Review of the Passive Solar Building Designs

Transcription

1 Review of the Passive Solar Building Designs (I) Mr. Jyotisman Saikia, II) Alangkrita Choudhury, III) Papori Das, IV) Rajlakshmee Saikia, (V) Supriya Baruah I) Assistant Professor, Department of Civil Engineering, Girijananda Choudhury institute of management and technology, Guwahati , India. II), III), IV) and V) B.tech Students, Department of Civil Engineering, Girijananda Choudhury institute of management and technology, Guwahati , India. Abstract It is an urgent need of today s present time for sustainable development. With ever growing infrastructure everyday construction and maintenance of buildings require huge amount of power usage. Passive solar building designing can be a key answer to this problem and a huge step towards sustainable development by meeting the power demands by solar energy usage. This paper is a suggestive and analytical, theoretical and indicative study of developments in solar passive building designing technology relevant to both developed and developing countries.the development of these areas is presented along with the scientific principles and various design concepts. Factors kept in mind for design strategies such as direct gain, indirect gain and isolated gain have been studied and described. Studies of site consideration, material availability and also economic cost have been taken into consideration. Some examples of previous successful designs both from Indian and Foreign buildings constructed during the past decades are detailed with their performances and remarks concluding the future and current trends have been indicated. A review of previous research works showing significant milestones in passive solar buildings has been studied and suggestions of new ideas have been incorporated. Hence it can be seen that power usage reduction in solar efficient building will enhance the sustainable development of a region. Keywords: passive solar buildings, sustainable development, economic considerations. INTRODUCTION Passive solar designs refer to the use of the sun s energy for the heating and cooling of living spaces. In this approach the building or some of its elements take advantage of natural energy characteristics 1 Page 1-7 MAT Journals All Rights Reserved

2 in materials and air created by exposure to the sun. These designs are simple, requires minimal maintenance and no mechanical system. Passive design is practiced throughout the world and has been shown to produce buildings with low energy costs, minimum maintenance and super comfort[1,2]. The cost of passive design elements can run the same or slightly more than the conventional buildings costs. It is assumed that design services are used in both approaches- passive solar design and conventional designs. The difference between a passive solar building and a conventional building is its design. Passive solar buildings are designed to take advantage of the local climate. The building s windows, walls and floors collects stores and distribute solar energy in the form of heat in winter and reject solar heat in summer. The most important characteristics of passive solar design is that it is holistic which is based on the integration of the building s architecture, materials section and mechanical system to reduce heating and cooling loads. It is also important to consider local climatic conditions such as temperature, solar radiation and wind. When creating climatic responsive, energy conserving structures that can be powered with renewable energy resources. In this project an attempt has been made and is analysed regarding the construction of passive solar designs on our region keeping in mind the conditions required for making such designs. PASSIVE SOLAR BUILDING DESIGN AND ITS IMPLEMENTATION. In passive solar building design, windows, floors, and walls are made to collect, store and distribute solar energy in the form of heat in the winter and reject solar heat in summer. This is called passive solar building design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices. The key to design a passive solar building is to best take advantage of the local climate performing and accurate site analysis. Elements to be considered include window placement and size, and glazing type, thermal insulation, thermal mass and shading[3-5].passive solar design techniques can be applied most easily to new buildings, but existing buildings can be adapted or retrofitted. Passive solar technologies use sunlight without active mechanical systems. Such technologies convert sunlight into usable heat (in water, air and thermal mass), cause air-movement for ventilating, or future use, with little use of other energy sources. A common example is a solarium 2 Page 1-7 MAT Journals All Rights Reserved

