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PASSIVE SOLAR ARCHITECTURE

DR. BN COLLEGE OF ARCHITECTURE, PUNE

SUBJECT: DISSERTATION

NAME: ANU OM ALREJA

CLASS: FOURTH YEAR B.ARCH

ROLL NO.: 2

Completion Certificate

This is to certify that Miss. Anu Om Alreja of Dr. BN College of

Architecture University Exam No.: Class: Fourth

Year B.Arch Roll No.: 2 has satisfactorily completed the required

amount of work for the Academic Year: as laid down

by the University/Institution.

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Head of the Department

External Examiner Internal Examiner Subject Teacher

ACKNOWLEDGEMENT

I would like to take this opportunity to extend my sincere thanks to my guide Ar. Arun Ogale, Ar. Shekhar Garud, Ar. Anagha Paranjape, Ar. Nachiket Patwardhan and Ar. Vasudha Gokhale for all help, support and guidance provided to complete my dissertation project.

I would also like to extend my sincere gratitude to our Principal Dr. Anurag Kashyap, Dr. Bhanuben Nanavati College of Architecture, for being a source of inspiration and support.

Thank you.

Regards,

Anu Om Alreja

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SYNOPSISIntroduction

The need Importance of energy conservation in buildings Pattern of energy consumption

Aim Objective Methodology Solar Passive Techniques

Passive heating Direct gain Indirect gain system Direct gain systems

Windows Glazed Wall

Glazed Atrium Indirect gain systems

Roof-based air heating system Thermal storage wall system (Trombe wall) Water wall Sun spaces Transwall

Passive cooling Passive cooling systems

Ventilation & Operable Windows Wing Walls Thermal Chimney Other Ventilation Strategies Passive Downdraft Evaporative Cooling (PDEC) System Earth berming Earth air tunnel (EAT) system Cooling Tower / Wind catcher / Wind Tower Evaporative cooling Roof pond system Courtyard

Case Studies H.P. STATE CO-OPERATIVE BANK BUILDING, SHIMLA INSPECTOR GENERAL OF POLICE (IGP) COMPLEX, GULBARGA THE RETREAT COMPLEX OF TERI AT GURGAON IN HARYANA

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ConclusionsReferences

Introduction

Passive solar architecture is an ancient concept. Modern science has provided quantitative support to ascertain its effectiveness. Solar passive architecture has large potential for energy conservation and can lead to a thermally comfortable indoor environment. It is defined as collection, storage, distribution and control of energy flow by natural processes of heat and mass transfer. Its working definition is - use of natural energy (sun, wind, etc.) to conserve conventional energy for achieving thermal comfort. Thermal comfort refers to comfortable indoor conditions (temperature, humidity, air movement).

The need

Buildings, as they are designed and used today, contribute to serious environmental problems because of excessive consumption of energy and other natural resources to construct a building & meet its demands for heating, cooling, ventilation & lighting which causes severe depletion of invaluable environmental resources. Studies show that residential and commercial sectors in India together account for 25% of the country’s total electricity consumption, a major portion of which is used in buildings. However, buildings can be designed to meet occupant’s need for thermal and visual comfort at reduced levels energy & resources consumption by incorporating solar passive techniques in a building design to minimise load on conventional systems (heating, cooling, ventilation and lighting). Thus in brief, an energy efficient building balances all aspects of energy use in a building: lighting, space-conditioning and ventilation, by providing passive solar design strategies.

Importance of energy conservation in buildings

Many audits conducted by MEDA (Maharashtra Energy Development Agency) in buildings show 30-40% saving potential with available technology in market.

The annual energy consumption per square metre of floor area ranges from 200 kWh and more, for residential sector.

40% savings in energy consumption will result in saving 46.8 billion units out of 117 billion units required for residential sector.

Pattern of energy consumption

Aim

To study different types of solar passive architectural and constructional techniques for designing different buildings and conclude the results.

Objective

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Source PercentageIndustrial 38%Agriculture 20%Domestic 24%Commercial 10%Railways 3%Streetlights 1%Others 4%

Total 100%

To promote energy efficient building designs i.e. to minimize energy use and the negative environment effects of building.

