ENERGY EFFICIENT ARCHITECTURAL PRACTICES IN INDIA
M.ARCH. SEMINAR REPORT
AR-800
By
SHASHI KANT SINGH(Roll Number: 13M801)
DEPARTMENT OF ARCHITECTURE
NATIONAL INSTITUTE OF TECHNOLOGY
HAMIRPUR (HP) - 177005, INDIA
November, 2014
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Index
Aim Objectives Research Methodology Literature Review Case studies Conclusion
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1.1 Aim:
To find out suitable heating/cooling passive systems which can optimize indoor temperatures for a certain climate in India w.r.t. Thermal Comfort.
1.2. Objectives:
• Analysis of available passive building systems in India.
• Understanding principles and properties of different passive systems available.
• Finding Relationship of passive design systems with different climates in India
1.3. Research Methodology:
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2. Literature review:
2.1 Energy
Energy is a property of objects, transferable among them via fundamental interactions, which can be converted in form but not created or destroyed. The joule is the SI unit of energy, based on the amount transferred to an object by the mechanical work of moving it 1 meter against a force of 1 newton.
Work and heat are two categories of processes or mechanisms that can transfer a given amount of energy. The second law of thermodynamics limits the amount of work that can be performed by energy that is obtained via a heating process—some energy is always lost as waste heat. The maximum amount that can go into work is called the available energy. Systems such as machines and living things often require available energy, not just any energy. Mechanical and other forms of energy can be transformed in the other direction into thermal energy without such limitations.
2.2 Sectorial Energy demand in India (As per International Energy Agency)
Sectorial energy demand reflects the economic structure of a country. In 1990, the building sector was India’s largest energy consumer, representing 42% of India’s total primary energy demand (TPED).The share of buildings dropped to 29% in 2009 and will decrease to about 18% in 2035. (Figure 1)
Figure 1.Sectorial Energy Demand, India
2.3 Energy Efficiency
Energy efficiency is a way of managing and restraining the growth in energy consumption. Something is more energy efficient if it delivers more services for the same energy input, or the same services for less energy input. For example, when a compact florescent light (CFL) bulb uses less energy (one-third to one-fifth) than an incandescent bulb to produce the same amount of light, the CFL is considered to be more energy efficient.
2.4 Renewable Energy Resources:
Renewable energy is any energy resource that is naturally regenerated over a short time scale and derived directly from the sun (such as thermal, photochemical, and photoelectric), indirectly from the sun (such as wind, hydropower, and photosynthetic energy stored in biomass), or from other natural movements and mechanisms of the
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environment (such as geothermal and tidal energy). Renewable energy does not include energy resources derived from fossil fuels, waste products from fossil sources, or waste products from inorganic sources. Renewable energy resources may be used directly, or used to create other more convenient forms of energy. Most renewable forms of energy, other than geothermal and tidal power, ultimately derive from solar energy. Energy from biomass derives from plant material produced by photosynthesis using the power of the sun. Wind energy derives from winds, which are generated by the sun's uneven heating of the atmosphere. Hydropower depends on rain which again depends on sunlight's power to evaporate water.
Figure 2.Renewable Energy Resources
2.5 Energy Efficiency in Buildings
Energy usage in a building can be categorized in the following subheads:
1. Construction Process Energy
2. Embodied Energy in Building Materials
3. Operational Energy
4. Maintenance Energy
Energy Resource efficiency in new construction can be affected by adopting an integrated approach to building design.
1. Incorporate solar passive techniques in a building design to minimize load on conventional systems (Heating ,cooling ,Ventilation ,and lighting)
2. Design Energy Efficient lighting and HVAC (Heating , Ventilation and air conditioning ) Systems
3. Use renewable energy systems (solar photovoltaic systems / solar water heater systems) to meet a part of building load.
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http://www.commerce.gov/sites/default/files/images/2011/march/dis-wind-farm.jpg
http://www.energynext.in/wp-content/uploads/2014/04/Solar-power-trading.jpg
Solar
Wind
Geothermal
Waves
4. Use low energy materials and methods of construction and reduce transportation energy.
Architects can achieve energy efficiency in the buildings they design by studying the macro and microclimate of the site , applying bioclimatic architecture principles to combat the adverse conditions .A few common design elements that directly or indirectly affect thermal comfort conditions and thereby the energy consumption in the buildings are listed below:
Orientation Landscaping Location of water bodies Ratio of built-form to open spaces Plan form Building envelope and fenestration
1. Orientation: The placement of the building in north-south direction, reduces the heat energy input in the building, increases overall ventilation and provide thermal comfort to the building.
2. Landscaping: Landscaping alters the microclimate of the site. It reduces direct sun from striking the building & heating up the building surfaces.
3. Location of water bodies: Water is a very good modifier of microclimate. It takes up large amount of heat in evaporation and causes significant cooling in hot and dry climate. On the other hand, in humid climates, water should be avoided as it adds to humidity.
