Energy Conversion Method Research Articles

Immobilization of metal active centers in reticular framework materials for photocatalytic energy conversion

To enhance the economy and society's sustainability, prioritizing innovative, green energy conversion methods is essential.

Study of an autonomous solar power plant for a motorhome

Problem. An RV combines two essential features desired by modern travelers: the ability to relax in unconventional locations while still being able to work remotely if your job requires remote access. However, if you're accustomed to the conveniences that rely on electrical power, you'll find yourself searching for places to connect to the centralized power grid. Alternatively, you'll need to seek solutions to this issue. One of the most intriguing and effective solutions is the installation of a low-power solar power station on the RV, based on photovoltaic modules. This solution enables you to park and enjoy any location you prefer while benefiting from all the available technologies powered by electricity. Goal. This study aims to investigate the installation of an autonomous solar power station on an RV and determine its electrical power generation capacity. Methodology. Analytical research methods were employed to explore the development and application of solar energy conversion methods and devices to generate electricity. Experimental research methods and mathematical techniques for processing experimental data were also utilized. Results. The RV type suitable for installing an autonomous solar power station has been identified, specifically the Roller Team Sirio 599. An investigation of its equipment in terms of electricity consumption has been conducted. Furthermore, a self-sustaining solar station has been proposed for the selected RV, and the electricity generation schedule of this station has been studied. The electricity consumption by RV appliances has been thoroughly examined. Originality. This study explored the volt-ampere characteristics of photovoltaic modules and their power generation dependency on the load. The investigated photovoltaic modules demonstrate maximum operational efficiency in the active load range from 3 ohms to 3.5 ohms. Practical Value. The research findings indicate that starting from March, the solar power station on the RV is fully capable of meeting its electricity consumption needs. In the winter months, particularly in November, in Ukraine's climate conditions, this solar power station may only cover a portion of electricity consumption needs. Considering that electrical devices are often used for heating the RV, this solar power station should not be relied upon as the primary source of electrical power.

Solar Water Splitting Device Integrated Carbon-Based Electrodes and Carbon-Based Perovskite Solar Cells

Producing hydrogen from integrated devices by solar-driven water splitting (SWS) is one of the most attractive methods for renewable energy conversion. However, their widespread use is hindered by their cost and poor performance. In this work, we developed an integrated device consisting of three series-connected carbon-based multi-porous-layered-electrode perovskite solar cells (MPLE-PSCs) 1-5 and carbon-based catalyst-decorated electrode couples (Figure 1a). Porous carbon electrodes with a graphite and carbon black mixture are used for the back contacts of solar cells, and pencil-lead graphite rods (PGRs) are used as electrocatalyst supports for water-splitting cells, which are much cheaper than existing materials. The performance of the PSC was compared between the 2 and 3-series, and the performance of the water-splitting cell with/without catalyst. In addition, each combination was compared.The solar to electricity efficiency (STE, same as power conversion efficiency: PCE) was 13.79% and 13.16% for the 2-series and 3-series, respectively. The electricity to hydrogen efficiency (ETH), calculated as V theoritical/V operating, 6 was 78.34% and 84.83%, for PGR and NiFe/PGR respectively. Furthermore, the matching factor (MF), calculated as (V operating × J operating)/(V max × J max), 6 for the <2-series PSCs>/<PGR> combination and the <3-series PSCs>/<NiFe/PGR> combination were 48.57% and 83.77%, respectively. Solar to hydrogen efficiency (STE), calculated as STE ×ETH × MF, improved from 5.25% to 9.35% for the optimized device (Figure 1b). These results show that low-cost and high-efficiency solar hydrogen can be produced by using Earth-abundant materials and by adjusting the maximum output of the device.(1) A. Mei, et al., Science 345, 295 (2014).(2) R. Tsuji, et al., Electrochemistry 88, 418 (2020).(3) R. Tsuji, et al., Photonics 7, 133 (2020).(4) D. Bogachuk, R. Tsuji, et al., Carbon 178, 10 (2021).(5) E. Kobayashi, R. Tsuji, et al., Cell Rep. Phys. Sci. 2, 100648 (2021).(6) Z. N. Zahran, et al., ACS Appl. Energy Mater. 5, 8241 (2022).Figure 1. Carbon-based solar water splitting. (a) Schematic diagram and (b) J-V curves of MPLE-PSCs and LSV curves of water electrolysis with PGR electrodes. Figure 1

