Economic and environmental impacts of insulation in district heating pipelines
Highlights
► In this study, the economic and environmental evaluations of thermal insulation in district heating pipeline are discussed. ► Based on LCC analysis, the optimum insulation thickness, energy saving, payback period and emissions are calculated. ► About three times more energy saving results by making 200 mm nominal pipe instead of 50 mm. ► Considering the economical and environmental advantages, the geothermal energy is a better choice and then fuel-oil.
Introduction
Energy saving has become the most important part of energy strategies of any country and will continue growing in importance in future, because of the fact that energy is a crucial factor for the social and economic development of societies, and energy consumption is rapidly increasing due to increasing population, urbanization, migration to large cities and improvement in standard of living. Because of the limited energy sources, fast energy consumption and environmental pollution coming from using the fuels, energy saving has become compulsory. Furthermore, it is not viable to design and implement energy saving plans without considering the environmental factors.
Turkey, with its young population and growing energy demand per person, its fast growing urbanization, and its economic development, has been one of the fast growing power markets of the world for the last two decades. Primary energy resources that are produced in Turkey are hard coal, lignite, asphaltite, petroleum, natural gas, hydroelectric energy and geothermal energy. Due to the very limited indigenous energy resources, Turkey has to import nearly 52% of the energy from abroad to meet its needs [1]. Its energy consumption can be examined generally under four main sectors such as industrial, building (residential/commercial), transportation and agriculture. Energy consumption in the building sector is one of the main parts of the total energy consumption in most countries. In Turkey, the energy amount used in the residential and commercial buildings is about 30% of total energy. In addition, it is 82% of energy for heating in the buildings [2]. Turkey is heavily dependent on expensive imported energy resources that place a big burden on the economy and air pollution is becoming a great environmental concern in the country. It is clear that energy saving is an important precaution that can inhibit air pollution, because the amount of carbon dioxide, sulphur dioxide, and particulates decrease with decreasing usage of energy. One of the main factors that determine the energy policies of countries is economic environmentally friendly energy production [3].
The sole purpose of a district heating system is to supply adequate heat to its customers. The consumer uses the heat to maintain indoor temperature at a reasonably constant level and counter for building heat loss to the surroundings. Most district heating systems use conventional fuel (oil, natural gas or coal) as the heat source. In some areas geothermal heat is used as the district heating source. The heat distribution in district heating systems is carried out by the use of either hot water or steam through a closed loop network, where the hot water or steam is piped to each consumer in the supply network, cooled down by the heat consumer, piped back to the heat centre and re-heated. To reduce the heat loss efficiently in such a heating system, the proper insulation should be selected by accounting for the purpose, environment, ease of handling, and installation cost. Industrial and chemical processing plants in particular contain intricate and costly piping configurations. Piping systems are also employed in many other situations including water supply, fire protection, and district heating/cooling applications. For example, un-insulated steam distribution and condensate return lines are a constant source of wasted energy [4]. Energy conservation in piping systems by adding insulation not only reduces heat energy requirement but also reduces its polluting products such as CO2, CO, SO2 and the dust particles. Several studies [5], [6], [7], [8], [9] may become handy when discussing the relationship between low-temperature district heating and grid losses in future district heating system when heading for sustainable energy solutions.
