Power Generation Applications Research Articles

Characterization of Bipolar Transport in Hf(Te1−xSex)2 Thermoelectric Alloys

Control of bipolar conduction is essential to improve the high-temperature thermoelectric performance of materials for power generation applications. Recently, Hf(Te1−xSex)2 alloys have gained much attention due to their potential use in thermoelectric power generation. Increasing the Se alloying content significantly increases the band gap while decreasing its carrier concentration. These two factors affect bipolar conduction substantially. In addition, the weighted mobility ratio is estimated from the experimental electronic transport properties of Hf(Te1−xSex)2 alloys (x = 0.0, 0.025, 0.25, 0.5, 1.0) by using the Two-Band model. From the bipolar thermal conductivity also calculated using the Two-Band model, we find that it peaks near x = 0.5. The initial bipolar conductivity increase of x < 0.5 is mostly due to the decrease in the weighted mobility ratio and carrier concentration with increasing x. For x > 0.5, the drop in the bipolar conductivity can be understood with significant band gap enlargement.

Defect-Engineering-Stabilized AgSbTe2 with High Thermoelectric Performance.

Thermoelectric (TE) generators enable the direct and reversible conversion between heat and electricity, providing applications in both refrigeration and power generation. In the last decade, several TE materials with relatively high figures of merit (zT) have been reported in the low- and high-temperature regimes. However, there is an urgent demand for high-performance TE materials working in the mid-temperature range (400-700 K). Herein, p-type AgSbTe2 materials stabilized with S and Se co-doping are demonstrated to exhibit an outstanding maximum figure of merit (zTmax ) of 2.3 at 673 K and an average figure of merit (zTave ) of 1.59 over the wide temperature range of 300-673 K. This exceptional performance arises from an enhanced carrier density resulting from a higher concentration of silver vacancies, a vastly improved Seebeck coefficient enabled by the flattening of the valence band maximumand the inhibited formation of n-type Ag2 Te, and ahighly improved stability beyond 673 K. The optimized material is used to fabricate a single-leg device with efficiencies up to 13.3% and a unicouple TE device reaching energy conversion efficiencies up to 12.3% at a temperature difference of 370 K. These results highlight an effective strategy to engineer high-performance TE material in the mid-temperature range.

Wind energy as a source of green hydrogen production in the USA

Abstract The study incorporates an overview of the green hydrogen-production potential from wind energy in the USA, its application in power generation and the scope of substituting grey and blue hydrogen for industrial usage. Over 10 million metric tons of grey and blue hydrogen is produced in the USA annually to fulfil the industrial demand, whereas, for 1 million metric tons of hydrogen generated, 13 million metric tons of CO2 are released into the atmosphere. The research aims to provide a state-of-the-art review of the green hydrogen technology value chain and a case study on the production of green hydrogen from an 8-MW wind turbine installed in the southern plain region of Texas. This research estimates that the wind-farm capacity of 130 gigawatt-hours is required to substitute grey and blue hydrogen for fulfilling the current US annual industrial hydrogen demand of 10 million metric tons. The study investigates hydrogen-storage methods and the scope of green hydrogen-based storage facilities for energy produced from a wind turbine. This research focuses on the USA’s potential to meet all its industrial and other hydrogen application requirements through green hydrogen.

Design and analysis of semi-submersible offshore floating wind and photovoltaic platforms

The ocean holds excellent potential for green energy, and the sea can provide green energy to humans. For offshore structures and green energy development, the current floating offshore system has a single function and cannot fully utilize green energy. Therefore, this paper combines the development of wind and solar power to design a floating offshore structure. The report determined the configuration design of the platform and decided to choose a semi-submersible platform, select the type and size of wind turbine and photovoltaic panel models, calculate the wind load and wave load that the platform is subjected to, and finally calculate the cost of the forum. The wind load on a single wind turbine is estimated to be 26590.14N, and the wind load on all PV panels is 216180N, costing about 18487 RMB/kW. In this paper, the close combination of photovoltaic and wind power generation can guarantee the effective implementation of renewable energy and then improve the wind power generation and photovoltaic power generation application system based on the effective combination of the two.

Characterization of tamarind biomass to substantiate the feasibility towards alternative fuel

Sustainable energy resources development from every possible route is the utmost priority in today’s modern scenario around the globe. This situation reaches highly alarming rate after the pandemic situation due to the shortcomings on ease transportation viability among all the countries. Therefore, the present work aims at developing a sustainable biofuel from Tamarind seed biomass samples and to evaluate its suitability for various power generation applications. The proposed work consists of three samples: tamarind shell (TAN1), tamarind nut with peel (TAN2) and tamarind nut without peel (TAN3) undergoing physicochemical and thermal analyses to analyse their feasibility as a biofuel. Fourier transform infrared spectroscopy (FTIR) concluded high oxygenated compounds mainly alcohols, esters and carboxylic acids were determined at higher wave numbers. Ultimate and proximate analyses gave high amounts of carbon, volatile matter and low nitrogen and ash content. Thermogravimetric (TG) analyses showed the maximum mass loss in the temperature range of 150 °C–400 °C and confirm the presence of volatile compounds. It was mainly due to the degradation of hemicellulose. Calorimetry test gave high heating value (HHV) results and those compared with the empirical values calculated using the ultimate analysis equation. TAN3 is selected as a promising feedstock for pyrolysis and the characterization results signify the presence of organic compounds and infer high energetic value and bio refining potential. The bio oil obtained was characterized and analysed using GC–MS, FTIR, and H NMR to assess the bio oil potential as alternative fuel and presented in this paper.

