Adopting Low-cost Alternative for Energy Saving
Case Study


General Information:


Client: ITC Green centre
City: Gurgaon
Climate: Composite
Operational schedule – 10 hours, 5 working days in a week
Area of the building: 15,799m² (out of which 9294 m² - conditioned area, 6505 m² - non-conditioned area)

Green Building Design Features:

Building Design

Orientation

  • ‘L’ shape design with main entrance towards north
  • Longer axes along NE and NW directions
  • By ‘L’ shape configuration, the width of the floor Plate is reduced for the same amount of floor plate area thereby allowing natural light to penetrate deep into the interior spaces.
  • It ensures that part of the façade is always shaded
Walls


 
Walls of air-conditioned zones in all blocks – 230mm AAC block with 70mm stone cladding and 12.5 mm plaster inside  
   
Roof



120mm RCC roof with 76mm ISO board on interior side

 
 Windows
  • Double glazing window (6-12-6)
  • Glass on north orientation has a lighter light transmission
  • The glazing for the building has been designed to maximize the effect of natural light, largely eliminating the need for artificial light during day time.
  • The high performance window glass, while allowing light inside, does not allow heat and also keeps office cool from inside during the day decreasing the load on HVAC systems
    Higher light Transmission Glass on North orientation for better day light integration
  • Optimum WWR which is less than ECBC standard (40%) helps in reducing external solar heat gain

Building Lighting

Lighting system
  • Luminaires used – mostly CFLs and T5 lamps in mirror optic fixtures, 36W fluorescent lamps and magnetic ballasts are used in storages, electrical and mechanical rooms
  • LPD – 7.2W/m2

  • The LPD (7.2W/m2) is less than the max allowed LPD of ECBC (10.8W/m2) which is very good
  • According to Energy Star, CFLs provide the same amount of light as an ordinary bulb using 75% less energy
  • T5 lights have higher efficiency and system miniaturization with daylight life about 18000 hours as compared to 8000 hours of standard fluorescent lamps
  • Good natural light available in office spaces
 
Daylight Controls
  • Switch off daylight sensors with Philips make (model no. LRI 1430/00 ENEC)
  • Daylight controls switch off lights when daylight is sufficient, reducing the energy consumption of the building

HVAC System Design
  • Central AC system with 3 screw chillers of 815 TR capacity
  • COP of the ITC Green Centre: 6.1
    ECBC recommended: 5.4
  • Rated Sq.mt/TR: 18
Energy performance of the building

Lighting Energy Performance of the Building

  • Annual Consumption (lighting) – 121301 KWh
  • Lighting Performance Index – 13 KWh/Sqmt/annum

Space Conditioning Energy Performance of the Building

  • Annual Consumption (A/C) – 596829 KWh
  • HVAC Performance Index – 64 KWh/Sqmt/annum
Annual energy consumption due to lighting & air conditioning (kWh): 871535

Overall Energy Performance Index due to lighting & air conditioning (kWh/m2): 55

Energy Saving Potential

Comparison of various parameters for ECBC compliant Composite case (ITC Green centre, Gurgaon) with conventional case

 
Parameters ECBC compliant case (Existing Building) features Conventional case
Building design Building longer axes along NE-NW directions

Building orientation: longer facades facing East-West
Windows are shaded while roof is not shaded No roof and wall shading
Building Envelope

No insulation on wall and roof
U value for Wall - 0.687 W/m2/K
U Value for Roof - 0.335 W/m2/K

No insulation on wall and roof
U value for Wall - 2.7 W/m2/K
U Value for Roof - 2.68 W/m2/K


Double Glazed windows (U value of glass -1.81 W/m2/K and Shading coefficient - 0.26)
WWR – 33%
Single Glazed windows (U value of glass -6.97 W/m2/K and Shading coefficient - 0.79)
WWR – 48%
Building Lighting Power density Lighting power density is 7.2 W/m2 Lighting power density 26.5 W/m2
Controls Daylight controls No controls or sensors
Building Chiller 3 water cooled screw chillers with COP of 6.1 (rated) 5 water cooled reciprocating chillers with COP of 4.01 (rated)
Energy performance Index (KWh/m2/yr) 55 261


Impact of Low energy strategies

The conventional case was run by incorporating low energy solar passive design strategies on the annual electricity consumption (kWh), electric load (kW) and cooling demand (TR) of the building.

Parameter comparison Conventional case Existing case (Low energy strategies)
Electrical load Base case 12% less than the conventional case
Cooling Load Base case 16% less than the conventional case
EPI Base case 22% less than the conventional case


Impact of ECBC Recommended Energy Conservation Measures:

The conventional case was run by incorporating ECBC envelope on the annual electricity consumption (kWh), electric load (kW) and cooling demand (TR) of the building.

Parameter comparison Conventional case ECBC compliant case
Electrical load Base case 60% less than the conventional case
Cooling Load Base case 55% less than the conventional case
EPI Base case 55% less than the conventional case

 

Overall Impact of ECBC and low energy strategies:

The conventional case was run by incorporating both the low energy solar passive design strategies and ECBC envelope on the annual electricity consumption (kWh), electric load (kW) and cooling demand (TR) of the building.

Parameter comparison Conventional case ECBC + Low Energy Case
Electrical load Base case 64% less than the conventional case
Cooling Load Base case 1% less than the conventional case
EPI Base case 63% less than the conventional case


Impact of ECBC, Low energy strategies, and ECBC+low energy strategies on conventional case for ITC building, Gurgaon




The above graph shows the variation in the Electrical load (kW), Coil load (TR) and EPI (energy performance index) for all the cases.

The below table gives the comparison of the impact of ECBC, Low energy strategies, and ECBC + low energy strategies on conventional case for ITC Green centre building for a composite climate.

Parameter comparison Existing case Conventional case Low energy strategy ECBC case ECBC+Low energy strategy
Electrical load 59% less than the conventional case Base case 12% less than the conventional case 60% less than the conventional case 64 % less than the conventional case
Coil Load 60% less than the conventional case Base case 16% less than the conventional case 55% less than the conventional case 62% less than the conventional case
EPI 52% less than the conventional case Base case 22% less than the conventional case 54% less than the conventional vase 63% less than the conventional case

 


   
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