To maximize use of renewable and natural resources in building environment. Building construction with optimum use of solar energy. Other forms of ambient energy in energy management. Thermal comfort for the inhabitants. To reduce maintenance cost.

Methodology

Research on solar passive features. Case studies of buildings in different climatic zones to understand the importance and

usefulness of solar passive features. Conclusions

Solar Passive Techniques

Solar passive techniques are incorporated in building design to minimise load on conventional systems (heating, cooling, ventilation and lighting). Passive systems provide thermal and visual comfort by using natural energy sources and sinks e.g. solar radiation, outside air, sky, wet surfaces, vegetation, internal gains etc. Energy flows in these systems are by natural means such as by radiation, conduction, convection with minimal or no use of mechanical means. The solar passive systems thus, vary from one climate to the other e.g. in a cold climate an architect’s aim would be to design a building in such a way that solar gains are maximised, but in a hot climate his primary aim would be to reduce solar gains, maximise natural ventilation and so on. The orientation of the building, site selection, materials and design features allow the home to collect, store and distribute the sun’s heat in winter, block the sun during summer, and provide for air circulation and natural day lighting.

The passive energy system involves collecting, storing, distributing and controlling of thermal energy flow through the natural principles of heat transfer. Various available options of passive architectural features like shape and orientation of the building, shading devices, earth berming, air movements etc., and developed passive concepts like trombe wall, water wall, wind tower, solar chimney, evaporative cooling etc. can be adopted as per the building requirements.

Passive solar systems rules of the thumb: The building should be elongated on East – West axis. The building’s south face should receive sunlight between the hours of 09.00 a.m through

03.00 p.m (sun time) during the heating season. Interior spaces requiring the most light and heating and cooling should be along the south

face of the building. Less used spaces should be located on the north. An open floor plan optimizes passive system operation. Use shading to prevent summer sun entering the interior.

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Passive heating

Advanced passive heating techniques are used by architects in building design to achieve thermal comfort conditions in cold climate.Passive solar heating systems can be broadly classified as:1. Direct gain systems2. Indirect gain systems

Direct gain

Direct gain is the most common passive solar system. In this system, sunlight enters rooms through windows, warming the interior space. The glazing system is generally located on the southern side to receive maximum sunlight during winter (in the northern hemisphere). 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, where it strikes thermal storage materials such as floors or walls made of adobe, brick, concrete, stone, or water. The direct gain system uses 60-75% of the sun’s energy striking the windows. The interior thermal mass tempers the intensity of heat during the day by absorbing heat. At night, the thermal mass radiates heat into the living space, thus warming the spaces.

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Solar Passive Techniques

Passive coolingVentilation & Operable

WindowsWing wall

Thermal ChimneyPDEC SystemEarth bermingEarth air tunnelCooling tower

Evaporative coolingRoof pond system

Courtyard

Passive heating

Direct gain

WindowGlazed wall

Glazed atrium

Indirect gainRoof space collectorThermal

storage wall system

Water wallSun spacesTranswall

Direct gain application

Direct gain can be achieved by various forms of openings such as clerestories, skylight windows, etc. designed for the required heating. Direct gain systems have been used for day-use rooms by architect Sanjay Prakash in the residence for Mohini Mullick at Bhowali. The user is extremely satisfied with the thermal performance of the direct gain system in this residence.

Direct gain systems have some limitations. They cause large temperature savings (typically 10 °C) because of large variations in input of solar energy. Strong sunlight, glare, and ultraviolet degradation of the house material are some disadvantages of direct gain systems. However, being relatively simple to construct and inexpensive, they are by far the most common systems used worldwide.

Indirect gain systemIn an indirect gain 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 the living space. The indirect gain system uses 30-45% of the sun’s energy striking the glass adjoining the thermal mass.

