P. Bhagat Singh, Chief Engineer, CPWD, Thiruvananthapuram & Dr. K M Soni, Chief Engineer, CPWD, Mumbai
A zero-energy or a net zero building is a building with zero net energy consumption from outside source, which means that the total amount of energy used by the building on an annual basis is almost equal to the amount of renewal energy produced at site. Such a building is self-sufficient in energy requirements and thus highly energy efficient. It contributes very little greenhouse gases, saves energy produced either from non-renewable or renewable sources somewhere else, and most of such buildings get half or more of their energy from the grid and return the same amount during non-peak hours of their use.
Architectural Concept
Indira Paryavaran Bhawan, the headquarters of the Ministry of Environment, Forests and Climate Change, in Jorbagh, New Delhi, was constructed by the Central Public Works Department (CPWD) as project management agency, in
The G+7 storeyed structure with 3 basements, has a plinth area of 32,000 sqm, is centrally air-conditioned with 400 TR capacity (HVAC), has 7 lifts, and all essential services like DG sets, UPS, IBMS, fire detection and fire-fighting systems, CCTVs, access control, automated parking, and other electrical, landscaping and horticulture services.
The building has the advantage of natural ventilation throughout, with a central courtyard between the North and South blocks. These blocks are connected through corridors with stone jaalis and balustrades above the 4th floor level. An entrance atrium of four storeys height has been made in the middle of the North block and in the entrance to the South block. The building has large span trusses at terrace and space frames in the central courtyard to support solar panels.
The AC plant room, electric substation, DG sets, fire-fighting pumps, robotic parking for 330 cars and sewage treatment plants are located in the basements. Pedestrian entry has been provided in the front with vehicular access on the sides.
To conform to the design and construction as per Platinum rating under LEED and 5-star rating under GRIHA, the building envelope has been designed to be ECBC compliant and orienting specific devices with envelope insulation to reduce heat intake. Trees have been preserved to the extent possible and local materials used, besides reflective roofing, low heat transmission glass, energy efficient materials and practices. Dholpur stone cladding has been provided over fly ash brick/AAC block walls up to two and half storeys.
Energy efficiency
The building has been made energy efficient through onsite solar power generation, reduction of conventional lighting load by enabling 75% day light use, generation of energy by deploying thin film transparent PV modules on space frame over the terrace and central courtyard, use of high efficiency lighting fixtures, astronomical/time switches and occupancy sensors.
Structural Concept
- About 40% energy saving achieved
- About 55% saving in use of water
- Against the conventional energy demand of 22 lakh units per year, actual energy demand was brought down to only 14 lakh units per year
- Entire energy demand of 14 lakh units generated through highest efficiency mono crystalline SPV panels
- Energy generation started from 19.11.2013
- Energy generated fed to NDMC grid from where supply is taken, thereby offsetting total energy demand
- Thus, annual electricity bill is zero or negative i.e. net revenue on account of excess solar power generation.
Natural stone Jalli and connecting corridors
The main building has been designed as RCC framed structure. It has two blocks connected with corridors from 2nd floor onwards. Each of these two blocks have been divided into three parts by providing two seismic joints of 250 mm width each. Normal grids are 6mX6m with column size 750mmX750mm. Seven storeyed composite columns have been erected over RCC columns of the basement. Moment connections and shear connections have been used for connecting members. Shear studs have been used and designed to form composite action of RCC slab and steel beams. A pre-camber has been provided in the beams of 19m span to control excessive deflection.
Structural steel decking system of Tata Bluescope (Tata Smart Deck) has been used for casting of slabs by eliminating conventional centering and shuttering.
To create total required area of 6000 sqm for supporting solar panels, the entire central courtyard was covered with a space frame. Additionally, MS supporting structure over the terrace was extended by providing cantilever, including at the fourth floor level on the southern side. In view of the high maintenance required for the solar panels, an adequate number of catwalks were provided in the entire supporting structure, with perforated bottom for easy draining of rain water. Out of the total area of 6000 m2, the area covered by panels is 4600 m2 and by catwalks it is 1400 m2.
