Aristotle T. Ubando

Cement-based thermoelectric materials have progressed from laboratory composites toward devices, including structural thermoelectric generators and modules made from industrial by-products. Prior reviews surveyed filler chemistries, carrier-type mechanisms, and techno-economics, identifying manufacturability, scalability, and interfacial reliability as persistent barriers. None, however, follows fabrication from the composite to component scale or draws on conventional module manufacturing for transferable solutions. This systematic review does both across 34 studies, consolidating interfacial findings into a design principle organized around two carrier regimes, electronic and ionic/mixed, with opposing process requirements. At the material level, the one direct comparison of fabrication routes, in which forming and curing also differed, reported conductivity and Seebeck changes of more than 100-fold; at the device level, voltage fell up to 21-fold below predictions from composite properties. Durability evidence spans hours for devices and months for embedded fibers. Against envelope conditions, the evidence is direct but short-term for roofs, compatible in the operating range but untested in service for facades and walls, pavement-only for ground contact, and absent for openings. Output at envelope-like temperature differences was limited to voltage or sub-microwatt power, below the minimum converter input, pointing to sensing and micro-harvesting rather than bulk power. Reporting, scale-up, durability, and cost gaps remain.

Auxetic metamaterials have garnered significant interest due to their unique mechanical behavior. These unique properties make their potential increasingly recognized for next-generation airless tire technology. This review presents a comprehensive overview of the fundamentals of auxetic metamaterial structures, from re-entrant honeycombs and chiral lattices to rotating units, triply periodic minimal surfaces (TPMS), and origami-based designs. Their deformation mechanisms were correlated to tire mechanical performance metrics. Key computational approaches, such as finite element analysis, machine learning techniques, and multi-objective optimization, that were used in existing studies are examined. The emerging AI-driven inverse design and surrogate modeling techniques described in the existing studies were also presented, which contribute to the rapid design of airless tires. A framework for the airless tire mechanical performance and the influencing variables is also presented based on the gathered data from literature to show how the auxetic behavior of the metamaterial and its base material properties affect the mechanical performance. The review further explores auxetic-enabled solutions to pressing tire engineering challenges while identifying persistent research gaps in fatigue life prediction, environmental adaptability, and large-scale production.

This study employs Computational Fluid Dynamics (CFD) to investigate the nitrogen gas flow patterns, feedstock particle size, turbulence zones, and the distribution of the solid volume fraction in a vertical pyrolysis reactor. By employing the Eulerian multiphase model and a transient solver, the analysis allows the investigation of whether the feedstock particle size is appropriate for maintaining good mixing and identifying potential turbulence zones during the feedstock loading stage. The results highlighted the critical importance of feedstock particle size and nitrogen gas velocity in maintaining adequate mixing. Using a time-averaged profile, feedstock with a 0.55 mm diameter and a bulk density of 536 kg/m3, combined with a continuous nitrogen gas supply at 0.485 m/s, resulted in significant bed expansion, twice the initial height. This ensures that the biomass feedstock particles do not settle at the bottom of the reactor, thus facilitating uniform heat transfer, which affects yield efficiency. The velocity of the feedstock with nitrogen gas peaked at 0.98 m/s. At 25% loading capacity, the solid-phase volume fraction decreases from 0.6 to a range of 0.1 to 0.3, indicating efficient mixing and heat transfer. It was observed that the proper nitrogen gas velocity also promotes uniform heating, enhancing the process’s overall performance.

With increasing carbon dioxide emissions from power and heat generation, various decarbonization strategies are being explored to produce clean energy. Polygeneration systems are a promising approach to supply the energy needed. These systems incorporate numerous processes and technologies to convert various raw materials into multiple energy streams. To capitalize on the vast ocean resources worldwide, reverse osmosis desalination (ROD) and indirect ocean capture (IOC) technologies are considered within polygeneration system. This study focuses on optimizing an ROD/IOC process unit incorporated in a polygeneration system that produces heating, cooling, purified water, and hydrochloric acid (HCl) according to demand. The optimization approach employs a mixed integer linear programming (MILP) model that considers net output, capacity, demand, and binary variable vectors. The model aims to maximize the profit while minimizing the carbon-associated price. The optimal results indicate the selection of a combined heat and power (CHP) unit operating at 7500 kW, the chiller at 1500 kW, the reverse osmosis desalination (ROD) unit at 130.5 tons per hour, and the electrolytic cell with a gaseous diffusion anode (EGDA) operating at 80 tons per hour. The system achieves a net positive profit between €447,000 to €4,691,000 per year depending on the carbon-associated price. A trade-off between the profitability and the carbon-associated price was established. This study contributes to the field of negative emission technologies (NETs) and emphasizes the importance of optimizing polygeneration systems for sustainable energy transition.