The Pennsylvania State UniversityFEASIBILITY STUDY OF DC POWER DISTRIBUTION AND CHILLED BEAM
SYSTEM AS AN ENERGY SAVING MEASURE
A Thesis in
ii
The thesis of Praveen R. Yadav was reviewed and approved* by the following:
James D. Freihaut
Jeya Chandra
*Signatures are on file in the Graduate School
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ABSTRACT
The increasing demand in energy savings in commercial buildings business has focused
attention on both DC power buses and chilled beam systems. Data centers are increasing rapidly
all over the world. DC power distribution in data centers has potential because the servers located
require DC power transmission for operation. The AC to DC conversion losses can contribute to a
significant waste of energy. Instead of using numerous conversions in power equipment could be
coupled directly to DC bus system having a variety of DC voltage levels available.
In this study, the efficiency of DC system is compared to the traditional AC system and
the results demonstrated that power losses in DC system with four conductors are minimal.
Different construction procedures will be enlisted to determine the cost-benefits of building
designs.
The Chilled beam system promises to be a great energy saving system relative to
conventional building cooling subsystems. However chilled beam systems have some drawbacks
and these will be highlighted and solutions are provided and a practical application of chilled
beams at a Hiranandani, Mumbai project is given. The simple cost and payback analysis of a
chilled beam system is calculated in this study.
The research illustrates the need to look at overall systems approaches to achieve
substantial energy savings in typical commercial building applications. And as vendor selection
plays a key role in improving the cost and quality of a particular project. TOPSIS analysis will be
performed to evaluate the best criterion affecting the function of selection.
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Chapter 2 Literature review .................................................................................................... 6
2.1 Introduction ................................................................................................................ 6
2.2 DC distribution - a revival of interest ........................................................................ 7
2.3 DC with PV system distribution ................................................................................ 8 2.4 Data center ................................................................................................................. 9
2.4.1 Power delivery system .................................................................................... 10 2.4.2 Flywheel .......................................................................................................... 12
2.5 Chilled beam system .................................................................................................. 13
Chapter 3 Research methodolgy ............................................................................................. 16
3.1 Research question ...................................................................................................... 16
3.2.1 Design parameters ........................................................................................... 17 3.2.2 Power loss calculation ..................................................................................... 18
3.2.3 Minitab analysis .............................................................................................. 21
3.3 Transformer losses ..................................................................................................... 21
Chapter 4 Construction ........................................................................................................... 26
4.2 Code compliance ........................................................................................................ 28
4.3 Lean principle ............................................................................................................ 28
Chapter 5 Results and analysis ............................................................................................... 35
5.1 NPV .......................................................................................................................... 35
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6.1 Conclusion ................................................................................................................ 45
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Figure 2-1: Data Center Greenhouse Gas Emissions, 2009–2015(Source: Pike Research,
2012) …………………………………………………………………………………………….3
Figure 2-2: U server power usage (Source: Intel)……………………………………………….7
Figure 2-3: PV- AC system (Source Florida Solar energy center, 2007)………………………..9
Figure 2-4: Photo of small scale demonstration comparing AC on right with 380 V DC systems
on left (Source Intel, 2007)………………………………………………………………………10
Figure 2-5: AC system (Top) and DC system (Bottom) (Source Intel)………………………....11
Figure 2-6: Heat transfer in chilled beam (Source ASHRAE)…………………………………..14
Figure 2-7: Air flow in active and passive chilled beam system (Source U.S. Department of
Energy)…………………………………………………………………………………………...15
Figure 2-9: Chilled beam plant layout (Source: Hiranandani Mumbai, Wipro project)………...23
Figure 2-10: Schematic diagram (Source: Hiranandani Mumbai, Wipro project)……………….24
Figure 2-11: Installation of chilled beam (Source: Trox)………………………………………...26
Figure 2-12: Stages involved in a project………………………………………………………...30
Figure 2-13: Vendor selection steps……………………………………………………………...32
Figure 2-14: Bar graph demonstrating vendor rating…………………………………………….34
Figure: A-1 Probability plot of ΔPac1…………………………………………………………...50
Figure: A-2 Probability plot of ΔPac3…………………………………………………………...51
Figure: A-3 Probability plot of ΔPdc2…………………………………………………………...52
Figure: A-4 Probability plot of ΔPdc4…………………………………………………………...52
Figure: A-5 Third floor layout…………………………………………………………………...53
Figure: A-5 Seventh floor layout………………………………………………………………...54
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LIST OF TABLES
Table 1-1: Flywheel cost of range 200kW at 20 sec (Source Sandia Report, DOE)………….12
Table 1-2: Battery cost of range 200kW at 20 sec (Source Sandia Report, DOE)...………....13
Table 1-3: Configuration for power loss calculation…………................................................19
Table 1-4: Power losses for cross section of 25mm 2 cable size................................................20
Table 1-5: Power losses for cross section of 35mm 2 cable size................................................20
Table1-6: Criterion data.............................................................................................................34
Table1-7: Payment schedule......................................................................................................37
Table1-8: Cost analysis..............................................................................................................37
Table1-10: Cost of conventional water cooled system..............................................................42
Table1-11: Payback analysis......................................................................................................43
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ACKNOWLEDGEMENTS
I would like to thank my advisor Dr. James Freihaut for his expertise, guidance and
encouragement throughout my studies at Penn State. I am extremely grateful to you for providing
me an opportunity to work under your mentorship. I am indebted to my co-advisor Dr. Paul
Griffin for his continuous support, direction and tremendous partnership throughout the research.
I would also like to thank Mr. Anurag Pareek (General Manager, ETA) for his time and
expertise. It was really a pleasure working with you and having email discussions about different
innovations in HVAC system.
Finally, but not least, I would like to thank my family. Without them I would not
have been here at graduate school. I’m grateful to my friends back home and here at Penn
State for their encouragement.
1.1 Background
According to the US Department of Energy (DOE) data centers consumed 61 billion kWh
of electricity in 2006. Based on the current trend it shows a growth rate of 12% every year in
energy consumption. These percentages are going to rise further if appropriate measures are not
taken. The US Department of Energy targets net- zero energy homes by 2020 and commercial
buildings by 2025.
There are numerous types of data centers in the US and across the world. The variety
ranges from banks, universities, government institutions to research facilities. To ensure the best
estimate of power consumption in data centers, it is important to get the load intensity and data
pertaining to existing data centers. The energy consumption of a typical rack server draws 20 kW
of power at 10 cents /hr which constitutes more than $17000/ year in electricity consumption.
Data centers comprise of many such racks constituting a tremendous energy consumption
building (Steve Greenberg, 2006).
