Conversion System Research Articles

Improving Conversational Recommendation System Through Personalized Preference Modeling and Knowledge Graph

Improving Conversational Recommendation System Through Personalized Preference Modeling and Knowledge Graph

Forecasting Thermoelectric Power Generation through Utilization of Waste Heat from Building Cooling Systems based on Simulation

The transformation of sustainable energy use is one of the main challenges facing the world today. Waste heat from industrial processes and conventional power plants is one form of energy waste that is often wasted. In this context, research on thermoelectric energy conversion systems is a very relevant and important topic to research. This research investigates about the potential for utilizing thermoelectric elements with stacked materials that utilize waste heat from building cooling systems. Numerical simulation was chosen to carry out further analysis regarding the potential energy produced and the efficiency of the materials used. Three-dimensional design and ANSYS is used as a three-dimensional simulation analysis tool. The research results show that thermoelectric systems with stacked materials have the potential to produce energy from waste heat. Material (Cu2Se+, BiTe+) (Bi2S3-, CuFeS-) with 10mm legs has the highest output power of 32.82mW whereas (PbSe+, BiTe+) (Bi2S3-, AgInSe-) with a leg length of 20 mm has the highest efficiency value of 25.97%, and a power value of 6.92mW. Full system research can produce values ​​that more closely resemble actual conditions.

Dual 3L-NPC Converter System With Improved Power Quality for Bipolar DC Distribution

Dual 3L-NPC Converter System With Improved Power Quality for Bipolar DC Distribution

Scrutinizing effect of temperature and pressure variation of a double-pressure dual-cycle geothermal power plant turbines on the temperature profile and heat gain of the heat exchangers

In geothermal power plants with dual pressure cycle technology, the optimisation of turbine inlet parameters depending on the pressure and temperature of the geothermal fluid is a very important parameter affecting the production capacity of such plants. In combined systems, where the second stage (low pressure) is fed by the first stage (high pressure), failure to determine the appropriate operating conditions leads to the problem of not achieving optimum performance. In this context, the study aims to develop a methodology for predicting the performance of the system, based on the geothermal water temperatures entering and leaving the heat exchangers, in order to clearly see the effect of the operations carried out within the scope of optimising the turbine inlet parameters on the system behaviour. In this study, EBSILON® Professional software developed by Steag GbmH was utilised to simulate the determined correlations. The effect of the heat exchangers (preheater, evaporator and superheater) in both stage-1 and stage-2 on the temperature profiles and heat gains were determined at 10–17 bar, 126.5–165 °C for Turbine-1 and 4–8 bar, 84–135 °C for Turbine-2. Optimum turbine inlet temperature and pressure have been determined for maximum heat input and exergy efficiency. In this context, each cycle in the Energy Converter System (ECS) was first simulated by changing the turbine input parameters and then thermal analyses of the system were performed using the performance outputs obtained from the simulation software. For turbine-1, it is observed that heat transfer decreases in stage-1 with increasing pressure and temperature, while heat transfer increases in stage-2 fed from stage-1. After 12 bar and 136 °C, the heat transfer of the ECS started to increase and the maximum heat transfer amount was reached at 17 bar and 155 °C. However, it was determined that the exergy efficiency of the ECS started to decrease after 15 bar and 147.6 °C. For turbine-2, it was found that the increase in pressure and temperature decreases the ECS heat transfer but increases the exergy efficiency. As a result of numerous iterations with EBSILON® Professional software, a maximum exergy efficiency of 50.53% was achieved in turbine-1 (15 bar, 147.6 °C) and turbine-2 (8 bar, 114 °C).

A novel PWM plus phase shift modulation strategy for three‐level isolated dual‐active‐bridge DC–DC converters

AbstractA hybrid‐three‐level isolated dual‐active‐bridge (HTDAB) DC–DC converter is widely used for grid‐interactive power converters. However, a traditional extended‐phase‐shift (EPS) modulation scheme would cause voltage‐level‐disorder (VLD) problems in HDAB DC–DC converter system because the output voltage of HTDAB would be clamped at a high‐ or low‐level during power transmission when the inductor current changes directions. Thus, the zero voltage sequence of the HTDAB cannot be stably maintained under EPS control, which not only leads to a significant difference between the actual transmission power and the target output power but also seriously affects the stability of the system control. To address this limitation, the reasons leading to VLD are analysed in detail, that is, an inappropriate PWM switching sequence at the output zero voltage level would occur under EPS control. Then, a novel PWM plus phase shift (PPS) modulation strategy is proposed, which can eliminate VLD completely. Finally, an experimental prototype is built to verify the effectiveness of the proposed PPS modulation scheme. The experimental results demonstrate that the PPS modulation method proposed in this article can effectively eliminate level disturbances and improve system stability.