4. Ratio of built form to open spaces: The volume of space inside a building that needs to be heated or cooled and its relationship with the area of the envelope enclosing the volume affects the thermal performance of the building. For any given building volume, the more compact the shape, the less wasteful it is in gaining/ losing heat. Also, the building form determines the airflow pattern around the building, directly affecting its ventilation.
5. Plan form: The ideal building form is greatly influenced by the local climate. The building form can minimize heat loss or gain, affect maximum day lighting, and maximize natural ventilation.
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Figure 3. Trends in Plan form according to climatic conditions
6. Building Envelope and fenestration:
External wall Thermal insulation Building material Roof Windows
− Size
− Orientation
− Shading device
− Natural ventilation
− Daylight
a. External Walls: Mathur and Chand (2003) believe that thermal resistance of a wall can be increased by introducing an air cavity. Similarly, Mallick (1996) asserts that variation in wall thickness can make a considerable difference in the comfort level of houses in tropical climates. The field measurements and computational energy simulations to examine the effectiveness of passive climate control methods such as facade construction in a typical 14 storey residential building of Singapore by Wong and Li (2007) depict similar views as of Mallick (1996). Wong and Li (2007) from their study concluded that the use of thicker construction on east and west external walls can reduce the solar radiation heat gain and hence, the cooling load can be reduced by 7%-10 % when the thickness of external wall is doubled (229 mm concrete hollow block instead of 114 mm concrete hollow block).
b. Thermal Insulation: Tham (1993) in his study of various energy conservation strategies obtained results that do not encourage wall insulation. His study concludes that by adding 50 mm of polystyrene as wall insulation, only 1.7 % reduction in total energy use is achieved. He also suggests that if savings in operation cost were compared to the cost of installation, wall insulation would
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Source:Norbert Lechner , Heating , Cooling, Lighting 4th Edition ,
not be economically feasible. This finding, yet again conflicts with the results of Bolatturk (2008) and Cheung (2005).
c. Building Materials: Gut and Ackerknecht (1993) recommend using the following building materials in tropical climates:1. Burnt clay bricks can be used in tropical climates because they have good thermal resistance and good regulating property against humidity.2. Timber has good thermal resistance and is a good regulator of humidity.3. Matting of bamboo, grass and leaves are good because they are not airtight and allow proper ventilation. Embodied Energy is the sum of all the energy required to produce any goods or services, considered as if that energy was incorporated or 'embodied' in the product itself. Low embodied energy construction is preferred which can be done by using:
Local/regional Materials (within 500km range as per GRIHA) Recycled Materials/ construction waste Low energy materials Rapidly renewable materials
d. Roof: The roof is an important element of design when it comes to conserving energy because this part of the building receives most of the solar radiation and its shading is not easy. Vijay Kumar et al. (2007) claim that Indian concrete roofs in single or two storey buildings with 150 mm thickness of reinforced cement concrete (RCC) and a weathering course (WC) having 75–100 mm thick lime brick mortar, account for about 50%- 70% of total heat transmitted into the occupant zone and are responsible for the major portion of electricity bill in air-conditioned buildings. Naharand Sharma in Tang and Etzion (2004), Vijay Kumar et al. (2007) and Alvarado and Martinez (2008) conclude that the heat entering into the building structure through roof is the major cause for discomfort in case of non-air-conditioned building or the major load for the air-conditioned building.Alvarado and Martinez (2008) studied the impact of a simple and passive cooling system in reducing thermal loads of one- storied roofs. Their results demonstrate that the aluminum– polyurethane insulation system with an optimal orientation reduces the midpoint temperature of a cement-based roof significantly. The results also exhibit that the roof insulation system can reduce the typical thermal load by over 70% while effectively controlling thermal fluctuations.
e. Windows: e.1. Size: Openings are important design elements for admitting daylight, air flow, providing cross ventilation and views. Gut and Ackerknecht (1993) recommend that windows should be large and fully openable, with inlets of a similar size on opposite walls for proper cross-ventilation in tropical climates. Liping et al. (2007) claim that ventilation and indoor air quality can be improved by increasing the window to wall ratios (WWR), but it would also increase solar heat gain. There has always been a conflict with daylight provision and exclusion of solar penetration in designing windows.
e.2. Orientation: Gut and Ackerknecht (1993) note that openings in hot and humid regions should be placed according to the prevailing breeze so that air
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can flow through the internal space. However, this is difficult to achieve in multi-unit housing.
e.3. Shading Device: Cheung et al. (2005) studied the effects of shading devices (overhangs and wing walls) along with five other passive design strategies on the cooling load for an apartment. The length of the overhang and wing wall were 1.5 meters each. Their results suggest that the longer the shading, the greater the reductions in both annual required cooling energy and peak cooling load. They concluded that the use of such shadings, achieved savings of approximately 5% in annual required cooling energy. However, according to Mowla (1985), the length of shading devices depends on the orientations, width of the opening, height of the openings, horizontal shadow angle (characterizes a vertical shading device) and vertical shadow angle (characterizes a horizontal shading device). Hence, it is not reasonable to conclude that shading devices should have arbitrary lengths in general for all orientations. Wong and Li (2007) used horizontal shading devices of lengths 0.3m, 0.6m and 0.9 m on both east and west facades of 14-storied building to study the effect on cooling load. Their results show that 3%, 7% and 10% energy can be saved by using 0.3 m, 0.6 m and 0.9 m respectively on east facades of the studied building. Similarly, 3%, 6% and 9% energy can be saved by using 0.3 m, 0.6 m and 0.9 m respectively on west facades of the studied building. This study by Wong and Li (2007) considers east and west orientations but does not consider other parameters such as width of the opening, height of the openings, horizontal shadow angle and vertical shadow angle.