Different powers saving techniques are being implemented in day to day life. The use of
direct current (DC) distribution plays a big role in energy saving in today’s market. The reasons
for DC distribution instead of AC settings will be described in the following sections. Various
current losses due to the transformers will be explicated. The initial investment and the estimated
payback for the DC system are calculated. The chilled beam system has proved to save about
60% more energy as compared to the water cooled and air cooled system. However, it still
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in this thesis.
TOPSIS method will be used for analyzing different suppliers based on several criteria, and
the important ones will be analyzed using the results. The initial cost and the payback of chilled
beam technology will be calculated. AC-DC conversion is used mostly in uninterrupted power
supplies (UPS) in the data centers mostly for the office buildings. The two components namely
core and the coil are the vital elements which drive losses in the transformer. The transformer
losses will be discussed in more detail to demonstrate the cut down in the initial investment for
DC bus structures.
1.1.1 “Green” fundamentals
“Green building” is a concept of designing, constructing and maintaining a building
with minimum CO2 emissions, by using natural resources in saving operation cost considerably. It
helps in reducing the overall cost of a project and increasing the longevity of equipment, thus
contributing to profits with environmental concepts in mind. Heating, ventilation and air-
conditioning (HVAC) and lighting system contributes to a great percentage of energy
consumption in a building. 30-50 % of total electricity consumption in U. S. office buildings
constitutes of electricity whereas in the Federal sector, it constitutes 25% of the consumption. On
average, the HVAC system consumes 52 % of the energy consumption in a commercial building
(LANL, 2002). It is important to analyze the peak load conditions before designing the building
load. Considering the peak occupancy of less than three hours duration, the outdoor air flow rate
can be evaluated on the basis of average occupancy for buildings, provided the average
occupancy used is not less than one-half the maximum (ANSI/ASHRAE Standard 62-1999).
Other factors like wall insulation, coefficients of heat transfer for window glasses, roof, etc. are
3
the parameters which can be controlled for an energy efficient building. The lighting system
should be designed prior to the HVAC system. Applying green concepts to chilled beam system
and DC bus structure can lead to great savings in the energy system. The design of a building
considering the day lighting controls and natural ventilation has a great effect on the HVAC
system. It is important to control the relative humidity while designing the chilled beam system.
Failure to do this will lead to condensation in the cabins. Analyzing the external factors compared
to the internal factors is more when considering the chilled beam design system.
With the increase in the number of data centers, the observation for Greenhouse gas
(GHG) emissions has become strenuous. Still the numbers of data centers are expected to
quadruple by 2020 (EPA report, 2007). The growth in technology, real estate, data storage and
transfer across the world has led to an inevitable growth of data centers. The trends for
greenhouse gas emissions from 2009-2015 are shown in the figure 2-1.
Figure 2-1: Data Center Greenhouse Gas Emissions, 2009–2015 (Source: Pike Research, 2012)
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A DC distribution system helps in eliminating transformer losses. This indicates that for every
watt of power utilized to process data, another 0.9W is required to support power conversion. In
addition, another 0.6 to 1 watt of power will be required for each watt utilized to cool the power
conversion equipment (Fortenbery, 2008).
The research hence examines the feasibility of DC distribution and chilled beam
systems as great energy saving measures.
1.2 Objective and outline
The objective of this research is to compare the energy efficiency of a DC distribution
with an AC distribution system in a data center. The power losses in both the system will be
calculated. The aim of the research is also to analyze the advantages and drawbacks of a DC
distribution compared to an AC system. Another goal of the research is to calculate the payback
period for a chilled beam system. Various construction details for the same will be outlined.
Minitab analysis will be used for comparing the different power losses parameters. The main
objectives of the research can be summarized as follows:
a) To study the DC distribution system compared to the conventional AC system
b) Calculating and comparing the efficiency and power losses of each system
c) Understanding the challenges encountered in design and installation of a chilled beam
system
d) Studying the overall cost involved in execution of a chilled beam system
e) Calculating the payback of a chilled beam system
f) Selection of vendors based on TOPSIS method
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Chapter 2 summarizes the existing findings in the literature about the DC distribution and
chilled beam system. It also provides the existing data pertaining to the efficiency of data centers.
DC distribution coupled with LED system will be described briefly. Chapter 3 provides an
overview of the research methodology with data collection and power loss calculation of both AC
and DC systems. A brief description of transformer losses and the battery system will be
explicated too in the following section. The layout of a chilled beam system with different HVAC
equipment will be explained in detail. Chapter 4 elaborates on the construction details like
installation, code compliance, lean principles and vendor selection using TOPSIS method.
Chapter 5 provides a simple payback calculation of the chilled beam system followed by Chapter
6 which summarizes the conclusion and future scope of work.
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Chapter 2
Literature review
2.1 Introduction
The research conducted on a DC distribution design is minimal. The focus of the research
is to help engineers and architects analyze the system more in terms of efficiency and cost saving
approach. Data centers in the current market go through numerous conversions steps to deliver
the power. Data centers already consume between 1.7 - 2.2 % of all electricity used in the USA,
and between 1.1 - 1.5 % globally (Koomey, 2010). The supply provided is alternating current
(AC) but the power requirements are DC. The power conversion loss for a 10 MW data center
comes to 2-3 MW (Karen George, 2006).
The uninterruptible power supply (UPS) in a data center provides conversion from AC to
DC and then back from DC to AC. The second process involves two conversions in data
processing equipment wherein the incoming AC supply is converted to DC and by the time the
power reaches the microprocessor from the main input there are approximately six conversions.
In data centers these power conversion devices operate at an efficiency of about 65-75
percentage, out of which the remaining is wasted. Also, cooling is required for the power
conversion devices due to the tremendous heat developed during the operation time. The potential
for DC distribution system is very high since switched mode power supply (SMPS) is found in
many devices like fax machine, copiers, laptop, desktop, fluorescent lighting etc. (George, 2006).
SMPS is used for converting AC power of 120 V/60 Hz to DC power for many devices.
This literature review provides the gist of existing work carried out on DC supply and
chilled beam system with the future scope they carry as a potential energy saving measures.
7
2.2 DC distribution – a revival of interest
Alternating current (AC) is used in today’s equipment due to higher reliability. In the
past, conversions were mostly avoided and a straight AC or DC method was used. Both had their
advantages and drawbacks (Graaff, 2010). AC distribution system is mostly used but DC
distribution system proves to have a good future potential for energy saving. The DC system is
used in many applications like telecommunications, automotive power system, sea and undersea
vehicles, railway electric and space power systems. Telecommunications system operates at 24 or
48 V DC with automobiles consuming 14 V DC. The consumption for railways is 600 or 750 V
DC (Javanshir, 2007). Server efficiency plays a vital role in saving energy at data centers. The
energy consumption of servers is high in data centers with electrical power as direct consumption
and heating, ventilation and air-conditioning (HVAC) as an indirect consumption for cooling the
equipment. Figure 2-2 provides the power consumption of servers (Godrich et al, 2005).
