“Modelling and Parametric Study of a Typical Office Segment for Thermal Comfort and Energy Consumption in New Delhi” By Abhinav Dhaka Internal Guide:Dr.S.Ghosh (VIT University) External Guide:Dr.ir.E.L.C. (Emilia) van Egmond – de Wilde De Ligny(Eindhoven University of Technology)
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“Modelling and Parametric Study of a Typical Office Segment for Thermal Comfort and Energy Consumption
in New Delhi”
ByAbhinav Dhaka
Internal Guide:Dr.S.Ghosh (VIT University)
External Guide:Dr.ir.E.L.C. (Emilia) van Egmond – de Wilde De Ligny(Eindhoven University of Technology)
Climatic Zone Map of India
New Delhi
• New Delhi is placed at an elevation of 215 meters
• Latitude 28.38 N and Longitude 77.12 E• Warm weather;Summer:45degC• Cold Weather;Winter:5degC
• Predicted Mean Vote PMV..an index that predicts the mean value of the votes of a large group of persons on the following 7-point thermal sensation scale.
• Predicted Percentage of Dissatisfied PPD..an index that predicts the percentage of thermally dissatisfied people.The percentage of a large group of people voting hot,warm,cool or cold on the following 7-point thermal sensation scale.
Heat, Ventilation, Air Conditioning and Thermal Comfort
• Major Aim:To provide an acceptable indoor climate
• International Standard: ISO 7730 - Moderate Thermal Environments-Determination of PMV and PPD Indices and Specification of the Condition for Thermal Comfort
• Indian Standard: Energy Conservation Building Code of India (2006)
Thermal Comfort
• Condition of mind which expresses satisfaction with the thermal environment
• Discomfort measure-PMV and PPD (Fanger,1982)
• Local Discomfort• Individual perceptions and preferences
Thermal Comfort(contd.)
• According to the new standard – Comfort requirements are specified to be acceptable by at least 80% of the occupants
• TC = 0.534TM + 11.9• Where TC = Predicted Indoor Comfort Temperature
• TM = Monthly Mean Outdoor Temperature
• For New Delhi, June :(TM = 38.33 deg C)
• TC = 0.534x38.33 + 11.9
• = 32.36 deg C
Definitions
• Parametric Analysis - An experiment designed to discover the differential effects of a range of values of an independent variable.
• Sensitivity Analysis - is the study of how the variation (uncertainty) in the output of a mathematical model can be apportioned, qualitatively or quantitatively, to different sources of variation in the input of a model
Parameters
• Orientation• Glazing Area• Glazing Type• Thermal Mass(Insulation and Materials)• Shading(External and Internal)
Base Case(contd.)• Floor: Synthetic Carpet(1cm) + Concrete(10cm)
• Vertical Fenestration(External): 8mm Single Clear Glass + Metal Frame
• Vertical Fenestration(Internal):4mm single Clear Glass
• No Vertical shading, no Interior shading
• Door: Wooden
Base Case(External Wall)
Base Case (Internal Wall)
Base Case (External Glazing)
Base Case (Roof)
U-Value
• The U-factor measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor of a window assembly
• U-factor ratings generally fall between 0.20 and 1.20
• Unit is W/m² K
SHGC(Specific Heat Gain Coefficient)
• is the fraction of incident solar radiation which enters a building as heat
• Based on solar energy transmittance + inwardly flowing fraction of absorbed solar energy on the entire window
Shading Coeffcient(SC)
• is defined as the ratio of solar heat gain through a particular glazing to the solar heat gain through a single lite of 1/8" clear glass
Emissivity
• The ability of a surface to reflect long-wave radiation
• Measured by its emissivity. Emissivity vanes from 1 (100% of long-wave radiation emitted) to 0 (0% emitted). For glass,
• The lower the emissivity, the lower the U-factor
Dry-bulb temperature: (IND_New.Delhi_ISHRAE.epw) Air temperature: N_Z_1 (final_mar-sept.aps)
Comfort index: N_Z_1 (final_mar-sept.aps) Predicted mean vote: N_Z_1 (final_mar-sept.aps)
Final_Glazing_50_Mar_Sept
Mar Apr May Jun Jul Aug Sep Oct
45
40
35
30
25
20
15
10
5
Te
mp
era
ture
(°C
)
14
12
10
8
6
4
2
0
-2
Pre
dicte
d m
ea
n vo
te
14
12
10
8
6
4
2
0
-2
Co
mfo
rt in
de
x
Date: Thu 01/Mar to Sun 30/Sep
Dry-bulb temperature: (IND_New.Delhi_ISHRAE.epw) Air temperature: N_Z_1 (final_mar-sept_glaze_50.aps)
Predicted mean vote: N_Z_1 (final_mar-sept_glaze_50.aps) Comfort index: N_Z_1 (final_mar-sept_glaze_50.aps)
Decline in Total Energy Consumption
Glazing Area(%) TEC(MWh)
100 1.76
90 1.72
80 1.61
70 1.591
60 1.567
50 1.542
40 1.517
Decline in Total Energy Consumption
Brickwork and Insulation TEC(MWh)
B20 1.754
B20+12mmCav 1.751
EPS 1.742
Polystyrene 1.743
Polurethane 1.742
Decline in Total Energy Consumption
Glazing Type TEC(MWh)
6mmDoub+12mmCav 1.712
12mmDoub+12mmCav 1.711
6mmDoub+12mmCav+Argon 1.705
6mmDoub+12mmCav+Low-e 1.707
Decline in Total Energy Consumption
Roof Insulation TEC(MWh)
EPS 1.533
Decline in Total Energy Consumption
Shading TEC(MWh)
Internal(Blinds) 1.386
Internal+External(Louvres) 1.226
Final+Glaze50
1.131(36.8% decline
from the base case)
Decline of Total Energy Consumption with respect to Parametric Variation
Final Model
Conclusion
• Sensitivity in Descending Order:– Shading Devices– Insulation(Roof Slab)(Only in Cases where the
model is considered to be on the top floor)– Glazing Area– Glazing Type– Insulation(Walls)
Conclusion
• It was concluded that internal and external shading devices had the most significant effect on thermal comfort in terms of PMV. This was followed by the effect of adding EPS insulation to the roof slab
• A steady decline of Total Energy Consumption after reducing the glazing area was observed which was closely matched by the decline of Total Energy Consumption by adding insulation to the roof slab and by adding internal and external shading devices
Conclusions
• It was concluded that reducing the glazing area, caused the Peak Hourly Load for the rooms facing East and West direction to drop by a greater extent when compared to rooms facing North and South direction. Therefore orientation of the building would be the determining factor in the case of energy consumption.