e.4. Natural ventilation: Ventilation is the movement of air. According to Watson & Labs (1983), ventilation has three useful functions in the building sector. It is used to:1. Satisfy the fresh air needs of the occupants2. Increase the rate of evaporative and sensible heat loss from the body3. Cool the building interior by an exchange of warm indoor air by cooler outdoor air.
Watson & Labs, 1983 explain that natural ventilation can be generated by the following two forces:1. Temperature difference between the outdoors and the indoors (thermal force). When a mass of air inside the room is heated, it expands and becomes less dense and rises. If openings are provided at different heights on the building’s envelope, the indoor pressure is higher at the upper opening and lower at the lower opening. These pressure differences generate an inward flow at the lower opening and an outward flow at the upper one. When thermal forces discharge air from a building, the action is termed as stack effect.
2. Wind flow against the building (wind pressure force). As wind blows against a building, the air in front of the building is compressed and creates a pressure zone. The air next to the leeward wall and above the roof expands and the pressure is reduced, creating a suction zone. These pressure differences between any two points on the building’s envelope determine the possibility for ventilation when openings are provided at these points (driving force) and
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if air can flow inside the building through openings with the higher pressure to openings exposed to a zone with lower pressure. Cross- ventilation is defined as the situation in which outdoor air can flow in through inlet openings, located in the pressure zone, and flow out via outlet openings located in the suction sections of the building
Guidelines for inducement of air motion for providing cross-ventilation as recommended by various authors are compiled as follows:
There should be windows on opposite walls: one window should be on windward wall and the other on leeward wall (Mathur & Chand, 2003). However, as residential buildings in India are compact and not outward oriented, all rooms do not have windows in opposite walls. In such cases, two windows may be designed instead of a single window. Another possibility might include a door on the opposite facade of a wall with the window to promote cross-ventilation. However, it would not be as effective as having two windows on opposite walls.
Windows located diagonally opposite to each other, with the windward window near the upstream corner, perform better than other window arrangements (Mathur & Chand, 2003). In typical residential buildings of India, not all rooms are provided with windows on opposite. Even if they are, as rooms are not very large (about 10 square metres) windows are placed in the center of the facade because placement of furniture depends on window location.
Figure 4 Orientation of openings, Source: Watson, D. & Labs, K. 1983.
Horizontal louvers like sunshades, over a window deflect the incident wind upward and cause a reduction in air motion in the zone of occupancy .A
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horizontal slot between the wall and horizontal louver prevents upward deflection of air and ensures a downward flow (Mathur & Chand, 2003).
Figure 5.Deflection by projecting slabs, Source: Gut, P. & Ackerknecht, D. 1993.
Jalousie or louvered windows facilitate nearly unrestricted air movement. Louvered walls of wooden boards for example can also help facilitate airflow when used as interior partitions. A louvered door is ideal for porches, exterior rooms and spaces where openness is desirable without sacrificing security. Jalousie windows offer two advantages. One, it offers almost unrestricted openness in unbolted position and second, they restrict rain penetration (Watson & Labs, 1983). Louvered windows were used in traditional buildings of India. They are no longer used today because of the costs involved. Louvers can be made of opaque glass or aluminium to reduce costs. Louvers of aluminium frame or screen walls can be used on the part on the window that stretches to the beam in case of big windows that extend either from skirting to beam or sill to beam. The louvered openings below the beam can allow discharge of heated air by thermal force known as stack effect.
Figure 6. Louvered door, Source: Watson, D. & Labs, K. 1983.
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Figure 7.Benefit of jalousie window: unrestricted openness in open position,
Source: Watson, D. & Labs, K. 1983.
Figure 8. Benefit of jalousie window: restrict rain penetration,
Source: Watson, D. & Labs, K. 1983.
Roof overhangs help air motion in the working zone inside buildings (Watson & Labs, 1983). However, this is only possible on the top most storey.
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Figure 9. Benefit of roof overhang, Source: Watson, D. & Labs, K. 1983.
Wall projections such as fin, wing wall can be used to direct wind flow into particular areas. (Watson & Labs, 1983). Compared to roof overhangs, fins seem to be more effective because they direct air flow in all floors. However, they might not always be easy to plan.
Figure 10. Wing wall outside window, Source: Watson, D. & Labs, K. 1983.
Parapets create greater ventilating-driving pressure by increasing air-damming action .They may also be used to divert airflow in the living zone (Watson & Labs, 1983). This feature is effective only on the topmost floor, below the roof. Remaining floors in the building shall not be benefitted from this design feature.