To generate 100% onsite power of the required capacity, covering of open to sky area in the central courtyard was designed to support the solar panels. For this, a space frame was provided at a height of 35 m. Complete fabrication was carried out in the factory by using stainless steel sections. Sizes of tubes used in the work are 48, 73, 114 and 168 mm diameter with thickness varying from 3.68 mm to 11.24 mm.
Since the area of covering of the central courtyard was inadequate for the required solar panels, the terrace of 2200 sqm was covered with MS box section with 6m cantilevers all around the building and 12m at the corners. Additionally, a 6m cantilever was provided at the 4th floor level on the south face of the building. Box sections measuring 250mm x 450mm to 250mm x 850 mm (depending on the span) were used for supporting the solar panels.
Electrical and Air-Conditioning
A view from corner
UPS power was supplied on centralized basis to support critical services such as emergency lighting, administration workstations, security system, building automation system, and network server room.
The building was designed for both air-conditioning and heating. The air conditioning load was estimated to be 400 TR for which two 240 TR water cooled screw chillers having one standby for conventional system and one 200 TR water screw chillers have been installed for chilled beam system. Total load of the system would have been around 800 TR if conventional system had been provided.
Energy-efficient chilled beam system of air conditioning with energy consumption less than 50% compared to conventional system, has been provided, except for the ground floor and 7th floor on the northern side. In these locations, a chilled beam system was not provided due to height of more than 3m and possible high humidity levels in areas like cafeteria, yoga room and gymnasium.
Active type chilled beam system was provided in the building comprising a casing with integral primary air duct fitted with sets of induction nozzles. The coils were used for cooling and heating operations (2-pipe system). The assembly had two separate chilled water coils with single supply and return connections. In the mixing section of the unit, conditioned secondary air was mixed with the primary air and discharged horizontally (Coanda effect) into the room via slots. The unit comprised external casing, edge profiles and suspension lugs.
A short section of insulated flexible duct was used to connect the primary air ducting to chilled beam ensuring that flexible duct connection to the beam was sealed air tight. A balancing damper was installed in primary air duct to facilitate air supply balancing of each beam to the scheduled static pressure at unit level. AHU's serving office areas envisaged with chilled beam system were provided with centrifugal fan, cooling coil and filter section. These air handling units were capable of delivering constant volume of air to the plenum of chilled beams.
Chilled beams were installed in all conditioned office spaces and corridors, receiving chilled water input at 16-17 degree Celsius to avoid any condensation on surface. In addition, dry fresh air was injected into the AHU room, which ultimately got mixed with the (return) air coming out from the conditioned spaces for formation of primary air. Then, the same primary air was injected into the plenum of active chilled beams, which passed through the small nozzles, creating negative pressure for induction. Finally, the induced air passed through the secondary chilled water coil inside the beam. Therefore, sensible cooling effect could be created without any condensation. Primary air conditions were designed in such a way that air can take care of latent load present inside the spaces.
Zero Net Energy Concept
This building is the first ever zero net energy multi storeyed building with 100% onsite renewable solar power generation. It has the highest green rating by GRIHA as 5 star and Platinum rating by LEED India. With a solar power system of installed capacity 930 KWp, it has the largest rooftop solar system in a multi storeyed building in India.
Brief details of solar power are given in the following;
Capacity of power generation : 930KWp
Annual power demand : 14 lakh units (KWh)
Annual power generation : 14 lakh units (KWh)
Total area of solar panels : 4600 sqm
Total area of the system including catwalks : 6000 m2
Photo voltaic panels : mono crystalline, 20% efficiency
Dedicated Outdoor Air handling units (DOAs) of variable volume type, double skin construction for noise control comprising centrifugal fans, cooling coil section, stainless steel double sloping drain pan for zero water retention, heat recovery wheel, cooling coil, and filter section were provided at terrace level over the space adjacent to the connecting corridors. The fresh air was pre-cooled by recovering energy from the centralized exhaust stream, thereby reducing the air conditioning load.
Eco-Friendly FeaturesServer rooms for networking in the building were air-conditioned through microprocessor-based dual coil floor discharge precision units installed consisting of centrifugal fan, chilled water and DX cooling coil, filter section, humidification/ dehumidification system, and outdoor condensing unit to handle high sensible heat generated in server room.