Sustainable Combination of Waste with Waste: Utilization of Biomass to Recover Critical Metals from Spent Lithium ion Batteries

The generation of e‐waste from lithium ion batteries (LIBs) is rapidly increasing due to the rising utilization of LIBs in portable electronics, and electric vehicles, with an average life span of 3‐5 years. The disposal of spent LIBs is a major environmental concern due to the presence of high percentages of toxic heavy metals and corrosive electrolytes. Efficient and sustainable recycling of spent LIBs has become immensely important, both environmentally and from a circular economy perspective, as LIBs serve as secondary sources of critical metals needed for renewable energy conversion and storage systems. We provide a concise review of metal recovery from spent LIBs using waste biomass in a green and sustainable approach for resource generation, in addition to the valorization of waste biomass. Biomass is used to recover metals from spent LIBs, acting as lixivient, reductant, and as absorbent. We have also discussed a reverse strategy utilizing ‘black mass’ from spent LIBs as catalyst for biomass conversion to value‐added products. The concept of “circular economy” is highlighted in a “killing two birds with one stone” approach through the utilization of biomass for the recovery of metals from spent LIBs and vice versa.

A hybrid algorithm for photovoltaic maximum power point tracking using Artificial Neural Network and Kinetic Gas Molecular Optimization

The quest for efficient photovoltaic (PV) energy conversion systems has led to the development of Maximum Power Point Tracking (MPPT) algorithms. In this paper, we propose a novel hybrid approach that combines the power of Artificial Neural Network (ANN) with the optimization capability of Kinetic Gas Molecular Optimization (KGMO) for MPPT. We present a high-level outline of the proposed algorithm along with example MATLAB code snippets for each step, highlighting its potential for improving PV system performance. This paper proposes a metaheuristic optimized multilayer feed‐forward artificial neural network (ANN) controller to extract the maximum power from available solar energy. Firstly, to improve the maximum power point (MPP) delivered by PV arrays and to overcome the drawbacks in the conventional MPPT method under irradiation variation, a hybrid MPPT controller is designed, in which the input parameters include the PV array voltage and current. The output parameter is the duty cycle of the DC/DC boost converter. The proposed approach abbreviated as ANN-KGMO MPPT controller is based on the Kinetic Gas Molecular Optimization (KGMO) Algorithm which is useful to train the developed ANN and to evolve the connection weights and biases to get the optimal values of duty cycle converter corresponding to the MPP of a PV array. Finally, the performance of the proposed control system is confirmed by simulation tests on a 2 kW PV system. In addition, the performance of an ANN-KGMO -based MPPT controller is also compared to the conventional perturb and observe (P&O) method. To analyze the results, simulations are performed by using MATLAB software.

Hydrogen and Solid Carbon Production via Methane Pyrolysis in a Rotating Gliding Arc Plasma Reactor.

Plasma-induced methane pyrolysis is a promising hydrogen production method. However, few studies have focused the decomposition of pure methane as a discharge gas. Herein, a rotating gliding arc reactor was used for the conversion of methane (discharge gas and feedstock) into hydrogen and solid carbon. Methane conversion, gaseous product selectivity, and energy usage efficiency(specific energy requirement for hydrogen production(SER)) were investigated as functions of operating parameters, e.g., specific energy input(SEI), residence time, and reactor design. SEI was positively(almost linearly)correlated with methane conversion and hydrogen yield and negatively correlated with SER. Conversion and efficiency of energy usage increased when reactor designs providing higher thermal densities were used. With the increasing flow rate of methane at constant SEI, the reaction volume and, hence, the residence time of the gas inside the reaction zone increased, which resulted in methane conversion and hydrogen selectivity enhancement. The solid carbon featured four distinct domains, namely graphitic carbon, turbostratic carbon, few-layer graphene, and amorphous carbon, which indicated a nonuniform temperature distribution in the reaction zone. But it seems that graphitic carbon dominates amorhphous one. This study highlights the potential of rotating gliding arc plasma systems for efficient methane conversion into hydrogen and valuable solid carbon products.