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Figure 11. Air-damming action of parapet , Source: Watson, D. & Labs, K. 1983.
Balconies open on three sides is preferable as it can create an increase in air movement for most of the orientations of building with respect to the incident wind (Mathur & Chand, 2003).
e.5. Daylight: Krarti et al. (2005) conducted a simplified analysis method to evaluate the potential of day lighting to save energy associated with electric lighting use in commercial buildings. Performance of day lighting were investigated for several combinations of building geometry, window opening size, and glazing type for four geographical locations in the United States. Their simulation results indicate that day lighting saves 31% of the total annual energy use from the artificial lighting system.
Figure 12. Natural Daylighting Concepts
2.6 Bioclimatic architecture
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http://web.utk.edu/~archinfo/Zero_Energy/images/SmartLab/daylighting.jpg
Bioclimatic architecture refers to the design of buildings and spaces (interior /exterior / outdoor) based on local climate, aimed at providing thermal and visual comfort, making use of solar energy and other environmental sources.
System, A set of things working together as parts of a mechanism or an interconnecting network
Active system
(Source: Engineering Dictionary, NCRS Construction Dictionary)
A solar heating and/or cooling system that requires external mechanical power to move the collected heat.
Passive system
(Source: Engineering Dictionary, NCRS Construction Dictionary)
An assembly of natural and architectural components which converts solar energy into usable or storable heat without mechanical power; generally the building's structure itself forms the solar system. Passive systems typically use large south-facing windows to gather heat.
2.7 Passive Heating Concepts:
1. Direct solar gain system
• In this system sunlight enters in the rooms through windows, warming the interior space.
• The glazing system generally located on the southern side to receive maximum sunlight
During winter.
• The glazing system is usually double glazed with insulating curtains to reduce heat loss during night.
• South facing glass admits solar energy into the building , wee it strikes thermal storage
Materials such as floors or walls made of adobe, brick, concrete, stone, or water.
• The direct gain system uses 60%-70% of solar energy striking the windows.
2. Indirect solar gain system
• In this system thermal mass is located between the sun and the living space
• The thermal mass absorbs the sunlight that strikes it and transfers it to be living space.
• The indirect gain system uses 30-40% of the sun’s energy striking the glass adjoining the thermal mass.
2.7.1 Indirect Solar Gain Systems
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1. Trombe Wall
• A trombe wall is thermally massive wall with vents provided at the top and bottom
• It may be made of concrete, masonry, adobe and it is usually located on the southern side.
• The outer surface of the wall is usually painted black for maximizing absorption and the wall is placed behind glazing with the air gap in between.
• Indoor temperatures can be maintained at about 15 ◦c when the outside temperature is as low as -11 ◦c(Source : Mazria 1979) .
• The total area of the each row of vent is about 1% of the storage wall area(Source: Levy , Evans, and Gardstein 1983)
Figure 13. Trombe Wall
2. Water Wall
• Water Wall are based on the same principle as that for Trombe wall, except that they employ water as the thermal storage material.
• Heat Transfer through water walls is much faster than that for trombe walls.
3. Roof based air heating Systems
• In this technique, incident solar radiation is trapped by the roof and is used for heating Interior spaces.
• The system usually consists of an inclined south facing glazing and a north sloping insulated surface on the roof.
• Between the roof and the insulation, an air pocket is formed which is heated by the solar radiation
• In Himachal Pradesh State Cooperative building south glazing is in the form of solar collectors warming the air and a blower fan circulating the air to the interior spaces.
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Figure 14. Roof based solar collector
4. Sunspaces
• A sunspace o solarium is the combination of direct and indirect gain systems.
• The basic requirement of buildings heated by the sunspace are:
a. glazed south faced collector space attached yet separated from the building
b. Living space separated from the sunspace by a thermal storage wall.
• The Himurja building in Shimla has a well-designed solarium on the south wall to maximize solar gains.
Figure 15. Sunspace/Solarium
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2.7.2 Passive Cooling Concepts
• Passive cooling systems are least expensive means of cooling a home which maximizes the efficiency of the building envelope without any use of mechanical devices.
• It rely on natural heat-sinks to remove heat from the building. They derive cooling directly from evaporation, convection, and radiation without using any intermediate electrical devices.
• All passive cooling strategies rely on daily changes in temperature and relative humidity.
• The applicability of each system depends on the climatic conditions.
• These design strategies reduce heat gains to internal spaces.
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- Natural Ventilation Shading Wind Towers Courtyard Effect
- Earth Air Tunnels- Evaporative Cooling Passive Down Draught Cooling Roof Sprays
Figure 16.Various Design strategies of passive cooling for different comfort variables
a. Passive Ventilation
• Outdoor breezes create air movement through the house interior by the 'push-pull' effect of positive air pressure on the windward side and negative pressure (suction) on the leeward side.
• In order to have a good natural ventilation, openings must be placed at opposite pressure zones.
