CASE STUDY #4
ENERGY EFFICIENCY
MEASURES IN JAPAN:
CASE STUDIES
EDITORS:
Akiko Abe, NEC
Eiji Taguchi, Intel
Makoto Karaki, ITOCHU Techno-Solutions
Miho Kato, ITOCHU Techno-Solutions
Yoshihiro Fujie, IBM Japan
PAGE 2
Executive Summary
The Green Grid (TGG) is a global consortium of end-users, policy-makers, technology providers, facility
architects, and utility companies dedicated to enhancing resource efficiency in data centers and business
computing ecosystems. This white paper aims to help domestic data centers improve their energy efficiency
activities by providing case studies about successful energy efficiency projects throughout Japan. These case
studies take into account situations such as geography, regulations, culture, and operating management
standards.
In the decision-making process for which projects to highlight, importance was placed on actual results that
had been observed in the process of practical demonstration. In addition to three case studies that won the
first “Most-Improved Data Center Energy Efficiency Award – Japan” for 2010, this white paper introduces other
case studies that demonstrate fully developed plans for improved energy efficiency that deal with situations
native to Japan.
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in any retrieval system of any nature without the written permission of the copyright owner.
PAGE 3
Table of Contents
I.
Data Center Award Winners ............................................................................................................................... 4
Grand Prix Award: Hitachi, Ltd. ............................................................................................................................... 5
Improvement Activities Based on Visualization of Operation Status .................................................................... 5
Performance Award: Fujitsu Limited....................................................................................................................... 6
Process Improvement Based on Continuous Visualization of Energy .................................................................. 6
Special Award: IDC Frontier, Inc.............................................................................................................................. 8
PUE Improvement Utilizing External Air for Large-Scale Data Center ................................................................... 8
II.
Facility Architecture Case Studies ..................................................................................................................... 9
Internet Initiative Japan, Inc.: Next-Generation Modular Data Center................................................................ 10
Hitachi: Green Solutions with a Modular Data Center......................................................................................... 12
III.
Electricity and Cooling Case Studies ............................................................................................................... 14
NTT Facilities, Inc.: Production Proof-of-Concept Study of the HVDC Power-Distribution Method .................... 15
AT ToKyo (@TOKYO): Air Conditioner Efficiency with a Thermal Storage System ............................................... 17
ITOCHU Techno-Solutions Corporation: Power Load Equalization with Sodium-Sulfur Battery System ........... 19
IV.
Data Center Operation Case Study .................................................................................................................. 22
NEC: Use of Energy Management System............................................................................................................ 22
V.
Conclusion ......................................................................................................................................................... 25
VI.
Acknowledgements........................................................................................................................................... 25
VII. About The Green Grid ....................................................................................................................................... 25
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PAGE 4
I.
Data Center Award Winners
In 2010, The Green Grid established data center awards (“Most-Improved Data Center Energy Efficiency Award
– Japan”) to highlight those organizations that effectively improved the energy efficiency of their data centers.
Award criteria include:

Use of quantitative evaluation criteria (such as power usage effectiveness [PUE™])

Presence of organization-wide strategic goals to reduce energy consumption

Establishment of a plan for concrete action to reduce energy

Continuous energy reduction activities and quantitative assessment of the results