Structural Modulation of Nanographenes Enabled by Defects, Size and Doping for Oxygen Reduction Reaction

Nanographenes are among the fastest‐growing materials used for the oxygen reduction reaction (ORR) thanks to their low cost, environmental friendliness, excellent electrical conductivity, and scalable synthesis. The perspective of replacing precious metal‐based electrocatalysts with functionalized graphene is highly desirable for reducing costs in energy conversion and storage systems. Generally, the enhanced ORR activity of the nanographenes is typically deemed to originate from the heteroatom doping effect, size effect, defects effect, and/or their synergistic effect. All these factors can efficiently modify the charge distribution on the sp2‐conjugated carbon framework, bringing about optimized intermediate adsorption and accelerated electron transfer steps during ORR. In this review, the fundamental chemical and physical properties of nanographenes are first discussed about ORR applications. Afterward, the role of doping, size, defects, and their combined influence in boosting nanographenes’ ORR performance is introduced. Finally, significant challenges and essential perspectives of nanographenes as advanced ORR electrocatalysts are highlighted.

Structural Modulation of Nanographenes Enabled by Defects, Size and Doping for Oxygen Reduction Reaction.

Nanographenes are among the fastest-growing materials used for the oxygen reduction reaction (ORR) thanks to their low cost, environmental friendliness, excellent electrical conductivity, and scalable synthesis. The perspective of replacing precious metal-based electrocatalysts with functionalized graphene is highly desirable for reducing costs in energy conversion and storage systems. Generally, the enhanced ORR activity of the nanographenes is typically deemed to originate from the heteroatom doping effect, size effect, defects effect, and/or their synergistic effect. All these factors can efficiently modify the charge distribution on the sp2-conjugated carbon framework, bringing about optimized intermediate adsorption and accelerated electron transfer steps during ORR. In this review, the fundamental chemical and physical properties of nanographenes are first discussed about ORR applications. Afterward, the role of doping, size, defects, and their combined influence in boosting nanographenes' ORR performance is introduced. Finally, significant challenges and essential perspectives of nanographenes as advanced ORR electrocatalysts are highlighted.

Role of cavity strong coupling on single electron transfer reaction rate at electrode-electrolyte interface.

The physicochemical properties of molecules can be modulated through polariton formation under strong electromagnetic confinement. Here, we discuss the possibility of exploiting this phenomenon to increase the electron transfer rate at an electrode-electrolyte interface. Electron transfer theory under strong electromagnetic confinement can be extended to the electrode-electrolyte interface, and single-electron transfer reactions can be simulated using Gerischer's theory. Although single electron transfer in free space is well described using Marcus theory, the vacuum electric field can facilitate an additional electron transfer pathway via virtual photon excitation under cavity strong coupling conditions. Therefore, this binary reaction pathway for single electron transfer can yield a quasi-two-particle electron transfer process. This quantum behavior can dominate when the mode volume is small and when there are a large number of molecules in the vacuum electric field. Exploitation of polaritons in single electron transfer reactions can lead to enhanced electrochemical energy conversion systems.

MC-CRS: enhanced conversational recommender system based on multi-contrastive learning

MC-CRS: enhanced conversational recommender system based on multi-contrastive learning

Alternating Donor-Acceptor Ladder-Type Heteroarene for Efficient Photothermal Conversion via Boosting Non-Radiative Decay.

The development of novel ladder-type conjugated molecules is crucial for advancing supramolecular chemistry and material science. In this study, we report a straightforward synthesis of new alternating donor-acceptor (D-A) ladder-type heteroarene, FCDTDPP, and demonstrate its application as photothermal agent for imaging and cancer therapy. FCDTDPP is constructed by vinylene bridge between cyclopentadithiophene (D) and diketopyrrolopyrrole (A) through intramolecular Friedel-Crafts type reaction. FCDTDPP exhibits unique combination of good molecular planarity, efficient intra/inter-molecular mixed D-A interactions, and local aromaticity. These features collectively contribute to its broad and intense absorptions with narrow bandgap in red band of the spectra, coupled with multiple vibrational absorption feature, thereby enhancing non-radiative decay process and resulting in efficient photothermal conversion property. FCDTDPP and its nanoparticles (NPs) exhibit superior photothermal conversion performance and stability under 660 nm laser irradiation. Moreover, in vitro studies reveal that FCDTDPP NPs possess excellent biocompatibility, low cytotoxicity, and robust photothermal therapeutic efficacy, a finding further corroborated by preliminary in vivo experiments in tumor-bearing mice. This work charts a novel course for the molecular engineering of organic photothermal conversion systems, propelling relevant research forward.

