Master of Philosophy (M.Phil.)

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Browsing Master of Philosophy (M.Phil.) by Author "Premasiri, HMR"

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    item: Thesis-Full-text
    Development of a methodology to assess the geothermal energy potential in Sri Lanka
    Nanayakkara, GD; Premasiri, HMR
    Assessing geothermal potential is a difficult task. It is a time and money consuming process. There are many methodologies, such as deep drilling bore holes and measure temperature by using thermal sensors, silicon solubility measurement, magneto telluric, etc. The used equipment for these methods, especially for drilling of deep bore holes are much expensive. If geothermal gradient is very low, the area cannot be effectively used to establish a geothermal power plant. Another method based on contents of amorphous silica in hot spring water is also used to determine the geothermal gradient. Main task of this study is to find a suitable cost effective method to assess the geothermal potential in Sri Lanka and to develop a lab scale plant. As a cheaply available geophysical technique, ground resistivity measurement was also used to measure the temperature. Increasing temperature again increases their resistance. This natural phenomenon has been used to develop a methodology to assess the geothermal potential in various countries. Resistivity surveys have been carried out in various places in Sri Lanka. Gathered resistivity data has been analyzed. Geothermal gradient calculation was done in Bogala Graphite Mines to study about the temperature gradient in Sri Lanka. Also this selected place was far away from hot spring areas and hence those hot springs had no influence to the collected data. This method is suitable to find temperature gradient of Sri Lanka. The average values of temperatures in those levels were computed and then geothermal gradient was calculated which is 28.0460C/km. This method gave some reliable information as to how the temperature gradient varies at crustal level of rocks in Sri Lanka. To calculate power generation, a laboratory model was developed with the possibility of applying varying parameters. Collected the annual average temperature data and predicted the temperature gradient of various districts. According to the calculations done, geothermal gradient in Sri Lanka is varying between 23 0C and 30 0C per km. This information has been used to develop the geothermal map of Sri Lanka. Laboratory plant was developed and its performances were studied for varying hot spring temperatures and all data gathered and analyzed. According to that the geothermal temperature gradient in Sri Lanka is suitable to generate electricity. But the water flow rate is not sufficient to produce more power.
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    item: Thesis-Abstract
    Development of conceptual geological model for the formation of hot water springs in Sri Lanka
    Premasiri, HMR; Wijesekara, DS; Weerawarnakula, S; Puswewala, UGA; Abeysinghe, AMKB
    As natures wonderful gift, several hot water springs occur in Sri Lanka though it does not fall within very active tectonic zone in the earth. They are mostly confined to the eastern sector of the island. However, hot water springs at Mahapelassa off Embilipitiya, Kanniyai off Trincomalee and Mahaoya are well known to people. These thermal springs show their out flow temperature ranging between 34°C to 56°C. The hottest springs lie at Kapurella (56°C), followed by Mahaoya (55°C), Marangala-Wahawa close to Padiyatalawa (42-45 ° C ), Mahapelassa (44-46 DC) and Nelumwewa, which was known earlier as Madawewa and now under a lake, records 45° C in mud samples (Fonseka 1994). The present research was aimed out mainly to model the formation of hot water springs in Sri Lanka based on geological and tectonic settings using geological, geophysical and Remote Sensing techniques while evaluating the hot water springs for their potential as energy resources or development as places for eco-tourism. Geological, structural and tectonic setting of the areas have been studied using geological, geochemical and geophysical techniques. Both field and libratory studies were carried out in order to compile geological and geophysical profiles and to determine geochemical and physical parameters of hot water springs in Sri Lanka. According to the results of this study, the major boundary between Highland Complex and Vijayan Complex show multiple thrust planes and shear zones showing imbrecated lithological slices of both Highland Complex and Vijayan Complex. Other than the ductile structures, brittle fractures, joints and fault planes extend as mega lineament for several kilometers. These lineaments produce good secondary aquifer conditions with adequate porosity. The surface mapping and geophysical evidence of the lineaments show that they are very deep and are interconnected. Therefore, they offer better pathways for surface water to percolate deep levels and return upwards with adequate pressure to reach the surface after heating. These structurally controlled hot water springs in Sri Lanka are associated with deep geologically weak zones of fracture or fault systems within the tectonically active thrust boundary. According to geochemical parameters and field evidence, hot water springs in Sri Lanka can be divided into three groups, Groupl: Mahapelassa Group 2: Kapurella, Mahaoya, Padiyatalwa , Palanoya and other around the Mahiyangana, Ampara and Group 3: Kannyai, Rathkhiriya and Adampane areas.). According to the chemical and physical parameters of hot water it can be concluded that Group (1) and Grou (3) are more suitable for therapeutic uses and have a good potential for development for eco-tourism. The Group (2) has hot water with low contaminations of salt, and show fairly high potential for generation of geothermal energy