OGS Green Philosophy

All the exterior walls are constructed as Cavity Walls. There is a 9” thick brick wall on the outside, then an air gap ranging from 4” to 10” and then a 4.5” or 9” wall on the inside. Thermally during the forenoon until about 3 O’ Clock the exterior walls absorb heat. Then when the sun in on its way down, this heat starts entering inside the building. This Air Gap in the cavity wall does not let this heat enter inside the rooms thus the energy required to air condition the rooms is greatly reduced.

While the classrooms are Air Conditioned, the corridors do not have any equipment provided. As we pump in the Treated Fresh Air in the rooms, maintaining the room pressure, the excess air spills out into the corridors and thus the corridors become comfortable. Further, non conditioned corridors also provide a buffer zone for students coming from warm outdoors and vice versa.

As explained above, the hot air always rises up. The buildings are so designed that all the rooms open into a big courtyard having a huge Atrium. This Atrium has clear openings on the top. This naturally creates the ‘Chimney Effect’ and all the hot air from all the rooms and corridors travel up the Atrium and is vented out into the atmosphere automatically. This ensures comfortable conditions indoors and without any use of additional energy.

We keep a Window to Wall ratio about 35. Following techniques are used in terms of keeping such huge glazing area and still not letting the outside heat enter the rooms:

Because of the air cavity total thickness of the outside walls are about 18” to 20”. Windows are then placed on the inner edge of the wall. This automatically gives a shade of 18” to 20” and thus the sun does not strike directly on the windows;

The Window profile used is UPVC which has a U Value of 1.7;

The glass is used in a Double Glazed Unit having 6 mm Reflective Glass on outside, 12 mm Gap filled with Argon Gas and 6 mm Clear Low ‘E’ Glass inside. Glass specification include U value of around 1.6, Solar Factor of around .35 and light transmission about 25%. The Low ‘E’, U Value and Solar Factor ensure that the outside heat does not travel inside the room. The 35% Window to Wall Ratio and 25% light transmission on one hand takes care of the glare thus no blinds/curtains are required and at the same time it ensures maintaining of sufficient Lux Levels inside the room and there is very less dependence on the artificial light.

We use energy efficient lighting system using CFL and T5 Lamps. All the Luminaires are selected which are Mirror Optics and focus all the light to the required area and not wasting any light. The Ballast used inside are electronic from reputed manufacturers. We benefit on two counts here. CFLs and T5s are the most energy efficient. And the mirror optics further reduce the requirement of number of Luminaires.

In peak summers the ambient temperature ranges around 42 – 45 degrees in this part of the world. Inside the buildings the Central Air Conditioning system maintains a temperature of 24 degrees which is comfortable to Human Beings. Worldwide Air Conditioning consumes about 65% of the total Energy used in buildings. At OGS we have very carefully taking certain out of the box measures that have resulted in reduction of HVAC load to great extent:

Central Air Conditioning Plant consists of Chillers (Compressors) as the main Machinery. We use “Screw” chillers which give efficient power consumption even on part loads. The IKW is 0.62 per Tonne. The Refrigerant used is R134A which again is green compliant;

While designing the Air Conditioning (HVAC) of a project, a careful working is performed determining the amount of Fresh Atmospheric Air to be pumped into the conditioned spaces. And since the temperature being maintained indoors is 24 degrees, it is the job of the Central Air Conditioning Plant to pick up the atmospheric air of 44 degrees, cool it down to about 23-24 degrees and them pump into the indoors. This consumes a lot of Air Conditioning Load and energy. Geothermally, 4 meters below the ground the temperature remains constant round the year. And this temperature is the average annual temperature of the place, which for the Delhi NCR is about 25-26 degrees. Therefore, we are routing the Atmospheric Air through Earth Air Tunnels 75 Metres Long buried 4 Meters below the ground. After travelling this 75 meters, this air picked up at 44-45 degrees cools down to about 28-30 degrees. Now we will cool this 28-30 degrees air to 24 degrees and pump inside. There are in all 6 Earth Air Tunnels of 1200 MM dia provided and each tunnel is reducing the HVAC load by 30 TR each meaning a total reduction of 180 TR. This results in less power consumption thus reducing the carbon footprint considerably;

In a school environment there are various timings at which various facilities operate. And at the same time it is very difficult to ensure that the air conditioning and lights of the respective areas are properly switched off during these off hours. Here we regulate the electricity through a PLC (programmable Logic Computer) which shuts off the supply at the non usage hours thus ensuring no wastage at all;

