Sustainability in Civil Engineering - Essay Example

SUSTAINABILITY IN CIVIL ENGINEERING What is sustainability Before we talk about Sustainability in Civil Engineering we should have a clear picture of what sustainability actually means. Sustainability in a very simple terms can be defined as, the ability to meet our current needs or objectives completely, without overlooking or compromising on the ability of the future world to meet theirs. So it can also be summarized as an act of maintaining a perfect balance of nature. Civil Engineering is a science that deals with the design and construction of physical and natural structures. Therefore, civil engineering, in itself, is a blend of social, economic and environmental objectives. Sustainability in civil engineering would therefore mean to have balance between these three objectives, both now and into the future. Why do we need it Sustainability in Civil engineering is becoming a major concern in the modern world. Lack of sustainability would prove to be not only detrimental to the planet but would also curb the growth and healthy progression of global business. A Case Study: Let us take an example of the Three Gorges Dam project in China, which clearly illustrates that, lack of sustainability in Civil engineering projects could undoubtedly cause serious social and environmental issues. The proposal for a dam on the Yangtze, the world's third largest river, took shape Eighty years ago and since then it had been in the plans of the Government of China. The Three Gorges dam which in under construction currently is expected to be completed by the year 2009. Upon its completion the dam will be around 600 feet high, 1.5 miles long, and will form a reservoir which is 400 mile long, in the middle section of the Yangtze River. This is supposed to be the largest dam project in the world. This project is expected to meet four important objectives, Flood control, Generation of Power, Improved navigation on the Yangtze River and Fresh water accessibility. The reports released by the Chinese government and the concerned contractors of the Three Gorges Dam do not emphasize on the negative impacts caused by this project on the environment, atmosphere and social life. The most important impacts on the environment include deforestation, excessive emission of greenhouse gases, loss of aquatic life and severe impact on water quality. When the project is completed there would be a dynamic change in the silt levels and water temperature. Due to this extensive silting the anticipated positive benefits of improved navigation and Energy production are questioned. The Yangtze River is known for its extreme silt content. The silt settled down at the bottom of the reservoir would slow down the water flow. Thus, the silt which has formed upstream would reduce the navigation. And the silt that gathers near the dam may reduce effective power generation. The environmental changes that occur during the construction of the Three Gorges Dam would also cause a significant loss of the aquatic, plant and wildlife species. The Chinese Academy of Sciences Mountainous Disaster and Environment Institute has divided the natural and social ecology and environment into 78 subsystems varying from climatology to terrestrial fauna. According to a study conducted by them, the report says that the Three Gorges Dam would affect nine subsystems positively, six of them neutrally and sixty three subsystems negatively. While we see the above environmental implications of the Three Gorges project, the social implication of this project involves the relocation and resettlement of more than a million people from the Yangtze basin area. The Chinese government initially estimated this number to be lesser than 0.75 million while the real number lies somewhere between 2-4 millon. The problem that might arise due to this is, most of the people who will be relocated are peasants and they are to be compensated by providing them with new lands. However, the lack of land in the area and high erosion levels make this impossible. Therefore, The Three Gorges dam which project can be thought of as a project that has a lot of negative effects which have overpowered the positive economic implications anticipated by the successful execution of the project. This example also illustrates that all the aspects of sustainability (i.e. environmental, economic and social) essentially overlap and relate with each other, so, the approach towards them should also be joined up. Achieving Sustainability Sustainability can be achieved by revising the techniques and operations in a few key areas of Civil engineering that include Energy Sources involved, Construction Materials used, Waste Materials generated and Pollution caused. Energy Sources The construction industry consumes energy in a numerous amounts of ways. Energy is vital in all phases of construction which involves Extracting the raw materials, manufacturing the end products used in construction, Transportation of materials and workforce, Building and powering structures and Maintenance and demolition of built structures. Therefore, a sustainable approach to Energy would be to minimizing the consumption of energy, making efficient use of energy and making use of renewable energy sources and alternative technologies. The Civil engineering designs must emphasize on being more energy efficient and more number of low