Strategically Designed Uniform MOF-Derived Nanoporous Carbon Aerogel for Efficient Solar-Driven Desalination by Control of Hydrophilicity and Thermal Conductivity.

Desalination techniques using the photothermal effect hold significant potential for producing fresh water from saline or polluted sources due to their low energy consumption. In the case of commercialized carbon materials are related to heat loss resulting from high thermal conductivity, and metal particles still have trouble in commercialization or cost-effectiveness. This is because a photothermal desalination evaporator must simultaneously exhibit high water evaporation performance, excellent energy conversion efficiency, sufficient hydrophilicity, and low heat loss. In this work, developing an efficient in situ energy utilization technology that instant light to heat energy conversion system based on ZIF-8/agarose-derived carbon aerogels, achieved by controlling hydrophilicity, thermal conductivity, and light absorption properties is reported. The carbon aerogel demonstrates excellent performances of improved capillary force, structural stability, and cost-effectiveness. The designed carbon aerogel, with a high surface area (524 m2 g-1), adequate hydrophilicity, and low density (0.07g cm-3), is buoyant enough to float on the water. A water evaporation efficiency of 1.53kg m-2 h-1 under 1 sun and a light-to-heat conversion of 85% are achieved, along with effective salt blocking through the size-controlled uniform ZIF-8 nanoparticles and optimized composition with agarose.

Geothermo-mechanical energy conversion using shape memory alloy heat engine

AbstractThe shift towards renewable energy sources like geothermal energy has become desirable due to the recurrent energy crisis and global warming challenges influenced by fossil fuels. Geothermo-mechanical energy conversion using shape memory alloy (SMA) heat engines presents a novel and sustainable approach for harnessing geothermal energy. Shape memory alloys, known for their ability to undergo reversible phase transformations driven by temperature changes, are ideal for thermal-to-mechanical energy conversion. This paper explores the design and performance of an SMA heat engine that utilizes geothermal heat sources to drive mechanical work. The engine operates by cycling between the high-temperature geothermal environment and a cooler sink, exploiting the shape memory effect to generate mechanical motion. By integrating geothermal energy and SMA technology, this system offers a potential solution for renewable energy generation, with applications in remote or off-grid locations. The paper also investigates output power and the thermodynamic efficiency. A model is formulated and the engine behavior is simulated. A series of experiments are conducted for engine output power and efficiency. The model is compared to the experimental data for validation. The engine developed a maximum power of 3.5, 8.5, and 11.5 watts at 60, 80, and 90 °C respectively. The proposed SMA-based geothermo-mechanical energy conversion system offers a promising solution for efficient, reliable, and scalable geothermal energy harvesting. This research contributes to the development of innovative, efficient geothermal energy conversion technologies, supporting global renewable energy goals and reducing greenhouse gas emissions. This innovative energy conversion mechanism could play a key role in the future of sustainable power generation.

Alternating Donor‐Acceptor Ladder‐Type Heteroarene for Efficient Photothermal Conversion via Boosting Non‐Radiative Decay

The development of novel ladder‐type conjugated molecules is crucial for advancing supramolecular chemistry and material science. In this study, we report a straightforward synthesis of new alternating donor‐acceptor (D‐A) ladder‐type heteroarene, FCDTDPP, and demonstrate its application as photothermal agent for imaging and cancer therapy. FCDTDPP is constructed by vinylene bridge between cyclopentadithiophene (D) and diketopyrrolopyrrole (A) through intramolecular Friedel‐Crafts type reaction. FCDTDPP exhibits unique combination of good molecular planarity, efficient intra/inter‐molecular mixed D‐A interactions, and local aromaticity. These features collectively contribute to its broad and intense absorptions with narrow bandgap in red band of the spectra, coupled with multiple vibrational absorption feature, thereby enhancing non‐radiative decay process and resulting in efficient photothermal conversion property. FCDTDPP and its nanoparticles (NPs) exhibit superior photothermal conversion performance and stability under 660 nm laser irradiation. Moreover, in vitro studies reveal that FCDTDPP NPs possess excellent biocompatibility, low cytotoxicity, and robust photothermal therapeutic efficacy, a finding further corroborated by preliminary in vivo experiments in tumor‐bearing mice. This work charts a novel course for the molecular engineering of organic photothermal conversion systems, propelling relevant research forward.