While we have saved the electrical energy by the above measure, there is still a lot of energy losses that happen with the chilled water flowing through the multi kilometer of chilled water lines irrespective of wherether the equipments of particular areas are being used or not. This is a passive loss which no one takes into consideration but has a huge impact on the Main AC Plant load. To arrest this, according to the usage time and pattern, we have divided all our buildings into various zones and intelligentally designed the chilled water piping providing motorised butterfly valved at the chilled water return of each zone. The PLC at the time of shutting the electricity of the non operational zone also shuts off this motorised valve thus cutting off the chilled water to unnecessarily run in the pipe lines of this zone. Thus on one hand reducing the pumping load and on the other arresting the unnecessary energy losses that otherwise are incurred with the excess flow of water in the non operative areas;

All the Fan Coil Units and Air Handling Units are fitted with Pressure Independent Balancing Cum Control Valves that regulate the flow of water required thus optimising the flow which results in reduced Water Flow and hence saving in Pumping energy;

All the Floor Mounted AHUs are fitted with Variable Frequency Drives which regulates the Air Flow according to the requirement. This optimisation reduces the total tonnage required for the AHU and hence reduces the load on the Chillers;

All the pumps are fitted with Efficiency Class 1 Motors which give a better energy efficiency which further increases on part loads:

Cooling Towers are selected with Lower Approach. This reduces the Condenser Water Temperature which in turn reduces the power consumption of chillers. Further the Towers are so designed where the highly efficient fans are selected which consume less power. For a 275 TR Cooling Tower, the total Fan KW is just 7.5;

Condensate Water Collection and Usage. Normally in any HVAC facility, the condensate water is channelized to the drain and goes waste. And actually, this is near Distilled quality water and that too at a very low temperature. We have channelized and collected the condensate water of all the FCUs and AHUs into a single table which then pumps this cold water to the cooling tower as the make-up water. This on one hand utilizes the water which otherwise goes waste. And on the other hand, providing chilled water to the Cooling Tower increases the efficiency of Chillers Condensate water by about 6% resulting in huge power savings.

Requirement of Fresh Air is multifold in the indoor sports areas. Yet the comfortable temperature has to be maintained for the sportsmen. We have used natural methods in attaining these. The indoor sports Arena are constructed in the Lower Ground Floor about 3 metres below ground level. This naturally keeps the temperature in moderate levels. Then we have introduced 50000 cfm of Fresh Air through Earth Air Tunnels which cools the Indoor Sports Arena. This way we are cooling these areas with 100% fresh air without any use of Chilled Water thus absolutely no load on the HVAC system.

OGS campuses are huge land areas. Here we do a ground coverage of only about 22%-25% and rest of the areas are open spaces, playfields, plantations etc. Thousands of trees of varied species are planted on the open areas. These plantations are strategically deployed. There is a dense plantation along the boundary walls mainly of trees that grow good height and are dense. So any air entering the campus is filtered through these trees. Further there is dense plantation done on the periphery of all the buildings which cuts the heat and keeps the buildings cool. Regular watering of these trees creates evaporation which in turn creates a cooler atmosphere.

Being huge terrace areas of buildings, all the storm water is channelized into the intelligently designed storm water drain network. The network is so designed that it not only accommodates the water that comes through rain in the campus area, but also the water that flows inside the campus because of the natural terrain and nallas from surrounding areas. This network then guides water again to the natural nallas to go out of the campus. Enroute good numbers of rain water harvesting pits are built and are strategically located near to a Bore Well so that these borewells get the recharge. All these years we have seen Bore Wells in the surrounding areas getting dry, but ours always remain charged and this is only because of the Harvesting System we have deployed.

Terraces are open to the sun heat and radiate a lot of heat inside. This increases the airconditioning load on the top floor of the building. Here again we go the natural way. We lay the Brick Bats over the RCC Roof for insulation. This is then plastered and then on top, broken China Mosaic of White and light colours are layed. This china mosaic reflects the heat from the sun and being of light colours do not absorb any heat either. And whatever little is left, the Brick Bats take care of not passing it through.

Watering such huge green campuses requires a lot of water. Here we meet about 80% of the requirement just by recycling the waste water. The Sewage Treatment Plant is designed to use least of chemicals and power. Total power required to run a 150 KLD Plant is 7.5 KW thus saving huge power costs. All the waste water is channelised to the in house Sewage Treatment Plant installed. All this sewage is treated in such a way that only a very little amount of sludge is left and all the water is treated and filtered with appropriate chemical properties to be used for horticulture. This water then is supplied to the carefully designed irrigation system which is designed after carefully assessing the amount of water required in various greens and plants. And the water that comes out from the STP is so rich in minerals that practically we do not require to use any fertiliser and the plants are always lush green!!Thus, we are not drawing any fresh water for irrigation.