A Multi-Criteria Decision-Support Framework for Evaluating Alternative Fuels and Technologies Toward Zero Emission Shipping Georgios Remoundos, Anna Maria Kotrikla, Maria Lekakou, Amalia Polydoropoulou, George Papaioannou, Ioannis Pervanas, George Kosmadakis, Stelios Contarinis Journal of Marine Science and Engineering, 2026 This paper presents an MAUT-based decision-support framework, developed within the NAVGREEN project, to enable the evaluation of alternative fuels and technologies in shipping decarbonization pathways toward zero-emission targets. The framework integrates stakeholder-derived weights elicited through the Analytic Hierarchy Process (AHP) and systematically evaluates alternatives across five criteria: cost, technological maturity, safety and regulatory compatibility, carbon footprint, and social acceptability. Alternatives are mapped into a common utility space through criterion-specific utility functions and aggregated into a composite utility score, enabling transparent and reproducible comparison of single and combined solutions. To strengthen applicability beyond a single illustrative application, the study incorporates a structured scenario and sensitivity analyses (policy stringency, infrastructure constraints, conservative regulatory environments, and weight and parameter perturbations) to assess ranking stability under plausible future conditions. A case study on an Ultramax bulk carrier is used solely to demonstrate the operability and workflow of the method, rather than to empirically validate technology choices across all ship types. Optional AI-assisted elicitation may be used as a supporting aid to harmonize indicative inputs when data are incomplete; however, validation of AI-generated estimates is outside the scope of the present study and is identified as future work.
Investigating the combustion, NO emissions and cyclic variability (CCV) in SI engine fueled with ammonia-hydrogen blends by two-zone quasi-dimensional model with two CCV governing mechanisms D.C. Rakopoulos, C.D. Rakopoulos, G.M. Kosmadakis, W. Tutak, M. Gruca International Journal of Hydrogen Energy, 2025 The cyclic variability (CCV) of performance, combustion, and nitric oxide (NO) emissions in spark-ignition (SI) engine fueled with various ammonia-hydrogen blends is investigated, employing previously validated, in-house, quasi-dimensional turbulent-combustion model tracking the flame-front propagation in engine-cylinder, expanded herein to treat ammonia-hydrogen blends. The model is validated successfully at steady-state against experimental data and then enhanced to study behavior of same attributes under CCV conditions comparing against experimental data, considering influence of two governing mechanisms, flame-kernel turbulence and fuel-air ratio variations. The steady-state numerical results included cylinder-pressure (CP), indicated mean effective pressure (IMEP), combustion-stages duration and NO emissions, using for CCV investigation mean-values, coefficients of variation, frequency-distributions and scatter-plot diagrams. The model allows computation of e.g. turbulent-intensity, integral-length and flame-speed, which afford elucidating the effects of ammonia enrichment with hydrogen. The COV of CP and IMEP decrease with hydrogen addition, peak temperatures COV are ∼1 % and for NO up to 40 %.
Quantitative Risk Analysis of Hydrogen for Ship Bunkering Operations O. Aneziris, I. Koromila, G. Kosmadakis, A. Stubos Innovations in Sustainable Maritime Technologyimam 2025 Ship Operations Autonomy Safety Digitalization Human Factors Logistics Shipyard Organization, 2025
INTEGRATION OF LIQUID ORGANIC HYDROGEN CARRIER WITH SOLID OXIDE FUEL CELL AND WASTE HEAT RECOVERY SOLUTIONS FOR MARITIME USE 38th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2025, 2025
DESIGN AND EXPERIMENTAL EVALUATION OF A FULL SCALE HIGH TEMPERATURE HEAT PUMP WITH VAPOUR INJECTION FOR MARINE WASTE HEAT RECOVERY USING LOW - GWP REFRIGERANT R1233ZD(E) 38th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2025, 2025
ENERGY AND THERMAL COMFORT INVESTIGATION OF A PASSIVE HOUSE BUILDING USING FIELD MONITORING DATA 38th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2025, 2025
ACHIEVING POSITIVE ENERGY BUILDING RENOVATION USING A UNIVERSAL ONE-STOP-SHOP PREFABRICATED SOLUTION 38th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2025, 2025
Comparing Prior and Learned Time Representations in Transformer Models of Timeseries Natalia Koliou, Tatiana Boura, Stasinos Konstantopoulos, Georgios Meramveliotakis, George Kosmadakis ACM International Conference Proceeding Series, 2024 What sets timeseries analysis apart from other machine learning exercises is that time representation becomes a primary aspect of the experiment setup, as it must adequately represent the temporal relations that are relevant for the application at hand. In the work described here we study wo different variations of the Transformer architecture: one where we use the fixed time representation proposed in the literature and one where the time representation is learned from the data. Our experiments use data from predicting the energy output of solar panels, a task that exhibits known periodicities (daily and seasonal) that is straight-forward to encode in the fixed time representation. Our results indicate that even in an experiment where the phenomenon is well-understood, it is difficult to encode prior knowledge due to side-effects that are difficult to mitigate. We conclude that research work is needed to work the human into the learning loop in ways that improve the robustness and trust-worthiness of the network.