Publishing of results and support of industry-wide improvement activities
The data center award-winners in this white paper are achieving these criteria. To be successful in their energy
efficiency efforts, award-winning organizations have three aspects in common: they consider energy efficiency
a strategic corporate initiative; they leverage PUE metrics, continuously monitor metrics, and share results; and
they take tangible steps toward improvement.
Energy efficiency as a strategic corporate initiative
For an organization to make effective gains in data center energy efficiency, it is important to have top-level
executive sponsorship promoting improved data center efficiency as an important issue. One key success
factor that award-winning organizations have in common is the establishment of objectives for data center
energy savings as an organization-wide goal. These organizations also have defined efforts to build a system
beyond the walls of a single division. For example, if an organization decides that one of its goals is to reduce
electrical utility expenses, that organization’s facilities management department would likely help drive the
effort, rather than solely the IT department.
Energy efficiency must be considered jointly by IT departments and facilities management departments to
make it easier to clearly identify legitimate investment and avoid bias. To overcome organizational boundaries
and ensure that effective actions are taken, it is critical to include the executive and to position energy
improvement policy as part of organization-wide strategy.
Use of PUE metrics
The basic idea behind the use of PUE metrics is that “the invisible cannot be improved.” It is essential to
introduce quantitative indicators to understand the degree of improvement that an organization has achieved
in its energy efficiency efforts. Organizations should adopt good quantitative indicators, incorporating energy
efficiency metrics such as PUE, understanding the effects of continuous measurement and analysis, and
responding when conditions change.
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PAGE 5
Solid improvement efforts
As they approach energy efficiency improvements in the data center, organizations should explore the best
economic situations while continuously implementing various measures to gain an understanding of true
energy usage. The specific approach, of course, depends on an organization’s particular situation, such as the
maturity of the data center, but that approach commonly involves closely observing PUE, determining the
causes of inefficiency, evaluating possible responses, and executing improvements. For example, to improve
air flow, organizations can respond in a variety of ways, including addressing blank rack panels, installing a hot
air exhaust return control board, and using aisle containment. Even more-mature data centers can find ways to
improve their energy efficiency.
When considering return on investment, organizations may find it possible to make cost-effective
improvements, but it may be better to conduct a strategic migration or data center consolidation. (See The
Green Grid white paper Assessment of EPA Mid Tier Data Center at Potomac Yard). Organizations also should
take a long-term approach toward energy efficiency improvements as part of an organization’s overall strategy.
GRAND PRIX AWARD: HITACHI, LTD.
IMPROVEMENT ACTIVITIES BASED ON VISUALIZATION OF OPERATION STATUS
Hitachi, Ltd. was required to contribute sustainable social and environmental management for a client
company. Data center operators were challenged to improve the total energy efficiency and IT optimization in
the company’s data center through the use of high-efficiency equipment in the facility. One area of particular
concern had to do with hot spot management, which was an issue because of the company’s increase in
servers.
Hitachi defined a strategic goal of reducing total data center energy consumption by 50% for five years starting
in 2007, which is when the company began its data center energy efficiency project, named “CoolCenter50,”
across the organization.
Approach and solution
For energy efficiency improvement, Hitachi took a three-pronged approach: Visualization, Assessment/Analysis,
and Improvement/Optimization. The company found that, by conducting these approaches continuously, it was
possible to achieve improvements in data center energy efficiency.

Visualization. This approach involves collecting the multidimensional data that applies to a data
center environment. The company found the following steps beneficial in its effort to gather
comprehensive data:
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PAGE 6

Hitachi monitored the temperature, humidity, and energy in the server room and installed power
meters on all power distribution panels, including those in the server room.

The company routinely patrolled for abnormalities in the server rack environment and facilities.

Hitachi checked the power status of the building management system that collects
measurements throughout the network, using anomaly detection to monitor environment status.

Assessment/Analysis. This approach involves analyzing the root cause of energy inefficiencies.
Hitachi found that it is important to evaluate and analyze the data periodically. It is effective to form a
small work group of data center operators and conduct analyses based on the opinions of the
operations team.

Based on the results of visualization, the company periodically conducted evaluation/analysis
meetings and examined collected data. It found that computational fluid dynamics (CFD)
simulation also can be used for environmental analysis.

As a result of its analysis, Hitachi found that an airflow shortage under the floor and an imbalance
between hot and cold air were the likely causes of hot spots.

Improvement/Optimization. This approach involves defining improvement goals and executing
various actions based on problems found in the “Assessment/Analysis” phase.

To improve the air flow shortage under the floor, Hitachi organized the cable under the floor,
installed a partition plate under the floor, relocated the free access panel, and changed the fan
placement for its grill panel.

To improve the mixing of hot and cold air, Hitachi installed a blank panel, reviewed the grill
position, and switched its air conditioner.
Results
As a result of air flow improvements, Hitachi achieved a 2°C temperature improvement at the top of the rack.
The company decommissioned two air conditioners as a result of hot spot improvement. Overall, progress is on
track for Hitachi to meet its five-year goal. The company continues to make various improvements, such as the
replacement of old air conditioners for higher-efficiency units, the use of water spray at external cooling units,
and so on.
PERFORMANCE AWARD: FUJITSU LIMITED
PROCESS IMPROVEMENT BASED ON CONTINUOUS VISUALIZATION OF ENERGY
Awareness of all energy usage is important in achieving energy savings, and it is also important to quantify CO2
emissions and total energy costs after energy efficiency efforts have been made. Total energy usage, CO2
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PAGE 7
emissions, and total energy costs are key data center metrics, and they help determine a company’s
environmental impact, level of corporate social responsibility (CSR), and profit model for data center
outsourcing. In January 2008, Fujitsu Limited started its Energy Visualization Project, an effort that supports
ongoing improvements in energy efficiency.
Approach and Solution
Fujitsu publishes a regular Energy & Environment Report to accelerate data center energy efficiency
improvement based on:

The conversion of non-electricity energy to CO2 emissions

Splitting shared facilities proportionally (air conditioning power based on ratio of IT power and lighting
power based on area ratio) and apportioning them appropriately to each customer

