Production & Supply Chain

This work provides a detailed evaluation of a novel biomass-fueled multigeneration system conceived to contribute to the growing emphasis on sustainable energy solutions. The architecture comprises a biomass gasifier an innovative cascaded organic Rankine cycle (CORC) incorporating a high-temperature mixture in the top cycle a proton exchange membrane electrolyzer (PEME) a Brayton cycle and waste heat utilization units all operating together to deliver electricity hydrogen (H2) and thermal output. A comprehensive thermodynamic modeling framework is established to evaluate the system’s performance across various operational scenarios. The framework emphasizes critical metrics including exergy efficiency levelized total emissions (LTE) and payback period (PP). These indicators ensure a holistic assessment of energy exergy economic and environmental considerations. Parametric studies demonstrate that enhancements in biomass mass flow rate and combustion chamber temperature significantly increase power output and H2 production while reducing the payback period underscoring the system’s flexibility and economic feasibility. Furthermore the study employs sophisticated machine learning optimization methods combining artificial neural networks (ANNs) with genetic algorithms (GA) to determine optimal operating conditions with minimal computational effort and maximum efficiency. When evaluated at nominal parameters the system records an exergy efficiency of 23.72 % achieves a PP of 5.61 years and yields an LTE value of 0.34 ton/GJ. However under optimized conditions these values improve to 35.01 % 3.78 years and 0.241 ton/GJ respectively.

Understanding water evolved gas and ionic transport in membrane-electrode-assemblies (MEAs) is essential for the development of high performance and durable anion exchange membrane water electrolyzers (AEMWEs). This study evaluates the MEA conditioning process operating conditions and short-term stability in a 1 M potassium hydroxide (KOH) electrolyte focusing on the underlying transport phenomena. We observe a significant initial voltage loss in continuous cell operation which could be associated with gas bubble accumulation transport layer or flow field passivation and changes in the catalyst oxidation state. Further we investigate the effects of materials and operational configurations including the membrane type and thickness and the electrolyte flow rate including KOH being fed to both electrodes as well as to the anode only. Furthermore the effect of membrane drying temperature on ex situ as well as in situ electrochemical performance is evaluated. Finally we discuss 700 h of AEMWE operation at 1 A/cm2 highlighting the underlying degradation phenomena.

Volatile fatty acid (VFA) accumulation is a common issue that compromises the performance of biological hydrogen methanation systems (BHMs). This accumulation is often triggered by fluctuations in hydrogen supply which can disrupt microbial activity and lead to system instability. To address this challenge this study investigated the impact of employing a microbial electrolysis cell (MEC) in BHMs to mitigate system instability and acid buildup. As such a conventional anaerobic digester (AD) and a microbial electrolysis cell both supplemented with exogenous hydrogen were evaluated for their performance in hydrogen methanation. The effect of exogenous hydrogen at high addition rates (>4:1 CO2:H2 molar ratio) under instantaneous and gradual injection modes was investigated. The results showed that the instantaneous addition of hydrogen resulted in the total failure of the anaerobic digestion system. Propionate accumulated in the system (>2 g/L) and resulted in low pH (pH=5.3). Methane production stopped and the reactor never recovered from hydrogen shock. However the microbial electrolysis system was able to withstand the instantaneous hydrogen addition and maintain normal operation under toxic hydrogen addition levels (>4:1 CO2:H2 molar ratio). Under the gradual injection mode both MEC and AD reactors remained reasonably unaffected; even though the hydrogen injection exceeded the stoichiometric molar ratio. This study provides a new perspective on the application of MECs for reliable operation and storage of surplus renewable energy via biological hydrogen methanation.