Trilateral Flash Cycle for efficient low-temperature solar heat harvesting- A case study Anastasios Skiadopoulos, Christina Antonopoulou, Konstantinos Atsonios, Panagiotis Grammelis, Apostolos Gkountas, Panteleimon Bakalis, George Kosmadakis, Dimitris Manolakos 36th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2023, 2023
PERFORMANCE AND ECONOMIC EVALUATION OF A REVERSIBLE HIGH-TEMPERATURE HEAT PUMP/ORC FOR WASTE HEAT RECOVERY IN THE MARINE SECTOR International Seminar on Orc Power Systems, 2021
Waste heat recovery with high-temperature heat pumps for steam generation: performance and cost effects ECOS 2021 34th International Conference on Efficency Cost Optimization Simulation and Environmental Impact of Energy Systems, 2021
Renewable Energy Based Systems with Heat Pumps for Supplying Heating and Cooling in Residential Buildings ECOS 2021 34th International Conference on Efficency Cost Optimization Simulation and Environmental Impact of Energy Systems, 2021
PRELIMINARY OPERATION ASSESSMENT OF A TWO-STAGE ORC ENGINE COMBINED WITH EVACUATED TUBE SOLAR COLLECTORS THROUGHOUT GREECE International Seminar on Orc Power Systems, 2021
THERMODYNAMIC LOW-ORDER MODEL FOR THE SIMULATION OF TWO-PHASE EXPANSION IN A TFC UNIT International Seminar on Orc Power Systems, 2021
Reverse electrodialysis heat-engine: Case studies of improving energy efficiency through recovery of low temperature excess heat Eceee Industrial Summer Study Proceedings, 2018
Comparative analysis of three simulation models applied on a motored internal combustion engine Proceedings of the 24th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2011, 2011
Simulation of a motored internal combustion engine using an improved CFD model Proceedings of the 23rd International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems ECOS 2010, 2010
Comparing the results obtained from a CFD and a Quasi-dimensional model used to investigate the effect of various piston bowl geometries of a HSDI Diesel engine under motoring conditions ECOS 2008 Proceedings of the 21st International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems, 2008
Evaluation of a new CFD model for internal combustion engines using hydrogen under motoring conditions ECOS 2007 Proceedings of the 20th International Conference on Efficiency Cost Optimization Simulation and Environmental Impact of Energy Systems, 2007
RECENT SCHOLAR PUBLICATIONS
A Multi-Criteria Decision-Support Framework for Evaluating Alternative Fuels and Technologies Toward Zero Emission Shipping G Remoundos, AM Kotrikla, M Lekakou, A Polydoropoulou, ... Journal of Marine Science and Engineering 14 (4), 346 , 2026 2026
Investigating the combustion, NO emissions and cyclic variability (CCV) in SI engine fueled with ammonia-hydrogen blends by two-zone quasi-dimensional model with two CCV … DC Rakopoulos, CD Rakopoulos, GM Kosmadakis, W Tutak, M Gruca International Journal of Hydrogen Energy 184, 151889 , 2025 2025 Citations: 5
Quantitative Risk Analysis of Hydrogen for Ship Bunkering Operations OAI Koromila, G Kosmadakis, A Stubos Innovations in Sustainable Maritime Technology—IMAM 2025: Ship Operations … , 2025 2025
Bringing reversible ORC-heat pump systems into the market: A perspective on the current obstacles and future application potential S Christopher, A Marco, K Sotirios, R Tryfonas, B Marcus, W Maximilian, ... 8th International Seminar on ORC Power Systems 2025 , 2025 2025
Development and evaluation of an advanced control algorithm of a heat pump system combined with PVT collectors for Domestic Hot Water production G Meramveliotakis, T Boura, G Kosmadakis, S Konstantopoulos The 38th International Conference on Efficiency, Cost, Optimization … , 2025 2025
Design and experimental evaluation of a full scale high temperature heat pump with vapour injection for marine waste heat recovery using low - gwp refrigerant R1233zd(e) G Meramveliotakis, A Gkountas, G Kosmadakis, P Bakalis The 38th International Conference on Efficiency, Cost, Optimization … , 2025 2025
Integration of liquid organic hydrogen carrier with solid oxide fuel cell and waste heat recovery solutions for maritime use A Pavlidi, G Meramveliotakis, G Kosmadakis, A Stubos The 38th International Conference on Efficiency, Cost, Optimization … , 2025 2025
