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Reuse of Abandoned Oil Wells Using a Geothermal-Based Hybrid ORC Unit/Thermoelectric Generator: Energy,Exergy, Thermo-economic Analyses and Multi-criteria Optimisation

Ali Ahmadi, Mohammad | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 52738 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Moosavi, Ali; Sadr Hosseini, Hani
  7. Abstract:
  8. In this thesis, three novel geothermal-based ORC systems are proposed to enhance efficiency and to recover the waste heat recovery. The proposed systems are modeled based on basic ORC system (concept 1), ORC system with internal heat exchanger (concept 2), and regenerative ORC system (concept 3). Accordingly, two thermoelectric generators are introduced into the systems to exploit the waste heat of the system. For this purpose, the condenser is replaced by a TEG unit, while the other TEG unit is employed to recover the waste heat of the reinjected geothermal fluid. A comprehensive numerical investigation is conducted to compare the proposed systems from thermodynamic and thermo-economic points of view. Furthermore, the most favorable proposed system is considered for optimization purposes using multi-criteria optimization using genetic algorithm. Accordingly, a Pareto frontier is extracted consisting of the optimal solutions along with the scatter distribution of the critical parameters. The results show that the second proposed concept has the highest exergy and energy efficiency among the studied systems. In addition, the concept concludes the highest power output from the employed TEG units. The results further show that first concept has the least associated cost with the system and lower payback period at the same time higher net power generation. The exergy efficiency and total product cost of the systems at the baseline are 59.39%, 57.92% and 60.27%, 25.8 $/GJ, 28.79 $/GJ, and 31.27 $/GJ respectively for 1st, 2nd, and 3rd proposedvi concepts. Results of the multi-criteria optimisation of the third concept reveal that the superheater temperature difference should be kept at higher values while the optimal range of the figure of merit is 0.9–1.6. To sum up, the proposed system can be designed practically to exploit the geothermal heat source and recover the waste heat of the system
  9. Keywords:
  10. Exergy ; Thermoelectric Generator ; Rankin Cycle ; Thermoeconomic Analysis ; Geothermal Energy ; Abandoned Oil Wells

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