In literature, there are many studies on different aspects of building insulation (i.e., [10], [11], [12], [13],) because of the large potential for energy savings. However, it is seen that there are a few studies conducted in cylindrical insulation (i.e., [14], [15], [16], [17],) in spite of the extensive use of pipelines and cylindrical heat exchangers in refineries, chemical industry, district heating/cooling, and power plants. On the other hand, studies to improve environmental impacts of building insulation are also few. Consequently, environmental impacts of cylindrical insulation are overlooked. And, studies focused on environmental impact of building insulation are: Çomaklı and Yüksel [18] found that the saving in the cold cities may be as much as 12.13 $/m2 of wall area over a lifetime of 10 years. Also, they investigated the environmental impact of thermal insulation thickness in buildings. They determined that CO2 emission amounts decreased 50% by means of optimum insulation thickness use and other energy saving methods in buildings. By conducting a study on optimum insulation thickness on external walls considering condensed vapour in existing buildings for Kutahya/Turkey, Arslan and Köse [19] determined the optimum insulation thickness as 0.060, 0.065, 0.075 m with a rate of 74.9%, 76.3% and 78.8% in the energy saving and air pollutants reduction for indoor temperature of 18, 20 and 22 °C, respectively. Dombaycı [20] focused on the environmental impact of optimum insulation thickness in external walls for the case of Denizli/Turkey. In the calculations, coal was used as the fuel source and expanded polystyrene as the insulation material. The results proved that when the optimum insulation thickness was used, energy consumption was decreased by 46.6% and the emissions of CO2 and SO2 were reduced by 41.53%. Yıldız et al. [21] found that if they apply a 0.06 m glasswool insulation in Ankara which was found to be the optimum, the CO2 emission decreases by approximately 35% when coal is burned. Uçar and Balo [22] calculated optimum insulation thicknesses and the emissions of CO2, SO2, CO, and NOx from the combustion of coal by the use of insulation on external walls of buildings in Elazığ/Turkey. The emissions of CO and NOx were reduced by 82% by applying the optimum insulation thickness. Kurt [23] investigated the effects of air gap on the optimum insulation thickness, insulation, and total costs, energy saving, payback period, fuel consumption, and emissions of CO2 and SO2 in the composite wall construction for a prototype building in a sample city, Karabük/Turkey. He found that when 2, 4, and 6 cm of the air gap thicknesses were used, the fuel consumption, and CO2 and SO2 emissions were decreased by 44.98, and 54.46%, respectively.
Energy consumption for space heating in Turkey is very high. Low quality fuel consumption together with the increasing energy demands for space heating have caused very high air pollution and poor air quality on occasion during heating period in Afyonkarahisar/Turkey. Afyonkarahisar is one of the coldest cities of Turkey. Afyonkarahisar has the most severe winter condition, where a large amount of energy is used to heat buildings. Buildings with low insulation thickness, increasing building construction and lack of passive solar applications in buildings are causes of increasing fuel consumption. For heating, coal is mostly consumed but fuel oil is used up less. There are about 25,126 buildings in Afyonkarahisar and about 48,000 tons coal, 15.6 million m3 natural gas, 9 million m3 geothermal fluid for geothermal heating and 4700 tons fuel-oil of fuel consumptions per year [24]. In this study, the thickness, energy-saving, payback period, annual fuel consumption and emissions of CO, CO2 and SO2 for insulation in district heating pipelines is determined depending on LCC analysis via P1-P2 method by considering the heat conductivity and price of the insulation material, average temperature in the region, fuel price for the heating and factors related to regulations, and the results obtained are evaluated.
Section snippets
Methodology
The heating piping pipeline considered in this study is shown in Fig. 1. It is a long straight pipe segment, installed in an environment at temperature and pressure, which are also identical to those of the dead state. The assumptions are a constant environmental temperature and constant thermodynamic properties at an appropriate mean temperature. Besides, the hot water for a district heating pipeline is pumped through the pipe with a constant velocity.
Result and discussions
In this study, economic and environmental impacts of insulation in district heating pipelines are investigated for heating loads in the city of Afyonkarahisar in Turkey by using the parameters shown in Table 1, Table 2, Table 3. Using the LCC analysis over a building lifetime of 10 years, the optimum insulation thicknesses for pipeline of district heating are calculated for five different types of fuel, namely, coal, natural gas, fuel-oil, LPG and geothermal fluid. Also, the energy savings,
Conclusions
In this study, economic and environmental impacts of insulation of district heating pipeline have been investigated. In the calculations, coal, natural gas, fuel-oil, LPG and geothermal energy was used as the fuel source and the rock wool as the insulation material. Also, the energy savings, payback periods and emissions of CO, CO2 and SO2 resulting from the use of insulation material and various nominal pipe sizes were evaluated. The results show that optimum insulation thickness changes
Acknowledgements
The authors are very grateful to the editor and the reviewers for their valuable and constructive comments, which have been utilized in improving the quality of the paper.
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