Assessment of the geothermal potential for energy generation in Sri Lanka

Abstract

Geothermal energy is the heat extracted from the subsurface of the earth. The heat loss of the earth is higher at plate boundaries compared in the tectonic plates. The global heat loss is about 44TW where volcanic eruptions in the range 2.4 – 4.0 TW. Sri Lanka has not located geologically favor conditions for geothermal energy development it has nine hot water springs in the eastern and southern region of the country. Out of nine 7 were located in the Vijayan complex. Geochemical analysis of geothermal water of 6 selected hot water springs and the resistivity depth cross sections for few magnetotelluric tested traverses were used for the assessment of geothermal potential in southern and eastern regions of Sri Lanka. Geothermal energy potential for 1 km3 reservoir near the six hot springs in southern and eastern of Sri Lanka can be calculated around 5.76 MW in Mahapelessa to 34.86 MW in Marangala. Based on the geochemical analysis, average temperatures of the geothermal reservoirs are around 120-160°C for MP, KI, KP and NW and for Marangala, Maha Oya 390 and 230°C respectively. Also the water from Kapurella, Nelum wewa, Maha Oya has representing the characteristics of volcanic water and Marangala as steam heated water. Available potentials according to the magnetotelluric studies were well beyond the economical depth of exploration so located deep in the available magnetotelluric cross sections. However according to the chemical analysing the presence of intermediate reservoirs in between the traverse can be expected in shallower. Night time infrared photography can be used to explore the surface hot water accumulations hence can explore new hot springs. Other than the chemical concentrations, isotopes characterization is useful to detect the origin of the geothermal water. To identify the exact dimensions of the reservoirs three dimensional magnetotelluric testing should be done near the hot springs.