Direct gain systems

Windows

The direct gain strategy is that sunlight enters the building through a large south-facing window (the collector) (in the Northern hemisphere) and is incident upon the floor and walls of the structure. The effectiveness of direct solar gain systems is significantly enhanced by insulative (e.g. double glazing), spectrally-selective glazing (low-e), or movable window insulation (window quilts, bifold interior insulation shutters, shades, etc.). Generally, Equator-facing windows should not employ glazing coatings that inhibit solar gain. Selection of different spectrally-selective window coating depends on the ratio of heating versus cooling degree days for the design location. Direct-gain systems are more dependent on double or triple glazing to reduce heat loss. In cold regions thermal glazing should be equivalent to or higher than, double glazing. Windows and roof lights provides direct path for admitting daylight.

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The direct gain system of the Bhowali house. The picture highlights the fully glazed walls for the day use rooms from inside.

Typical double glazed aluminium window

Depending on climate, the total direct gain glass should not exceed about 12% of the house's floor area. Beyond that, problems with glare or fading of fabrics are likely to occur, and it becomes more difficult to provide enough thermal mass for year-round comfort.

Glazed Wall

Buildings with rectangular floor plans are elongated on an east-west axis and have a glazed south-facing wall; a thermal storage media exposed to the solar radiation which penetrates the south-facing glazing in winters. There is storage of solar energy in thermal mass followed by the natural distribution of this stored solar energy back to the living space, when required, through the mechanisms of natural convection and radiation. Overhangs or other shading devices sufficiently shade the south-facing glazing from the summer sun. There are windows on the east and west walls, and preferably none on the north walls.

Disadvantages: Some glazed wall variants may still be at a disadvantage in cloudy or very cold climate.

Glazed Atrium

This is a northern climate variant of the open courtyard -a building form with a long architectural tradition in most parts of the world. The addition of roof glazing provides protection

from rain and wind, and a moderate resistance to heat flow. Usually located centrally within a building, with the glazing mainly confined to its roof. The large area of glazing on the envelope of these structures entails the admission of considerable amounts of solar. The atrium temperature is higher than those of the adjoining indoor spaces but within the comfort range; heat can flow naturally to adjoining rooms by opening doors or windows. Where the parent building is mechanically heated such heat flow can be expected to displace conventional heating thus saving energy.

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Glazed Wall

Glazed Atrium

Indirect gain systems

Roof-based air heating system

In this technique, incident solar radiation is trapped by the roof and is used for heating interior spaces. In the Northern Hemisphere, 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 solar radiation. A moveable insulation can be used to reduce heat loss through glazed panes during nights. There can be variations in the detailingof the roof air heating systems. In the Himachal Pradesh State Cooperative Bank building, the south glazing is in the form of solar collectors warming the air and a blower fan circulating the air to the interior spaces.

Advantages: It can have better exposure to sun and thus collect more energy. It does not interfere with elevations of the building.

Glazed wall and roof space collector are ingenious device for capturing incident solar radiation that would otherwise be lost, without exposing indoor space to temperature and sunshine fluctuations.

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Roof space collector

Thermal storage wall system (Trombe wall)

A trombe wall is a thermally massive wall with vents provided at the top and bottom. It may be made of concrete, masonry, adobe, and is usually located on the southern side (in the northern hemisphere) of a building in order to maximize solar gains. The outer surface of the wall is usually painted black for maximizing absorption and the wall is directly placed behind glazing with an air gap in between. Solar radiation is absorbed by the wall during the day and stored as sensible heat. The air in the space between the glazing and the wall gets heated up and enters the living spaces by convection through the vents. Cool air from the rooms replaces this air, thus setting up convection current. The vents are closed during night, and heat stored in the wall during the day heats up the living space by conduction and radiation. Trombe walls have been extensively used in the cold regions of Leh. Various forms of Trombe walls have been tried and tested in the Ledeg hostel at Leh. It is

noteworthy that in buildings with thermal storage walls, indoor temperature can be maintained at about 15oC when the outside temperature is as low as -11oC. Generally, thickness of the storage wall is between 200 mm and 450 mm, the air gap between the wall and glazing is 50-150mm, and the total area of each row of vent is about 1% of the storage wall area. The trombe wall should be adequately shaded for reducing summer gains.