Utilization of PUE as a measurement
Because measurement points are different for different locations in each data center, Fujitsu does not
compare the results of its data centers to each other. Rather, the company’s goal is to improve the energy
efficiency of each data center independently.
Fujitsu undertook the following steps to publish its Energy & Environment report:

Examine the current energy usage status at each data center

Gather feedback from operations and management teams at each data center

Define common information-gathering methods

Define work flow and information flow from initial data gathering to the publishing of the report

Develop a report macro to help automate worksheet updates
Results
In January 2009, Fujitsu published its initial Energy & Environment Report. The fact that the company could
share real findings involved with the operation of centers and could recognize efficiency issues was a
significant achievement. Some of the findings in the report include those associated with:

Temporary increases in energy self-generation operation as a result of electric power outages by legal
facility inspection

Temporary increases in air conditioning energy before and after the installation of new equipment
As part of its continuous improvement efforts, the company is planning to:

Increase the breadth of content in its report

Improve reporting speed

Add report content based on Japan Data Center Council (JDCC) guidelines
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SPECIAL AWARD: IDC FRONTIER, INC.
PUE IMPROVEMENT UTILIZING EXTERNAL AIR FOR LARGE-SCALE DATA CENTER
IDC Frontier, Inc. built its Kita-Kyushu data center in 2008. To improve the data center’s energy efficiency, the
company adopted the external air utilization method and now uses the dry-side economizer method. IDC
Frontier was able to cost-effectively implement these economizers, considering both the return on investment
(ROI) and the cost impact on data center customers.
When the company began to rely on large-scale external air utilization, there was no meaningful production
data about the use of dry-side economizers under Japan-specific weather conditions, which include hot, humid
summers and cold, dry winters. This lack of data—and the scale of IDC Frontier’s implementation—made the
project challenging. The Kita-Kyushu data center must have a high level of reliability because it is a hosting
data center that also houses services. Because downtime was not an option, the company executed a largescale proof-of-concept study to establish production operations that could meet both economic and reliability
requirements.
Approach and Solution
IDC Frontier evaluated the following two approaches: the isolation of cool and hot air for improved cooling
efficiency and external air utilization using a dry-side economizer.
Isolation of Cool and Hot Air for Improved Cooling Efficiency
To improve cooling efficiency, IDC Frontier used a hot-aisle containment design to implement hot-air and coldair isolation. (The company also considered cold-aisle containment but selected hot-aisle containment because
of cost and operational efficiency advantages.) The hot-aisle containment design may not be effective at lower
power density levels, such as 6 kilovolt-ampere (kVA) per rack, but it works efficiently at much higher power
density levels, which will be required in the near future. To maximize cooling efficiency, IDC Frontier raised the
floor height to 1 meter, which is higher than the floor height in typical Japanese data centers. The company did
not position cables under the raised floor, which supports smooth air flow as validated by CFD simulation. To
optimize cooling efficiency, IDC Frontier is continuously improving air flow; for instance, it installed blank rack
panels, which the company provided free of charge to its customers.
External Air Utilization Using Dry-Side Economizers
IDC Frontier challenged itself to improve PUE by implementing the external air cooling method using dry-side
economizers. To confirm the efficiency of this method, the company executed a large-scale proof-of-concept
project, which included 100 racks with 6 kVA power loads. The company used actual servers as well as
alternative server emulation hardware to fill all 100 racks. Through its proof-of-concept project, IDC Frontier
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PAGE 9
found that it could reach optimized energy efficiency levels utilizing external air as 10% of the total cooling air
capacity. Overall cooling power consumption was reduced by 40%.
To optimize external air usage from a cost standpoint, the company needed to develop operational expertise.
IDC Frontier needed to balance intake fan power consumption and external air temperature, tuning the fan
speed to achieve greater efficiency and to establish the most cost-effective operation. For example, when the
external air temperature is low, fans initially take in a large amount of air, gradually reducing that intake
amount by carefully controlling fan speeds.
It should be noted that IDC Frontier considered the reuse of hot air exhaust from the hot aisle, but it is difficult
to change hot air exhaust into energy. The company decided to direct its hot air exhaust directly to a
greenhouse that was built just outside the data center and now successfully produces paprika, dragon fruit,
and other fruits and spices.
Results