Figure 2-2: U server power usage (Source: Intel)
8
The payback of a server constitutes cooling and electrical costs which proves to exceed the cost
of server lifetime (Belady, C.L. 2007). With the increasing infrastructure, energy consumption
and cost the focus has moved towards the DC system. DC system helps in reduction of
conversion stages thus reducing the number of equipment and cost.
2.3 DC with PV system
A photovoltaic system consists of many PV cells. The material generally used is
crystalline silicon (Messenger et al, 2004). The PV panels capture the solar energy and transfer it
to the charge controller where the voltage is altered as per the load requirements. Figure 2-3
shows how a PV system works in detail for an AC system. For a DC system the necessity of an
inverter is eliminated since the source provided is DC directly. The combination of DC with PV
and LED lighting works best for saving energy, but there are some problems which need to be
overcome. The architects, designers, contractors and project managers need to be educated more
about the DC system. DC system was very successfully used some years back. It is very efficient
when the power delivery is for longer distances. Later, Westinghouse introduced the concept of
AC system which is currently used in today’s market. DC system is safer compared to AC system
due to less voltage operation (Bellis, 2007). 12 V, 24 V, 48V are the voltages used for a DC
system.
9
Figure 2-3: PV- AC system (Source Florida Solar energy center, 2007)
The batteries used in a PV system are used for energy storage. It is beneficial when the
load consumption is required at night. The batteries must be efficient in charging and discharging
function to a great extent and hence lead-acid batteries fits the criterion. The advantages
associated with the use of a PV system are that it uses a clean source of energy i.e. solar; hence
the chances of gas emissions are reduced considerably. It is renewable and cell life is more than
20 years (Northeast Sustainable Energy Association, 2001).
Fluorescent lighting is used in combination with a PV system due to its energy saving
results. The use of DC incandescent lighting has not proved to be a great success whereas light
emitting diode (LED) operating on DC voltage can be a great alternative with photovoltaic (PV)
system. The advantages of using LED are low energy consumption and maintenance. Its
performance is high at cold temperatures and it can be combined with DC source directly.
2.4 Data center
This section provides a comparison of operation of both AC and DC systems in a data
center. Uninterrupted power supply (UPS) is used in an AC system for the safety and quality of
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power delivery. Most data centers use the N+1 concept where a backup is always provided if
there are chances of failure of equipment. It demonstrates that there might be maximum load of
50% on each equipment if the backup is installed (Ton et al, 2005). Today, many data centers
prefer going for an advance step of 2N system where the backup system is also provided a
backup.
2.4.1 Power delivery system
For embracing a new DC system in data centers, it is important to analyze the existing
AC system. The AC data centers usually use 600 V AC or 480 V AC (Ton et al, 2007). Figure 2-
4 shows AC and DC system installed in a facility followed by a schematic Figure 2-5 providing a
comparison of both systems.
Figure 2-4: Photo of small scale demonstration comparing AC on right with 380 V DC systems
on left (Source Intel, 2007)
In the normal AC distribution system, the UPS has two conversion stages where the AC
power is converted to DC and again converted back from DC to AC. The data processing
equipment function at 208/220VAC hence, the power needs to be transferred from 480 V AC to
208 V AC. The reduction in the double conversion at the UPS can be achieved by a bypass
11
supply and helping to move towards the other conversion when encountered with other
disturbances. The other method can be usage of delta-conversion for a UPS (Mulcahy, 2006).
A battery system is used at the DC-AC conversion stage to provide a backup during
interruption in AC power. There are many alternatives which can be used instead of a battery. A
flywheel is one of them, which serves the purpose in a much more efficient manner. Later, there
are two conversions at the power supply unit stage where again a DC supply is required for the
servers. There are many power conversion steps taking place in this system and hence it
demonstrates a lot of energy loss both internally and externally taking place in the whole system.
As shown in Figure 2-5 below, in a DC system only one power conversion takes place
through the rectifier in the UPS and a flywheel system is used for the energy backup. The second
conversion DC-DC takes place in the power supplying unit (PSU). Thus it demonstrates that the
number of equipment and the power conversion stages from the beginning to end is reduced.
Figure 2-5: AC system (Top) and DC system (Bottom) (Source Intel)
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2.4.2 Flywheel
The energy storage system has faced many problems in developing the flywheel as a
potential device. The companies are aiming for a wheel size of 30- 50 kWh with conversion rate
of 10-20 kW. The estimated energy related cost for a 50 kWh system is about $1000/kWh, and
the power related component is about $300/kW. Efficiencies of 0.95 with more longevity and no
replacements for 20 years are expected (Schoenung et al, 2003). The power density of a flywheel
is more compared to batteries and can prove to be a successful combination with data centers due
to high floor space costs.
Flywheels have a higher initial cost compared to batteries but have a longer life and
lower operation and maintenance cost. Thus, it seems to be a reliable alternative in terms of cost
effectiveness compared to the usage of batteries. Tables 1-1 and 1-2 give a brief cost comparison
of both the storage systems.
Table 1-1: Flywheel cost of range 200kW at 20 sec (Source Sandia Report, DOE)
Flywheel costs
Replacement cost $ 16000/kW-h
13
Table 1-2: Battery cost of range 200kW at 20 sec (Source Sandia Report, DOE)
Battery costs
Replacement cost $ 300/kW-h
2.5 Chilled beam system
For 20 years, chilled beam system have been used successfully in Europe and are gaining a
rapid popularity in USA and worldwide. It was first invented in 1975 in Norway. The chilled
beam system consists of pipes running through the ceiling with the cooling coil exposed to the
office areas. They provide cooling through natural convection and radiation method. The current
chilled beam system requires a dedicated outdoor air system (DOAS) and air tight building for
running the system efficiently. Ventilation air forms the main source for humidification and can
be controlled either by using dehumidifiers or dew point control sensors (Mumma, 2001). Figure
2-6 gives an overview of the heat transfer system in a chilled beam. Radiation cooling helps in
reducing energy consumption from 15 % to 20%. It reduces the heat produced by ventilation fans
and also cools the occupancy area (John, 2004). There is a prediction of 42 % less energy
consumption by DOAS system when compared to the variable air volume (VAV) system.
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Figure 2-6: Heat transfer in chilled beam (Source ASHRAE)
Space plays a big role in today’s construction market. To meet the increasing needs of
sensible load and maintaining the duct size, chilled beam serves the purpose. Basically, there are
three types of chilled beam viz. active, passive and multi-service chilled beam with lighting,
speaker, etc. system installed in it for multiple purposes. They can be either active or passive.