Integrated device for multiscale series vibration reduction and energy harvesting

A multi-degree-of-freedom device is proposed, which can achieve efficient vibration reduction as the main objective and energy harvesting as the secondary purpose. The device comprises a multiscale nonlinear vibration absorber (NVA) and piezoelectric components. Energy conversion and energy measurement methods are used to evaluate the device performance from multiple perspectives. Research has shown that this device can efficiently transfer transient energy from the main structure and convert a portion of transient energy into electrical energy. Main resonance and higher-order resonance are the main reasons for efficient energy transfer. The device can maintain high vibration reduction performance even when the excitation amplitude changes over a large range. Compared with the single structures with and without precompression, the multiscale NVA-piezoelectric device offers significant vibration reduction advantages. In addition, there are significant differences in the parameter settings of the two substructures for vibration reduction and energy harvesting.

Coupling model for the gradient loading creep behavior of nickel-based single-crystal superalloys

The emergency situation caused by the abnormal service of an aeroengine, such as gradient loading, directly leads to blade rupture. Considering the effect of gradient loading on creep, a coupling creep model of nickel-based single crystals under gradient loading conditions is proposed based on crystal plastic theory and thermodynamic damage theory. Internal state variables—elastic strain, plastic strain and damage—are introduced to describe the thermodynamic irreversible process of a system. An anisotropic creep damage evolution equation represented by the damage strain energy release rate Y is deduced by the energy conversion method. The gradient loading creep behavior predicted by the finite element calculation is in good agreement with the experimental results.

Enhancing waste resource efficiency: circular economy for sustainability and energy conversion

This study explores optimizing waste resource efficiency through the Circular Economy (CE) framework. Motivated by the imperative to enhance resource efficiency and mitigate waste’s environmental impact, we examine the CE concept’s extension of product life cycles, while minimizing waste. We conduct a comprehensive review to explore the core CE principles across all stages of the product lifecycle and provide an in-depth analysis of waste treatment practices in Poland, emphasizing potential energy conversion methods like biogas production and incineration. Our findings underscore the importance of prioritizing waste incineration plant design for quicker payback, aligning with circular rational economic practices. Strategies such as improving biogas production, establishing solid bio-waste fermentation facilities, promoting sortable packaging, and incentivizing sustainable sorting emerge to optimize waste management. These findings highlight the pivotal role of economic, environmental, and energy considerations in shaping sustainable waste management strategies.

Design and energy, exergy, and exergoeconomic analyses of a novel biomass-based green hydrogen and power generation system integrated with carbon capture and power-to-gas

The conversion of thermal energy into electrical power through combustion in combined cycle power plants is a prevalent method of energy conversion. Sustainable energy management requires effective energy storage, and power-to-gas (P2G) technology is a recent solution to this problem. In this research work, a novel biomass-based power plant is proposed, this specific type of biomass is composed of industrial wood chips and wheat straw chopped wood with a 3.48:1 mass ratio and 19 wt% moisture. Detailed energy, exergy, and exergoeconomic analyses are performed for each component, considering various ambient and system conditions. This power plant is also equipped with a carbon capture and storage system, by which combustion's carbon dioxide is separated, and a power-to-gas energy storage system, by which hydrogen and oxygen gases are produced, allowing it to produce synthetic natural gas by the methanation process with various industrial applications and reduce carbon emissions. The energy and exergy analyses show that the overall energy efficiency and exergetic efficiency of the plant are 56.49 % and 35.48 %, respectively, which are highly acceptable and feasible. The combustion chamber is the primary location of exergy destruction, accounting for 52 % of the total exergy destruction in the cycles, followed by the methanation unit (15 %) and the turbine (12 %). Furthermore, the effect of modified ambient and manual operational parameters on the overall performance of the plant is analyzed, increasing the gas turbine inlet temperature improves the plant's energy efficiency to 57 %; but leads to a negative impact on its exergy efficiency (32 %), which manufacturing barriers make it difficult to increase beyond 1600 °C. Building the plant in a warmer geographic location barely impacts the energy efficiency; however, it may cause a decline as high as 1 % in the exergy efficiency.

