Techno-economic analysis and supply chain optimisation for CCS and bioenergy in hard-to-abate sectors

This thesis investigates the feasibility of deploying carbon capture and storage (CCS) and bioenergy in hard-to-abate sectors through techno-economic analysis and supply chain optimisation. It focuses on (i) dispatchable fossil fuel power plants serving as backups in power systems with high penetrations of variable renewable electricity (VRE), and (ii) sectors such as cement, steel, and industries that rely on combined heat and power (CHP) systems. First, a techno-economic model is developed to assess the cost of CCS integration into natural gas combined-cycle gas turbine (CCGT) power plants to account for the kinds of capacity factors expected in high VRE power systems. Results show that as CCGT capacity factors decrease due to VRE expansion, CCS costs per tonne of CO₂ captured rise significantly, strongly affecting the levelised cost of electricity (LCOE) for the CCGT. For example, at 70% CCGT capacity factor and NG price of 40 €/MWh, a CO₂ emission price of around ~170 €/tCO₂ is needed for the LCOE with CCS to remain lower than without CCS. At 30% CCGT capacity factor, this figure is over 300 €/tCO₂. Higher NG prices require even greater CO₂ prices to sustain cost-effectiveness. Sensitivity analysis indicates that reducing the fixed costs of capture systems is more beneficial than enhancing capture efficiency, especially for low capacity factor operations. Building on these results, the study investigates the broader impact of low capacity factor power plants on the entire CCS supply chain through a case study for the island of Ireland. Techno-economic models are developed for CO₂ capture from cement, metals production, and CHP-dependent industries, along with transportation models (via truck, pipeline and ship) and CO₂ storage. Ten scenarios, with and without fossil fuel power plants and CHP industries, are evaluated. Findings reveal that, for the same quantity of CO₂ processed, building shared infrastructure only for emission sites with long-term CO₂ supply certainty (e.g., process emissions from cement and metal industries) reduces total infrastructure costs by up to 34% compared to initially accommodating all sources and subsequently losing CO₂ supply from fossil fuel based emission sites. Finally, the work examines bioenergy supply chains, focusing on hydrothermal carbonisation (HTC) of wet biomass residues to produce hydrochar as a coal substitute in steel mills. A Swedish case study covering 21 paper plants and two steel mills is conducted, assuming a configuration with (i) onsite HTC, due to the high moisture content of paper sludge, and (ii) centralised drying and pelletisation. Techno-economic models are developed for all stages. The study emphasises the importance of a non-linear optimisation approach to identify optimal hub locations and sizes without predefined sets, demonstrating a 35% cost reduction compared to decentralised configurations for the case study. The findings also indicate that maintaining lower moisture levels in pressed cakes, which is a HTC intermediate product, is essential not only for minimising transportation costs but also for enabling fewer hubs to fully leverage the cost advantages of economies of scale. Overall, this thesis makes novel contributions to advancing CCS and bioenergy supply chain research. It examines the feasibility of CCS integration in power plants with low capacity factors and explores other influencing parameters. Additionally, it highlights the need for careful emission site selection before full-scale CCS implementation in hard-to-abate sectors. Finally, it demonstrates the advantages of non-linear optimisation for determining optimal hub locations and sizes in bioenergy supply chains.

Funder

European Commission, F-CUBED Horizon 2020 project (Grant Agreement No. 884226)
Sustainable Energy Authority of Ireland (SEAI) Project No. RDD447

Publisher

University of Galway

Rights

CC BY-NC-ND

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Collections

University of Galway Theses (PhD Theses)