Water wall

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Water walls are based on the same principle as that for trombe walls, except that they employ water as the thermal storage material. A water wall is a thermal storage wall made up of drums of water stacked up behind glazing. It is usually painted black to increase heat absorption. It is more effective in reducing temperature swings, but the time lag is less. Heat transfer through water walls is much faster than that for trombe walls. Therefore, distribution of heat needs to be controlled if it is not immediately required for heating the building. Buildings that work during the daytime, such as schools and offices, benefit from the rapid heat transfer in the water wall.Overheating during summer may be prevented by using suitable shading devices.

Sun spaces

A sun space or solarium is the combination of direct and indirect gain systems. The solar radiation heats up the sun space directly, which in turn heats up the living space (separated from the sun space by a mass wall) by convection and conduction through the mass wall. In the northern hemisphere, the basic requirements of buildings heated by sun space are (a) a

glazed south facing collector space attached yet separated from the building and (b) living space separated from the sun space by a thermal storage wall. Sunspaces may be used as winter gardens adjacent to the living space. The Himurja building in Shimla has well designed solarium as integral part of south wall to maximise solar gain.

Transwall

Transwall is a thermal storage wall that is semitransparent in nature. It partly absorbs and partly transmits the solar radiation. The transmitted radiation causes direct heating and illumination of the living space. The absorbed heat is transferred to the living space at a later time. Heat loss through the glazing is low, as much of the heat is deposited at the centre of the transwall ensuring that its exterior surface does not become too hot. Thus, the system combines the attractive features of both direct gain and Trombe wall systems.

A transwall has three main components: • Container made of parallel glass walls set in metal frame • Thermal storage liquid, which is generally water • A partially absorbing plate set at the centre of the transwall, parallel to the glass walls

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Sun Space

It is installed on the south side of the building (in the northern hemisphere), located directly behind double glazing. To prevent the growth of micro-organisms in the storage, an inhibiting agent may be added.

Passive cooling

In this type of cooling solar thermal energy is not used directly to create a cold environment or drive any direct cooling processes. Instead, passive solar building design aims at slowing the rate of heat transfer into a building in the summer, and improving the removal of unwanted heat. There are many design specifics involved in passive solar cooling. It is a primary element of designing a zero energy building in a hot climate.

Passive cooling systems 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.

The relatively simple techniques that can be adopted to provide natural cooling in the building are reduction of solar and connective heat import by:

orientation of building shading by adjoining building landscaping window shading devices surface finishes

Reduction of heat transmission in the building by: thermal insulation air cavities

Passive cooling systems

Ventilation & Operable Windows

A primary strategy for cooling buildings without mechanical assistance (passive cooling) in hot humid climates is to employ natural ventilation. In the Austin area, prevailing summer breezes are from the south and southeast. This matches nicely with the increased glazing on the south side needed for passive heating, making it possible to achieve helpful solar gain and ventilation with the following strategies:

Place operable windows on the south exposure. Casement windows offer the best airflow. Awning (or hopper) windows should be fully

opened or air will be directed to ceiling. Awning windows offer the best rain protection and perform better than double hung windows.

If a room can have windows on only one side, use two widely spaced windows instead of one window.

Wing Walls

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Wing walls are vertical solid panels placed alongside of windows perpendicular to the wall on the windward side of the house. Wing walls will accelerate the natural wind speed due to pressure differences created by the wing wall.

Thermal Chimney

A thermal chimney employs convective currents to draw air out of a building. By creating a warm or hot zone with an exterior exhaust outlet, air can be drawn into the house ventilating the structure.Sunrooms can be designed to perform this function. The excessive heat generated in a south facing sunroom during the summer can be vented at the top. With the connecting lower vents to the living space open along with windows on the north side, air is drawn through the living space to be exhausted through the sunroom upper vents. (The upper vents from the sunroom to the living space and any side operable windows must be closed and the thermal mass wall in the sunroom must be shaded.)

Thermal chimneys can be constructed in a narrow configuration (like a chimney) with an easily heated black metal absorber on the inside behind a glazed front that can reach high temperatures and be insulated from the house. The chimney must terminate above the roof level. A rotating metal scoop at the top which opens opposite the wind will allow heated air to exhaust without being overcome by the prevailing wind. Thermal chimney effects can be integrated into the house with open stairwells and atria.

