STUDY OF POWER CONSUMPTION AND TEMPERATURE PROFILE
IN GLAZED BUILDINGS
Praveen Jain1, Jitendra Kanoongo2 and Tripti Goyal3
1
Department of Mechanical Engineering, Malviya National Institute of Technology, J.L.N. Road
Jaipur. 302017 E-mail:-jainpraveen_1986@yahoomail.co.in
2
Department of Mechanical Engineering, Malviya National Institute of Technology, J.L.N. Road
Jaipur. Pin-302017, Phone: 9351299957, e-mail:jitendrakanoongo@gmail.com
3
Department of Civil Engineering, Malviya National Institute of Technology, J.L.N. Road,
Jaipur-302017, Phone: 9314421280, e-mail:tripti_eck
Abstract
In modern constructions, window glazing plays an important role in designing and in deciding the energy
efficiency of the buildings. In our study, we carried out energy simulations on a zone of a building by varying the
window glazing in terms of its area, type of glazing and its orientation. The study is carried out for Indian
climatic condition (using the weather data file of New Delhi) with the simulation software TRANSYS. This will
facilitate the user to choose combination of window glazing area, its type and its orientation for comfort to the
occupants in non air-conditioned and to optimize energy savings in air-conditioned building. Because more the
energy consumption for air conditioning more uncomforting will be corresponding non air conditioned building.
The study of the yearlong simulation for the air-conditioned zone shows that the power consumption in east
direction with single glazing is highest and the power consumption in north direction with double-glazing is
lowest.
Keywords: glazing area, window orientation, power consumption in building, air conditioning Optimization.
Introduction
Windows being the integral component of a building play a vital role in deciding the energy demand of a
building. The optimum scenario is to specify a window area in which there in an ideal balance between daylight
provision and the energy consumed by the artificial lighting & air conditioning. Such a window area may be
referred as the ideal window for which energy consumption of the building is lowest. This Study shows that
cooling demands can mainly be reduced by reducing the window size, chaining the type of glazing, changing the
material used in the construction of walls of building , & changing the orientation of building & many other
factors. The optimized window area and the corresponding specific energy consumption have been calculated for
different climates in India & for different orientations. Our study is done by providing glazing area of 10%, 20%,
30%…100%. Corresponding orientations in east, west, North and South direction.
To achieve energy efficiency in a building one should reduce the thermal loads coming on it these thermal loads
are the interior load on the building due to climate and the internal load due to people, lighting etc.
Proper zoning of different components and ventilation can reduce the overall impact of internally generated heat
loads. Depending on the weather the thermal load can occur in three major ways:
A) Penetration of direct sunlight
B) Conduction of heat through walls
C) Infiltration of outside air
Objective
The objective is to find an optimum glazing area for conditioned and non conditioned building in all the six
climatic zones of a country using computer simulation.
Study of Power Consumption and Temperature Profile in Glazed Buildings 165
Detailed analysis of the energy consumption (heating ventilation air condition) of a building is nearly impossible
without computers. Thus computer modeling and simulation has become a very important technology for
assisting engineers with their non-trivial task of designing/analyzing the building.
Software tools help designers by allowing the designers to ->
A) accurately predict the thermal behavior of a building
B) design the most energy efficient building possible
C) consider the building as single integrated system
An energy simulation tool is software which emulates the dynamic interaction of heat, light, mass (air moisture)
within the building to predict its energy and environmental performances it is exposed to climate, occupants and
conditioning systems.
Tool Used
In this paper we will give the data’s of energy consumption, calculated by using the simulation software
TRANSYS-16 .The software calculates hour by hour building energy consumption over an entire year
[8760hours] using weather data for the location under consideration (Delhi in our case) Input to the program
consist of a detailed description of the building being analyzed.
Location Lat [°N] Lon [°E] Elevation[m]
New Delhi 28.58 77.20 212 1
TRNSYS is a complete and extensible simulation environment for the transient simulation of systems, including
multi-zone buildings. It is used by engineers and researchers around the world to validate new energy concepts,
to the design and simulation of buildings and their equipment, including control strategies, occupant behavior,
and alternative energy systems. A TRNSYS project is typically setup by connecting components graphically in
the Simulation Studio. Each Type of component is described by a mathematical Model in the TRNSYS
simulation engine and has a set of matching Performa’s in the Simulation Studio.
The simulation engine is programmed in FORTRAN and the source is distributed. The engine is compiled into a
Windows Dynamic Link Library (DLL), TRNDll..Due to the complexity of a multizone building the parameters
of building are not defined directly in the TRNSYS input file. Instead, two files are assigned containing the
required information, the building description (*.BLD) and the ASHRAE transfer function for walls (*.TRN).
Methodology
Simulation were carried on a single room building (h= 3m, w= 4m, l= 4m) on all four walls with an option to
provide window in any of the four walls.
The following assumptions were taken into account while developing the input for simulations.
¾ The building is not surrounded by any other structure, thus no shadow forms on any of the building
components.
¾ The inside set point is 25 C for cooling season and 18 c for heating season.
¾ The building is in use for 24 hours a day
166 Advances in Energy Research (AER – 2006)
The following constant parameters and variables taken into account while developing the input file for
simulation.