energy or Energy saving materials must be deployed. Recycling can be increased in order to minimize energy used in transportation and disposal of waste products and manufacturing of new products. Incorporating Renewable energy sources into the design of civil engineering projects will improve the sustainability of a project considerably by generating energy in a more effective manner, improving the comfort of the occupants and reducing the pollution levels caused by typical non-renewable energy sources. Renewable Energy sources Renewable energy is the inexhaustible power that can be generated from nature's resources like Sun, Wind, Water, Plants and Earth. Renewable energy sources for civil engineering designs include: Passive Solar design techniques - for natural heating, cooling and day lighting Solar thermal systems- For hot water heating and ventilation air preheating Photovoltaic cells - for electricity generation Wind systems - for electricity generation and water pumping Geo thermal heating systems - for water and space heating Passive Solar design techniques The most important feature of Passive Solar design technique is that it depends on integration of aspects like architecture of the building, construction materials and mechanical systems to reduce heating and cooling loads. It also takes into account local climactic conditions such as solar radiation, temperature and wind to create climate responsive and energy saving constructions. The advantages of this technique include: Increase in user comfort and productivity and Reduced Greenhouse Emissions. Passive Solar heating involves the following process The collection of Solar energy through properly oriented windows The storage this energy in thermal masses (Which consists of building materials with high heat capacities) The distribution of solar energy back into living spaces through natural methods of convection and radiation. Passive solar heating has four generic approaches. They are Sun-tempered, direct gain, indirect gain and Isolated gain. The primary types of constructions which benefit from the Passive solar heating design are: Barracks and other low-rise housing in Temperate and cold climactic regions Small PX facilities which are less than 10000 square feet in area. Warehouses and Maintenance facilities Solar Thermal Systems Solar thermal systems produce heat which can be used directly or can be converted into electricity. In a simple Solar thermal application, a discrete solar collector accumulates the solar radiation and either heats air or water for domestic, commercial or industrial use. The solar panel is usually a flat plate collector that consists of a metal box with a glass or plastic cover and a black absorber plate at the bottom. The Absorber plates are generally painted with materials that absorb and retain heat better than ordinary black paint. Absorber plates are usually made with good conducting metals like aluminum or copper. Also, the sides and bottom of the collector are insulated in order to minimize heat loss. The solar thermal systems are further classified into Active and Passive systems. Passive systems are those which do not require any mechanical equipment for heating while Active systems require collectors to absorb and collect radiation and fans and pumps for circulating the heated air or heat absorbing fluids. Further the solar collectors can further be classified into Non-Concentrating and Concentrating collectors. In Non-concentrating collectors, the collector area and the absorber area are the same. Flat plate collectors are very common and are used when temperatures below than 2000 degrees Fahrenheit are enough, for example for space heating. In Concentrating collectors the collector area is usually hundreds of times greater than the absorber area. These types of collectors are used in applications where high temperatures are desired such as for steam production, for Generation of electricity (Solar thermal power) and for thermal detoxification process. Solar thermal power Solar thermal power plants use sun's rays to heat fluids. Heat transfer systems are used to produce steam from the fluids. The steam is converted into mechanical energy in a turbine and electrical energy through a generator which will be coupled to the turbine. There are three main types of Solar Thermal power technologies that are in vogue. Parabolic trough Solar dish Solar power tower Photovoltaic energy Photovoltaic energy is the conversion of energy from the sunlight into electricity. A photovoltaic cell commonly referred to as a PV is used for this purpose. It is a semiconductor device that is made from silicon alloys. Sun light is composed of Photons (Particles of Solar energy). Each photon carries different amounts of energy which corresponds to different wavelengths of solar spectrum. The photons which strike a photovoltaic cell might either be reflected pass through or absorbed. Those photons which are absorbed provide the energy to generate electricity. When enough amount of energy is absorbed by the PV cell semiconductor material, Electrons will be dislodged from the material's atoms. As the negative charge carrying electrons leave their positions, and travel towards the front surface of the cell an imbalance of charge is created in between the front and rear portions of the PV cell. This results in the creation of a voltage potential like the positive and negative