Performance investigation of a wave-driven compressed air energy storage system

The intermittent nature of waves causes a mismatch between the energy supply and demand. Hence an energy storage system is essential in the utilization of wave energy. This paper proposes a novel wave-driven compressed air energy storage (W-CAES) system that combines a heaving buoy wave energy converter with compressed air energy storage. Wave drives the heaving buoy to convert the wave energy to mechanical work that pumps water into a water-air compression chamber to form a liquid piston compressor. Air is compressed in the chamber and the wave energy is stored in the air. A numerical model was first developed in ANSYS-AQWA and validated using experimental data. Then this model was applied to evaluate the hydrodynamic characteristics, power generation capacity and thermodynamic behaviour of the W-CAES system under different wave conditions. Furthermore, the impacts of geometric parameters of the wave energy converter and compression chamber on the system performance were investigated. Results indicated that energy storage power was improved as the hydraulic cylinder area and storage pressure increased. The energy storage efficiency and round-trip efficiency could reach 60.5 % and 47.1 %, respectively under the isothermal compression process. By comparing the proposed W-CAES system with the conventional wave energy converter prototype under the same conditions, it showed that the proposed system yielded an increase in power output by up to 30 % under Tasmania wave conditions under an isothermal compression. The overall system wave capture factor is more sensitive to wave height than wave frequency. The capture factor can be as high as 20 % under Tasmania wave conditions. This study provides a new method for efficient wave energy conversion and storage.

Solar harvesting through multiple semi-transparent cadmium telluride solar panels for collective energy generation

Among major energy conversion methods, photovoltaic (PV) solar cells have been the most popular and widely employed for a variety of applications. Although a PV solar panel has been shown as one of the most efficient green energy sources, its 2D surface solar light harvesting has reached great limitations as it requires large surface areas. There is, therefore, an increasing need to seek solar harvest in a three-dimensional fashion for enhanced energy density. In addition to a conventional 2D solar panel in the x-y area, we extend another dimension of solar harvesting in the z-axis through multiple CdTe solar panels arranged in parallel. The high transparency allows sunlight to partially penetrate multiple solar panels, resulting in significantly increased solar harvesting surface area in a 3D fashion. The advantages of the 3D multi-panel solar harvesting system include: i) enlarged solar light collecting surface area, therefore increased energy density, ii) the total output power from multiple panels can exceed that of the single panel, and iii) significantly reduced surface area needed for densely populated cities. With five CdTe solar panels of different transparencies in parallel, the multilayer system can produce collective output power 233% higher than that of the single solar panel under the same surface area when arranged in descending (i.e., PV panel with the highest transparency on top and lowest at bottom). The PCE of the multi-panel system has also increased 233% in descending order indicating the viability of 3D solar harvesting. The multi-panel system will dimensionally transform solar harvesting from 2D to 3D for more efficient energy generation.

Review on Microfluidic Technology Based Synthesis of Fe-based Nanoparticles for Catalyst in Fuel Cell

Conventional combustion based energy generations, reliant on fossil fuels, poses significant environmental harm. In contrast, fuel cells offer an efficient and eco-friendly energy conversion method, capable of integrating with renewable sources and contemporary energy carriers to support sustainable development and energy security. Consequently, fuel cells are considered the promising energy conversion devices of the future. However, extensive research reveals that the cost of catalysts constitutes the most substantial portion of the overall fuel cell cost. To tackle this cost constraint, considerable advancements have been achieved in the development of cost-effective, precious metal-free electrocatalysts. Common methods for the preparation of metal nanomaterials (NPs) have more stringent requirements, lower deposition efficiency and higher costs. In addition, conventional preparation methods without precisely control of reagent concentration, mixing and temperature during the preparation process, makes it difficult to obtain the same results with poor reproducibility, restricting the industrial fabrication of high performance nanomaterials. Microfluidic reactors have advantages of efficient mixing, high heat and mass transfer, low reagent consumption, precise control of reactant components, residence time, reaction temperature and other parameters. They can also be coupled with multi-step reactions, greatly reducing the preparation time while obtaining composite nanomaterials with excellent dimensional homogeneity. In this review, we mainly discuss the microfluidic technology-based synthesis of PGM-free catalyst used in fuel cell.

