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    A comparative investigation of eco-friendly fly ash-based geopolymer mortar produced by using electrical and heat curing: Mechanical properties, energy consumption and cost
    (Elsevier Sci Ltd, 2024) Urunveren, Husamettin; Beycioglu, Ahmet; Resulogullari, Emriye Cinar; Disken, Nihal Bayramoglu
    This study investigates the eco-friendly fly ash-based geopolymer mortar (GM) production using electrical curing (EC) and heat curing. Within the scope of the study, GM produced using the EC method was compared with GM produced using the heat curing (HC) method in terms of mechanical properties, energy consumption, and cost. The study consists of a preliminary experiment to determine the parameters to be used, mortar experiments using the limited parameters defined in preliminary experiments, and an energy consumption and cost analysis. In the preliminary experiments, different mix designs produced according to different MS modulus and Na 2 O concentrations were studied to decide an applicable range for temperatures of HC and an applicable range for voltages of EC. In the second stage, EC and HC were compared according to temperature changes in GMs, current changes in GMs, and compressive strength (CS). As a final stage, an energy consumption and cost analysis were performed to compare two curing methods according to the updated dollar-based unit prices for electricity per kWh for industrial uses in various countries in February 2024. Results showed that the MS modulus should be at least 1.2 and the Na 2 O concentration should be 10 % on average to obtain a workable mortar. The compressive strength of all mortars with any MS modulus increased up to 100 degrees C and then decreased HC applied samples. Stress values of 20, 25, 30, and 35 volts are applicable and the highest compressive strength values could be obtained with 25 volts, and 6 h of application is sufficient at 25 volts EC. MS module is a key parameter in current and temperature change. In EC application, 30 volts is the threshold value, and when an electrical voltage above 30 volts is applied, the mortar 's internal temperature suddenly reaches the peak value and the desired compressive strength results cannot be achieved. According to the cost analysis, it is seen that the HC electricity cost is 6.78 times more than the EC cost. A comprehensive efficiency calculation is strongly recommended for future studies. It has also been concluded that geopolymers could gain strength at much lower voltage values, so they have the potential to consume less electrical energy in comparison to conventional concrete.
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    Öğe
    High-Gain Multiport DC-DC Converter Topologies for Renewable Energy Applications: A Comprehensive Review
    (Taylor & Francis Inc, 2024) Disken, Nihal Bayramoglu; Savrun, Murat Mustafa
    Renewable energy sources have emerged as favorable alternatives for meeting ever-increasing global energy demand. To harness the maximum efficiency from renewable sources, dc-dc converters play a crucial role. While the design of dc-dc converters varies depending on specific application, certain features such as multiport capability and high gain are generally desirable. Multiport structures offer advantages such as compactness and cost reduction, allowing for the efficient integration of various energy sources, storage units, and loads. On the other hand, high gain characteristics enable the step-up of output voltages from renewable energy sources to usable levels. In recent years, numerous converter topologies proposed to address these requirements and enhance overall system performance. This study aims to assist and provide guidance to researchers in the field by reviewing and comparing the most recent advancements in the design and implementation of multiport high-gain dc-dc converters for renewable energy applications. Through a comprehensive analysis of the existing literature, the primary objective of this study is to facilitate knowledge transfer, identify research gaps, and inspire future research endeavors in this domain. By synthesizing the knowledge gained from these studies, researchers can contribute to ongoing advancement of multiport converter technology in the context of renewable energy applications.