3 on the equator-side of a building. Passive cooling is the use of the same design principles to reduce summer cooling requirements. Some passive systems use a small amount of conventional energy to control dampers, shutters, night insulation, and other devices that enhance solar energy collection, storage, and use, and reduce undesirable heat transfer. Passive solar techniques include direct and indirect solar gain for space heating, solar water heating systems based on the thermo siphon, use of thermal mass and phase change materials for slowing indoor air temperature swings, solar cookers, the solar chimney for enhancing natural ventilation, and earth sheltering. More widely, passive solar technologies include the solar furnace and solar forge, but these typically require some external energy for aligning their concentrating mirrors or receivers, and historically have not proven to be practical or cost effective for widespread use. Low grade energy needs, such as space and water heating, have proven, over time, to be better applications for passive use of solar energy. Direct gain is the process by which sunlight directly enters a building through the windows and is absorbed and temporarily stored in massive floors and walls. PRINCIPLES OF PASSIVE SOLAR DESIGN The principles of passive solar indirect gain is the process by which the sun warms a heat storage element- such as a trombe wall- and the heat is later distribute to interior space by convection, conduction and radiation, The design for a comfortable energy efficient house can be summarized in a very simple way: Insulation Insulation is used to slow the flow of heat in and out of the house-heat from the sun is used more effectively in the houses that are well insulated. Insulation helps to maintain more constant internal temperatures and reduces the need for heating in winter and cooling in summer. Glazing Glazing is used to bring heat from the sun into the house-though glass. As such windows must be selected; placed, sized carefully as it is a poor insulator (windows should be double glazed as a minimum to reduce heat loss). Addition of Thermal Mass Using heavy weight materials to soak up heat from the sun and release it slowly into the house when temperatures drop. A house with appropriate mass will maintain more comfortable temperatures-it will 3 Page 1-7 MAT Journals All Rights Reserved

4 overheat less often and not get as cold overnight. Stoppage of Air Leakage Using weather-stripping, high-quality sealants and less complicated house designs is a good option to reduce air leakage. Once the house is well-insulated and appropriately glazed, the biggest potential heat is loss is through draughts around windows, doors and other construction joints. Shade Moreover, using external shading to manage the heat gain from the sun well designed window systems must not only collect heat from the sun when desirable, but also exclude it at times when it might cause overheating. Ventilation Using open able windows and other ventilation to reduce overheating and maintain good indoor air quality is also a good option. Appropriate placement of windows for good cross flow of air through rooms will make them more effective for cooling on hot days. Good ventilation also helps to reduce condensation and remove cooking and other odors. Other important factors that we should consider while designing a house, such as site selection, house placement and orientation. It is important to consider these, in combination with the above factors, when designing a comfortable energy efficient house. ADVANTAGES OF PASSIVE SOLAR HEATING AND DESIGNING A PASSIVE SOLAR BUILDING When considering solar energy to power our home and appliances, it pays to look at the idea of passive solar heating. Many people see solar energy as a way forward during times of very high heating bills, so there are many advantages of passive solar power in the design of passive solar buildings. Costs Passive solar heating is not a new idea but it is something which is frequently used in modern buildings and homes. It considerably reduces the amount of heating required from other sources and also reduces carbon emissions and that is the important factor to think about. Efficiency Passive solar energy makes more of the efficiency within the heating system of your home. It is not the main source of heating, hence the term passive, but it acts as a subsidiary and auxiliary form of heating which can be engaged as and 4 Page 1-7 MAT Journals All Rights Reserved

5 when needed. Building design Designers of new buildings now try to optimize the amount of energy they can derive from the sun. Careful planning helps to collect as much of sun s heat as possible to reduce much of the need for gas or electric heating. Building materials Serious considerations are to be taken for materials and fabrics that offer great insulation. Renewable energy Everyone is searching for the ultimate in renewable and sustainable sources these days and the sun is the answer to getting free renewable solar heating. It creates no carbon footprint whatsoever and you can take reasonably cheap steps to alter your home sufficiently enough to reduce your household bills by implementing passive solar heating. Air and ventilation Not only passive solar heating is beneficial for heating our home sufficiently but also we can rely on it to cool our home during hotter periods, which is known as passive cooling. While building a new home, planting trees on the south side of the home during summer will offer shade from the heat and in the winter, when they have dropped their leaves, we will get warmth coming in too. BENEFITS AND CHALLENGES A huge benefit of solar design is that it saves money that would otherwise be spent on utilities toward and heating and cooling bills. It is a clean and efficient use of energy that is readily available and occurs naturally, as long as the sun continues to rise and fall, its energy can be harnessed. Because of this constant, the sun s energy can be harnessed simply by designing the home oriented to the predictable movements of the sun. Another benefit is the positive impact on the air quality in the winter. A well-designed passive solar building will use less energy resources for heating and cooling. A sunny place like Colorado that has 300+ sunny days can be an ideal place for passive solar design, yet that still means that there are 65 cloudy days when the sun may not be able to provide adequate energy and heat. Passive solar design can greatly offset supplementary energy costs. But it alone may not provide all the heat or energy that is needed by a household or 5 Page 1-7 MAT Journals All Rights Reserved

