WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

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Author: search.filters.author.Koca, KemalHas files: No

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  • Article
    Exergy-Based Evaluation of High-CO2 Biogas/Diesel RCCI Combustion Heat Flow for Enhanced Mixture Distribution, Power Output, and Fuel-Energy Performance
    (Pergamon-Elsevier Science Ltd, 2026) Dalha, Ibrahim B.; El-Adawy, Mohammed; Wong, Nur Leena W. S.; Man, Hafsalina C.; Said, Mior A.; Koca, Kemal; Abdulsalam, Muhammed
    Utilising high-CO2 biogas in compression-ignition engines poses significant challenges due to poor mixture reactivity, inefficient combustion, and increased energy degradation. This work addresses these difficulties by conducting experimental research on a port-injection at the valve reactivity-controlled compression ignition (PIVE-RCCI) strategy. This study addresses these concerns by conducting experiments on a PIVE-RCCI technique to improve mixture distribution and combustion efficiency in biogas-diesel engines. The engine was modified to provide biogas through the inlet valve, allowing for controlled variations of biogas injection pressure (BIP: 1-4 bar) and port swirl ratio (PSR: 0-80%) at 1600 rpm and 4.9-5.7 bar IMEP. Energy and exergy analyses were used to determine the effect of intake flow dynamics on temperature uniformity, heat transfer, and power generation during combustion. The results reveal that normal airflow conditions minimise accounted heat loss, indicating higher thermal efficiency (ITE) and increased output power across all BIPs. In contrast, introducing a strong intake swirl dramatically improves combustion performance. The 80% PSR configuration resulted in the lowest exergy destruction and the maximum energy recovery potential, with an ITE of 26.54% at 4 bar BIP. Increasing BIP increased power output, whereas the optimal combustion work was found at 1 bar BIP and 40% PSR. The optimal working conditions were 1 bar BIP, 80% PSR, and 5.45 bar IMEP, which resulted in 26.00% exergy destruction, 39.38% destruction-to-released exergy ratio, 86.00% exergy-energy ratio of heat transfer, and 63.78% exhaust exergy-energy ratio. This work's novelty lies in integrating biogas injection, intake swirl control, and exergy-based evaluation to measure mixture distribution and energy recovery in high-COQ biogas RCCI combustion. The findings offer useful operational guidance for increasing energy efficiency and advancing the commercialization of renewable gaseous fuels in RCCI engines. As a result, operating the engine at half load, 80% PSR, and atmospheric air pressure (1 bar) conditions significantly enhanced the combustion efficiency and energy utilisation.
  • Article
    Strategic Modeling of Hybrid Smart Micro Energy Communities: A Decision-Oriented Approach
    (MDPI, 2026-02-10) Perez-Sanchez, Modesto; Coronado-Hernandez, Oscar E.; McNabola, Aonghus; Erdfarb, Alex; Ramos, Helena M.; Demircan, Isil; Koca, Kemal
    Hybrid renewable energy systems are increasingly important for enabling sustainable and resilient energy supply in rural smart communities, yet existing tools often lack the ability to integrate environmental variability, multi-technology interactions, and economic-environmental assessment in a unified framework. This study presents Hybrid Smart Micro Energy Community (HySMEC), a novel modeling approach that combines high-resolution meteorological data, technology-specific generation models, detailed demand characterization, and financial analysis to evaluate hybrid configurations of hydropower, solar PV, wind, battery storage, and grid interaction. Hourly simulations capture seasonal dynamics and system behavior under realistic technical efficiencies, investment costs, and emission factors, enabling a transparent assessment of energy flows, self-consumption, and grid dependence. The results show that hybrid systems can achieve competitive economic performance, low Levelized Costs of Energy, and significant CO2 emission reductions across diverse rural community profiles, even when space or demand constraints are present. The analysis confirms the technical feasibility and environmental benefits of integrating multiple renewable sources with storage, highlighting the importance of self-consumption ratios in improving system profitability. Overall, HySMEC provides a robust and scalable tool to support data-driven design and optimization of distributed energy systems, offering valuable insights for researchers, planners, and decision-makers involved in sustainable rural energy development.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Unit Sizing and Feasibility Analysis of Green Hydrogen Storage Utilizing Excess Energy for Energy Islands
    (MDPI, 2026-01-14) Koca, Kemal; Dursun, Erkan; Bekci, Eyup; Ucar, Suat; Akpolat, Alper Nabi; Tsami, Maria; Borg, Ruben Paul
    This study examines whether green hydrogen production using combined wind and solar energy on Marmara Island can meet the island's electricity demand and fuel the fuel needs of a hydrogen-powered ferry. A hybrid system consisting of a 10 MW wind farm, a 3 MW solar PV system, and a PEM electrolyzer sized to meet the island's hydrogen demand was modeled for the island, located in the southwestern Sea of Marmara. The hydrogen production potential, energy flows, and techno-economic performance were evaluated using HOMER-Pro 3.18.4 version. According to the simulation results, the hybrid system generates approximately 62.6 GWh of electricity annually, achieving an 82.8% renewable energy share. A significant portion of the produced energy is transferred to the electrolyzer, producing approximately 729 tons of green hydrogen annually. The economic analysis demonstrates that the system is financially viable, with a net present cost of USD 61.53 million and a levelized energy cost of USD 0.175/kWh. Additionally, the design has the potential to reduce approximately 2637 tons of CO2 emissions over a 25-year period. The results demonstrate that integrating renewable energy sources with hydrogen production can provide a cost-effective and low-carbon solution for isolated communities such as islands, strengthening energy independence and supporting sustainable transportation options. It has been demonstrated that hydrogen produced by PEM electrolyzers powered by excess energy from the hybrid system could provide a reliable fuel source for hydrogen-fueled ferries operating between Marmara Island and the mainland. Overall, the findings indicate that pairing renewable energy generation with hydrogen production offers a realistic pathway for islands seeking cleaner transportation options and greater energy independence.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Measurements of Flow Characterization Revealing Transition to Turbulence Associated With the Partial Flexibility-Based Flow Control at Low Reynolds Number
    (Springer Heidelberg, 2024-07-26) Koca, Kemal; Keskin, Sinem; Sahin, Rumeysa; Veerasamy, Dhamotharan; Genc, Mustafa Serdar
    In order to comprehend the flow characteristics of both controlled and uncontrolled SD7062 wind turbine airfoils with local flexible membrane material throughout a variety of angles of attack at a Reynolds number of 1.05 x 105, an experimental investigation was conducted. The time-dependent force measurement, the hot-wire experiment with a boundary layer and glue-on probes, and the oil-flow visualization technique were all utilized in the present study to measure the flow over the airfoil and examine the laminar-turbulent transition, laminar separation bubble, and the impact of a special flow control method that uses flexibility. A comprehensive intermittency analysis by utilizing hot-wire results was employed to obtain the flow physics effects of the local flexibility the first in the literature. The key results of the experiment demonstrated that the stall was delayed from alpha = 10 degrees to 12 degrees by the local flexibility. The hot-wire results are dedicated to laminar, transitional and turbulent regions and the transition phenomena at different locations over the suction surface of the airfoil in the analysis graphs. As demonstrated by the results of the oil-flow visualization experiment, in the uncontrolled case, the laminar separation bubble formed over the airfoil at alpha = 8 degrees between x/c = 0.16 and x/c = 0.42. The use of flexible membrane material over the airfoil provided that the oscillation of this material triggered the transition to turbulence and a bypass transition, which resulted in the reattached flow.