Life cycle assessment of food waste energy and resource conversion scheme via the integrated process of anaerobic digestion and hydrothermal carbonization

Anaerobic digestion is the mainstream method for energy conversion of food waste, but dewatering and resource utilization of its digestate is the downstream technical obstacle. In this study, an energy and resource utilization scheme via the integrated process of anaerobic digestion and hydrothermal carbonization of food waste is proposed, among which the hydrothermal carbonization not only is used to remove water from digestate in a non-phase change manner with low energy consumption but also convert digestate into hydrochar. Moreover, the scheme has the least environmental impact compared to the anaerobic digestion and composting treatment by life cycle assessment. In particular, it has a lower impact potential (−141.46 kg CO2 eq) than anaerobic digestion (−38.87 kg CO2 eq) for the global warming category, indicating that the addition of hydrothermal carbonization can bring better environmental benefits. This study provides a reference for the development of disposal technology for food waste.

Comparison of Pulse Width Modulation Techniques for Diode-Clamped and Cascaded Multilevel Inverters

Multilevel inverter technology has become the most significant method of energy conversion from DC to AC for uninterrupted power supply. The quality of the power supply depends on the appearance of harmonics, which is considered a problem that needs to be overcome. This paper demonstrates the use of a new modulation technique to reduce the harmonics in both diode-clamped and cascaded multilevel inverters, examining its Total Harmonic Distortion (THD) compared to other PWM methods. Simulations were carried out in MATLAB/Simulink for five-level diode-clamped and cascaded multilevel inverters. The simulation results of both multilevel inverters using the sinusoidal PWM, modified reference PWM, modified carrier PWM, and modified reference and modified carrier PWM methods showed that the latter had the best THD performance for both inverter types, especially for the cascaded multilevel inverter.

Tuning the electrocatalytic efficacy of nano-dumbbell shaped nickel selenide anchored cobalt telluride towards oxygen evolution

In the wake of environmental enigmas including global warming and the exhaustion of traditional hydrocarbon sediments, the usage of eco-friendly power generation is of paramount importance today. Alternatives to traditional fossil fuels such as hydrogen are clean, safe, and environmentally friendly. Moreover, hydrogen as a renewable energy source, as the only by product of burning hydrogen is water. Many electrochemical energy conversion methods rely on the oxygen evolution reaction (OER), but creating effectual, economical electrocatalysts for it has proven difficult. The multifunctional electrocatalyst, nickel selenide-anchored cobalt telluride, has been found to be effective in catalyzing oxygen evolution processes in alkaline medium. CoTe and NiSe, generated hydrothermally, exhibit promising electrocatalytic activity. However, their composite NiSe@CoTe, possesses higher OER durability. The presence of NiSe in the CoTe matrix responses a powerful OER responses due to the synergistic effect in alkaline environment. The NiSe@CoTe nanocomposite shows minimal Tafel value (39 mV/dec) and lower overpotential (247 mV) to attain a current density of 10 mA/cm2, whereas the pristine CoTe and NiSe needed higher overpotential to attain same current density. Following 16 h of utilizing the same catalyst, OER stability was maintained with 88 % current density retention.

Constructing built-in electric field via ruthenium/cerium dioxide Mott-Schottky heterojunction for highly efficient electrocatalytic hydrogen production

Ensuring the consumption rate of noble metals while guaranteeing satisfactory hydrogen evolution reaction (HER) performance at different pH values is imperative to the development of Ru-based catalysts. Herein, we design a Mott-Schottky electrocatalyst (Ru/CeO2) with a built-in electric field (BEF) based on density functional theory (DFT). The Ru/CeO2 achieves the criterion current density of 10 mA cm−2 at overpotentials of 55 mV, 80 mV, and 120 mV in alkaline, acidic and neutral media, respectively. Both theoretical calculations and experimental analysis confirm that the improved HER activity in the Ru/CeO2 catalyst could be due to the successful construction of BEF at the interface between the prepared Ru clusters and CeO2. Under the action of BEF, the electron-deficient Ru atoms can optimize the adsorption energy of H* and H2O and thus promote HER kinetics. Furthermore, the Ru/CeO2 catalyst delivers a power density of approximately 94.5 mW cm−2 in alkaline-acidic Zn-H2O cell applications while maintaining good H2 production stability. In this work, we optimize the electrocatalytic performance of the Ru/CeO2 catalyst through examination of the interfacial BEF electrical charge, which combines hydrogen production with power generation and provides a promising method for sustainable energy conversion.

