High Performance Commercial Buildings in India: Adopting Low-cost Alternative Passive Strategies for Energy Saving

Case Study

Wipro Limited

General Information:

Client: Wipro Limited
City: Kolkata
Climate: Warm & Humid
Operational schedule –24 hours, 6 working days in a week
Area of the building : 11079.2m² (out of which 7621.0 m² - conditioned area, 3458.2 m² - Non- conditioned area)

Green Building Design Features:

Building Design

Orientation

Tower 1 & 2: Longer axis N-S
Tower 3 & Cafeteria: E-W
Learning Center – N-E

The orientation of Towers 1 & 2 helps in reducing solar heat gains.

Orientation of window openings of Tower 1 & 2 on N-S helps in reducing cooling loads and reducing the overall air-conditioning requirement and hence saves energy.

The proper building orientation plays an important role with regard to solar radiation and wind.

Landscape

The three towers are planned around courtyards which are green spaces around the building blocks.

Maintains comfortable micro-climate and contribute towards energy conservation. Trees reduce direct solar heat, provide shade and prevent heating up of building surfaces and heat island effect.

Also helps in maintaining a lower ambient temperature around the buildings and hence better microclimate.

Building Envelope

Walls

Walls of air-conditioned zones in all blocks - 230 mm brick with 12.5 mm plaster

Roof

Roof Towers 1,2,3, learning centre, and guest house

Window

6 mm brown single windows

(SC – 0.52, U-value of Glass – 5.7 W/m2K) WWR – 11.1%

Tinted single glazed window helps in reducing solar heat gain. Optimum WWR which is less than ECBC standard (40%) helps in reducing external solar heat gain.

Building Lighting

Day light integration

Due to less window wall ratio, daylight integration has not been the focus in this building.

Small windows at the seating areas can reduce thermal discomfort.
The reduced percentage of window area to wall area helps in reducing the external heat gain into the building.

Lighting system

6% of the total connected load for the building (273 kW of indoor lighting, 30 kW of outdoor lighting)
Luminaires used mostly – one efficient recessed type luminaires with twin 36 W CFLs
LPD – 6.9 W/m2
The LPD (6.9 W/m2) is less than the maximum allowed LPD of ECBC (10.8 W/m2) which is very good.
According to Energy Star, CFLs provide the same amount of light as ordinary bulb using 75% less energy.
It also generates 75% less heat, reducing cooling costs.

HVAC system Design

Central plant with 4 chillers of 2 types with 1610 TR cooling capacity

Screw type chillers
Centrifugal chillers

Energy Performance of the Building

Lighting Energy Performance of the Building

Annual consumption (lighting) – 917501 kWh
Lighting Performance Index – 23 kWh/sq.mt/annum

Space Conditioning Energy Performance of the Building

Annual consumption (A/C) – 7798385 kWh
Operating cooling demand – 196 sq.ft/TR

Annual energy consumption due to lighting & air conditioning (kWh): 445335

Energy Performance Index of the building (KWh/sq.mts of built up area/annum): 219

Energy Saving Potential

Impact of Low energy strategies:

Parameter comparison	Conventional case	Existing case (Low energy strategies)
Electrical load	Base case	6% less than the conventional case
Cooling Load	Base case	17% less than the conventional case
EPI	Base case	5% less than the conventional case

Impact of ECBC envelope:

Parameter comparison	Conventional case	Existing case (ECBC envelope)
Electrical load	Base case	5% less than the conventional case
Cooling Load	Base case	13% less than the conventional case
EPI	Base case	5% less than the conventional case

Impact of ECBC recommended LPD:

Parameter comparison	Conventional case	Existing case (ECBC envelope)
Electrical load	Base case	12% less than the conventional case
Cooling Load	Base case	9% less than the conventional case
EPI	Base case	13% less than the conventional case

Impact of ECBC recommended chiller efficiency:

Parameter comparison	Conventional case	Existing case (ECBC envelope)
Electrical load	Base case	9% less than the conventional case
Cooling Load	Base case	No change
EPI	Base case	7% less than the conventional case

Impact of HVAC controls:

Parameter comparison	Conventional case	Existing case (ECBC envelope)
Electrical load	Base case	16% less than the conventional case
Cooling Load	Base case	No change
EPI	Base case	16% less than the conventional case

Impact of ECBC recommended energy conservation measures:

Parameter comparison	Conventional case	Existing case (ECBC envelope)
Electrical load	Base case	23% less than the conventional case
Cooling Load	Base case	23% less than the conventional case
EPI	Base case	21% less than the conventional case

Impact of ECBC recommended energy conservation measures:

Parameter comparison	Conventional case	Existing case (ECBC envelope)
Electrical load	Base case	38% less than the conventional case
Cooling Load	Base case	30% less than the conventional case
EPI	Base case	35% less than the conventional case

Comparison of various parameters for solar passive building (Wipro) with conventional case:

Parameters	Solar passive Case	Conventional Case
Building design	Building longer facades are 45 degree inclined to North No roof and wall shading	Building orientation was changed to longer facades facing East-West No roof and wall shading
Building Envelope	No insulation on wall and roof. U value for Wall -1.92 W/m2/K U Value for Roof-2.74 W/m2/K Single Glazed windows( U value of glass -5.7 W/m2/K and Shading coefficient-0.52)	No insulation on wall and roof. U value for Wall -1.92 W/m2/K U Value for Roof-3.35 W/m2/K Single Glazed windows( U value of glass -6.14 W/m2/K and Shading coefficient-0.815)
Building Lighting Power density	Lighting power density is 6.9 W/m2	Lighting power density changed to 20 W/m2
Building Chiller	2 water cooled screw type chillers having a COP 2.6-2.9 2 water cooled Centrifugal water cooled chiller having a COP 4.0-4.3	Air cooled screw chillers with COP of 3.2
Energy performance Index (KWh/m2/yr)	219	335