IDC Frontier measures PUE on a monthly basis and uses that measurement to internally monitor and evaluate
energy efficiency. By utilizing external air for its proof-of-concept project, the company improved PUE. The
company uses external air for about 10% of its total cooling air and has reduced overall power consumption by
40%. By monitoring PUE, IDC Frontier now has the ability to respond quickly to efficiency degradation
situations, and it can develop immediate action plans to help execute its continuous improvement efforts.
II.
Facility Architecture Case Studies
Container-type data center design has several merits, such as lower construction and operation costs and
shorter construction periods, compared with existing data center–specific building designs. Containerizing data
centers is considered an effective solution for reducing total cost of ownership.
Large-scale Internet portal data centers (IPDCs) are already using containerization in North America. Until
recently, however, no major containerized data centers were installed in Japan due to several regulations, such
as the Building Standard Law, fire laws, and traffic laws. Recently, these regulations were changed, and
hosting data center players began to implement containerization in their data centers.
To improve energy efficiency in any data center, it is critical to synchronize the operation of IT equipment and
facility equipment management. It tends to be easier to manage that synchronization in containerized data
centers because of their small size, and organizations can expect increased energy efficiency as a result.
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In the Internet Initiative Japan, Inc. case study below, the company adjusted its operation mode to meet Japanspecific seasonal variation. It is notable that the company took care to prepare three operation modes for its
air/cooling system, thus maximizing energy usage efficiency.
The Hitachi case study below highlights energy efficiency improvements for an existing data center facility and
office building server room facility using a modular design concept that comes from the unit idea in
containerized data center designs.
Using an in-house modular structure makes it easier to improve efficiency through the right combination of
spot/local cooling system management and IT workload management, which is similar to a container-type data
center. The modular design also is flexible to modify and can be used to upgrade an existing facility, which
enables a small initial investment and step-by-step expansion.
Energy efficiency improvement is a long-term journey. Organizations need strategies that take them from the
mid-term to the long-term, and they need consistent action to get optimized financial results. These case
studies demonstrate that unit-based facility structures can support easy implementation of integrated IT
workload and cooling equipment management to improve energy efficiency, as well as to improve facility
flexibility. Additionally, when organizations use the newest high-efficiency cooling equipment technology, they
can expect to improve PUE scalability.
INTERNET INITIATIVE JAPAN, INC.: NEXT-GENERATION MODULAR DATA CENTER
If data center service providers do not take steps to improve their environmental impact and the costs
associated with that impact, it is difficult for them to survive. By reducing power consumption and improving
PUE, services providers can create healthier businesses. Such is the case with Internet Initiative Japan, Inc. For
the company to become more energy efficient, it needed to develop advanced cooling solutions to dramatically
improve its existing cooling efficiency. After conducting its own research, Internet Initiative Japan reached the
conclusion that the external air cooling method was the most appropriate for its particular circumstances.
The company, which is a telecommunications provider, set a target of making a high power density—more than
10 kVA/rack—available to any place within Japan, with the exception of Okinawa Island. Because air flow
management becomes too complicated on the floor of traditional large-scale data centers through the external
air cooling method, the company selected a containerized data center design to realize its goal.
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Approach and Solution
The company’s solution needed to meet local regulations and support Japan’s unique climate. The containers
that Internet Initiative Japan uses are specifically designed to meet Japanese regulations. For instance, their
exhaust fans and fire extinguishers meet Japanese fire department law, and they meet safety guidelines under
Japanese facility regulations. At first, the company evaluated the idea of importing containers that were
compatible with International Organization for Standardization (ISO) standards, but, considering transfer and
maintenance cost, it made the decision to create its own containers in Japan.
To effectively support the Japanese climate—with four distinct seasons, each with its own weather conditions—
the company designed three selectable operation modes (external air operation during spring and autumn,
internal air conditioner mode for summer, and mixed mode for winter—see Figure 1). The damper in the airhandling module is managed by inverter control, and sensors monitor temperature and humidity.
Figure 1. The three modes reflect normal seasonal weather conditions in Japan
Results
By designing three operation modes, the data center can effectively react to both daily and seasonal