Artificial Intelligence Methods for Analysis and Optimization of CHP Cogeneration Units Based on Landfill Biogas as a Progress in Improving Energy Efficiency and Limiting Climate Change

Combined heat and power generation is the simultaneous conversion of primary energy (in the form of fuel) in a technical system into useful thermal and mechanical energy (as the basis for the generation of electricity). This method of energy conversion offers a high degree of efficiency (i.e., very efficient conversion of fuel to useful energy). In the context of energy system transformation, combined heat and power (CHP) is a fundamental pillar and link between the volatile electricity market and the heat market, which enables better planning. This article presents an advanced model for the production of fuel mixtures based on landfill biogas in the context of energy use in CHP units. The search for optimal technological solutions in energy management requires specialized domain-specific knowledge which, using advanced algorithmic models, has the potential to become an essential element in real-time intelligent ICT systems. Numerical modeling makes it possible to build systems based on the knowledge of complex systems, processes, and equipment in a relatively short time. The focus was on analyzing the applicability of algorithmic models based on artificial intelligence implemented in the supervisory control systems (SCADA-type systems including Virtual SCADA) of technological processes in waste management systems. The novelty of the presented solution is the application of predictive diagnostic tools based on multithreaded polymorphic models, supporting making decisions that control complex technological processes and objects and solving the problem of optimal control for intelligent dynamic objects with a logical representation of knowledge about the process, the control object, and the control, for which the learning process consists of successive validation and updating of knowledge and using the results of this updating to determine control decisions.

Sustainable utilisation and transformation of the thermal energy from coalfield fires: A comprehensive review

Coalfield fires provide high-temperature heat storage at relatively shallow depths, their overburden and upper strata contain immense amounts of thermal energy, which is identical to the reservoir condition of shallow geothermal energy. Therefore, heat waste resources produced by coalfield fires can be developed and utilised as low-medium grade geothermal resources. By comparing the available methods for thermal energy extraction and conversion, it was found that the heat transfer technology using two-phase closed thermosyphon and thermoelectric conversion using thermoelectric conversion device were the most suitable for use in coalfield fire areas. As a highly effective heat conduction scheme, the two-phase closed thermosyphon was proposed as a feasible means of thermal energy extraction. Meanwhile, thermoelectric conversion device was utilised to transform thermal energy directly into electrical energy to realise the reuse of the waste heat. Some influencing factors on the heat transfer properties of two-phase closed thermosyphon were analysed, and efficiency of the thermoelectric conversion device was investigated. The thermoelectric parameters for these thermoelectric materials of interest were evaluated, and several effective methods for the improvement of thermoelectric conversion efficiency were exposed. In addition, an enhanced thermoelectric conversion and utilisation system with increased conversion efficiency was proposed. The results presented in the current study can provide a theoretical basis and technical support information for the feasible management and adequate control of coalfield fires and utilisation of the resulting thermal energy.

Electromagnetic effects and accurate wall-temperature measurement method under directly electric heating mode