• Also, designers often choose to enhance natural ventilation using tall spaces called stacks in buildings
• With openings near the top of stacks, warm air can escape whereas cooler air enters the building from openings near the ground.
• The windows, play a dominant role in inducing indoor ventilation due to wind forces.
• In most homes, exhausting the warm air quickly can be a problem.
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Source:Passive Cooling , Research and Design, AIA , fall 1979, volume 2 , number 3
• With the design of high ceilings throughout the breeze zone combined with clerestory windows at the 14′ ceiling height on three walls, the rising hot air is allowed to escape which in turn does two things.
• Firstly the rising air creates a low pressure zone on the cool mass floor, pulling air along the floor from other areas of the house as well as any open doors.
• Secondly the rising and escaping air creates an interior low pressure that should pull in large volumes or exterior air from the patio doors.
• Depending on the primary wind direction and which doors are opened relative to time of day and shade, we can create a breeze of cooler incoming air.
Figure 17.Passive Ventilation system
b. Shading:
• Solar control is a critical requirement for both cooling-load dominated and passively solar-heated buildings.
• The most effective method of cooling a building is to shade windows, walls and roof of building from direct solar radiation.
• Heavily insulated walls and roofs need less shading.
• Can use overhangs on outside facade of the building.
Each project should be evaluated depending on its relative cooling needs:
• Extend the overhang beyond the sides of the window to prevent solar gain from the side.
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Wind tower in Jodhpur Hostel to catch favorable cool wind from south-west for passive cooling
• Use slatted or louvered shades to allow more daylight to enter, while shading windows from direct sunlight.
• Reduce solar heat gain by recessing windows into the wall.
Figure 18. Window Shading
c. Wind Towers:
• In a wind tower, the hot air enters the tower through the openings in the tower, gets cooled, and thus becomes heavier and sinks down.
• The inlet and outlet of rooms induce cool air movement.
• After a whole day of air exchanges, the tower becomes warm in the evenings.
• During the night, cooler ambient air comes in contact with the bottom of the tower through the rooms.
• The tower walls absorb heat during daytime and release it at night, warming the cool night air in the tower.
• Warm air moves up, creating an upward draft, and draws cool night air through the doors and windows into the building.
• The system works effectively in hot and dry climates where fluctuations are high.
• A wind tower works well for individual units not for multistoried apartments.
• In dense urban areas, the wind tower has to be long enough to be able to catch enough air.
• Also protection from driving rain is difficult.
d. Courtyard Effect:
• Due to incident solar radiation in a courtyard, the air gets warmer and rises.
• Cool air from the ground level flows through the louvered openings of rooms surrounding a courtyard, thus producing air flow.
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Figure 19.Wind Tower
• At night, the warm roof surfaces get cooled by convection and radiation.
• If this heat exchange reduces roof surface temperature to wet bulb temperature of air, condensation of atmospheric moisture occurs on the roof and the gain due to condensation limits further cooling.
Figure 20. Courtyard Effect
• If the roof surfaces are sloped towards the internal courtyard, the cooled air sinks into the court and enters the living space through low-level openings, gets warmed up, and leaves the room through higher-level openings.
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Courtyard as a moderator of internal climate
Figure 21. Principles of Courtyard Design
e. Earth Air Tunnels:
• Daily and annual temperature fluctuations decrease with the increase in depth below the ground surface.
• At a depth of about 4 m below ground, the temperature inside the earth remains nearly constant round the year and is nearly equal to the annual average temperature of the place.
• A tunnel in the form of a pipe or otherwise embedded at a depth of about 4 m below the ground will acquire the same temperature as the surrounding earth at its surface.
• Therefore, the ambient air ventilated through this tunnel will get cooled in summer and warmed in winter and this air can be used for cooling in summer and heating in winter.
Figure 22. Earth air tunnel system
• This technique has been used in the composite climate of Gurgaon in RETREAT building.
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PASSIVE SPACE CONDITIONING USING EARTH AIR TUNNEL SYSTEM
• The living quarters (the south block of RETREAT) are maintained at comfortable temperatures (approx. 20-30 degree Celsius) round the year by the earth air tunnel system, supplemented, when-ever required, with a system of absorption chillers powered by liquefied natural gas during monsoons and with an air washer during dry summer.
• Each room in the south block has a 'solar chimney; warm air rises and escapes through the chimney, which creates an air current for the cooler air from the underground tunnels to replace the warm air.
• Two blowers installed in the tunnels speed up the process.
• The same mechanism supplies warm air from the tunnel during winter.
f. Evaporative cooling:
• Evaporative cooling lowers indoor air temperature by evaporating water.
• It is effective in hot and dry climate where the atmospheric humidity is low.
• In evaporative cooling, the sensible heat of air is used to evaporate water, thereby cooling the air, which, in turn, cools the living space of the building.
• Increase in contact between water and air increases the rate of evaporation.
• The presence of a water body such as a pond, lake, and sea near the building or a fountain in a courtyard can provide a cooling effect.
• The most commonly used system is a desert cooler, which comprises water, evaporative pads, a fan, and pump.
