. Other
reports referenced here indicate the annual increase
has driven the average to $0.12. For energy costs
by state: http://www.eia.doe.gov/fuelelectric.html
This site indicates the national average is $0.089/kWh,
but it includes many low-cost, low-density states
that distort the average for more populated areas.
The site also shows state-by-state averages, so
you can use state-specific data when doing the calculation.
- Scaramella, J., "Enabling Technologies for Power
and Cooling," Technical Brief, IDC 2006 - Page three
projects power consumption per rack moving from
1kW in 2000 to 6-8kW in 2006 and above 20kW in five
years (2011).
- Rasmussen, N., "Implementing Energy Efficient
Data Centers," APC, 2006 - Bottom of page three
uses the $0.12/kWh data point and estimates the
annual electrical cost per kW of IT load to be $1,000
and posits a "10 year life of a typical data center"
to extend the "lifetime" cost to $10,000/kW of IT
load. Dividing 0.12kWh into $1,000 yields 8,333
hours, translating to slightly more than 95% uptime.
Source: APC, Electrical Efficiency Measurement
for Data Centers, WP #154
- "EPA Report to Congress on Server and Data Center
Energy Efficiency," EPA August 2007 - The graphic
below summarizes some of the findings of the report
that have subsequently become the basis for the
PUE calculation comprehended by The Green Grid.
Using these percentages, the relationship between
the IT load and other energy consumers in the data
center can be estimated.
- "EPA Report to Congress on Server and Data Center
Energy Efficiency," EPA August 2007 - Table ES-1
on page 6 summarizes the estimated efficiency gains
that clients can expect to realize for various levels
of efficiency programs and technologies. It ranges
from 30-80%.
- Rasmussen, N., "Implementing Energy Efficient
Data Centers," APC, 2006 - Pages 13-14 provide range
estimates for various improvements. It also provides
insights into limitations of each approach and considers
additional strategies.
- "Guidelines For Energy-Efficient Datacenters,"
The Green Grid, February, 2007
About 42U
Since 1995, 42U has been a leader in providing
data center efficiency
solutions for data center and facilities managers. Our vendor and technology
agnostic approach leverages our best-practice expertise in monitoring, airflow
analysis, power, measurement, cooling, and best-of-breed efficiency technologies
to help data center managers improve energy efficiency, reducing power consumption
and subsequently lowering energy costs.
This work is licensed under a
Creative Commons Attribution-No Derivative Works 3.0
Unported License.
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