1. Zone volume-48 m3
2. Wall type- Concrete wall
Solar absorptance- front-0.6 back-0.6
Convective heat transfer coefficient front-11.376 kJ/hkm2 back- 88.812 kJ/hkm2
Geosurf--0.1 view factor to sky--0.5
Wall thickness- 0.244m
Density- 2400 kg/m3
Thermal conductivity- 7.56kJ/mK
Thermal capacity- 0.8 kJ/kgK
3. Window:-
Convective heat transfer coefficient: - front-11kJ/hm2k back- 64kJ/hkm2
2
Glazing u-value (kJ/hkm ) g-value frame area
Single glazing 5.8 0.855 0.15% of window area
Double glazing 1.4 0.589 0.2% of window area
Frame 8.17
5. Internal gains:-
• Specific gains -------- 14w/m2
• Occupant density .1 occupant/m2
• Lighting:- Light on if total horizontal radiation < 120w/m2
Light off if total horizontal radiation > 200w/m2
• Specific light----- 10w/m^2
6. Heating :- Radiative part of heating 0%
Set temperature for day time 18 deg.c
Set temperature for night time 18 deg.c
Specific heating power 100 w/m2
7. Cooling :- Specific cooling power 100w/m2
Temperature for cooling on 25deg.c
8. Infiltration- .2(1/h)
VARIABLES: window area (10%, 20%, 30%----100%)
Orientation of window (east, west, north and south)
Glazing (single &double)
Results and Discussion
The year long simulation study gives the following results in the form of power consumption curves and
temperature profile for different days.
7500
7000
6500
6000
ption(inkw.)
5500 east-single
erconsum
north-single
south-single
5000 west-single
pow
4500
4000
3500
3000
10% 20% 30% 40% 50% 60% 70% 80% 90% 99%
glazing area
Figure2: power consumption for a year with single glazing
Study of Power Consumption and Temperature Profile in Glazed Buildings 167
40
35
30
PRATURE
23 Mar 10%
21 Dec 10%
23 Sept 10%
TEM
21 june 10%
Series5
25
20
15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
HOURS
Figure 3: temperature profile with south facing single glazed window
42
40
38
36
34
32
PRATURE
30
23 Mar 90%
21 Dec 90%
28
23 Sept 90%
TEM
21 June 90%
26
24
22
20
18
16
14
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
HOURS
Figure 4: temperature profile with south facing single glazed window
1. Year long Power consumption is found to be maximum for east direction and minimum for north
direction irrespective of glazing area. Because the sun rises in east and from morning onwards east
facing window will be exposed to maximum part of direct thermal radiation. So taking the window
in east direction, zone temperature start’s to rise in morning itself and it reaches its maximum by
the afternoon and due to the thermal inertia of building power requirement for cooling increases.
And in Indian climatic condition in the most of the time of a year cooling is desirable for comfort of
occupants hence power consumption for year increases. Where as in north oriented window is
never exposed to direct solar radiation and thus power consumption is minimum. If we compare
south and north, by the study of temperature profile on the different days of a year we found that
temperature for north direction is always lower than that of south hence cooling requirement for
south is more than that of north. As west is exposed to direct radiation of sun after mid day hence it
has got more power requirement than that of north and lesser than that of east.
2. Comparison between south or west oriented single glazing shows that yearlong power consumption
is lower for south if area of window glazing is below 35 percent of wall area and for glazing area
above 35 percent of wall area power consumption is found to be lower for west direction. It is
because of low window area in west direction doesn’t allow greater amount of direct radiation of
sun and in south direction above 35 percent glazing area direct solar radiation entering the zone
increases .and these direct radiation of sun is mainly responsible for increased cooling demand of
glazed buildings.
168 Advances in Energy Research (AER – 2006)
6500
6000
5500
ption(inkw.)
5000
east-double
north-double
powerconsum
south-double
west-double
4500
4000
3500
3000
10% 20% 30% 40% 50% 60% 70% 80% 90% 99%
glazing area
Figure 5: power consumption for a year with double glazing
33
31
29
27
PRATURE
25 23 Mar 10%
21 June 10%
23 sept 10%
TEM
23 21-Dec 10%
21
19
17
15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
HOURS
Figure 6: temperature profile with south facing double glazed window
35
33
31
29
27
prature
23 Mar 90%
21 june 90%
25
Tem
23 sept 90%
21 dec 90%
23
21
19
17
15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
Figure 7: temperature profile with south facing double glazed window
1. Power consumption is maximum for east direction and minimum for north direction irrespective of
glazing area same as we found with single glazing. The reason for being so is also the same.
2. Similarly comparison between double glazing placed in south or west direction shows that power
consumption is lower for south if area of window glazing is below 47 percent of wall area and for
Study of Power Consumption and Temperature Profile in Glazed Buildings 169
glazing area above 47 percent of wall area yearlong power consumption is found to be lower for west
direction. As we have seen in the case of single glazing, here also the intersection of power
consumption curve at 47 percent is result of increased direct solar radiation.
Comparing both the curves it is evident that, it may be any direction yearlong power demand for air
conditioning purpose for double glazed window is lower than that of single glazing at any window area
because of lower Also power consumption always increases with increase in window area because of
increase in direct solar radiation entering building zone.
Conclusion
With the help of obtained results, following guide lines can assist the designers of modern buildings in deciding
the orientation and area of window, to ensure lesser power consumption for air conditioning purpose.
1. If we have no restriction in window direction, window should be given in north because, in compare to
all other directions it ensures minimum power consumption for any window area.
2. Window in east direction should be avoided if possible to minimize the air conditioning electricity bills.
3. If direction of window is restricted, with help of energy consumption graphs one can judge increase in
power consumption corresponding to the increase in window area. And thus with respect to power
consumption an optimum window area can be choosed.
4. If a choice to be made between south and west direction for window positioning, using single glazing
south direction should be preferred over west for window area less than 35 percent of wall area and
using double glazing south direction should be preferred over west for window area less than 35 percent
of wall area.
A selection of direction, glazing and window area which ensures lower power consumption for air conditioning
purpose will also ensures more comfort to occupants of similar non air conditioned building. Because energy
requirement for air conditioning shows its deviation from comfort condition. Hence in the case of non- air
conditioned buildings also a better widow judgment can be given.
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