Active chilled beams have an air handling unit (AHU) where the air is forced through
the duct system and consists of piping arrangement for the coils. It consists of one AHU system
serving a bigger zone. Passive chilled beam systems use the natural convection method where the
heat dissipated by the occupants is cooled by the cooling coils through convection process.
Mostly active chilled beams find more application compared to the passive system. Chilled beams
maintain the sensible cooling load whereas the latent load is taken care by the AHU. To avoid
condensation, it is important to maintain the chilled beam water temperature above the dew point
temperature in a room. The figure 2-7 gives a brief description of air flow in both the active and
passive systems.
15
The advantages associated with the chilled beam system are that it has no moving parts.
This eliminates noise and reduces maintenance to a great extent. There is no large duct sizing
required and the space can be utilized for other services. Fan usage is reduced to a great extent
due to pumping of water and serves as a great energy saving measure.
The disadvantages of the system are that the initial investment compared to the variable
air volume (VAV) system is more. To avoid condensation, maintaining room conditions isr vital
and chilled beam installation must be arranged considering the electrical equipment like printers,
fax, copiers, etc. The data availability on execution and designing of chilled beam projects is
minimal which leads to lack of familiarity with the technology in engineers.
Figure 2-7: Air flow in active and passive chilled beam system (Source U.S. Department of
Energy)
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3.1 Research question
The aim of the research is to analyze the existing system and to provide alternative methods to
improve it. This research will highlight the following issues:
a) The efficiency of DC system will be calculated in comparison with the AC system
b) The cost estimation for a Chilled beam system will be calculated
c) Selection of vendors is a vital element in today’s procurement industry. Different lean
techniques will be discussed in further section.
The steps taken were:
a) Existing research work
The existing work carried out in the field of power distribution was analyzed. The chilled
beam system history was studied in detail. Chapter 2 provides a good detail of the literature
review studied.
b) Advice from the industry
The data was obtained from professionals working on existing projects carried out in the DC
power distribution system. The methods established for working on chilled beam system
projects were also taken in to consideration.
c) DC system efficiency
The data of cable size and voltage requirements were obtained for calculating the efficiency
in comparison with the AC system.
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d) Chilled beam system
A schematic diagram is important to get the brief function of the HVAC system. The
technical details of AHUs, valves, ventilation fans will be provided and the selection of
appropriate size according to the load requirements will be made.
e) Procurement
After the design completion and selection of equipment sizing procurement stage follows
wherein selection of vendors is critical. TOPSIS method is used to make a perfect selection
considering various parameters.
f) Cost analysis
The detailed cost of equipment will be provided and payback analysis will be done for the
project accordingly.
g) Construction
Finally the construction standards for both the systems will be discussed more elaborately in
later section.
3.2 AC and DC distribution system
In this section single phase AC, three phase AC, DC consisting of two and four conductors
will be analyzed assuming the cables are same for both AC and DC condition. The efficiency for
each system will be calculated with different cable lengths and cross section.
3.2.1 Design parameters
It is important to design an efficient system considering the payback in effect. The
parameters which play an essential role in the efficiency are:
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2) Cable size considering cross section area and length
3) Single phase AC, Three phase AC, Two and four conductors DC installation
4) Power factor (cos Ø)
5) Power rating (P)
For a three phase system, there are five wires consisting of three conductors, one neutral and a
ground. A single phase consists of three wires, with two being conductors and one as a ground.
Similar concepts can be applied to two and four conductor pole in DC system.
3.2.2 Power loss calculation
Power losses in AC and DC single phase and three phase system will be calculated in the
following section .
The cable resistance can be calculated as follows from equation (3.1) [19]
R = (3.1)
ρ0 = 0.0178 mm 2
0 C
AC single phase:
Active and reactive current are calculated as in equation (3.2) and (3.3) respectively
I a= P / Vac1 (3.2)
Ir = Ia * tan Ø (3.3)
Iac1= P/Vac1*cosØ (3.4)
ΔPac1 = 2* I 2
2 Ø* V
2 ac1 (3.5)
AC three phase:
Active and reactive current is calculated as in equation (3.6) and (3.7) respectively
I a= P / √3 *Vac3 (3.6)
Ir = Ia * tan Ø (3.7)
Iac3= P/√3 Vac3*cosØ (3.8)
Therefore, the power loss is:
ΔPac3 = 3* I 2
2 Ø* V
2 ac3 (3.9)
DC with two conductor:
There is no reactive current in a DC system and hence coinciding takes place
Idc2= P/Vdc (4.0)
ΔPdc2 = 2* I 2
2 dc (4.1)
DC with four conductor:
Here the load is shared equally among two conductors and therefore the current is
Idc4 = P/2 *Vdc (4.2)
ΔPdc4 = 4* I 2
dc4R= P 2 *R/V
AC single phase voltage (Vac1) Vac1= 120 V
AC three phase voltage (Vac3) Vac3= 480V
DC voltage level (Vdc) Vdc= 380V
Cross-section area of cable (A) 25mm 2 , 35 mm
2
Power factor (cos Ø) 0.7, 0.8, 0.9, 1
Power losses were calculated for each system and the results demonstrated that the DC with
two conductor power losses are very low when compared with single phase AC system, whereas
it is high when compared with three phase AC system. DC with two conductor losses are almost
double the losses when compared to DC with four conductor system. DC with four conductor
system when compared with three phase AC system explicates that the losses depends on the
power factor to a great extent. To prove this later a minitab analysis is performed on the power
losses compared to each parameter .
Table 1-4: Power losses for cross section of 25mm 2 cable size
Length (m) Power factor Area(mm2) Power rating (W) Resistance Iac1 Iac3 Idc2 Idc4 ΔPac1(%) ΔPac3(%) ΔPdc2(%) ΔPdc4(%)
100 0.7 25 8000 0.08 95.2381 13.7627305 21.05263158 10.5263158 14.51247166 0.4545906 0.709141274 0.354570637
200 0.7 25 8000 0.16 95.2381 13.7627305 21.05263158 10.5263158 29.02494331 0.90918121 1.418282548 0.709141274
300 0.7 25 8000 0.24 95.2381 13.7627305 21.05263158 10.5263158 43.53741497 1.19330033 2.127423823 1.063711911
100 0.8 25 8000 0.08 83.3333 12.0423892 21.05263158 10.5263158 11.11111111 0.34804593 0.709141274 0.354570637
200 0.8 25 8000 0.16 83.3333 12.0423892 21.05263158 10.5263158 22.22222222 0.69609186 1.418282548 0.709141274
300 0.8 25 8000 0.24 83.3333 12.0423892 21.05263158 10.5263158 33.33333333 0.92812248 2.127423823 1.063711911
100 0.9 25 8000 0.08 74.0741 10.704346 21.05263158 10.5263158 8.77914952 0.27499925 0.709141274 0.354570637
200 0.9 25 8000 0.16 74.0741 10.704346 21.05263158 10.5263158 17.55829904 0.54999851 1.418282548 0.709141274
300 0.9 25 8000 0.24 74.0741 10.704346 21.05263158 10.5263158 26.33744856 0.74249799 2.127423823 1.063711911
100 1 25 8000 0.08 66.6667 9.63391137 21.05263158 10.5263158 7.111111111 0.2227494 0.709141274 0.354570637
200 1 25 8000 0.16 66.6667 9.63391137 21.05263158 10.5263158 14.22222222 0.44549879 1.418282548 0.709141274
300 1 25 8000 0.24 66.6667 9.63391137 21.05263158 10.5263158 21.33333333 0 2.127423823 1.063711911
21
Table1-5: Power losses for cross section of 35mm 2 cable size
Also the results demonstrated that with increase in the cable cross section the power losses
decrease.