environmental changes. During the proof-of-concept study for this project, Internet Initiative Japan recorded a
partial PUE (pPUE™) of 1.06 using the external air cooling method for its containerized data center.
The company also validated operation at a higher temperature during the proof-of-concept study. When the
temperature is too high, the server fan speed can increase too much and increase power consumption, so
Internet Initiative Japan found that it was critical to maintain balanced operation. The company also found that
it needed expertise in air operation management to effectively utilize external air, especially in the mixed
operation mode.
The company used a slanting rack placement design to support various IT equipment sizes. This design also
helped the company reduced the container’s width to meet typical Japanese sizes for transfer, which call for
containers of less than 2.5 meters in width.
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PAGE 12
Using the knowledge garnered from this proof-of-concept project, Internet Initiative Japan opened several more
energy-efficient data center parks at Matsue City in Shimane Prefecture in April 2011. These data centers are
ideal for use in a cloud environment.
HITACHI: GREEN SOLUTIONS WITH A MODULAR DATA CENTER
In Japan, generally speaking, the product life cycle for IT equipment is 3 to 5 years, but the life cycle for data
center facilities is more than 10 years. Because of this difference in life cycle, data center facilities have not
being able to accommodate the development of high-density IT equipment, and old air conditioning systems
are causing energy waste.
Land prices are high in Japan, so organizations seek out space-saving IT equipment and data center facilities,
which is why many organizations consider modular data center designs. These designs tend to save electricity
and space, and they lend themselves to flexibility and agility in responding to facility floor requirements. These
designs also make it possible for organizations to start from a small scale and gradually expand.
Approach and Solution
Hitachi chose a unique modular data center design. The unit is 3.6 m〜10 m × 6.3 m in size and can support a
rack with maximum electricity consumption of 25 kilowatts (kW).
Hitachi designed the local cooling system with a power distribution board and air conditioner that are placed
within the module, and the combination of server rack and rack-type air conditioner help achieve cooling
efficiency. (See Figure 2.) This design prevents air stagnation and efficiently cools the entire module. As a
result, servers can be placed densely, which reduces the number of racks required.
Figure 2. Hitachi’s cooling system design
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To achieve an efficient local cooling system, Hitachi introduced a natural coolant circulation method. The
natural coolant circulation method uses the differences in facility height instead of energy to circulate the
coolant, and it cools the server room by heat of vaporization with coolant. (See Figure 3.) This system also
makes it possible to cool the coolant through the use of outside air. The system can use multiple controls for
heat exchange and answers clients’ requests to not bring water into the data center.
Figure 3. Hitachi’s coolant circulation system design
Results
During its experimentation, Hitachi found that using this local cooling system cut electricity consumption by a
maximum of 67% percent, compared with the power consumption of the same IT equipment plus air
conditioner used in normal data centers1. The company also reduced the data center floor area by a maximum
of 80% percent. (See Figure 4.)
1
Compared with the power consumption of IT equipment plus air conditioner in normal data centers, assuming that their IT
equipment is the same.
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PAGE 14
Power of
67%
Cooling
Reduction
Power of IT
Power of IT
equipment
equipment
Traditional
This Modular
Data
Data Center
Center
Figure 4. This isCenter
a comparison between the power consumption in a traditional cooling system and that of
natural coolant circulation using a containerized local cooling method23
In Japan, where land prices are high, saving space can have a significant economic effect and can also help
Hitachi achieve energy savings. Hitachi not only introduced this unique system in its own Yokohama data
center, but it also could use the system to effectively improve existing data centers outside Japan (such as
Telehouse and Green Data Systems in Europe) and when refurbishing server rooms in many existing tenant
buildings.
III.
Electricity and Cooling Case Studies
When it comes to data centers, organization have many options in terms of how they handle electricity and
cooling. The NTT Facilities, Inc. case study below shows an AC/DC power conversion loss-reduction approach
using high-voltage direct current (HVDC) power distribution. In this case, grid power is provided by AC within the
data center, DC power is provided within IT equipment, and power distribution includes an uninterruptable
power supply (UPS) system, which includes AC/DC conversion points. NTT Facilities improved its power
distribution efficiency by minimizing conversion loss in power distribution.
It should be noted that an efficiency comparison must be made between AC power distribution and DC power