Figure 24.Evaporative Cooling
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A TYPICAL SECTION SHOWING PASSIVE SOLAR FEATURES OF WALMI BUILDING,BHOPAL
Figure 23. Earth air tunnel systems with supplemented air flow
g. Passive Down Draught Cooling:
• In this system, wind catchers guide outside air over water-filled pots, inducing evaporation and causing a significant drop in temperature before the air enters the interior.
• Such wind catchers become primary elements of the architectural form also.
• Passive downdraught evaporative cooling is particularly effective in hot and dry climates. It has been used to effectively cool the Torrent Research Centre in Ahmedabad.
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Figure 25. Passive down draught cooling
h. Earth Sheltered Buildings
Figure 26. .Earth sheltered building
i. Roof sprays
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DETAILS OF THE PASSIVE DOWN DRAUGHT COOLING INLETS
Figure 27. Roof spray concept
2.8. Cumulative Representation of Building systems for Energy Efficiency
Figure 28. Building Systems and energy efficiency
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Optimised thermal mass as per ECBC
Optimised WWR as per ECBC
Use of renewable energy sources
Census of India 2011,Administrative Atlas of India ECBC 2007
2.9. Climatic Zones in India
Building Form
2.10. Implications on Building Shape:
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2.12 . Preferred passive solar design features as per the climate
Cold and Cloudy
Cold and Sunny
Composite
Hot and dry
Moderate
Warm and Humid
Building Orientation
● ● ● ● ● ●
Form and Shape
● ● ● ● ● ●
Roof Spray ●
Earth Sheltering
● ● ● ●
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Passive down draught cooling
● ●
Evaporative Cooling
● ●
Earth Air Tunnels
● ● ● ●
Courtyard Effect
● ● ● ●
Wind Tower
● ● ●
Shading ● ● ● ●
Natural Ventilation
● ● ●
Trombe Wall/Water wall
● ●
Roof Collectors
● ●
Sunspaces ● ●
3. CASE STUDIES
3.1. INSPECTOR GENERAL OF POLICE (IGP) COMPLEX, GULBARGA
Location: Gulbarga, Karnataka Climate: Hot and dry
Brief description of the building:
This building is a ground and two-storeyed structure designed by Kembhavi Architecture Foundation to house the offices of the Inspector General of Police, Gulbarga. The building is constructed using innovative materials. For example, the external walls are composite walls (i.e. granite blocks on the outer side and rat-trap bond brick walls on the inner side) and the roof is made of filler slab. The U-values of the walls and roof are 1.53 W/m2-K and 2.15 W/m2-K respectively. The building is roughly rectangular with the longer axis along the north-south direction. Most windows face east or west. A layout plan of the building is given in Fig. 29. As the building is located in a hot and dry climate, evaporative cooling has been used for providing comfort. Most of the offices are cooled by passive downdraft evaporative
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cooling (PDEC) tower system. Figure 30 shows a photograph of the building as well as a sketch section of a typical PDEC tower to explain its principle.
Energy conscious features:
- Passive downdraft evaporative cooling (PDEC) towers for providing comfort
- Tinted glasses to reduce glare
- Alternative building materials such as composite walls to reduce heat gain and filler slabs to reduce the quantity of concrete in the structure
- A central atrium to enhance cross ventilation and provide day lighting
- Solar PV lighting and pumps, rainfall harvesting and water conservation facilities Incorporated
Figure 29. Layout plan of I.G.P. Complex, Gulbarga
Performance of the PDEC system:
The building is in the final stage of construction. The PDEC system’s design is based on the “shower tower” (discussed in Chapter 3) concept developed by Givoni [2]. Preliminary measurements taken in May and September, 2005 showed that the temperature of the air exiting from the tower is lower by about 10°C and 4°C respectively, compared to that of ambient air. Figure 31 presents the hourly values of the temperature of air exiting from the tower on a typical day in September. The corresponding measured values of ambient temperature are also plotted for comparison. Additionally, the figure shows the theoretically calculated values based on Givoni’s model of the shower tower. It is seen that the measurements agree reasonably well with the predictions. Figure 32 shows the estimated performance of a tower in various months during daytime. It presents the results of exit temperature of air leaving the tower and the corresponding ambient dry bulb temperature. It is seen from the figure that the performance of the cooling tower is quite satisfactory in the summer months. The drop in temperature is about 12 - 13 °C in March, April and
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May. Considering that the PDEC system is used in these months, the predictions of the energy savings of the building per annum, as compared to an air-conditioned building maintained at 27.5 °C, are as follows:
Estimated Cost of PDEC system = Rs. 17,50,000
Estimated savings per annum = Rs. 3,52,000
Simple payback period = 5 years (approximately)
Figure 18. Photographs of IGP Complex, Gulbarga and sketch showing the principle of a PDEC tower
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Figure 31.Comparison of measured and predicted temperature of air exiting PDEC Tower
Figure 19. Monthly prediction of the temperature of air exiting the PDEC tower
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3. 2 .AUROVILLE ECOHOUSE, AUROVILLE
Location: Auroville, Pondicherry Climate: Warm and humid
Brief description of the building:
The Ecohouse was built in 1976 by a team co-ordinated by Dr. C. L. Gupta at
Auroville. This house can be considered as one of the first prototypes of an ecologically sustainable building to be constructed in India in modern times. It is a two storeyed structure with longer axis along the east-west direction, designed for catching wind. A courtyard is provided in the building which is cooled by Venturi effect. The overhangs above the windows and doors are designed for optimal shading from the sun. A sketch plan and section of the Ecohouse are given in Fig. 33.
