How Cooling Towers Affect the Performance of CO₂-based Geothermal Systems - Joint thesis with Factor2Energy

Summary

Beschreibung Geothermal power plants represent a reliable alternative to conventional power generation, offering baseload electricity production without the intermittency associated with wind or solar energy. Traditionally, geothermal electricity has been generated using water-based systems, either through direct flash cycles or binary Organic Rankine Cycle (ORC) plants. Over the past decade, an alternative technology based on supercritical carbon dioxide (sCO₂) circulating in the subsurface has emerged and has been investigated in numerous research projects as a potential next-generation geothermal power (NGP) system. These systems offer several thermophysical advantages compared to classical hydrothermal concepts, such as enhanced heat transport properties, improved thermosiphon effects, and potentially reduced pumping requirements [1, 2, 3]. Previous work has demonstrated the thermodynamic potential of sCO₂-based geothermal systems across a wide range of boundary conditions, and first-order cost assessments indicate that they may be competitive with state-of-the-art geothermal technologies under certain conditions. A distinguishing feature of these systems, however, is their strong sensitivity to surface conditions: because the CO₂ is cooled and recompressed at the surface before being re-injected, the achievable cycle performance depends directly on the cooling temperature that can be reached. Compared with conventional hydrothermal plants, NGP concepts are therefore far more dependent on the choice and operating conditions of the cooling system, which makes cooling tower technology a decisive factor for both performance and cost. Despite this, the influence of different cooling tower types on the performance of sCO₂-based geothermal power has so far received little systematic attention. The main objective of this thesis is to model and implement different cooling towers (dry, wet, direct fresh-water cooling, etc.) within our main internal calculation software tool in Python. Particular attention will be given to the differences between the technologies, the conditions under which each can be used, and the cost of each. The work will further address the impact on cost and LCOE when a given technology cannot be used and a shift to another becomes necessary, for example, when a lack of makeup water rules out wet cooling towers. Work steps: • Literature review and evaluation of previous work • Develop a computational model (Python) to simulate different cooling technologies • Harmonize boundary conditions and design constraints to run parametric and sensitivity analyses • Extend the analysis to include economic evaluation, comparing different technologies in terms of LCOE • Compare the technologies and identify favourable operating regimes • Documentation of the work Literature: [1] Adams et al.: A comparison of electric power output of CO2 Plume Geothermal (CPG) and brine geothermal systems for varying reservoir conditions, Applied Energy 140, 265-377 (2015) [2] Randolf, J.B., Saar, M.O.: Coupling carbon dioxide sequestration with geothermal energy capture in naturally permeable, porous geologic formations:implications for CO2sequestration. Energy Procedia 4, 2206–2213, (2011) [3] Van Brummen, A. C., Adams, B. M., Wu, R., Ogland-Hand, J. D., & Saar, M. O. (2022). Using CO₂-plume geothermal (CPG) energy technologies to support wind and solar power in renewable-heavy electricity systems. Renewable and Sustainable Energy Transition, 2, 100026. doi.org/10.1016/j.rset.2022.100026 Voraussetzungen Please send the application (CV and grade list) to c.schifflechner<script>document.write('@');</script> <noscript>(at)</noscript>tum.de