- Chilled beam system of HVAC
- Geothermal heat exchange system
- Regenerative lifts
- Fully automated car parking in basements
- Building orientation in E-W direction
- Blocks connected with corridors and central courtyard
- Building envelope designed to ensure daylight in 75% occupied areas
- Plantation and grassing in more than 50% area
- Grass pavers in circulation areas
- Terrace garden
- Energy efficient air conditioning system and lighting
- Conversion of braking energy into electricity in lifts
- Chillers and AHUs with VFDs, heat recovery wheels and thermostat controls for HVAC
- LED lights, occupancy and Lux level sensors
- 930 KWp rooftop solar power plant
- Low discharge water fixtures
- Landscaping with no hard paving eliminating heat island effect
- Fly ash-based products in construction
- Sewage treatment plant of 30 kLD capacity.
Extended roof at 4th floor and terrace level
The building was also provided with a heating system. Hot water generators of total installed capacity 240 KW were provided in the AC Plant room.
Energy Efficient Lifts and Fire Services
Energy efficient elevators were provided with a regenerative drive option, working as a generator when a heavy car returns to ground floor or an empty car goes up. Instead of turning the braking energy to heat, the electricity has been fed back to the network. It could save up to 25% of the energy consumed by a typical 13-person elevator. The power regenerated from the elevator was to be used for power requirement of the elevators. However, suitable tapping point for regenerated power of each elevator was provided for other uses.
An addressable fire alarm detection system was installed for the entire complex. The complex was under "A" category of fire zoning as per National Building Code. Accordingly, the project was designed with 200 kL of fire tank, sprinkler system, hydrant system, CO2 extinguishing system, hand held extinguishers and clean agent fire protection system.
All services were controllable and could be monitored using IBMS for greater reliability and to effect optimum level of operating engineering services system.
Solar panels at roof top
Vertical closed loop system of geothermal heat exchange system to reduce the load on the HVAC system was adopted for the first time in a government building in India on such a large scale. The system utilises advantage of difference between ambient temperature and the temperature below ground level. The system has vertical closed loop system done with 32 mm diameter HDPE U – loops, 180 in number and 80m deep each. It resulted into reduction of 160 TR load on cooling tower and consequent reduction in consumption of water.
Robotic Car Parking Concept
All three basements have been used for automatic parking system. First basement was designed for car entry and exit lobby and puzzle parking system, and the second and third for robotic dolly parking system. There were two ramps: one for car entry and the other for exit. First basement has a capacity of 49, second basement of 126 and third of 170. A vehicle will always be parked on steel stalls installed floor. The dolly always carries the car, supporting it from the bottom area of the 4 wheels.
During the operation, the user keeps his car in the entrance lobby and moves out. The elevator lifts the car from the entrance lobby and moves along Z exit to the required floors. Floor shuttle dolly picks the car from elevator and delivers the same on a transfer stall and returns for the next command. The shuttle on the specified floor moves on track along Y exit and the dolly goes out from shuttle along the X exit and comes back by the same path. The shuttle with dolly and cars moves (along X exit) and aligns with an empty parking stall and returns to the shuttle.
The retrieval operation is exactly as above but in reverse order. Main components of the parking system include robotic dolly, shuttle, elevator, boom barrier and auto gate, car stopper at entry lobby, CCTV and signage, PLC panel, car stall, control room, ticket counter and service voltage transformer panel.
Acknowledgements
- CPWD engineers and architects associated with the project, particularly Shri Rajesh Kaushal, Senior Architect and Shri A K Gupta, Executive Engineer.
- Consultants:
- EQMS India for environment services
- Deependra Prashad Architects and Planners for green building certification
- Spectral Services - MEP consultants
- INSDAG - structural consultant
- V R Techniche for automated car parking
- Other contractors and consultants engaged in the project
https://en.wikipedia.org/wiki/Zero-energy_building#India
Bhagat Singh, P. (2017), First Net Zero Energy Government Building. http://cpwdpims.nic.in/display_cpwd/technical_ltr/tech.aspx
