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

Case Study

General Information:

Client: Microsoft India Development Centre
City: Hyderabad
Climate: Hot & Dry
Operational schedule – 10 hours, 5 working days in a week
Area of the building: 55,741m² (out of which 45,057 m² - conditioned area, 10,683 m² - non-conditioned area)

Green Building Design Features:

Building Design

Orientation

Building orientation NE-SW which helps to reduce the solar
heat gains in this hot climate region

Window

Double glazing window with 25mm thick glass
1200mm wide sun shading and internal roller screens
The external window sun shading cuts off the direct sunlight which causes glare, keeping out the sun’s heat, block uncomfortable direct sun and soften harsh daylight contrasts
The double glazed window glass, while allowing light inside, does not allow heat and also keeps office cool from inside during the day

Walls

All blocks - 400mm block with 25mm thick water repellant coating, 50mm thick air gap & 40mm thick stone cladding

Roof

U-value: 0.232W/sqm degK

The insulation under the RCC prevents the heat of the sun reaching the inside of the building and maintains the comfort level of the room by decreasing the AC load

Building Lighting

Day lighting

Glazed Atrium for the natural daylight (U-Value: 5.7 W/sq m deg K and SC of 0.53)
Abundance of daylight is available in the atrium which is completely day lighted zone and no artificial lights are
required during the daytime in the atrium
Natural light is available in the circulation areas at the periphery of the building

Lighting system

Lighting system accounts for 5.71% of total load
Luminaires used: direct/ indirect lighting luminaires with electronic ballasts and lamps in workstation areas, CFL with dimmable electronic ballast and lamps in conference areas, CFL recess mounted down – light luminaires with glass at bottom in cafeteria
The lighting scheme in the open office area is divided into general lighting and task lighting
LPD – 8.15 W/m2
The LPD (8.15W/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 ordinary bulb using 75% less energy
To save energy, the general lighting levels in the office area is reduced and to meet the desired higher illuminance levels at task pane, task lights have been installed in all the workstations

Daylight controls

Occupancy sensors in the conference room and closed cabins
Dimmable ballast integrated luminaires in the conference room
Reduce energy by turning the lights on when someone enters and switches off when the room is empty
The dimmable ballast integrated luminaires in the conference room give the flexibility of varying the
illuminance levels as required

HVAC System Design

Central AC plant with 2372TR (four numbers of 460TR carrier water cooled centrifugal and two numbers of 265.8TR carrier air cooled screw chillers)

COP of the water cooled chillers is 6.6 at ARI condition and that of the air cooled ones is 3.23, which is better than ECBC recommended values of 6.3 and 3.05 respectively
Rated Sqmt/TR – 19
Air cooling towers and closed circuit fluid coolers have either two speed motors, pony motors, or variable speed drives controlling the fans

Energy performance of the building

Lighting Energy Performance of the Building

Annual Consumption (lighting) – 1095925 KWh
Lighting Performance Index – 20 KWh/Sqmt/annum

Space Conditioning Energy Performance of the Building

Annual Consumption (A/C) – 5658371 KWh
HVAC Performance Index – 126 KWh/Sqmt/annum

Annual energy consumption due to lighting & air conditioning (kWh):6754296

Overall Energy Performance Index due to lighting & air conditioning (kWh/m2): 150

Comparison of various parameters for ECBC compliant Hot & Dry case (Microsoft Building, Hyderabad) with conventional case

The table below summarizes the calibrated existing ECBC model case, conventional case generated over the existing building in hot & dry climate zone.

Parameters	Solar passive Case (Existing Building) features	Conventional Case (Building features)
Building orientation	Building orientation : Longer facades of the building facing East-West	Building orientation: Longer facades of the building facing East-West
Building orientation	Windows are shaded while roof is not shaded	Windows, Walls and Roof are not shaded
Building Envelope	Insulation on roof with air gap for walls U value for Wall -1.85 W/m2/K U Value for Roof- 0.2322 W/m2/K	No insulation on wall and roof. U value for Wall-1.98 W/m2K U Value for Roof: 1.76 W/m2K
Building Envelope	Window glazing : U value of glass -1.66 W/m2/K and Shading coefficient-0.28 WWR : 70%	Window glazing : U value of glass -6.17 W/m2/K and Shading coefficient-0.61 WWR : 70%
Building Lighting Power density	Lighting power density is 8.15 W/m2	Lighting power density 20 W/m2
Controls	Occupancy sensors	No controls or sensors
Building Chiller	Water cooled Centrifugal chiller 460*4 kW/TR = 0.558 (COP = 6.6 at ARI conditions)	PTAC units having EER of 8.4 and Fan power as 0.000134 bhp/cfm
Energy performance Index	150	208

Energy Saving Potential

The conventional case defined above was selected to run different energy saving options and to finally quantify the energy saving potential which can be realized in Hot & Dry climate by incorporating the low design strategies, ECBC envelope, and the best case (incorporating both low energy strategies and ECBC measures)

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	16.96% less than the conventional case
Cooling Load	Base case	19.50% less than the conventional case
EPI	Base case	8.41% less than the conventional case

Impact of ECBC Envelope

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	34.78% less than the conventional case
Cooling Load	Base case	24.06% less than the conventional case
EPI	Base case	15.35% less than the conventional case

Overall Impact of ECBC Envelope 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	41.46% less than the conventional case
Cooling Load	Base case	33.13% less than the conventional case
EPI	Base case	19.16% less than the conventional case

Impact of ECBC, Low energy strategies, and ECBC+low energy strategies on conventional case for Microsoft building, Hot and Dry climate

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 Microsoft building for a composite climate.

Parameter comparison	Existing case	Conventional case	Low energy strategy	ECBC case	ECBC+Low energy strategy
Electrical load	40% less than the conventional case	Base case	17% less than the conventional case	35% less than the conventional case	41% less than the conventional case
Coil Load	5% less than the conventional case	Base case	19% less than the conventional case	30% less than the conventional case	34% less than the convention al case
EPI	28% less than the conventional case	Base case	17% less than the conventional case	38% less than the conventional vase	30% less than the conventional case

ECBC Complaint Building, Microsoft India Development Centre, Hyderabad