| Abstract |
A sustainable energy future for Turkey depends on a balanced low-carbon energy mix with continued access to geothermal resources since they are abundant, domestic, renewable and able to supply base load and high energy security. Over 30 years of utilization of hydrothermal systems enabled Turkey to break into the 1 GW Geothermal Country Club as of August 2017. Today, with an installed capacity of 1615 MWe ‘low-hanging fruit’ of geothermal energy have gone whereas enhanced geothermal systems (EGS) offer the chance to exploit more from the geological settings, previously taken as non-economic. This study aims to investigate the untapped potential of Kozak granodiorite as an enhanced geothermal reservoir to generate thermal and electrical power. Kozak pluton in Dikili-İzmir geothermal field is selected to be assessed with four different production scenarios, based on artificial reservoir volume and production purpose. Accessible resource base and recoverable heat energy are calculated by employing a probabilistic approach- Monte Carlo simulation. A sensitivity analysis is performed for the effects of reservoir parameters on heat potential. Sustainability attributes of the discussed cases are evaluated in terms of saved CO2 amount and saved money by employing a local energy source rather than an imported one. Based on the existing accessible resource base and recoverable heat in place calculations, net electrical power is 8 MWe for Kozak-EGS, with 90% probability. This amount increases to 17 MWe, with 50% probability and to 32 MWe, with 10% probability. On the other hand, net thermal power is 150 MWt for Kozak-EGS, with 90% probability. This amount increases to 300 MWt, with 50% probability and to 560 MWt, with 10% probability. Sensitivity analysis showed that the thickness and the area of the reservoir formation are the inputs that have greatest impact on accessible resource base and the recoverable heat energy outputs for real volume case. This is due to the large band of uncertainty regarding the bulk volume as a result of limited data. Since the reservoirs in EGS applications are man-made, a unit volume case is also considered for Kozak granodiorite reservoir. For a unit volume of 1 km3, based on P90 estimates, Kozak-EGS generates 3.8 MWe. This amount increases to 6.7 MWe, with 50% probability and to 10 MWe, with 10% probability. On the other hand, net thermal power is 72 MWt, with 90% probability. This amount increases to 118 MWt, with 50% probability and to 172 MWt, with 10% probability. In this case, the temperature and the recovery factor are the inputs that have greatest impact on the accessible resource base and the recoverable heat energy outputs for the unit-volume case. To highlight the sustainability attributes of the present study; the unit-volume case of Kozak EGS is selected to be compared with natural gas, the dominant player in Turkey’s energy supply. 3.8 MWe generated from 1 km3 of Kozak-EGS reservoir saves 13.4 million kg of CO2 and $ 1.2 million annually without any regulation for CO2-related tax. With a CO2 tax regulation such as 13.6 euro per tons of CO2, annual saved amount changes to $1.4 million from the operating companies’ perspectives. |