SOLAR PASSIVE ARCHITECTURE

Transcription

1 Chapter-7 SOLAR PASSIVE ARCHITECTURE Sangeeta Gangwar, Dy. Dir. (BS-Arch.), (m) For Internal Circulation Only Page: 1

2 INTRODUCTION Traditional Architecture are environment friendly. They are developed with regard to local climatic conditions and have features which provide thermal comfort inside the building in a natural way. Modern Architecture on the other hand is regardless to local climate and depends on the conventional energy for achieving desirable thermal comfort levels. However, in the recent past, there is growing concern for conserving energy and the environment this renewed intense in the aspects of architecture which lead to thermal comfort led to the development of the subject on solar heating and cooling of buildings. Solar heating of building can be categorized in two. One, in which building is healed by simply replacing oil / fuel fired heating plants by solar heating system i.e. where water is heated by solar collectors and then hot water is passed through radiators to heat the building. Here, no major changes are required in the building design. The other, on the other hand, the building itself is designed to accomplish the task of heating. Here, solar heat is collected through the large south facing glazed windows as well as through various collectors and is absorbed and stored in thick masonry walls, floors or water filled containers. The heat thus collected is then distributed by natural convective flow patterns within the building to achieve desired thermal comfort level inside the building. Solar passive Architecture is distinguished with this category of solar heating. Analysis of above passive heating system will show that there are five distinct elements. These are solar heat (1) Collector For Internal Circulation Only Page: 2

3 (2) Absorber (3) Storage (4) Distribution and (5) Controls or heat regulation devices. The success of solar passive architecture depends on these five elements. There are various techniques/features by which these five elements can be achieved for desirable thermal comfort inside the building. The following features are integrated in the design of various types of residential quarters (Type I to Type V, 500 quarters) for I.T.B.P. at Leh. Is situated in cold and sunny climatic zones in mountainous regions of high altitude 11,000 ft. with little vegetation. The winter is long and severe with temperature -15 degree C and with fairly clear sunshine throughout the year. It offers ideal condition for integrating solar passive Architecture in the building. Features integrated in the designs are:- (1) Orientation (2) Maximum surface area of wall exposed to sun (3) Direct gains (4) Solarium (5) Trombe wall (6) Solar heat storage (7) Hollow concrete block walls for preventing heat loss and thick stone walls to absorb solar heat gain. For Internal Circulation Only Page: 3

4 1.) ORIENTATION:- Since in the passive solar heating concept, solar heat is to be collected through the large South facing glazed windows as well as through various collectors The orientation of building with respect to movement of the sun plays vital role. It is there fore, essential that desired orientation is analyzed properly and then the building is designed accordingly. In the above housing proposal, there are 3 sites located on either sides of the main road which runs North South direction. One battalion (Ist Bn) is located on west side of the road and its called west campus. Other two battalions (3rdBN&21stBn) are located on the other side i.e. east side of the road and are called East Campus. The designs of all Type I to Type V residential quarters in the above proposal have been evolved on these concepts. 2. Surface area of wall exposed to the sun In the designs of all types of residential quarters, living and bed rooms have been staggered to maximize the surface area of walls exposed to the sun. 3. Direct Gains. Large double glass windows have been provided on the South facing walls of living and bed rooms for solar heat gains (direct gains). 4. Solarium The verandah/balcony has been covered with double glazing to act as solarium for direct solar heat gains. For Internal Circulation Only Page: 4

5 5. Trombe Wall/Tap In 1881, Prof. E.L. Morse was grated a patent on a glazed South facing dark wall for keeping the house warm. This was regarded as the first conscious scientific application of solar energy for passive heating. This concept was later, further developed in France by Prof. Trombe in 1972 and is called Trombe wall after his name. The details of Trombe wall is shown in the drawing. The south facing external wall is painted black and covered with double glazing. The external glass shall be of toughened glass and the inner glass may be ordinary glass. The gap between wall and the inner glass shall be 10cms. It has air inlet at bottom both from outside and inside the room and air outlet at the top (lintel level) inside the room and air out let at the top lintel level) inside the room solar heat is collected the trombe wall and absorbed by black painted wall which in turn the heat cold air getting in through inlet at bottom (skirting level). As the air is heated, it becomes lighter and rises above and enters the room through the outlet provided at the top. This warm air is circulated in the rooms by convective flow pattern and when cooled becomes heavier and gets in the Trombe wall through the air inlet at bottom (skirting level). These inlet and outlet have been prided with closing devices for closing it during night. Area of Trombe wall should be 50% of south facing wall and the south facing wall should be at least 25% of total wall area of the room. 6.Solar heat storage. A courtyard with thick stone wall has been provided in the central location of the quarter. This courtyard is covered with double glazed roof. For Internal Circulation Only Page: 5

6 The external glass should be of toughened glass and the inner glass may be of ordinary glass. Solar heat is gained to this glazed courtyard and is absorbed in the thick stone wall, solar heat thus absorbed radiates heat in the rooms at night and maintains the thermal comfort level in the rooms. The warm air in the courtyard flows to the rooms through the inlets. The glazed roof is provided with insulated covering system which prevent the heat loss during night. 7. Hollow concrete block walls and thick stone walls. Hollow concrete block walls have been provided on the walls which are exposed to the sun for preventing heat loss and conserve heat inside the rooms. Thick stone walls have been provided on the other sides which are not exposed to the sun to absorbed the solar heat gain during the day time and to radiate heat at night time to maintain the thermal comfort inside the rooms. Energy efficient housing for I.T.B.P. at Leh. Features integrated in the designs are:- (i) (ii) Orientation Maximum surface area of wall exposed to sun. For Internal Circulation Only Page: 6