Other Ventilation Strategies Make the outlet openings slightly larger than the inlet openings. Place the inlets at low to medium heights to provide airflow at occupant levels in the

room. Inlets close to a wall result in air “washing” along the wall. Be certain to have centrally

located inlets for air movement in the center areas of the room. Window insect screens decrease the velocity

of slow breezes more than stronger breezes. Screening a porch will not reduce air speeds as much as screening the windows.

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Top View of Wing Walls Airflow Pattern

Summer Venting Sunroom

Thermal Chimney

High mass houses can be cooled with night ventilation providing that fabric furnishings are minimized in the house.

Keep a high mass house closed during the day and opened at night.

Passive Downdraft Evaporative Cooling (PDEC) System

A system of inlet and outlet shafts.

Locations, sizes and heights : generate required air movement.

A fine spray of water cools the air at entry.

6-9 air change rates per hour observed.

Strategy:o Hot season:

evaporative cooling.

o Monsoon: cooling off, induce ventilation by

fans.o Winter:ventilation

minimised(inlets closed by

shutters)

Design of PDEC System

Ambient hot-dry air is trapped, cooled by evaporation of water and then introduced in the building. Simple system based on shower spray system developed by B. Givoni. PDEC system works very well in the summer months. For example, in May, the temperature of cooled air leaving the tower is about 25°C while the corresponding ambient temperature is about 38 °C. Thus, the drop in day-time temperature is significantly high in May, i.e. about 13 °C.

Implications of PDEC system:

Advantages:•Low cost single pass system•Easy to maintain•Entry of birds and pests prevented•Charcoal tray to filter out dust•Sophisticated water treatment is not required•Single tower serving multiple floors•Can be used for pre-cooling the building at night

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Thermal Chimney Effect Built into Home

Disadvantages:•High humidity•Noise due to spraying of water

Earth berming

Earth is piled up against exterior walls and packed, sloping down away from the house. The roof may, or may not be, fully earth covered, and windows/openings may occur on one or more sides of the shelter. Due to the building being above ground, fewer moisture problems are associated with earth berming in comparison to underground/fully recessed construction.

This technique is used both for passive cooling as well as heating of buildings, a feat which is made possible by the earth acting as a massive heat sink. Summer as well as winter variations die out rapidly with increasing depth from the earth's surface. This temperature at a depth of a few meters remains almost stable throughout the year. Thus, the underground or partially sunk buildings would provide both cooling (in the summer) and heating (in the winter) to the living space. Besides, load fluctuations are reduced by the addition of earth mass to the thermal mass of the building. The infiltration of air from outside is reduced.

The earth sheltered structure has to be heavier and stronger to withstand the load of the earth and the vegetation above. Besides, it should be suitably waterproofed and insulated to avoid ground moisture.

Additional cooling if required can be provided by circulating air through ducts built underground (where the temperature is low). The same ducts can provide some degree of preheating for the fresh outside air during the cold periods.

Earth air tunnel (EAT) system

Daily and annual temperature fluctuations decrease with the

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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 and therefore the ambient air ventilated though 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. Earth air tunnel has been used in the composite climate of Gurgaon in the RETREAT building. The living quarters (the south block of the RETREAT) are maintained at comfortable temperatures (approximately between 20 °C and 30 °C) round the year by the earth air tunnel system, supplemented, whenever required, with a system of absorption chillers powered by LPG during monsoons and with an air washer during dry summer. However, the cooler air

underground needs to be circulated in the living space. 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.

Cooling Tower / Wind catcher / Wind Tower

This system can work effectively in hot and dry climate, where daily variations in temperatures are high with high temperature during day time and low temperature during night time. The openings of the wind catcher are provided in the direction of the wind , and outlets on the side take advantage of the pressure difference created by wind speed and direction.

The principle of the wind catcher :

•Day timeThe hot air enters the tower through the openings and cooled when it comes incontact with the cool tower and thus becomes heavier and turns down.When an inlets is provided to the rooms with an outlet on other side there is a draftof cool air. The wind tower becomes warm in the evening, after a whole day of heatexchange.