By directly imposed electrical energy on metal materials with low voltage but high current to generate Joule heat is an effective energy conversion method. The corresponding temperature will quickly reach the predetermined value. It is also an effective way to achieve homogeneous heating or local non-uniform heating in the heterogeneous conductive elements, thus directly electric heating is widely used in scientific experiments and industrial practices. However, direct electrical heating method may effect by electromagnetic effect (skin effect or proximity effect) and interfere on the sensor, results in inconsistent temperature distribution or inaccurate temperature, even under the condition with power frequency (f = 50 Hz or 60 Hz). In the present paper, a comparative experimental investigation on temperature distribution of multiple parallel blocks at steady and transient process under DC and AC heating mode have been measured by infrared camera and thermocouples. It is found that the temperature measured by AC heating is always lower than that measured by DC heating under the same apparent power applied effected by electromagnetic effect. Three different sensor installations used for temperature measurement is also discussed and found an effective installation method. The electric field and temperature field in parallel blocks is further analyzed by electromagnetic-thermal coupling multiphysics solver after model verification. Moreover, another experiment discovered that the imposed external DC potential will generate a non-linear interference to the measured temperature, the temperature sensor with a good insulation can get more accurate result. These result can provide a technical guidance for direct electrical heating scientific researches and industrial application.

Mechanism insights for efficient photocatalytic reforming of formic acid with tunable selectivity: Accelerated charges separation and spatially separated active sites

Photocatalytic reforming of formic acid (FA) is considered a promising energy conversion method for producing solar fuels and valuable chemical feedstocks to achieve the carbon-neutral goal. However, the application of FA photocatalytic reforming has been restricted by the low efficiency and relatively fixed selectivity due to limited knowledge about the reaction mechanism. Herein, we study the efficient CdS/W2N3 photocatalyst system for photoreforming of FA with tunable selectivity to realize the conversion of products from H2 to syngas under simulated sunlight. Widely tunable CO:H2 ratios between 0 and 2.18 along with a record-high apparent quantum yield (AQY) of 61.00% (H2) and 76.84% (syngas) at 420 nm have been demonstrated. Both theoretical investigation and experimental results show that intrinsic N vacancies and spatially separated active sites are vital factors in achieving tunable selectivity. This work provides a insightful information to construct and understand the photocatalytic system for efficiently reforming of FA with tunable selectivity.

Ag Sputter-Deposited on MnO2-Carbon Nanotube Nanocomposites as Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media

As energy demand increases, new energy conversion methods are also sought. In this study, two MnO2 and multiwalled carbon nanotube (MWCNT) composites were prepared and decorated with silver using magnetron sputtering, to evaluate their electrocatalytic activity towards the oxygen reduction reaction (ORR). Three nominal thicknesses of Ag layers were used, 5, 10 and 20 nm. The physicochemical characterisation was carried out using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, as well as X-ray photoelectron spectroscopy. The substrate materials (MnO2-MWCNT) were also investigated by X-ray diffraction analysis. The electrochemical studies of the ORR revealed that the activity and stability of the composite catalysts depend on the substrate material and the Ag layer thickness.

A green and sustainable water evaporation-induced electricity generator with woody biochar

The generation of electricity through the natural process of water evaporation has emerged as a promising method of energy conversion. However, many advanced generators utilizing this technique, known as water evaporation-induced electric generators (WEIGs), feature a complicated fabrication process and lack output stability, hindering their practical use in real-world applications. In this study, we present a facile fabrication of an efficient WEIG based on woody biochar (WBC). WBC was prepared from lignocellulosic feedstocks (LCFs) in a tube furnace and then mixed with ethyl cellulose (EC) and ethanol to acquire a homogeneous slurry. WEIG was then fabricated in air pyrolysis after casting the slurry with a silicone pad. A key advantage of this material is the presence of hydrophilic functional groups in WBC, which allows for constant, sustainable generation of electricity from water without the need for additional hydrophilic treatments. For the first time, we thoroughly examined the formation process of WBC and evaluated the impact of WBC derived from three different components of LCFs on electricity generation. Additionally, we analyzed the electricity generation mechanism of WBC-based WEIG and the influence of botanical origin, particle size, and carbonization temperature of WBC on the electrical properties. Our findings indicate that lignin-rich WBC is particularly well-suited for use in WEIGs, suggesting the potential for widespread adoption of LCFs in hydro-voltaic power generation. Under ambient conditions, a single WEIG device was able to achieve a maximum open-circuit voltage (VOC) of 0.42 V and a short-circuit current (ISC) of 528 nA. Furthermore, when multiple devices were connected in series, a VOC of 7 V was attained, sufficient to power small commercial electronics. The implementation of these findings has the potential to pave the way for the development of green energy generators through the utilization of water evaporation on WBC.