7 (iii) (iv) (v) (vi) Direct gain. Solarium. Trombe wall. Solar heat storage. (vii) Hollow cone. Block walls for preventing heat loss and thick stone walls to absorb solar heat gam. Solarium or Greenhouse This is a combination of direct gain and indirect gain concepts. For Internal Circulation Only Page: 7

8 A glass enclosure called solarium or green house is attached to the thermal storage walls of the building on south side. Solarium or green house receives heat by direct gain while the room receives heat by indirect gain through the thermal storage wall. (i) (ii) Collectors:- Direct gain Indirect gain. Direct Gain:- Sunlight is allowed to enter the building directly through south facing window and heat internal walls, floors etc. to provide thermal comfort. Indirect gain:- (i) Thermal storage wall (ii) Trombe wall (iii) Solarium or green house. For Internal Circulation Only Page: 8

9 Thermal storage wall:- Thermal Storage wall is provided on south side between incoming solar radiation and the room.the externally glared thermal wall gets heated due to absorption of solar radiation at its outer surface and radiates heat during night. 5. Distinct elements/features of passive solar heating:- These are solar heat. (i) Collector (ii) Absorber (iii) Storage (iv) Distribution (v) Controls or heat regulating devices. Computer simulation for energy sufficiency in the in building shows in graphs winter and summer performance of revised design. For Internal Circulation Only Page: 9

10 CONCLUSIONS:- Based on the analytical study of the simulation results for the ITBP-Quarter I building and the corresponding stud of the recommended design changes, it is evident that the building thermal performance can be enhanced by with the necessary changes. The outlined recommendations are as follows:- 1.) Addition of single height/double height glass house facing south adjoining at least 2 rooms on ground and two rooms on first floor as may be applicable. 2.) 10 cm thick insulation on East, West and North walls except toilet, kitchen and store areas as these act as buffer zones against the cool winds. 3.) 15 cm thick roof insulation, partly above roof slab and partly below roof slab. 4.) Interchange positions of trombe walls and direct gain windows to avoid shading of trombe by adjoining staggered walls. 5.) Replace hollow concrete blocks in trombe wall by solid concrete blocks. Extreme Cold, Dry and Sunny Climate (Leh) N-S orientation to get maximum sun (buildings on southern slopes). Shape of the built-form Sun space on south side Location of building blocks to avoid shadows Orientation of rooms on south, service areas kept on north side Provison of Trombe walls on south facing façade to collect heat Provision of atrium (solar heat chamber) provided with thick walls, pebbled flooring and solar collector louvers at roof level (to be closed at night) and clustering the rooms around atrium to prevent heat loss Extreme Cold, Dry and Sunny Climat (Leh) Provision of Solarium at entrance facing south to maximize heat gain during day and prevent heat loss at night. Provision of thick stone walls on north façade to act as thermal heat absorbent for heat retention. Provision of vertical thermal insulation at foundation level to prevent heat dissipation by conduction. For Internal Circulation Only Page: 10

11 Systematic maintenance of energy efficient devices and user awareness. Gains anticipated:- 13 Degree C temperature difference between indoor and outdoor temperature. Composite (Delhi, Indore) Hot & Dry (Ajmer) Climate N-S Orientation of the buildings. Shape of the building to get maximum N-S facades. Location of functions (rooms) in the right orientation Window area as 15-20% of floor area Control of direct penetration of solar radiation and shadow pattern through provision of recessed windows, fins, louvers, Chajjas overhangs etc. and tinted glass panes. Adequate ventilation for maximum air-flow and wind management Provision of open courtyards. Provision of atrium covered with fiber glass pyramids at roof tops. Location and size of windows in the rooms for better air circulation. Earth berm upto cill height of external walls to direct cool breeze into the rooms. Reduction of conduction of heat through walls & roof Rat-trap bond cavity external walls. Perforated parapet walls. Composite (Delhi, Indore) Hot & Dry (Ajmer) Climate Reduction of conduction of heat through walls & roof Rat-trap bond cavity external walls. Perforated parapet walls. Insulation of roofs Provision of inverted earthenware posts on roof Provision of china mosaic finish on roof top Combination inverted earthenware pots and china mosaic finish on roof. Provision of thermocol or similar material for over deck roof insulation. Landscaping to improve microclimate and to provide shading to sun facing facades. Transmission through ground floor For Internal Circulation Only Page: 11

12 Heating Strategies For Internal Circulation Only Page: 12

13 Gains anticipated:- 5 degree C Temperature difference between indoor and outdoor. Provision of Atriums covered with fiber glass pyramids at roof top South wall for high summer sun and low summer sun For Internal Circulation Only Page: 13

14 Appropriate design guidelines based on these simple techniques have been accessible. These can be incorporated very easily in building designs. Further they can also be used as retrofitting techniques in any building. END For Internal Circulation Only Page: 14