•Night timeDuring night the reverse happens: the cooler air comes in contact with the bottom ofthe tower through the rooms; it gets heated up by the warm surface of wind tower

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and thus an air flow is maintained in the reverse direction.

A combination of sensible cooling in the ground and evaporative cooling with the flow ofair induced by the wind catcher. Wind towers with indirect evaporative cooling systems have been integrated with HVAC system for pre-cooling fresh air.

Limitations1.Concepts of wind catcher can work well an individual units of house and not in multi-storeyed building.2.In a dense urban area the wind tower has to be very high to be able to catch enough air.3.The surface of the wind tower accumulates dust and heat transfer from the surface of wind tower to the air becomes slower.4.If the wind direction is unpredictable, it is better made openings of the inlet wind catcher on all four sides.

Evaporative cooling

Evaporative cooling lowers indoor air temperature by evaporating water. It is effective in hot-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 rate of evaporation. The presence of a water body such as a pond, lake, sea etc. 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 of water, evaporative pads, a fan, and pump. Evaporative cooling has been

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Evaporative Cooling Tower

Wind Tower Evaporative Cooling

tried as a roof-top installation solar energy centre, Gurgaon. However, the system has now become defunct due to poor water supply in the area.

Roof pond system

This system can provide both heating and cooling. 6-12 inches of water are contained on a flat roof, usually stored in large plastic or fiberglass containers covered by glazing. During the cooling season, an insulated cover is removed at night to expose the water to cool night air. The water absorbs heat from below during the day, and radiates it out at night. The temperature within the space falls as the ceiling acts as a radiant cooling panel for the space, without increasing indoor humidity levels. During the heating season, the insulated cover is removed during the day. The water absorbs heat from the sun, and radiates it in to the building below. In cold climates such as ours, an attic pond beneath pitched glazing is more effective than a flat roof pond.

The limitation of this technique is that it is confined only to single storey structure with flat, concrete roof and also the capital cost is quite high. Roof ponds require somewhat elaborate drainage systems, movable insulation to cover and uncover the water at appropriate times, and a structural system to support up to 65lbs/sq ft dead load.

CourtyardPrinciple of the courtyard:Due to the incident solar radiation in the courtyard, the air in the courtyard becomes warmer and rises up. To replace it, cool air from the ground level flows through the openings of the room, thus producing the air flow. During the night, the process id reversed. The cooled surface air of the roof sinks down to the court and this cooled air enters the living spaces through the low level openings and leaves through higher level openings. This system

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Roof pond cooling

Roof pond heating

Model of courtyard house

can work effectively in hot and dry climates, where day time ventilation is undesirable, as it brings heat inside and at night the air temperature becomes cooler and it can ventilate the building.

Limitations1.When the courtyard receive intense solar radiation, much heat will be conducted and radiated into the rooms as against the induced draft of air which may be problematic.2.The intense solar radiation can produce glare for the inside room.The best way is to keep the courtyard shaded and only partially open to sky.

Case Studies

H.P. STATE CO-OPERATIVE BANK BUILDING, SHIMLA

Location : Shimla, Himachal PradeshClimate : 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 below.

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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) perannum, 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

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Section and plan of H. P. state co-operative bank, Shimla

INSPECTOR GENERAL OF POLICE (IGP) COMPLEX, GULBARGA

Location : Gulbarga, KarnatakaClimate : Hot and dryBrief 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. 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 cooling (PDEC) tower system. Figure below 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 daylighting. Solar PV lighting and pumps, rainfall harvesting and water conservation facilities incorporated.