6 building. If a home is designed and built well, it will greatly rely upon other forms of heating and cooling energy costs. While it also cuts down on pollution associated with electricity, natural gas or coal. A passive solar home can be supplemented with active solar, an electric grid tie in, natural gas, coal or diesel generators, or geothermal heating and cooling. There are many different possibilities and configurations. This is the challenge within the design of passive solar dwellings, to be beautiful in form, enjoyable and highly practical. It is this challenge that is embraced and finds fascination in. DESIGN CONSIDERATIONS The following are general recommendations that should be followed in the application of passive solar heating technology in the design of passive solar building: Paying careful attention when constructing a durable, energy-conserving building envelope. Addressing orientation issues during site planning. To the maximum extent possible, reduce glass on the east and west sides and protect openings from prevailing winter winds. Specifying windows and glazing that have low thermal transmittance values while admitting adequate levels of incoming solar radiation (higher solar heat gain coefficient. The amount of glazing will depend on building type and climate. Ensuring that the south glass in a passive solar building does not contribute to increase summer cooling. In many areas shading in summer is just as critical as admitting solar gain in winter. Designing for natural ventilation in summer with operable windows designed for cross ventilation. Ceiling fans or heat recovery ventilators offer additional air movement. In climates with large diurnal temperature swings, opening windows at night will release heat to the cool night air and closing the windows on hot days will keep the building cool naturally. Elongating the building along the east west axis to maximize the south facing elevation and the number of south-facing windows that can be incorporated. Improve building performance by employing high-performance, low-e glazing or nighttime, moveable insulation to reduce heat loss from glass at night. 6 Page 1-7 MAT Journals All Rights Reserved

7 Locating obstructions, such as landscaping or fences, so that full exposure to the sun is available to south windows from 9 a.m. to 3 p.m. for maximum solar gain in water. Including overhangs or other devices such as trellises or deciduous trees for shading in summer. Making sure that there is adequate quantity of thermal mass. In passive solar heated buildings with high solar contributions, it can be difficult to provide adequate quantities of effective thermal mass. EXAMPLES OF PASSIVE SOLAR BUILDINGS There has been recent interest in the utilization of the large amounts of surface area on skyscrapers to improve their overall energy efficiency. 22 Bishops gate tower in London, found that a 35% energy decrease in demand can theoretically be achieved through indirect solar gains, by rotating the building to achieve optimum ventilation and daylight penetration, usage of high thermal mass flooring material to decrease temperature fluctuation inside the building, and using double or triple glazed low emissivity window glass for direct solar gain. Passive design is the key to sustainable building and hence is way towards sustainable development. It responds to local climate and site conditions to maximize building users comfort and health while minimizing energy use. It achieves this by using free renewable source of energy such as sun and wind to provide household heating, cooling, ventilation and lighting, thereby reducing or removing the need for mechanical heating or cooling. Using passive design can reduce temperature fluctuations, improve indoor air quality and make a home drier and more enjoyable to live in. It can also reduce energy use and environmental impacts such as greenhouse gas emissions. Interest in passive design has grown particularly in the last decade or so, as a part of movement towards more comfortable and resource efficient building. REFERENCES 1. Athienitis AK, Santamouris M , Thermal analysis and design of passive solar buildings 2. Balcomb JD- 1992, Book on Passive solar building 3. Cook J osti.gov, Passiv 4. cooling 5. Mazria E osti.gov,passive solar energy book CONCLUSION 7 Page 1-7 MAT Journals All Rights Reserved