3.2.3 Minitab analysis
Regression is performed on the power losses in single AC system as response to the length
and power factor being predictors. The results obtained showed p value for resistance of 0.000
which is less than 0.05 hence, rejected null hypothesis and indicated that length and power factor
forms a significant parameter for the power losses in AC single phase system (Appendix-1). The
results obtained for power losses in three phase AC system indicated that power factor and length
forms a significant indicator too(Appendix-2). (Appendix-3) and (Appendix-4) gave a good result
for the relationship in DC2 and DC4 system.
3.3 Transformer losses
The conversion of power takes place in switch mode power supplies (SMPS), uninterrupted
power supplies (UPS) which consists of numerous amount of minute converters. The major losses
in a transformer are coil and core losses. Core losses account for zero load to full load condition
whereas the coil losses account for the power fed to the load. The transformer losses have a great
impact on power loss in an AC system. The results obtained from the figure below shows that for
Length(m) Power factor Area(mm2) Power rating (W) Resistance Iac1 Iac3 Idc2 Idc4 ΔPac1(%) ΔPac3(%) ΔPdc2(%) ΔPdc4(%)
100 0.7 35 8000 0.05714286 95.2380952 13.76273 21.05263 10.52632 10.36605 0.3247076 0.506529 0.253265
200 0.7 35 8000 0.11428571 95.2380952 13.76273 21.05263 10.52632 20.7321 0.6494151 1.013059 0.506529
300 0.7 35 8000 0.17142857 95.2380952 13.76273 21.05263 10.52632 31.09815 0.8523574 1.519588 0.759794
100 0.8 35 8000 0.05714286 83.3333333 12.04239 21.05263 10.52632 7.936508 0.2486042 0.506529 0.253265
200 0.8 35 8000 0.11428571 83.3333333 12.04239 21.05263 10.52632 15.87302 0.4972085 1.013059 0.506529
300 0.8 35 8000 0.17142857 83.3333333 12.04239 21.05263 10.52632 23.80952 0.6629446 1.519588 0.759794
100 0.9 35 8000 0.05714286 74.0740741 10.70435 21.05263 10.52632 6.270821 0.196428 0.506529 0.253265
200 0.9 35 8000 0.11428571 74.0740741 10.70435 21.05263 10.52632 12.54164 0.3928561 1.013059 0.506529
300 0.9 35 8000 0.17142857 74.0740741 10.70435 21.05263 10.52632 18.81246 0.5303557 1.519588 0.759794
100 1 35 8000 0.05714286 66.6666667 9.633911 21.05263 10.52632 5.079365 0.1591067 0.506529 0.253265
200 1 35 8000 0.11428571 66.6666667 9.633911 21.05263 10.52632 10.15873 0.3182134 1.013059 0.506529
300 1 35 8000 0.17142857 66.6666667 9.633911 21.05263 10.52632 15.2381 0 1.519588 0.759794
22
geneartion of 1 Watt power another 0.9 Watt is required for power conversion and another 0.6 to
1 Watt is required for cooling the heat generated by the equipment.
Figure 2-8: Conversion losses(Source: Intel Corp)
The figure above explains the losses taking place due to conversion in each equipment. It
demonstrates that for generating 100 W of load another 175 W is wasted .
23
Figure 2-9: Chilled beam plant layout (Source: Hiranandani Mumbai, Wipro project)
24
The figure 2-9 above provides a chilled beam plant layout at Hiranandani Powai, Mumbai with 3
chillers of 125 TR and primary pumps of 125 mm diameter inlet (2-working and 1-standby).
Figure 2-10: Schematic diagram (Source: Hiranandani Mumbai, Wipro project)
25
The figure 2-10 is the schematic of whole project with the plant layout and two floors
with chilled beam system installed. The separate layout for floor-3 and floor-7 with chilled beam
system are attached in the appendix-5 and appendix-6
26
4.1 Chilled beam installation
Chilled beam being a new system in Mumbai conditions hence a mockup was installed
to ensure that the conditions of installations are met. 3/8 inch diameter rods were used for
suspending the chilled beam on four corners. Flexible air ducts were used for connecting the
ducting part of chilled beam. A flexible hose was used for the connection to the MS chilled water
pipe line. The life of the hose is around 15 years.
Figure 2-11: Installation of chilled beam (Source: Trox)
27
After the chilled beam is installed, grid installation takes place. The threaded rods are attached
with fasteners to adjust it according to the grid height. Using Hexagonal nut with washer works
best for the following condition. Installation of chilled beam was crucial in the project due to
variance in coordination drawing and a small difference in height would lead to an enormous
reworking of grid and chilled beam installation. The chilled beam used on the project was
Flaktwood make. The chilled water line was completely insulated with thick TF quality Rigid
Polyurethane Foam (RPUF) insulation with FRP finish. This type of insulation is different
compared to the one used in normal water cooled and air cooled system insulation. To ensure that
all debris is removed from the pipe it is necessary to flush the whole system before connecting to
the chillers and chilled beam. Later, a pressure test is conducted to check for the welding joint
leakages. Air purge valves must be provided in the chilled water line for removal of trapped air in
the system. Flaktwood chilled beams had separate purge valves for each beam to ensure the
removal of air. Maintaining the working of a chilled beam system is very crucial due to its
condensation problems. Dew point temperature of a space must be maintained before providing
the chilled water in space. Maintaining positive pressure in the lobby area is very important as to
avoid the entry of outside air. The air temperature is assumed to be 2 degrees more than the room
temperature due to the difference in room air and chilled water entering temperature. 3 sets of
Centrifugal back pullout type chilled water pump sets with mechanical seal to deliver 21 lps at
12°C against 27 m head was installed with 2 working and 1 standby condition. 825 numbers of
chilled beams were installed for both floors. 3000 square meter of GSS ducting with 24 Gauge
specifications and flexible ducting of 150 mm diameter was measured for the project. The details
of equipment with cost will be provided in the later section. Chilled beam coils need to be clean
regularly considering the filters used in AHU and the dust in the room. The access is quite easy to
the coil and most beams offer easy coil access from below the ceiling.