A fine-tuning enhanced RAG system with quantized influence measure as AI judge

This study presents an innovative enhancement to retrieval-augmented generation (RAG) systems by seamlessly integrating fine-tuned large language models (LLMs) with vector databases. This integration capitalizes on the combined strengths of structured data retrieval and the nuanced comprehension provided by advanced LLMs. Central to our approach are the LoRA and QLoRA methodologies, which stand at the forefront of model refinement through parameter-efficient fine-tuning and memory optimization. A novel feature of our research is the incorporation of user feedback directly into the training process, ensuring the model’s continuous adaptation to user expectations and thus, improving its performance and applicability. Additionally, we introduce a Quantized Influence Measure (QIM) as an innovative “AI Judge” mechanism to enhance the precision of result selection, further refining the system’s accuracy. Accompanied by an executive diagram and a detailed algorithm for fine-tuning QLoRA, our work provides a comprehensive framework for implementing these advancements within chatbot technologies. This research contributes significant insights into LLM optimization for specific uses and heralds new directions for further development in retrieval-augmented models. Through extensive experimentation and analysis, our findings lay a robust foundation for future advancements in chatbot technology and retrieval systems, marking a significant step forward in the creation of more sophisticated, precise, and user-centric conversational AI systems. We make the dataset, the data processing package huggify-data, the model, and the app publicly available for the community.

Preface to the special issue on conversational recommender systems: theory, models, evaluations, and trends

Preface to the special issue on conversational recommender systems: theory, models, evaluations, and trends

Lewis acid sites in hollow cobalt phytate micropolyhedra promote the electrocatalytic water oxidation.

The acid-base microenvironment of the metal center is crucial for constructing advanced oxygen evolution reaction (OER) electrocatalysts. However, the correlation between acidic site and OER performance remains unclear for cobalt-based catalysts. Herein, Lewis acid sites in hollow cobalt phytate micropolyhedra (M-CoPA, M = Cu, Sr) were synthesized by a cation-exchange strategy, and their OER performances were studied systematically. Experimentally, Lewis acid Cu2+ sites with stronger Lewis acidity exhibited superior intrinsic activity and long-term stability in alkaline electrolytes. The spectroscopic and electrochemical studies show Lewis acid sites in hollow cobalt phytate micropolyhedra can modulate the electronic distribution of the adjacent cobalt center and further optimize the adsorption strength of oxygenated species. This study figures out the effect of Lewis acid sites on the OER kinetics and provides an effective way to develop high-efficiency electrocatalysts for energy conversion systems.

Experimental investigation on thermodynamic and environmental performance of a novel ocean thermal energy conversion (OTEC)-Air conditioning (AC) system

In the field of isolated island energy supply, the OTEC system is considered promising due to its large storage capacity, and pollution-free characteristics. To improve energy efficiency, polygeneration systems have gradually become a research hotspot for their low cost and high return features. In this context, a novel Ocean Thermal Energy Conversion system integrated with an air conditioning unit (OTEC-AC) is introduced, demonstrating capabilities in electricity, cooling capacity, and fresh water production by experiments. The effects of various flow rates and temperatures of the heat and cold sources, along with the air-conditioning system water flow rate on the system performance is explored. Besides, the overall performance of the OTEC-AC is compared with four representative OTEC models. The results indicate that there is a threshold for the influence of cold and heat source flow rate on the performance of power generation system. The OTEC-AC system shows a highest net power of 132.6 W, cooling capacity of 2.14 kW, condensate production of 3.24 kg/h, and achieves a system exergy efficiency and CO2 reduction of 34.7 % and 5801 kg/year, respectively. The annual CO2 reduction per kilowatt of installed capacity of the system is increased by 135.6 %, compared with the conventional OTEC system.