Testing and characterisation of a scroll compressor with vapour injection using R454C as a drop in refrigerant in a water source heat pump G Meramveliotakis, G Kosmadakis, S Karellas International Journal of Refrigeration 176, 359-372 , 2025 2025 Citations: 8
Development of an ammonia combustion model integrated in a 3D-CFD code for assessing the performance and NO emissions of an ammonia-hydrogen fueled spark-ignition engine GM Kosmadakis, DC Rakopoulos, W Tutak, A Jamrozik, CD Rakopoulos International Journal of Hydrogen Energy 99, 739-751 , 2025 2025 Citations: 10
Hybrid solar-biomass residential micro–Combined Heat and Power systems driven by the Partially Evaporating Organic Rankine Cycle–A case study in Southern Europe A Skiadopoulos, G Kosmadakis, X van Heule, S Lecompte, M De Paepe, ... Thermal Science and Engineering Progress 55, 102906 , 2024 2024 Citations: 8
Comparing Prior and Learned Time Representations in Transformer Models of Timeseries N Koliou, T Boura, S Konstantopoulos, G Meramveliotakis, G Kosmadakis Proceedings of the 13th Hellenic Conference on Artificial Intelligence, 1-9 , 2024 2024
Exergy analysis in highly hydrogen-enriched methane fueled spark-ignition engine at diverse equivalence ratios via two-zone quasi-dimensional modeling DC Rakopoulos, CD Rakopoulos, GM Kosmadakis, EG Giakoumis, ... Energies 17 (16), 3964 , 2024 2024 Citations: 5
Industrial waste heat potential and heat exploitation solutions G Kosmadakis Applied Thermal Engineering 246, 122957 , 2024 2024 Citations: 33
Parametric comparison of a CPVT performance evaluation under standard testing procedures-ISO 9806: 2017 and IEC 62108: 2016-for an automated and manual 2-axis tracking solar … D Cabral, G Kosmadakis, E Mathioulakis Energy Reports 11, 1242-1255 , 2024 2024 Citations: 9
Predicting Solar Heat Production to Optimize Renewable Energy Usage T Boura, N Koliou, G Meramveliotakis, S Konstantopoulos, G Kosmadakis arXiv preprint arXiv:2405.09972 , 2024 2024 Citations: 2
Optimal control of a heat pump-based energy system for space heating and hot water provision in buildings: Results from a field test BV Mbuwir, D Geysen, G Kosmadakis, M Pilou, G Meramveliotakis, ... Energy and Buildings 310, 114116 , 2024 2024 Citations: 30
Waste heat upgrading with high-temperature heat pumps for assisting steam generation in ships: performance, cost and emissions benefits G Kosmadakis, G Meramveliotakis, P Bakalis, P Neofytou Applied Thermal Engineering 236, 121890 , 2024 2024 Citations: 29
Assessing the cyclic variability of combustion and NO emissions in hydrogen-methane fueled HSSI engine via quasi-dimensional modeling under the influence of flame-kernel … DC Rakopoulos, CD Rakopoulos, GM Kosmadakis, GC Mavropoulos Energy 288, 129813 , 2023 2023 Citations: 20
Numerical modeling of flashing in TFC expanders for the efficient exploitation of low-grade heat A Skiadopoulos, G Kosmadakis, S Lecompte, M De Paepe, D Manolakos Thermal Science and Engineering Progress 46, 102171 , 2023 2023 Citations: 3
Modeling of an integrated renewable-energy-based system for heating, cooling, and electricity for buildings M Pilou, G Kosmadakis, G Meramveliotakis Energies 16 (12), 4691 , 2023 2023 Citations: 7
MOST CITED SCHOLAR PUBLICATIONS
Industrial waste heat: Estimation of the technically available resource in the EU per industrial sector, temperature level and country M Papapetrou, G Kosmadakis, A Cipollina, U La Commare, G Micale Applied Thermal Engineering 138, 207-216 , 2018 2018 Citations: 652
Estimating the potential of industrial (high-temperature) heat pumps for exploiting waste heat in EU industries G Kosmadakis Applied Thermal Engineering 156, 287-298 , 2019 2019 Citations: 236
On site experimental evaluation of a low-temperature solar organic Rankine cycle system for RO desalination D Manolakos, G Kosmadakis, S Kyritsis, G Papadakis Solar Energy 83 (5), 646-656 , 2009 2009 Citations: 203