28
The code compliance used for the project was
1) CBC Title 24 (based on IBC 2006) Volume 2 1614A.1.12 ASCE 7, Section 13.5.6.2
(Used for installation of chilled beam with the connecting rod)
2) ASHRAE 62-1989 IAQ STANDARD: “VENTILATION FOR ACCEPTABLE
INDOOR AIR QUALITY”
3) IS 7896 ( Outside ambient condition for air- conditioning)
4) IS 9736 ( Acoustics in building)
5) IS 13095 ( Butterfly valve selection)
6) IS 277 and SMACNA ( GSS ducting)
7) ANSI-UL-555-1985 (Fire Dampers)
8) ANSI (Piping system)
4.3 Lean principle
The concept of lean comes from the Toyota Production System (Koskela 1992). Lean concepts
have proved to be beneficial in many fields. Implementation of lean in construction will lead to
great improvement in reducing the waste and increasing the efficiency of a project. Great amount
of waste is generated on the construction site due to inaccuracy in delivery, overproduction and
reworks. Lean is a continuous cycle which identifies the problem, focusses on it, makes changes
for improvement, standardizes the process and looks for further improvement in the process. The
different tools used in Lean are 5S, Kaizen, JIT, Value Stream mapping and Kanban.
5S involes sorting, stabilizing, sweeping, standardizing and sustaining the practice. It could be
utilized in maintaining a work place environment, thereby contributing to the reduction of rework
29
and hazardous conditions. Value stream mapping(VSM) provides an overview of manpower and
material flow from the beginning of the project till its completion. It can be utilized in tracking
the hidden wastes taking place at each stage of the construction project. Just in Time (JIT) and
Kanban go hand in hand to a great extent. It helps in reducing inventory and carrying cost and can
be very well utilized in determining oe reducing the storage capacity at various construction sites
location. Kanban is used to determine what, when and how much to produce in the manufacturing
industry. It would be a great tool in construction industry to know which material needs to be
produced according to the various conditions involved at the site. Kaizen means continuous
improvement of a particular process. Safety is of a great concern on the construction site and it
can be improved by segregating it into three areas viz. safe area, mid safe and out of control area.
Each area can be focussed in depth and more improvements can be made in the problem areas to
change over to one safe area.
The main fundamentals which explains lean are:
1) Identifying the end user requirements and implementing changes from the planning stage
onwards.
2) Following the value stream map and breaking down each stage into steps and making
improvements at each step.
3) Developing clean and arranged work place which ensues safety and completion of project
within a time range.
Figure 2-12: Stages involved in a project
The figure 2-12 explains each stage involved in the completion of a project.
a) Planning:
This stage forms the backbone of the project. GANTT charts for scheduling purpose are
prepared. The approvals for drawings, technical submissions need to be obtained. The
estimation of material requirements are made. Decisions need to be made for the future
according to the space sizing available and hence forecasting forms an important tool for this
stage.
b) Procurement:
In this stage different vendors need to be selected for different projects and evaluating the
parameter is very essential for making a selection. In a later section, minitab analysis is
performed on different parameters to evaluate the important elements necessary for making a
vendor selection. Job and purchase orders are also prepared, and compared with the job cost
analysis in this stage.
Execution of project involves complete construction activities from receiving the material on
site, storing in the storage house, keeping a track of inventory and the sequence of material
required according to the installation steps. Interaction with the client, manpower
management and implementing safety rules forms a part of this stage. Various Lean tools can
be implemented on this section for further improvement in the process and reduction in
waste.
d) Commissioning:
Pressure testing, duct leakage tests, etc. are performed in this stage. This process basically
starts the functioning of equipment. All tests are conducted to ensure quality in the equipment
usage.
4.4 Vendor selection
In today’s market vendor selection forms an important step due to the tremendous profit
generated at this stage. It is difficult for a firm to progress in quality and cost unless the vendor
base is strong. Various parameters like quality, delivery, material cost, labor cost and capacity
will be compared to evaluate the best vendor, thus maximizing the profit margin of a project.
The TOPSIS method is used for making a selection. It is a multi-criterion decision making tool
where different attributes are compared and the optimal solution is achieved. Weights are
assigned for the criteria according to the maximum order of preferences and later normalizing is
done for each criterion. The last step helps in calculating the distance between the ideal solution
with respect to the best and worst selected option, thus helping us understand the scope for
improvement.
Six steps are followed which can be very well utilized in many fields for making a vendor
selection. An example of a piping vendor is used to demonstrate the model. Different criterion
viz. quality and delivery are rated on the scale of 1 to 10. Capacity, labor and material cost data is
collected from Hiranandani project, Mumbai.
32
The figure 2-13 gives a brief description of the whole process:
Figure 2-13: Vendor selection steps
Step 1: Decision matrix construction
D = X1 B11 B12 B13 B14….. B1j B1n
X2 B21 B22 B23 B24….. B2j B2n
.
.
(4.4)
A matrix is created in the first stage with vendor criteria being placed in the row
Step 2: Normalizing
rij = bij/ √∑bij 2 where i= 1 to m and j = 1 to n
(4.5)
This process is used for scaling the criterion into a dimensionless unit.
Vendor 1 Vendor 2 Vendor 3, etc.
Criteria
.
.
(4.6)
This step is used for assigning the weights to the criterion according to the preferences
Step 4: Calculating the best and worst solution
A * = {(max Vij| j J), (min Vij| j J), i = 1, 2,...., m}
= {V * 1, V
* n}
A - = {(min Vij| j J), (max Vij| j J), i = 1, 2,...., m}
= {V - 1, V
- 2, ............, V
- j,............, V
- n} (4.7)
The final solution of best and worst vendor is selected at this stage
Step 5: Distance comparison between each criterion
S * i = √∑(Vij- Vj
S - i = √∑(Vij- Vj
2 i = 1 to m (4.8)
The best and worst results are compared with the other alternatives using this equation
34
Step 6: Relative closeness of each criterion with the ideal solution
Ci * = S
- i / S
* i + S
- I i = 1 to m (4.9)
The data used for different vendors considering different criterion is as follows:
Table1-6: Criterion data
1 9 6 30 8 400
2 9 5 32 10 600
3 4 4 40 15 300
4 5 7 50 11 200
5 2 8 52 14 500
6 5 9 35 9 550
7 4 3 38 7 450
8 3 4 42 20 480
9 8 5 44 13 525
10 3 8 52 12 225
Quality and delivery rate is scaled from 1 to 10 with weights of 0.3 and 0.2. Material, labor cost
data is collected and capacity of pipes is in meters. Weights of 0.2, 0.1, and 0.2 are assigned to
material, labor cost and capacity respectively.