Energy conscious features:
- Optimum orientation of built form for cooling by ventilation
- Shading of windows to reduce heat gain
- Alternative building materials such as (i) structurally insulated roof units (size 1.0m X 0.5m), developed by Central Building Research Institute, Roorkee,
(ii) jack arches of hollow ceramic Gunna tiles
- A courtyard to enhance cross ventilation and provide daylighting
- Other features such as solar cooker integrated in south facing kitchen, rainfall harvesting system, biogas plant for waste management and production of methane gas for cooking, an aero- generator for domestic electric load and a thermosyphon solar water heater are also incorporated into the building design
Performance of the house:
The house has no fans and is reported to be one of the coolest houses in Auroville as observed by the occupants.
Figure 20. Section and sketch plan of Ecohouse, Auroville
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3.3. CENTRE FOR APPLICATION OF SCIENCE AND TECHNOLOGY FOR RURAL AREAS (ASTRA), BANGALORE
Location: Bangalore, Karnataka Climate: Moderate
Brief description of the building:
The building is a ground and one-storeyed structure and is used as an office building. The salient feature of the building is the use of various alternative building materials that are affordable, environment friendly and energy efficient. It was built in 1999 in the campus of the Indian Institute of Science, Bangalore. Figure 34 shows the typical floor plan of the building. A photograph of the building is given in Fig. 35
Energy conscious features:
- Sized stone masonry with composite mortars in foundations, steam-cured stabilized blocks for ground floor load-bearing walls, and soil-cement blocks for the first floor walls. The external exposed walls are coated with transparent silicone paint for protection from erosion- Precast chajjas and brackets are made of ferrocement- Reinforced blockwork lintels are used above openings such
as doors and windows- Soil-cement block filler slabs are used for floors and roof. An additional weatherproof course using tiles is provided on the roof
Performance of the building:The cost of construction of this building was Rs. 4247 per square metre of plinth area in 1999. The component-wise cost of the building and the corresponding percentage of total cost are presented in Fig. 36.
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Figure 21. Ground floor plan of ASTRA building, Bangalore
Figure 22. Photograph of ASTRA building, Bangalore
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Figure 23.Component-wise distribution of costs of ASTRA building at I.I.Sc.,
Bangalore
3.4. SOLAR ENERGY CENTRE, GURGAON
Location: Gurgaon, Haryana. Climate: Composite (predominantly hot)Brief description of building:It is a single storeyed research centre. The buildings include a guest house, a workshop, offices and laboratories. Being situated on a large open plot of land, the buildings are spread out and possess courtyards around which the various activities are clustered. A plan and section of the administrative block of the same is given in Fig. 38.
Energy conscious features:- Roof surface evaporative cooling system- Appropriate planning in which laboratories requiring air conditioning are put together in a well-insulated building- Hollow concrete block walls to resist heat gain by conduction- Reflective finish on roof surface
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- Windows designed for cross ventilation and daylighting. The east and west facing windows incorporate openable louvered shutters
Performance of the building:The Solar Energy Centre conducted a post-occupancy evaluation of this building. It was observed that the roof surface evaporative cooling (RSEC) system caused a lowering of temperature by 2-3ºC in comparison with rooms without RSEC system. Figure 37 shows the comparison of measured temperatures of the reception room (with RSEC system) with those of A.O. room and verandah, both being without RSEC system. One advantage of the RSEC system is that it cools in a healthy manner as it does not humidify the ambient air of the room. On the other hand if a desert cooler were to be used, it would pump moist air inside the room and increase the humidity, which would cause discomfort and affect the health of occupants.
Figure 24.Comparison of indoor temperatures – Solar Energy Centre, Gurgaon
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Figure 25.Administration block of Solar Energy Centre, Gurgaon
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3.5. H.P. STATE CO-OPERATIVE BANK BUILDING, SHIMLA
Location: Shimla, Himachal Pradesh Climate: Cold and Cloudy
Brief description of building:This building is a ground and three-storeyed structure with its longer axis facing the east-west direction. The smaller northern wall faces the prevailing winter winds from the north-eastern direction. The building shares a common east wall with an adjoining structure. Its west façade overlooks a small street from which the building draws its main requirements of ventilation and daylighting. A plan and section of the building showing the various passive techniques
incorporated is given in Fig. 39.