distribution. The NTT Facilities case study demonstrates improvements in a particular data center–specific
2
The ratio of IT equipment power and air conditioner power is taken from Japan Electronics and Information Technology
Industries Association (JEITA) announce document (June 2009).
3
Calculated as coolant natural circulation system + chiller + cooling tower.
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PAGE 15
situation. The Green Grid has conducted power distribution analysis and has produced several white papers on
this topic, including Quantitative Analysis of Power Distribution Configurations for Data Centers and Issues
Relating to the Adoption of Higher Voltage Direct Current Power in the Data Center.
Using an HVDC solution is one effective method to consider when looking to simplify an organization’s power
distribution structure. Traditional telecommunications data centers have been using 48 volt (V) DC power
distribution, but by using HVDC, they can improve cable space utilization and flexibility. NTT Facilities has taken
great care to address safety concerns having to do with HVDC, and the company has done considerable work
regarding the standardization of HVDC safety for everyone’s benefit.
The second and third case studies in this section—AT Tokyo (@Tokyo) and ITOCHU Techno-Solutions
Corporation—discuss power consumption leveling, another approach to data center power consumption
management that takes advantage of the difference in cooling loads during the day and at nighttime. If an
organization can store energy at night and use that stored energy during the day, it can better manage its grid
power usage levels. This peak shift can reduce the grid power load, and, if a data center can get a lower price
for its nighttime grid power supply, it can also reduce its total cost of ownership.
Following the March 2011 earthquakes in Japan, the country has faced a continuing shortage in its grid power
supply. These case studies show a peak shift method that is particularly effective, especially considering such
grid power supply constraints.
NTT FACILITIES, INC.: PRODUCTION PROOF-OF-CONCEPT STUDY OF THE HVDC POWERDISTRIBUTION METHOD
The data center industry has become interested in DC power distribution—which has been used in
telecommunications systems—from a reliability and efficiency standpoint. But there are concerns about
traditional 48 V DC power distribution in terms of the thickness of the power cable, which can have a negative
impact on operation and cable space. To resolve this issue, NTT Facilities realized that it was necessary to
develop a HVDC power distribution method. Since this is new development project, the company needed to
ensure that its design was secure enough to safely manage HVDC; at the same time, it needed to ensure
standardization, which was an added challenge.
Approach and Solution
NTT Facilities needed its design to support the increasingly higher power density of IT equipment, which often
causes issues because of thicker cabling and space constraints. The company decided to upgrade its voltage
to 380 V and reduce the amount of current, which enables the use of thinner power cables. This solution also
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PAGE 16
reduces cabling costs, and it can improve cooling efficiency by reducing the problems caused by raised floor
power cable distribution.
HVDC distribution systems use a higher level of voltage compared with traditional AC power distribution, which
means that it was critical to design equipment that is safe for human operation. To protect against electric
shock, NTT Facilities designed a new HVDC support power plug and receptacle, with features such as a newly
designed ground line that minimizes impact to the human body. (See Figure 5.) In this design, power-connecter
parts are all covered so that people cannot inadvertently touch them, and the design, which has an integrated
mechanical off switch, protects people from the arc that is caused when pulling off the plug.
Safty Lock, to be
standardized by IEC about
location of lock position
CASE STUDY #2
CASE STUDY #2
Figure 5. NTT took safety into account when designing its HVDC system
Results
NTT Facilities executed this production proof-of-concept effort from January 29, 2009 to October 30, 2009.
During the project, actual total power consumption (including IT equipment, power distribution, and cooling
equipment) was reduced by 18%, compared with current the company’s regular AC power distribution. (See
Figure 6.) This reduction translates into a cost reduction of 410,000 JPY (U.S. $5,326) per year for this data
center.
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PAGE 17
20
1.0
23.02kW
0.24kW
0.0
19.05kW
-1.0
-1.66kW
15
-2.56kW
9.59kW
7.94kW
10
5
-3.98kW
10.33kW 10.09kW
-2.0
-3.0
3.34kW
Reduction result [kW] r
Energy consumed [kW] r
25
-4.0
0.78kW
0
-5.0
System overall
Power system loss
A/C system
(A)
(B)
HVDC system
UPS system
ICT equipment
(C)
Reduction result
Figure 6. Reductions in total power consumption using the new HVDC design
Because of the successful proof-of-concept project, other parts of NTT Facilities have become interested in
pursuing HVDC for increased energy efficiency. NTT’s laboratory has already decided to implement HVDC for
production use, and NTT Group started production implementation of HVDC in 2011.
AT TOKYO (@TOKYO): AIR CONDITIONER EFFICIENCY WITH A THERMAL STORAGE
SYSTEM
Japan has limited energy resources of its own—it can only supply 4% of the nation’s total energy requirements4.