35
Figure 2-14: Bar graph demonstrating vendor rating
Later a matlab code is written for making a vendor selection which is attached in appendix-B.
The results obtained from figure 2-14 demonstrated that vendor 2 proves to be the best alternative
among other vendors.
TOPSIS method proves to be comprehensive with a pragmatic approach in the industry. It helps
in making a decision when multiple choices are available and an optimum solution is required.
36
5.1 NPV
Managing cash flow is an important task in any project. NPV (Net Present Value) is
defined as the sum of the present values (PVs) of the individual cash flows. It is also the
difference between the present value of cash inflows and the present value of cash outflows that
would take place at a future date. In simple terms, NPV is determining the current value of a
future profit. In this project, we calculate the NPV of different projects because NPV analysis is
sensitive to the reliability of future cash inflows that an investment or project will yield. If the
NPV of a prospective project is positive, it should be accepted. However, if NPV is negative, the
project should be probably rejected because the cash flow will be also negative. We use the
following formula to calculate the NPV value:
∑ ( ) ( )
i: Weighted Average Cost of Capital (WACC)
(1+i) -t : Present Value Interest Factor (PVIF)
CF: Net cash flow at time period p
N: Numbers of time periods
37
When a company is going to bid for a contract, project managers are confronted with the
problem of scheduling project activities that are subject to resource constraints such as power
supply, raw materials resources etc. The project managers have to consider if they have enough
energy and resources to accomplish this job. Thus they have to focus on projects that yield the
maximum profit so as to effectively utilize the resources to its fullest potential as much as
possible. There are two ways of increasing the utilization of the resources and it would be to win
the bids for the high profit projects and to keep the project duration as low as possible in order to
reduce the cost. In this scenario, the concept of NPV plays a vital role in choosing between
projects.
Project managers make their decisions based on the NPV value of the project. We
obtained data from ETA India, which is a provider of HVAC (Heating, Ventilating, and Air
Conditioning) solutions, for the following four projects with its contract payment and project
duration.
Chilled beam project (6 months) ($ 222,222.22)
The four cash flow payment chunks based on the time periods at which they took place are:
A) Bank guarantee
C) Installation
D) Final commissioning
Chilled beam project:
The following cash flows were taken from the M/s Wipro Project
Bank guarantee - 10%
Installation - 10%
3 days 35,555.55 0
3 months 248,888.88 1,111,567
6 months 35,555.55 180900
6.67 months 35,555.55 200124.1
+ (248,888.88-280,456)/ (1+0.05) 3/12)
+ (35,555.55-31246.7)/ (1+0.05) 6/12)
+ (35,555.55-34612.3)/ (1+0.05) 6.67/12)
Profit = 2.7%
There were numerous factors considered for this project. Though the terms and condition
for the project were feasible still it didn’t made a good margin compared to the others. The
reasons for it were that the project had a completely new concept and due to the novelty factor the
company had to invest a lot of money. The reason for undertaking such a project was to create a
niche in the market by employing a first of its kind technology. This head start could be used to
the company’s advantage in the future.
5.2 Cost analysis of chilled beam system
Table1-8: Cost analysis
2.0 CHILLED
39
4.0 Sheet Metal
5.0 Flexible
150 mm dia 850 M 2.61 0.48 2220.62 408.65 Make :
CMS
5.2 150 mm dia
Ravistar
Ravistar
Ravistar
9/10 mm thick 3000 Sqm. 2.46 1.25 7405.96 3750 Make :
Armaflex
Jindal for
10.0 Insulated Class
'C' MS chilled
Jindal for
mm insulation
e 65 mm dia + 30
mm insulation
f 50 mm dia + 20
mm insulation
g 40 mm dia + 20
mm insulation
41
mm insulation
i 25 mm dia + 20
mm insulation
10.1 Butterfly
valves with
extended stem
with
a 125 mm dia 14 Nos 65.01 24.98 910.20 349.72 Make:
Advance b 100 mm dia 15 Nos 51.77 20.05 776.55 300.77
c 50 mm dia 21 Nos 31.6 10.19 663.86 214.09
d 40 mm dia 16 Nos 28.18 8.22 450.89 131.57
10.2 Installation of
a 125 mm dia 3 Nos. 4.08 29.78 12.26 89.36
b 100 mm dia 3 Nos. 3.50 23.89 10.51 71.69
c 50 mm dia 3 Nos. 2.33 12.11 7.00 36.35
10.3 2 or 3-way
b 100 mm dia 3 Nos. 95.16 20.05 285.49 60.15
c 50 mm dia 6 Nos. 59.05 10.19 354.31 61.17
10.4 Dual plate
with 20 mm
a 125 mm dia 3 Nos. 83.00 24.98 249.00 74.94 Make:
Advance b 50 mm dia 6 Nos. 30.18 10.19 181. 61.17
11.0 WAREE /
MASS make
Guru
Guru
13 20 mm thick 50 M 9.17 3.15 458.53 157.69 Make:
42
Sintex
piping 50 M 3.39 0.96 169.80 48.07
15.0 25 mm dia
purge valves 6 Nos. 12.66 3.84 75.96 23.07 Make:
Anergy
17.0 Installation of
15 TR Air
18 Refrigerant
Copper Piping
ETA
TOTAL 526103.808 41409.3773
Type of chilled beam Active (Flaktwood make)
Number of chilled beam 825
Required total cooling capacity 60 W/m 2
Area 2200m 2
Total capacity 132000W
watt for a chilled beam)
1320000
Taxes @ 12.5% 165725
Total Cost of system 1913956.73
The chilled beam system is compared with the conventional water cooled system and the
data recorded for the same is as follows.
44
Monthly kWhrs 98kWhrs
Total cost of electricity estimate (Electric
panels, main chiller panel, wiring and labor)
1903206
Cost of electricity 0.12/kWhr
Electricity rise 9%
Chilled beam system Total cost
Cost of electric consumption 1320000
Chilled beam cost 422431.73
kWhrs per month 98
kWhrs per year 1176
(Electric panels, main chiller panel, etc.) 1903206 W/m2
Labor cost 3500
Electricity rise 9%
Table1-11: Payback analysis
The maintenance of a chilled beam involves hose replacement which has a life of 15 years and
valve replacement which has a life of 25 years. Basic dust cleaning can be done by the removal of
cover. Hence, theoretical results indicated that the payback for a chilled beam system is 18 years
and it demonstrated that electricity consumption plays a key role in achieving an efficient system
in the long run. The initial installation cost of the chilled beam system proves to be expensive
whereas the maintenance is less compared to the normal conventional system.
Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Year 11 Year 12 Year 13 Year 14 Year 15 Year 16 Year 17 Year 18
Payback
1913918.47 1914528.451911181.71 1911545.49 1911942.01 1912374.21 1912845.3 1913358.781909549.73 1909766.66 1910003.11 1910260.84 1910541.76 1910847.96
Electricity
sales+
1908847 1909000.69 1909168.12 1909350.71
396.52 432.2 471.09 513.48 559.62 609.98236.45 257.73 280.92 306.2 333.75 363.78 Electricity
cost 141 153.69 167.52 182.59 199.02 216.93
Initial
6.1 Conclusion
This thesis aimed at demonstrating chilled beam and DC system as two significant potential
energy saving measures. The application of either system is uncommon and literature review
assisted in understanding existing projects. The DC system is compared with the conventional AC
power distribution system and the calculation of power losses associated with AC to DC
conversions for different applications were taken into consideration. The power loss of 0.35%
was recorded for the DC with four conductor system. DC bus powered servers can be used in
place of those that rely on AC to DC power conversions , reducing energy losses in the
conversions.
For cooling systems a payback of 18 years was calculated for the chilled beam system relative to
a conventional cooling system approach with the estimates drawn from detailed layouts and
equipment specification for a specific application. To ensure that the overall project is running
efficiently, Lean concepts can be utilized in the construction industry. Vendor selection is a
critical step in project management and TOPSIS method is used to demonstrate how a selection
can be made at a faster rate when the number of potential suppliers is large and one optimum
selection has to be made. The results indicated that vendor 2 proves to be the best fit compared to
the other options. The research focuses on providing a better understanding of both the direct DC
bus system and the chilled beam system for future application. One of the challenges encountered
was limited availabilty of data on DC bus system and associated first costs. Hence, certain
assumptions were made in the analysis which are based on the material availabilty in the market.
47
Also available skilled manpower has less knowledge about the system operation and maintenance
and the changes to the existing system will take some time.
A specific chilled beam system was selected for the payback analysis and a detailed analysis can
be done to achieve a better and efficent product based on the application. The construction of a
chilled beam system was discussed in detail with all the improvements which can be made to the
existing system. The research makes an attempt to evaluate the practical applications of both
systems.
6.2 Future research
There are a few areas which can be explored for the future study in both systems. The data
centers with DC power are more reliable than with AC system. The existance of data for DC
voltages higher than 48V is not readily available. More building maintenance and operator
training will be needed to encourage the application of the DC system over AC distribution
systems for data centers with a high density of computer devices. Photovoltaic LED lighting
system in combination with a DC bus system proves to be an effective measure. More research
can be done on DC bus structure coupled to an on-site power generation and battery storage
system to check the availability of any other gas fed fuel cell systems for internal load dominated
spaces. Evaluating the mixed DC can be another area of research. It is important to seek DC
distribution data from the existing projects. Chilled beam application is successful in Europe to a
great extent and is emerging in the US and new markets in Asia. Condensation forms a vital
problem in chilled beam system. It can be controlled by modulating the water temperature and
flow rate. More research can be conducted on ways of eliminating the condensation. Educating
engineers about the humidity factor and more inner room condition research will help in
improving the system. . A number of combination system can be studied in depth. For example
48
combining the chilled beam system with a solar heat pump, heat storage and evaporation tower
possess a good scope of improvement in the overall system.
49
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The regression equation is
Predictor Coef SE Coef T P
Constant 41.711 6.519 6.40 0.000
Length (m) 0.103785 0.009919 10.46 0.000
Power factor -49.072 7.244 -6.77 0.000
S = 2.80540 R-Sq = 94.5% R-Sq(adj) = 93.3%
Analysis of Variance
Residual Error 9 70.83 7.87
Total 11 1293.74
3 300 43.537 38.496 1.679 5.041 2.24R
R denotes an observation with a large standardized residual.
6050403020100-10-20
99
95
90
80
70
60
50
40
30
20
10
5
1
ΔPac1(%)
Figure: A-1 Probability plot of ΔPac1
52
Predictor Coef SE Coef T P
Constant 1.8931 0.4699 4.03 0.003
Length (m) 0.0019544 0.0007150 2.73 0.023
Power factor -2.0237 0.5222 -3.88 0.004
S = 0.202228 R-Sq = 71.4% R-Sq(adj) = 65.1%
Analysis of Variance
Residual Error 9 0.36807 0.04090
Total 11 1.28798
12 300 0.0000 0.4556 0.1211 -0.4556 -2.81R
R denotes an observation with a large standardized residual.
2.01.51.00.50.0-0.5
99
95
90
80
70
60
50
40
30
20
10
5
1
ΔPac3(%)
Figure: A-2 Probability plot of ΔPac3
53
43210
99
95
90
80
70
60
50
40
30
20
10
5
1
ΔPdc2(%)
Figure: A-3 Probability plot of ΔPdc2
2.01.51.00.50.0
99
95
90
80
70
60
50
40
30
20
10
5
1
ΔPdc4(%)
Figure: A-4 Probability plot of ΔPdc4
54
55
56
Appendix-B
%vendor selection method clc; clear all; close all;
quality=[9; 9; 4; 5; 2; 5; 4; 3; 8; 3]; quality=quality/sum(quality);
deli=[6; 5; 4; 7; 8; 9; 3; 4; 5; 8]; deli=deli/sum(deli);
mat_rate=[30; 32; 40; 50; 52; 35; 38; 42; 44; 52]; mat_rate=mat_rate/sum(mat_rate);
lab_rate=[8; 10; 15; 11; 14; 9; 7; 20; 13; 12]; lab_rate=lab_rate/sum(lab_rate);
capacity=[400; 600; 300; 200; 500; 550; 450; 480; 525; 225]; capacity=capacity/sum(capacity); %creating the decision matrix D=[quality deli mat_rate lab_rate capacity]; %Normalizing the Decision matrix for i=1:10 r(i,:)=1./(sqrt(sum(D(i,:).^2))).*D(i,:); end
%weight matrix weights=[0.3 0.2 0.2 0.1 0.2]; for i=1:10 weights_full(i,:)=weights; end V=weights_full.*r;
A_ideal=[max(V(:,1)),min(V(:,2)),min(V(:,3)),min(V(:,4)),max(V(:,
for i=1:10 s_neg(i)=sqrt(sum((V(i,:)-A_neg).^2));
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end
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