تجزیه و تحلیل هزینه برای ضخامت های بهینه و اثرات زیست محیطی مواد عایق مختلف
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|23397||2014||8 صفحه PDF||سفارش دهید||5001 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Energy and Buildings, Volume 49, June 2012, Pages 552–559
In this study, the optimum thickness of thermal insulation used to reduce heat gain and losses in buildings is investigated under dynamic thermal conditions by using the climatic conditions of Elazığ, Turkey. Numerical method based on an implicit finite difference procedure which has been previously validated is used to determine yearly cooling and heating transmission loads, yearly averaged time lag and decrement factor under steady periodic conditions. These loads are used as inputs to an economic model for the determination of the optimum insulation thickness. The optimum insulation thicknesses, energy savings and payback periods are calculated by using life-cycle cost analysis over lifetime of 20 years of the building. Results show that the optimum insulation thicknesses vary between 5.4 and 19.2 cm, energy savings vary between 86.26 and 146.05 $/m2, and payback periods vary between 3.56 and 8.85 years for different insulation materials. The environmental impacts of thermal insulation are also investigated. It is seen that by applying optimum insulation thickness in uninsulated wall, yearly fuel consumption and emissions are decreased by 68–89.5% depending on insulation materials.
Today, world energy consumption contributes to pollution, environmental deterioration and global greenhouse emissions. Increases in energy consumption are driven by population growth and economic development that tend to increase energy use per capita. Thus the inevitable increase in population in the near future and the economic development that must necessarily occur in many countries pose serious implications for the environment. Since the early 1980s the relationship between energy use and environmental impacts has received much attention, and a number of international activities have focused on this topic . The energy consumption is distributed among four main sectors such as industrial, building (residential/commercial), transportation and agriculture . Globally, buildings are responsible for approximately 40% of the total world annual energy consumption. Most of this energy is for the provision of lighting, heating, cooling, and air conditioning. Increasing awareness of the environmental impact of carbon dioxide (CO2) and nitrogen oxides (NOx) emissions and chlorofluorocarbons (CFCs) triggered a renewed interest in environmentally friendly cooling, and heating technologies. Under the 1997 Montreal Protocol, governments agreed to phase out chemicals used as refrigerants that have the potential to destroy stratospheric ozone. It was therefore considered desirable to reduce energy consumption and decrease the rate of depletion of world energy reserves and pollution of the environment. One way of reducing building energy consumption is to design buildings, which are more economical in their use of energy for heating, lighting, cooling, ventilation and hot water supply . The employ of thermal insulation is one of the most effective ways of building energy conservation for cooling and heating. Therefore, the selection of a proper insulation material and determination of optimum insulation thickness are particularly vital . It is well known that the heat-transmission load decreases without a limit with increasing insulation thickness, however, the rate of decrease drops quite fast as the thickness increases. From a purely conservation point of view, the designer should select an insulation material with the lowest possible thermal conductivity and the highest thickness that the owner can afford. However, the cost of insulation increases linearly with its thickness, and there is a point, for each type of insulation material, beyond which the saving in energy consumption will not compensate for the extra cost of insulation material. Thus, there must be an optimum insulation thickness at which the total cost of the insulation material plus the present worth of energy consumption over the lifetime of the building is a minimum . In literature, there are many studies on the determination of the optimum insulation thicknesses on the building walls. The most of these studies use degree-days (or degree-hours) concept which is a simple and crude model applied under static conditions , , , , ,  and . However, more accurate results were obtained with numerical and analytical methods considering the transient thermal behaviour of building envelope. While some authors used dynamic time dependent method based on the finite volume implicit procedure to compute the yearly transmission loads through the wall under steady periodic conditions , , ,  and , the others used an analytical method based on Complex Finite Fourier Transform  and . Air pollution is becoming a great environmental concern in Turkey. Air pollution from energy utilization in the country is due to the combustion of coal, lignite, petroleum, natural gas, wood and agricultural and animal wastes. On the other hand, owing mainly to the rapid growth of primary energy consumption and the increasing use of domestic lignite, SO2 emissions, in particular, have increased rapidly in recent years in Turkey . In literature, there are also a few studies on environmental impact of thermal insulation. Çomaklı and Yüksel  investigated environmental impact of heat insulation used for reduction heat losses in buildings. They determined that CO2 emission amounts decreased 50% by means of optimum insulation thickness used and other energy savings methods in buildings. Dombaycı  investigated the environmental impact of optimum insulation thickness. In the calculations, coal was used as the fuel source and the expanded polystyrene as the insulation material. He found that when the optimum insulation thickness is used, the emissions of CO2 and SO2 are decreased by 41.53%. Mahlia and Iqbal  investigated potential cost savings and emission reductions achieved by installing different insulation materials of optimum thickness in building's walls. The paper also investigated the effect when air gaps are introduced in the wall. They found that by introducing optimal thickness of different insulation materials and by having air gaps of 2, 4 and 6 cm, energy consumption and emissions can be reduced by 65–77%, in comparison to a wall without insulation or air gaps. In another study, the effects of air gap in the composite wall construction on the optimum insulation thickness, total cost, energy saving, payback period, fuel consumption, and emissions of CO2 and SO2 were investigated for a prototype building in a sample city, Karabuk . The present study aims determination of optimum thicknesses and environmental impacts of different insulation materials under dynamic thermal conditions. Thermal parameters such as the yearly cooling and heating transmission loads, yearly averaged time lag and decrement factor are calculated under steady periodic conditions by using an implicit finite difference method which has been previously validated. Transmission loads are used as inputs to an economic model for the determination of the optimum insulation thickness over lifetime of 20 years of the building. The optimum insulation thicknesses, energy savings, payback periods, fuel consumption, and emissions of CO2 and SO2 are calculated for four different insulation materials.
نتیجه گیری انگلیسی
This study deals with determination of optimum thicknesses and environmental impacts of different insulation materials under dynamic thermal conditions. The yearly cooling and heating transmission loads, yearly averaged time lag and decrement factor are presented versus insulation thickness and compared four different insulation materials. The yearly transmission loads are used as inputs to an economic model for the determination of the optimum insulation thickness over lifetime of 20 years of the building. The optimum insulation thicknesses, energy savings, payback periods, fuel consumption and emissions of CO2 and SO2 are calculated for four different insulation materials. The results show that the optimum insulation thicknesses vary between 5.4 and 19.2 cm, energy savings vary between 86.26 and 146.05 $/m2, and payback periods vary between 3.56 and 8.85 years depending on different insulation materials. It is seen that RW has the lowest value with optimum insulation thickness of 5.4 cm, while GW has the highest value with optimum insulation thickness of 19.2 cm. Besides, it is seen that when optimum insulation thickness is used, yearly fuel consumption varies between 2.95 and 6.27 kg/m2 year, CO2 emission varies between 6.37 and 19.55 kg/m2 year and SO2 emission varies between 0.013 and 0.040 kg/m2 year depending on insulation materials.