However, the country has created a well-balanced power generation environment, maximizing the respective
advantages of different types of power generation methods, including nuclear power, thermal power, and
hydropower. This balance takes into consideration such aspects as supply stability, environmental impact, and
economic efficiency.
Over the course of a single day, power demand fluctuates significantly between nighttime off-peak and daytime
peak. During the summer, demand may fluctuate as much as 50%. Therefore, flattening the power demand
curve and using nuclear power generation—which releases no greenhouse gases—can be an environmentally
friendly choice.
4
http://www.enecho.meti.go.jp/topics/hakusho/2010energyhtml/2-1-1.html
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PAGE 18
AT Tokyo (@Tokyo) wants to encourage the generation of alternative energy, such as hydroelectric and thermal
power, to flatten the demand curve. Hydroelectric power is the power to pump water from a lower to an upper
reservoir to create water reserves that are discharged during the daytime to drive the turbines that generate
power. With thermal power, at-home heat pumps heat water as demand arises. The company is providing
financial support for energy-saving systems such as these, with the goal of reducing environmental impact and
total energy costs.
Approach and Solution
System configuration
Heat source equipment: centrifugal chiller (turbo refrigerator)
1,400RT / 700RT
Total
2,100RT
Thermal storage tank: 5,000 ㎥ class
Cooling
Tower
Turbo Chiller
AHU
chilled water
Thermal Storage Tank
Figure 7. The thermal power design suggested by AT Tokyo (@Tokyo)
The design calls for the thermal storage system to run a centrifugal chiller using electricity generated during
nighttime and to store cold water for 5,000 ㎥ class thermal storage. (See Figure 7.) Thermal energy will be
applied to daytime air conditioning so as to reduce the amount of CO2 emissions that run down the centrifugal
chiller during daytime.
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PAGE 19
Freezing machines, which provide cooling water for the data center air conditioner, should run during nighttime
rather than daytime to improve effectiveness based on coefficient of performance (COP). Furthermore, freezing
machines can be run with rated operation. Additionally, the operation rate will rise because daytime running
power can be covered by a thermal storage tank..
Results
The AT Tokyo (@Tokyo) established the following findings (see Figure 8) when comparing its thermal system
design with an unused thermal storage system, keeping in mind combustion gas from the electric generation
plant:
Energy-saving effect of shifting nighttime energy:
11,290 kilowatt-hour (kWh)
Environmental effect of load reduction:
SOx：39.4%（approximately 3 kg/day）
Heat Storage Operation
Heat Radiation from storage
Cooling Operation
0:00
8:00
22:00
0:00
Figure 8. A thermal power system can be more energy efficient by taking advantage of normal temperature
changes
ITOCHU TECHNO-SOLUTIONS CORPORATION: POWER LOAD EQUALIZATION WITH
SODIUM-SULFUR BATTERY SYSTEM
Most data centers were built more than 10 years ago and were designed without taking “green” considerations
into account. When improving the energy efficiency of commercial data centers, organizations need to figure
out how to alter or replace the facility without stopping the systems. Additionally, these improvements require a
significant investment, so organizations must ensure that improvements will result in reductions in operating
costs to offset that investment.
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PAGE 20
ITOCHU Techno-Solutions has a data center that was established in 1988, and the company began to make
energy efficiency improvements to it a few years ago. Some of those improvements included the visualization
of energy efficiency in reference to PUE, a step-by-step transition to energy-efficient equipment, a change to the
server room layout by separating hot and cold aisles, and alterations aimed at cost reduction.
Approach and Solution
As previously discussed, the amount of air conditioning equipment used in Japanese data centers varies widely
in terms of electricity usage during the day versus at night. ITOCHU Techno-Solutions wanted to make
improvements to equalize the burden, which would conserve energy and provide economic savings.
To do so, ITOCHU Techno-Solutions opted to use sodium-sulfur batteries, which use beta alumina ceramics for
the electrolyte layer. These batteries use sulfur (S) in the cylinder that serves as the positive electrode, and
they use liquid sodium (Na) that serves as the negative electrode. A sodium-sulfur battery can discharge and
charge at around 300° C and is said to be one of the most efficient, energy-intensive, and long-life battery
systems.
Figure 9. Use of sodium-sulfur batteries can help equalize energy use at the ITOCHU Techno-Solutions data
center (Source: Tokyo Electric Power)
Moreover, ice thermal storage air conditioning systems are also highly efficient and offer excellent energy
savings. By combining ice thermal storage and sodium-sulfur batteries, ITOCHU Techno-Solutions can store
electricity during the night, when energy tariffs are less expensive, and power can be discharged during peak
daytime hours to equalize power use and reduce electricity costs. (See Figure 9.)
System configuration:

Sodium-sulfur battery system—750 kw

Ice thermal storage air conditioning system—125 RT
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PAGE 21

heat storage tanks x 4—49,216.8 million joules (MJ)
Results
ITOCHU Techno-Solutions found that it could reduce peak power usage by 6.3% because of the shift toward
storing nighttime energy. (See Table 1.)
Electric Power Shift
Generating Power
(A)
400 kW
Output Time
(B)
11 hours
Electric Power Shift
(C)＝(A）×(B)＝
4,400 kWh
Heat Storage
(D）
24,608.4 MJ
COP
(E）
2.43
Electric Power Shift
(F）＝(D）÷(E）÷3.6MJ/kWh＝
2,813 kWh
(G）＝（C)＋(F）＝
7,213 kWh
Consumption Power by Day
(H)
113,534 kWh
Percentage of Night Shifting
(I) ＝(G)÷(H) ＝
6.30%
Total
Electric Power Shift
Percentage
Table 1. The difference in electricity consumption when storing nighttime power for use during the day
As mentioned above, by combining a sodium-sulfur battery and an ice thermal storage air conditioning system,
ITOCHU Techno-Solutions can use inexpensive nighttime electricity and produce cool thermal energy by using
cool air at night. The company therefore equalizes its power usage, which leads to a reduction in electricity
costs. Additionally, the use of nighttime electricity, which is less carbon-intensive than daytime electricity, could
also lead to the reduction in greenhouse gas emissions.
The design that ITOCHU Techno-Solutions is using could be effective as an emergency generator as well.
Because the facility does not involve any combustion and toxin emissions are not a concern, it has a cleaner
environment than many other in-house emergency generators.
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PAGE 22
IV.
Data Center Operation Case Study
The last energy efficiency case study highlights the way that an organization handles the daily operations of its
data center. If an organization can allocate appropriate IT resources according to need and can match the
operational status of IT equipment to the needs of the facility, it can reduce energy usage. However, automated
operations can be an issue for data centers because it is difficult to maintain increasingly complex IT
infrastructures. Proper operations can result in real-time power savings, and organization can improve PUE by
preventing human error when it comes to effective operations.
In the case study below, NEC controlled surplus equipment by powering off IT equipment and automating air
control based on the load using power-saving software. Although NEC is using newer technology, the future
standardization of the API and accumulation of a knowledge base will help organizations adopt similar
practices.
NEC: USE OF ENERGY MANAGEMENT SYSTEM
In recent years, data center operators have been required to manage greenhouse gas emissions based on
various regulations, and many have set targets for emissions reduction. They also have been required to define
solutions to improve PUE.
While organizations work to reduce emissions and improve PUE, they run the risk of making their air
conditioning unbalanced due to the IT equipment load change. Some organizations have experienced
problems with exhaust wrap and hot spots.
Approach and Solution
To solve these problems, NEC found that it is effective to monitor IT equipment in the server room and control
the operation mode of that equipment. Specifically, the company uses power control software to monitor the
operation of IT equipment to increase overall energy efficiency. The IT equipment uses self-reliant power
control and load control. The three main control functions manage power consumption, redundant server
power-off, and elimination of hot spots.
Power consumption control
NEC implemented two methods to control total power consumption of the entire system. (See Figure 10.) One
method protects the maximum amount of power control, and the other controls power to the virtual servers
through power management. Together, these functions autonomously control power usage.
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PAGE 23
Figure 10. The two means of controlling power consumption used by NEC (Source: Tokyo Electric Power)
Redundant server power-off control
When a system has multiple servers, it also has multiple levels of server loads, which can prevent the effective
use of server resources. By shifting server loads to a specific physical server, that server will be able to
maintain the proper load level, and the redundant servers can be turned off. (See Figure 11.) NEC can do this
during periods of low load operation at night and early morning.
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PAGE 24
Figure 11. NEC can avoid wasting power by concentrating its workload on a single server during off-peak
hours (Source: Tokyo Electric Power)
Hot spot elimination
By installing sensors in various places, such as on servers and racks, NEC can measure temperature, humidity,
and power state, and it can detect hot spots or heat regions. (See Figure 12.) The company can optimize
overall energy usage in the server room by reallocating any jobs that create heat to low-workload servers and
automatically adjusting air flow and direction.
Relocate
Relocate server
server for
for
heat
heat equalization
equalization
monitor
monitor humidity,
humidity,
temperature,
temperature, electricity
electricity
detect
detect hot
hot spot
spot
temperature
g
a
co ir-c
nt on
ro di
ls tio
ni
n
M
on
ito
rin
g
High
Low
Handle
Handle hot
hot spots
spots by
by
controlling
controlling air
air conditioning
conditioning
Figure 12. NEC optimizes energy usage through the elimination of hot spots in its data center (Source: Tokyo
Electric Power)
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PAGE 25
Results
NEC achieved a power savings of 30% by using power control software to better control the server room. If the
company had tried to handle that level of management manually, it may have experienced a prolonged
analysis time as well as errors, depending on the skill of the administrator. By using power control software,
the company sped up its control process and removed the risk of human error.
V.
Conclusion
Organizations can use the case studies provided in this white paper to make sound decisions about how to
undertake energy efficiency improvements in their own data centers. Organizations can gain insight about
some of the positive—and often innovative—steps that the highlighted companies have taken and can
determine how best to balance risk and potential improvements with regard to total cost of ownership, reduced
environmental impact, and greater overall efficiency,
VI.
Acknowledgements
The Green Grid would like to thank the companies that participated in the energy efficiency efforts that are
featured in this white paper:
VII.

AT TOKYO Corporation

Fujitsu Ltd.

Hitachi Ltd.

Internet Initiative Japan, Inc.

IDC Frontier, Inc.

ITOCHU Techno-Solutions Corporation

NEC Corporation

NTT Facilities, Inc.
About The Green Grid
The Green Grid is a non-profit, open industry consortium of end users, policy makers, technology providers,
facility architects, and utility companies collaborating to improve the resource efficiency of data centers and
business computing ecosystems. With more than 170 member companies around the world, The Green Grid
seeks to unite global industry efforts, create a common set of metrics, and develop technical resources and
educational tools to further its goals. Additional information is available at www.thegreengrid.org.
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in any retrieval system of any nature without the written permission of the copyright owner.