terminals of a battery. When the front and rear surfaces are connected though an external load, electricity flows. PV cell is the basic building block of the Photovoltaic system. However the power produced by a single cell is as low as 1-2 watts. In order to increase the power output several individual PV cells ,most commonly squares of silicon, are wired together and laminated within a thin, protective glass case to make a module cells and several hundreds of modules are further connected to form an array. The term array refers to the entire power generating plant where hundreds and thousands of watts of power is generated. Photovoltaic systems have several advantages like Bulky mechanical generators are not required to generate power The PV arrays of any desired size can be installed very quickly A very sustainable form of energy as it causes minimal environmental impact, as it neither requires water for system cooling nor generates any byproducts. Wind Systems Wind energy is being used by man for hundreds of years now. Windmills were used in farms for pumping water or grinding grain. In today's world, windmills modern equivalent, the Wind turbines, are being used to generate electricity from the wind's energy. Wind turbines are mounted on tall towers to capture the maximum wind energy. At an altitude of 100 feet from ground level, they can take the advantage of faster and less turbulent wind. Turbines have propeller like blades which capture the wind's energy. In general 2-3 blades are mounted on a shaft, which forms a rotor. The propeller blade acts like an aero plane wing. When the wind blows, a low-pressure air pocket is created on the downwind side of the blade. This low-pressure air pocket pulls the blade towards it causing the rotor to spin, which is called a 'lift'. The wind's force on the front side f the blade is called the 'drag'. A 'lift' is much stronger than a 'drag'. A combination of these two causes the rotor to rotate like a propeller and the shaft which is turning, spins a generator, which in turn produces electricity. Wind turbines can be made use of as standalone applications or they can be connected to a utility power grid. Stand-alone wind turbines are utilized for water pumping and communications. Wind turbines an also be combined with the photo-voltaic systems. To provide energy for utilities, a large number of wind turbines are closely built together to form a wind plant. Today, wind plants are being used by several electricity providers to provide electricity to their customers. Also, in windy areas, several peasants and ranchers use wind turbines and minimize their electricity bills. The wind turbines have been designed such that they provide high reliability, minimal maintenance and lower wind resources. Complete wind power systems using batteries and modern power electronics can replace small diesel and propane powered generators. They are also environmental compliant Geo thermal systems Geo thermal energy systems as the name specifies, obtain heat energy from earth. Several technologies have been developed to reap benefits from geo thermal energy. The energy from earth can be captured from several sources like Hot water or steam reservoirs that are embedded deep in the earth's crust and these can be accessed by drilling Geo thermal reservoirs that are present near earth's surface The shallow ground from the earth's surface which maintains a relatively constant temperature of 50-60 degrees Fahrenheit. Due to a variety of geo thermal resources present, they can be made use of on both large and small scales.Geo thermal energy is being utilized in the following ways Direct use Geo thermal hot water is being used by many applications that require heat Like heating buildings, drying of crops, heating water at farms and also several industrial applications like pasteurizing milk Geo thermal Power The hot water and steam from the reservoirs can be used by Geo thermal power plants to drive generators and generate electricity for the customers. There are three types of geo thermal power plants: dry steam, flash steam and binary cycle. Dry steam power plants extract energy directly from underground wells of steam. The steam is directly piped from the underground wells to a power plant where it is directed to turbine-generator units. Flash steam power plants are very common. These power plants use the geo thermal reservoirs of water which have temperatures greater than 360 degrees Fahrenheit. This water flows up from the reservoir on its own pressure. When it flows upward, the pressure of water is reduced and a part of its converted into steam. This steam is then separated from water and directed to turbine-generator units. The leftover water and the condensed steam are sent back into the reservoir. Binary cycle power plants make use of water at lower temperatures of about 225-360 degrees fahrenheit.These plants utilize the heat from the hot water to boil a working fluid, which is usually an organic compound with a low boiling point. This working fluid is vaporized in a heat exchanger and is used to rotate a turbine. The water is sent back to the reservoir where it gets reheated again. In the entire process the water and the working fluid are kept separate, in order not to mix with each other. Therefore there will be no air emissions in this entire process. Heat pumps The shallow surface of the earth maintains a constant