Session: 30-14 Waste Heat Recovery & Geothermal

Paper Number: 123967

123967 - Performance of sCO2 Cycles for Waste Heat Recovery and Techno-Economic Perspective As Gas Turbine Bottoming Cycle 

Supercritical carbon dioxide (sCO₂) cycles are a promising technology offering compact and cost-effective means of energy generation. Their flexibility makes them widely adaptable to various heat sources, including the waste heat from gas turbine (GT) exhaust gases. In their simple cycle configurations, GTs typically reach a maximum efficiency of around 40%. The cycle efficiency can be enhanced to approximately 60% by introducing a bottoming cycle. Yet, the substantial investments required for traditional steam cycles render them less appealing for smaller GTs. This creates an opportunity for sCO₂ cycles, but a comprehensive overview of their performance in various applications remains lacking. There is thus a clear need to compare sCO₂ potential with that of conventional steam cycles across a range of applications, particularly for heat sources spanning from 200°C to 800°C. Moreover, their applicability to various industrial scenarios based on existing installations is lacking from a techno-economic standpoint. To address these needs, the performances of four promising sCO₂ cycles are evaluated with Aspen Plus and compared with the simple steam cycle. Our analysis is then extended applying those cycles to 20 industrial GTs, considering efficiency, capital costs, and LCOE. We also explore the integration of sCO₂ cycles in larger CCGT units incorporating amine-based carbon capture systems. Our analysis yielded performance maps demonstrating that sCO₂ cycles exhibit comparable performance to conventional steam technology. Notably, our findings reveal that sCO₂ cycles offer significant techno-economic advantages as bottoming cycles for smaller GTs. However, when it comes to larger GTs, such as the SGT5 9000HL combined with a three-pressure steam cycle, sCO₂ can only outperform them at elevated pressure levels exceeding current technological standards (more than 300 bar). Delving deeper into the inherent distinctions between these two technologies, we found that sCO₂ cycles facilitate cogeneration, offering an attractive alternative. To integrate the heat requirements of amine-based carbon capture systems, we have designed various approaches, but steam cycles have always proved more suitable because of the thermal stability of amines. In conclusion, our research promotes sCO₂ cycles as a mean to enhance the efficient utilization of energy in both existing and forthcoming GT installations and other heat recovery applications. The findings underscore the cost-effectiveness and adaptability of sCO₂ cycles, particularly as bottoming cycles for smaller gas turbines, while larger gas turbines present a challenge. Our work conducted with Aspen sheds light on the substantial promise of sCO₂ cycles, encouraging further exploration and implementation of these systems in the energy sector.

Presenting Author: Vincent Thielens University of Mons

Presenting Author Biography: Vincent THIELENS has recently graduated in mechanical engineering with a specialist focus on energy from UMONS. He works in collaboration with UMONS and Engie Laborelec on sCO2 cycles and their use in waste heat recovery. THIELENS is also involved in the optimization of energy systems to achieve higher energy savings and studies the impact of EGR on CCGT coupled with amine-based carbon capture. THIELENS contributes to developing innovative solutions for efficient and environmentally-friendly energy production systems.

Authors:

Vincent Thielens University of Mons
Frederiek Demeyer Engie R&I Laborelec
Ward De Paepe University of Mons