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” concept developed by Givoni. 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 below 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 below shows the estimated performance of a tower in various months during daytime. It

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Layout plan of I.G.P. Complex, Gulbarga

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 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. 17,50,000Estimated savings per annum = Rs. 3,52,000Simple payback period = 5 years (approximately)

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Photographs of IGP Complex, Gulbarga and sketch showing the principle of a PDEC tower

Comparison of measured and predicted temperature of air exiting PDEC

The RETREAT (Resources Efficient TERI Retreat for Environment Awareness and Training) complex of TERI (The Energy and Resources Institute) at Gurgaon in Haryana

Site Address / Location: Gual Pahari, GurgaonClimatic Zone: CompositeBuilding Type: InstitutionalArchitect(s): Sanjay Prakash and TERIClient/ Owner: The Energy and Resources Institute

Introduction:RETREAT is a part of the 36-hectare TERI campus at Gual Pahari, about 30 km south of Delhi, in the northern state of Haryana. It is a

30-room training hostel with conference facilities for 100 people, dining space and a kitchen, recreational area, computer room, and a library. The basic design process is to minimize energy demand in the building through passive concepts such as solar orientation, latticework for shading, insulation, and landscaping.

Key Sustainable FeaturesOrientation, insulation, and design of the building.

Wall insulation with 40-mm thick expanded polystyrene and roof insulation using vermiculite concrete (vermiculite, a porous material, is mixed with concrete to form a homogenous mix) topped with China mosaic for heat reflection.

Building oriented to face south for winter gains; summer gains offset using deciduous trees and shading.

South side partially sunk into the ground to reduce heat gains and losses. East and west walls devoid of openings and are shaded.

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Monthly prediction of the temperature of air exiting the PDEC tower

Earth air tunnel for the south block Four tunnels of 70m length and 70cm diameter each laid at a depth of 4 m below the ground to

supply conditioned air to the rooms. At a depth of 4 m below ground, temperature remains 26 °C (in Gurgaon) throughout the year. Four fans of 2 HP each force the air in and solar chimneys force the air out of rooms. Assisted cooling by air washer in dry summer and a 10 TR dehumidifier in monsoon.

Solar hot water system 24 solar water heating panels (inclined at 70 degrees instead of 45 degrees) integrated

with parapet wall.

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Lighting Innovative daylighting by means of skylights.

Building management system Monitors building parameters (temperatures, humidity, consumption, etc.)

Performance The winter temperature in the rooms heated by solar gains and earth air tunnel systems

was recorded to be 22 °C (average night-time condition) when the ambient temperature was about 10 °C.

In the dry summer month of May, a room temperature (in the rooms cooled by earth-air tunnels combined with evaporative cooling system) of 28 °C (average daytime condition) with 45%-50% relative humidity was recorded when the ambient temperature and relative humidity were 40 °C and 30%, respectively.

In the humid summer months, a room temperature (in rooms cooled by the earth-air tunnel supplemented by ammonia absorption chillers) of 30 °C and 65% relative humidity were recorded with the ambient condition being 38 °C at 70% relative humidity.

The conference rooms cooled by ammonia absorption chillers maintain an average temperature of 25 °C at 55% relative humidity.

The building being only partially loaded as yet now consumes a maximum of 40 units of electricity per hour. The PV system generates an average of 55 units per day on a sunny day.

Conclusions:

From the above case studies it can be concluded that solar passive techniques are really effective in controlling the temperature, day light, etc within a building as per the users comfort, location and climate of the area in which the building is located.

Solar passive architecture is a very helpful and a very cost effective technique to control the climatic conditions within a building.

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Since it uses the non conventional solar energy source, use of solar passive architecture can also save the limited conventional energy sources, which are traditionally used as energy sources for a building, from getting depleted.

Hence the use of solar passive architecture systems can prove to be a more effective method than the conventional methods for temperature control in a building.

Advantages of solar passive architecture:1. Environmental friendly2. Low energy bills3. Comfortable living conditions4. Low maintenance5. Clean and hygienic6. Durable7. No operating noise

A maximum saving of 60 – 70% on conventional fuels required for space heating during winters and cooling during summers can be achieved.

Large windows and views, sunny interiors, open floor spaces, warmer in winters and cooler in summers resulting in comfortable living conditions even during power failures, durable reduced operational cost, independent from future rises of fuel costs, clean environment to combat growing concern over global warming and ozone depletion are the main features.