Conclusions
• The prospect of adding brickwork and insulation to the external walls had bought down the Peak Hourly Room Load (North Zone) from 7.786 kW to 7.281 kW
• Orientation follows the rule that buildings facing North-South should be properly insulated with double glazed façade on the East-West and the glazing needs to be reduced or completely eliminated for this orientation. Further studies need to be initiated in order to mark the influence of the change of slightest of orientations on the building energy consumptions.
Recommendations
• Internal Gains need to be controlled and checked for excessive heat generation and the environment plays a pivotal role in determining the internal gain exuberated from presence of people.
• Remote sensors that bring in the dimming effect in areas that receive plenty of sunlight for major part of the day need to be monitored and managed for effective usage of light sources.
Recommendations
• Insulation falls short in contributing towards a greener path when it comes to summer season in the composite climate of New Delhi. However the insulation of roof is vital to the transmittance of shortwave radiation which is absorbed by the thermal mass of the room. The thickness and properties need to be verified before usage of such materials before they are installed and a cost benefit analysis needs to be done prior to the usage of the same.
Recommendations• Area required for fenestration needs to be
hardlined for performance when it comes to a building that orients itself in an East-West Direction. Glazing material with low-e coating filled with argon gas suffers from a shortcoming that makes it a hassle to refill the argon gas from time to time. Once again a proper analysis is required to assess the criteria, location and purpose of the building before determining the amount of fenestration that the building would require.
Recommendations
• Unnecessary leakage or infiltration could be avoided to a greater extent if the joints around windows and external doors are sealed properly, so as to allow the least amount of infiltration through openings.
Recommendations
• Studies that take the winter season into account with the addition of night time or day time ventilation need to be taken up so as to get a hindsight on the annual performance of a building with the right choice of active and passive systems.
Final Note• Thermal Comfort or Comfortability is completely
subjective in nature and the results are an indication not a guideline towards the design of buildings that utilize the power consumption they are offered to the maximum which can be reduced by various design strategies. However it should be kept in mind that perceptions of a group of people is always accurate in first hand encounters and are subject to have a degree of eccentricity in case of a simulation software like IES.
References• M.C. Singh, S.N. Garg, Ranjna Jha (2008), “Different glazing systems and their impact
on human thermal comfort—Indian scenario”, Building and Environment,Vol. 43, pp 1596 – 1602.
• Elisabeth Gratia and Andre De Herde (2003), “Design of low energy office buildings”, Energy and Buildings, Vol. 35, pp 473 - 491.
• Krishan Kant and S.C. Mullick (2003), “Thermal comfort in a room with exposed roof using evaporative cooling in Delhi”, Building and Environment, Vol.38, pp 185 – 193.
• Vinod Gupta (1992), “Energy Conservation in Office Buildings”, Architecture and Design, pp 57 – 61.
• Marie – Claude Dubois (2001), “Impact of Shading Devices on Daylight Quality in Offices” Department of Construction and Architecture, Lund University, Lund, Sweden.
References• Anamika Prasad and Robert W Jones (2001), “A Methodology for Thermal
Comfort Enhancement in Housing Design, New Delhi, India”, Seventh International IBPSA Conference, pp 521 -528.
• Charlie Huiezenga, Hui Zhang, Pieter Mattelaer, Tiefeng Yu and Edward Arens and Peter Lyons (2005), “Window Performance for Human Thermal Comfort”, Centre for Built Environment.
• R.J. de Dear and K.G. Leow and S.C. Foo (1991), “Thermal Comfort in Humid Tropics: field Experiments in air conditioned and naturally ventilated buildings in Singapore”, International Journal of Bio-meteorology, Vol.34, pp 259 - 265.
• Simon G. Hodder and Ken Parsons (2007), “The effects of solar radiation on thermal comfort”, International Journal of Bio-meteorology, Vol.51, pp 233 – 250.