Critical evaluation of current heat transfer models used in CFD in-cylinder engine simulations and establishment of a comprehensive wall-function formulation CD Rakopoulos, GM Kosmadakis, EG Pariotis Applied Energy 87 (5), 1612-1630 , 2010 2010 Citations: 202
Techno-economic analysis of high-temperature heat pumps with low-global warming potential refrigerants for upgrading waste heat up to 150 C G Kosmadakis, C Arpagaus, P Neofytou, S Bertsch Energy Conversion and Management 226, 113488 , 2020 2020 Citations: 188
Simulation and economic analysis of a CPV/thermal system coupled with an organic Rankine cycle for increased power generation G Kosmadakis, D Manolakos, G Papadakis Solar Energy 85 (2), 308-324 , 2011 2011 Citations: 176
Assessment of methodologies and data used to calculate desalination costs M Papapetrou, A Cipollina, UL Commare, G Micale, G Zaragoza, ... Desalination 419, 8-19 , 2017 2017 Citations: 150
Economic assessment of a two-stage solar organic Rankine cycle for reverse osmosis desalination G Kosmadakis, D Manolakos, S Kyritsis, G Papadakis Renewable Energy 34 (6), 1579-1586 , 2009 2009 Citations: 149
Identification of behaviour and evaluation of performance of small scale, low-temperature Organic Rankine Cycle system coupled with a RO desalination unit D Manolakos, G Kosmadakis, S Kyritsis, G Papadakis Energy 34 (6), 767-774 , 2009 2009 Citations: 142
Experimental comparative assessment of butanol or ethanol diesel-fuel extenders impact on combustion features, cyclic irregularity, and regulated emissions balance in heavy … CD Rakopoulos, DC Rakopoulos, GM Kosmadakis, RG Papagiannakis Energy 174, 1145-1157 , 2019 2019 Citations: 127
Investigating the EGR rate and temperature impact on diesel engine combustion and emissions under various injection timings and loads by comprehensive two-zone modeling CD Rakopoulos, DC Rakopoulos, GC Mavropoulos, GM Kosmadakis Energy 157, 990-1014 , 2018 2018 Citations: 122
Comparative Evaluation of Ethanol, -Butanol, and Diethyl Ether Effects as Biofuel Supplements on Combustion Characteristics, Cyclic Variations, and Emissions … DC Rakopoulos, CD Rakopoulos, EG Giakoumis, NP Komninos, ... Journal of Energy Engineering 143 (2), 04016044 , 2017 2017 Citations: 109
Performance investigation of concentrating solar collectors coupled with a transcritical organic Rankine cycle for power and seawater desalination co-generation C Li, G Kosmadakis, D Manolakos, E Stefanakos, G Papadakis, ... Desalination 318, 107-117 , 2013 2013 Citations: 109
Investigating the effect of crevice flow on internal combustion engines using a new simple crevice model implemented in a CFD code CD Rakopoulos, GM Kosmadakis, AM Dimaratos, EG Pariotis Applied Energy 88 (1), 111-126 , 2011 2011 Citations: 105
Methane/hydrogen fueling a spark-ignition engine for studying NO, CO and HC emissions with a research CFD code GM Kosmadakis, DC Rakopoulos, CD Rakopoulos Fuel 185, 903-915 , 2016 2016 Citations: 101
Investigation of piston bowl geometry and speed effects in a motored HSDI diesel engine using a CFD against a quasi-dimensional model CD Rakopoulos, GM Kosmadakis, EG Pariotis Energy Conversion and Management 51 (3), 470-484 , 2010 2010 Citations: 100
Parametric theoretical study of a two-stage solar organic Rankine cycle for RO desalination G Kosmadakis, D Manolakos, G Papadakis Renewable Energy 35 (5), 989-996 , 2010 2010 Citations: 93
CFD modeling and experimental study of combustion and nitric oxide emissions in hydrogen-fueled spark-ignition engine operating in a very wide range of EGR rates GM Kosmadakis, CD Rakopoulos, J Demuynck, M De Paepe, S Verhelst International Journal of Hydrogen Energy 37 (14), 10917-10934 , 2012 2012 Citations: 91
Experimental investigation of a low-temperature organic Rankine cycle (ORC) engine under variable heat input operating at both subcritical and supercritical conditions G Kosmadakis, D Manolakos, G Papadakis Applied thermal engineering 92, 1-7 , 2016 2016 Citations: 87
Comparative thermodynamic study of refrigerants to select the best for use in the high-temperature stage of a two-stage organic Rankine cycle for RO desalination G Kosmadakis, D Manolakos, S Kyritsis, G Papadakis Desalination 243 (1), 74-94 , 2009 2009 Citations: 86
