key: cord-0078392-j6ugsubq authors: Chandrasekharam, D. title: Enhanced geothermal systems (EGS) for UN sustainable development goals date: 2022-05-20 journal: Discov Energy DOI: 10.1007/s43937-022-00009-7 sha: d0089ce8b728b176dc718170800845f6e5510410 doc_id: 78392 cord_uid: j6ugsubq nan the countries have huge EGS resources and how this energy source will help the countries to mitigate climate-related issues and secure food and water are highlighted here. The Western Arabian shield hosts numerous granite intrusives (Fig. 1 ), spread over a cumulative area of 161,467 sq. km, with high concentration of radioactive elements (U, Th, and K) and the radiogenic heat production (RHP) of these granites varies from 5 to 134 µW/m 3 [6, 7] ). The temperatures measured in certain bore-holes along the western margin of the shield gave geothermal gradients exceeding 80 °C/km. Temperature estimates at 2 and 3 km depth gave values of 230-300 °C [6, 7] ). Earlier EGS projects established in Soultz-sous-Forets, France and Cooper basin, Australia [9, 11] , estimated that 1 km 3 of such high radiogenic granites can generate 79 × 10 6 kWh of electricity. Assuming a 2% recovery of heat from such granites, the power generation capacity of the Midyan granite alone (Fig. 1) , located at the NW corner of the shield, exceeds 160 × 10 12 kWh. Fluid flow and heat transfer models using ANSYS/CFX demonstrate that this amount can be enhanced further to support industrial applications [14] . Saudi Arabia, though energy independent, is a water-stressed country and depends on groundwater for agriculture and domestic needs. The annual groundwater recharge is only 2.4 billion m 3 while the groundwater extraction is 20 billion m 3 . This additional water is withdrawn from the non-renewable (fossil) aquifer-the Saq-Ram sandstone aquifer. This is not a sustainable solution to meet water demand. Hence the country depends on food imports. Saudi Arabia's food imports have exceeded 70 million tons and the country has banned wheat production due to a lack of water for irrigation [8] . The country is unable to support per-capita "pita" (bread) production of 88 kg/y. Thus, wheat imports have surged from 1.9 to 3.03 million tonnes. To support other agricultural and domestic water supply, the country depends on 128 desalination plants, supported by fossil fuel-based energy, supplying freshwater at an energy input of 5 kWh/m 3 (MSF: Multistage Fractionation, [10] ). The source of energy being fossil fuel the emissions are around 5.43 kg CO 2 /m 3 of freshwater generated. EGS (with ScCO 2 as extraction fluid) has three advantages for Saudi Arabia. It can provide base-load uninterrupted energy, and freshwater (food security) and reduce CO 2 emissions. Turkey's EGS potential is also huge and similar to Saudi Arabia. High radiogenic Eocene and Miocene granites are spread over a cumulative area of 6910 sq. km along western Anatolia (Fig. 2) . Although the RHP of the granites of western Anatolia is lower than that of Saudi Arabian granites, the advantage Turkey has is the disposition of high-temperature isotherm (Curie point temperature-depth) at a very shallow depth (6 to 12 km [1, 3] and a foundered continental and thinned crust due to the Alpine-Himalayan orogeny. However, the heat flow values of western Anatolian region are very high (~ 154 W/m 2 ), which is higher than the heat flow values of the Arabian shield. The reservoir temperatures estimated based on the bottom-hole temperature of drill holes is about 180 °C at 3 km [3] . These granites can generate a minimum amount of 546 × 10 9 kWh [4] . Turkey has established a strong geothermal culture with its hydrothermal resource, generating 1658 MWe and providing district heating and greenhouse cultivation support. Turkey ranks the third position in the world with its geothermal energy generation. With the development of EGS, Turkey will emerge as a strong country establishing United Nations' Sustainable development Goals SDG) in another few years. With a high-temperature regime at shallow depth, the cost of drilling will drastically be come down allowing a lower levelised cost of electricity (LOCE). The entire western Anatolian region will be an experimental ground to perform innovative technology related to EGS, like developing loop technology to harness heat, carbon dioxide sequestration, supercritical carbon dioxide fluid circulation to extract heat and develop innovative methods to create fracture networks in the granites at 3 km depth. This provide an opportunity to refine the EGS technology. While the unit cost of energy projected based on earlier EGS projects (Soultz-sous-Forets, France and Cooper basin, Australia) was around 6 to 7 Eurocents, EGS projects in Turkey will provide a realistic unit cost of power in future. Like Solar PV [5] , EGS has no carbon footprint and the land footprint is very low. EGS will provide sound energy-water-food security to all the countries and remove the fiscal disparity between the countries and people and lead the world towards a net-zero emissions scenario. Geothermal resources for sustainable development: case study: Turkey Techno-economic performance of closed-loop geothermal systems for heat production and electricity generation Carbon dioxide emissions mitigation strategy through enhanced geothermal systems: western Anatolia High radiogenic granites of western Anatolia for EGS: a review CO 2 emissions from renewables: solar pv, hydrothermal and EGS sources CO 2 emission and climate change mitigation using the enhanced geothermal system (EGS) based on the high radiogenic granites of the western Saudi Arabian shield High heat generating granites of Western Saudi Arabian Shield. World Geothermal Congress Water for the millions: focus Saudi Arabia The relative costs of engineered geothermal system exploration and development in Australia Renewable energy driven innovative energy efficient desalination technologies Enhanced geothermal systems: the Soultz-sous-Forêts project Enhanced geothermal systems (EGS) using CO 2 as working fluid-a novel approach for generating renewable energy with simultaneous sequestration of carbon On production behavior of enhanced geothermal systems with CO 2 as working fluid A simplified coupled hydro-thermal model for enhanced geothermal systems Acknowledgements DC thanks TUBITAK (project No:120C079) for its support in this work. Author contributions 100% contribution by me. The author read and approved the final manuscript. 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