temperature between 50-60 degree Fahrenheit in all the seasons. So, geo thermal heat pumps take advantage of this feature to heat and cool buildings. Geo thermal heat systems use less energy when compared to the conventional heating systems and they are more efficient too. Construction materials It is estimated that around 50% of all global resources are used in the construction industry. Therefore, it is very important that there should be a more sustainable approach while we choose materials for construction. There are several tools that exist that determine the environmental cost of a product that has been manufactured, in the context of economic and social benefit. The tools like Life-cycle assessment, eco-labeling and Embodied Energy audits would help a civil engineer to choose materials and suppliers to evaluate the balance between short term costs and long term environmental and social benefits. The finishes and materials selected should have low toxicity in order to maintain high quality indoor air. The following features are to be considered to make construction materials more sustainable. Using Recycle content By recycling the waste content from post industrial and post building, into usable building products the demand on the existing natural products would reduce and the waste stream produced would minimize. By recycling the waste materials, the energy they contain is being made use of instead of being wasted. Important building materials that have the potential of being reused are Glass, Plastics, Metals, wood and Concrete or bricks. Using Natural materials The total energy required to produce a material is usually referred to as the embodied energy of that particular material. Natural materials usually have low embodied energy and low toxicity associated with them, when compared to man-made materials. So they are less damaging to the environment. Many materials like Wood are renewable. Therefore when natural materials are incorporated into construction the architecture becomes more sustainable. Using Local Materials By using locally manufactured construction materials, the transport distances are shortened and thus air pollution reduces. Moreover, the materials that are produced locally are better suited to meet the climactic conditions of that area, and they are always economical. Though it is practically not possible to use local materials all the time, the materials imported must always be selective and as low as possible. Using Energy Efficient materials Energy efficiency is key feature that helps in making a building material environmentally more sustainable. The ultimate objective of using an energy efficient material is to keep the amount of generated energy at a construction site s low as possible. The energy efficient building materials can be measured by R-value, Shading coefficient, Luminous efficiency or fuel efficiency, depending on their type. The construction materials which slow the transfer of heat through the building's skin must be preferred. Also, Quantitative measures of building material's efficiency are available, which will help the personnel in choosing the right kind of material. Using Non-toxic or less toxic materials Obviously, using such material is very beneficial for the personnel who construct a building or for future occupants of the building. Many materials affect the indoor air quality and pose health hazards to the occupants. The proposal to make buildings airtight in the wake of the oil crisis in 1970's has led to a health hazard called as the 'sick building syndrome'. This problem occurs when the ventilation is not adequate to purge odors and chemicals emitted by some building materials, which might be hazardous and even carcinogenic. The resins which are being used by plywood, particleboard and the chemicals which are used in foam insulation, have been indicated at in sick building syndrome. Hazardous materials like Formaldehyde, ammonia and benzene are present in many building materials and cleaning solutions. Therefore, high air cycling rates are to be deployed when these materials are used. Using Bio degradable materials A materials potential to naturally decompose when it is discarded is referred to as its bio degradability. Organic materials are rapidly biodegradable while others like steel take a long time. Another point that has to be considered is whether the material in question will produce any hazardous substances while it degrades. Pollution Many types of pollution are associated with the construction industry, which include noise, dust, water and toxicity. The fact is that, 50% of the global warming gases are emitted from the construction industry. Therefore, pollution is a serious issue that has to be addressed by civil engineering if the industry aims to be more sustainable. REFERENCES Passive Solar Heating by Judy Fosdick and Tierra Concrete Homes FEMP Renewable Energy Case Study - A Solar Success Story at Moanalua Terrace The Three Gorges Dam Project in China: history and consequences-Marta Ponseti (ESTRATS, Gesti del Patrimoni SL) and Jordi Lpez-Pujol (Chinese Academy of Sciences) An Examination of China's Three Gorges Dam Project Based on the Framework Presented in the Report of The World Commission on Dams-Samuel Robert Fishleigh Allin Qualities, Use and Example of Sustainable Building materials - Jong-Jin Kim, Assistant Professor of Architecture, and Brenda Rigdon Read More