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Figure 26. Section and plan of H. P. state co-operative bank, Shimla
Energy conscious features:- South-facing Trombe wall and sunspace heats up the interior- South-facing solar collectors on the roof provide warm air, which is circulated by means of ducts- North face is protected by a cavity wall that insulates the building from prevailing winter winds
- Western wall is provided with insulation as well as double glazing
- Daylighting is enhanced by providing light shelves. Skylight on the terrace also provides daylighting
- Air lock lobbies are provided to reduce air exchange
Performance of the building:
The predictions of the energy savings of the building (component-wise) per annum, as compared to a conventional building are as follows:
West wall (double glazing and insulation) = 43248 kWh
Roof insulation = 23796 kWh
Roof top solar collector = 10278 kWh
Trombe wall = 7398 kWh
Total = 84720 kWh
3.6. S.O.S. TIBETAN CHILDREN'S VILLAGE, CHOGLAMSAR [8]
Location: Choglamsar, Leh Climate: Cold and dry
Brief description of the building:
Twenty existing ground storey structures acting as dormitories have been retrofitted with an attached green house and vented Trombe walls, in the extremely cold region of Leh. The original construction consists of solid adobe for walls (U-value 1.64 W/m2-K) and wooden roof with mud topping (U-value 2.44 W/m2-K). The floor is of wooden deck over a crawl space. A sketch plan and section of a typical building are given in Fig. 40
Techniques:
- The common room in the centre is provided with an attached greenhouse facing south for trapping heat. The extended floor of the greenhouse consists of solid masonry to provide good thermal storage mass of 1.44 MJ/m2-K. The green house is fitted with a movable internal shade for the ceiling. The common room receives heated air by opening the vents of the adjacent glass wall of the green house.
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- Two end rooms on the south side are provided with double glazed, vented trombe walls for heating.
Performance of the building:
Figure 41 gives the measured temperature data, namely, the maxima and minima for the Trombe wall room, green house, a room without solar heating (control room) and ambient temperature. It is seen that in winter months, the maximum and minimum temperature can be appreciably higher than both the ambient temperature as well as the room without solar heating (control room).
Figure 27.Sketch plan and elevation of S.O.S building, Choglamsar
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Figure 28.Monthly mean measured temperature – (S.O.S. Tibetan children’s
4. Conclusion:
After analyzing the available passive design strategies and case studies it has been found that temperature difference of 10-25 ◦c can be optimized in the indoor environment by applying the passive design features. Beside the thermal mass of the building, orientation and building shape also have serious impact on the indoor environment. The solar passive design options should be used to create energy efficient thermal comfort in the building interiors .Although analytical analysis and practical implementation both have already been done by various professionals but more research is needed for the perfect solar passive building design features in the composite climate as it comprises of various seasonal varieties and related challenges.
References:
1. Dr Anupama Sharma, KK Dhote,R Tiwari , Climatic Responsive Energy Efficient Passive Techniques in Buildings
2. Norbert Lechner Heating, Cooling, Lighting 4th Edition
3.Passive Cooling , Research and Design, AIA , fall 1979, volume 2 , number 3
4. Energy Efficient Buildings in India , TERI
5. Enegy Conservation Building Code 2007
6. Census of India 2011
7. Koenigsberger, et al. .Manual of Tropical Housing and Building (Part I) : Climatic Design.. Part I, Longman Press, India, 1975.
8. V Gupta. .Energy Conservation Indian Myths and Realities.. Architecture Design, vol 9, no 3, May-June, 1992.
9. A Krishan and M R Agnihotri. .Bio-Climatic Architecture: a Fundamental Approach to Design.. Architecture Design, vol 9, no 3, May-June, 1992.
10. S Prakash. .Energy Conscious Architecture: an Endless Quest.. Architecture Design, vol 9, no 3, May-June, 1992.
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11. http://mnre.gov.in/ Ministry Of New And Renewable Energy
12. Prajapati J., Draft Report - design of passive downdraft evaporative cooling towers for proposed I.G.P. Complex at Gulbarga, Monarch - Architects and Designers, Mumbai, 2005.
13. Givoni B., Peformance of the ‘shower’ cooling tower in different climates, Renewable Energy, 10, 173, 1997.
14. Gupta C.L., Personal communication, 2005.
15. Report on alternative building technologies, Centre for Sustainable Technologies and Department of Civil Engineering, Indian Institute of Science, Bangalore, 2003.
16. Kumar A., Negi B.S. and Agarwal P.K., Preliminary - monitoring and performance evaluation of roof surface evaporative cooling system –a technical report, Solar Energy Centre, MNES, Gurgaon, 1998.
17. Nayak J.K., Hazra R., Prajapati J., Manual on solar passive architecture, Solar Energy Centre, MNES, Govt. of India, New Delhi, 1999.
18. Lall A. B., Re-development of H. P. state co-operative bank building at mall road - Shimla, MNES Project Report, New Delhi, 1996.
19. Gupta C.L., Solar passive buildings for developing countries, Proceedings of Indian Academy of Sciences (Engg. Sciences), Sadhana, 18, pp 77-104, Part 1, 1993
20. Tahmina Ahsan, Passive Design Features for Energy-Efficient Residential Buildings in Tropical Climates: the context of Dhaka, Bangladesh, Stockholm 2009
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