Winter room temperature: 22oC (when ambient temperature is about 10oC) Summer room temperature: 28oC and humidity at 45 – 50% (when the ambient

temperature is about 10oC and humidity 30%)

Economics:The incorporation of passive solar features in a new house will not normally require extra expenditure. The houses under consideration can be divided in three main categories:

1. Houses where choice of proper orientation and site planning and efficient functional planning is possible, energy efficiency can be achieved at no major extra cost.

2. Houses for which there is less availability of sunlight, less independence in selecting the site and orientation, there is an increase of only 5-10% in cost which may be required for greater levels of insulation, special heating and cooling requirements. However, due to lesser fuel / electricity consumption year round, this incremental cost can be recovered in 5 – 7 years.

3. Houses which are to be retrofitted with space heating solar passive systems like Trombe wall, sun space, space for heating of green houses, adding insulations will require extra funds.

Unlike fossil fuels, solar energy is available just about anywhere on earth. And this source of energy is free, immune to rising energy prices. Solar energy can be used in many ways – to provide heat, lighting, mechanical power and electricity.

Passive house

The dark colours on this thermogram of a passive house (right) show how little heat is escaping compared to a traditional building (left).

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References:

Manual on solar passive architecture: energy systems engineering IIT Delhi and Solar Energy Centre, Ministry of Non-conventional Energy Sources, Government of India, New Delhi)

Bansal N K, Hauser G, Minke G. Passive building design: A handbook of Natural climatic control.

Nayak J K, Hazra R. Development of design guidelines by laws.

Thomas A Fisher. 1992AIA, November 1992

TERI report 96RT__ Window design optimisation

Mazria E. 1979The Passive Solar Energy book, Rodale Press, Pennsylvania

Levy M. E., Evans D., and Gardstein C., The Passive Solar Construction Handbook, Rodale Press, Pennsylvania, 1983).

http://www.tt.fh-koeln.de/semesterprojects/lake%20nasser%2003_04/House%20Plan/Ventilation%20and%20cooling.pdf

http://www.ese.iitb.ac.in/events/other/renet_files/21-9/Session%203/passive%20solar%20architecture(J.K.Nayak).pdf

http://www.ese.iitb.ac.in/events/other/renet_files/21-9/Session%204/Design%20guidelines%20for%20energy%20effcient%20building(%20J.A.Prajapati).pdf

http://bookstore.teriin.org/docs/books/Introduction-%20energy%20eff%20biuldings.pdf

http://www.techno-preneur.net/technology/New-technologies/Energy/buildings.htm

http://en.wikipedia.org/wiki/Passive_solar_building_design#Direct_solar_gain

http://mhathwar.tripod.com/thesis/solar/solar_architecture.htm

http://www.nmsea.org/Education/Homeowners/passiv2.gif

http://www.smarterhomes.org.nz/design/glazing/double-glazing-glass-options/

http://www.wbdg.org/resources/psheating.php

http://www.azsolarcenter.org/tech-science/solar-architecture/passive-solar-design-manual/passive-solar-design-manual-heating.html

http://www.building.co.uk/Pictures/web/n/l/m/43prodsTECHNAL_TANATORI_MXS.jpg

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http://www.reidsteel.com/images/dsc01144.jpg

http://www.sustainable-buildings.org/index.php?option=com_cstudy&task=details&sid=24

http://www.learn.londonmet.ac.uk/packages/clear/interactive/matrix/c/cool_period.html

http://mnes.nic.in/booklets/solar-energy/ch7.pdf

http://www.azsolarcenter.com/design/images/fig7.gif

http://www.engineering.com/portals/0/images/sunspace.gif

http://www.cenerg.ensmp.fr/english/themes/cycle/images/Image17.gif

http://www.sustainable-buildings.org/wiki/index.php/Transwall

http://passivesolar.sustainablesources.com/

http://en.wikipedia.org/wiki/Solar_air_conditioning#Passive_solar_coolinghttp://en.wikipedia.org/wiki/Earth_sheltering

http://www.learn.londonmet.ac.uk/packages/clear/thermal/buildings/passive_system/earth_berming.html

http://www.yourhome.gov.au/technical/fs46.html

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