Screening Metal Electrodes for Thermoelectric PbTe.

Historically, both p- and n-type PbTe show extraordinary thermoelectric figures of merit within 300-600 °C for power generation applications. A full realization of the potential of these high-performance thermoelectric materials on a device level largely depends on the electrical and thermal contacts with the metal electrodes. Chemical inertness with a slow diffusion could be an important criterion for the selection of metal electrodes. In this work, the diffusion of the total 12 potential metal electrodes in PbTe diffusion couples are focused on and sorted, suggesting the superiority of Co as an electrode for its low diffusion coefficient and interfacial contact resistivity, inertial to PbTe and compatibility in temperature for sintering. The strategy used in this work is believed to be applicable to the selection of electrodes for other thermoelectric materials.

Algorithm for Cycle-To-Cycle Firing TDC Identification Based on Wasted Spark Duration Measurements in Small Engines

Spark ignition (SI) engines are often used as distributed power generation applications. They ensure quick deployment, cost effective electricity, and are a valid choice for back-up power. An essential aspect for small size engines is to improve control margins without increasing the number of sensors. It is not uncommon to employ fixed ignition timing for such power units, with so called wasted spark systems. These feature two spark events per cycle, one during compression and one during the exhaust stroke. On the other hand, ever more complex control systems are applied for this engine category in the search for better efficiency and lower emissions. Control of actuators that is phased with the working cycle could represent a significant advantage in this context. A method previously developed for identifying top dead center (TDC) phasing offline was applied as an algorithm capable of performing the required task while the engine is running. It is based on current measurements in the secondary ignition circuit of systems that feature wasted spark operation. Validation was performed on a 50 cm3 SI unit connected to a 1 kW power generator. Statistical distribution during sequences of 1000 cycles recorded at five different levels of load was used for testing TDC identification capabilities. Results were also compared to evaluations based on engine speed measurements. The overall TDC identification success rate of the proposed algorithm was found to be over 99.8%.

Reduced graphene oxide composite nanowood for solar-driven interfacial evaporation and electricity generation

Solar-driven interfacial evaporation (SDIE) is considered one of the most promising technological approaches to solve the freshwater shortages. Based on renewable wood, we fabricated the nanowood loaded with reduced graphene oxide (RGO@Nanowood) with high SDIE performance. Its superior performance benefits from three aspects: Firstly, the cellulose network in nanowood treated by delignification contains many hydrophilic groups, which significantly improves the hydrophilicity and can combine with water molecules through hydrogen bonds to generate more activated water, thereby reducing the enthalpy of evaporation. Secondly, the photothermal conversion capability of RGO@Nanowood was significantly improved by loading RGO with an impregnation-reduction method. Finally, the 2D water supply strategy achieves an ideal balance of water transport and thermal management and controls the water content within the pore channels to expose more evaporation space. Under simulated sunlight (1.0 kW m−2), the evaporation rate and evaporation efficiency of RGO@Nanowood were 2.26 kg m−2h−1 and 92.71 %, respectively. In the outdoor experiment, the daily freshwater production of 6.39 kg m−2 was obtained on sunny days. Furthermore, the hydroelectric effect of RGO@Nanowood under solar-driven evaporation proved its potential for power generation applications.

Laser Directed Energy Deposition-Based Additive Manufacturing of Fe20Cr5.5AlY from Single Tracks to Bulk Structures: Statistical Analysis, Process Optimization, and Characterization

Laser directed energy deposition (LDED) can be deployed for depositing high-performance materials for various engineering applications. Alumina-forming steel is a high-performance material that possesses excellent corrosion and oxidation resistance, finding application in the power generation sector. In the present work, LDED using powder feeding (LDED-PF) was used to deposit Fe20Cr5.5AlY alloy using single-track, multi-track, and multi-layer deposition on SS 316L substrate. Response surface methodology (RSM)-based optimization was used to optimize the single-track deposition. The relationship between the track geometry parameters and the build rate with the LDED-PF processing parameters was studied. Further, the nonlinear relationship among the major process parameters was developed and an analysis of variance (ANOVA) was utilized to find significant parameters. The multi-track deposition yielded densely clad layers with a columnar grain structure. The presence of complex oxide slag of Y, Al, and Zr on the clad layer was detected. A micro-hardness of 240–285 HV was observed in the clad layer, with a hardness of 1088–1276 HV at the slag layer. The multi-layered structures showed a relative density of 99.7% with columnar growth and an average microhardness of 242 HV. The study paves the way for the deposition of dense alumina-forming steel structures for building components for power generation applications.

High-performance Marangoni hydrogel rotors with asymmetric porosity and drag reduction profile

Miniaturized rotors based on Marangoni effect have attracted great attentions due to their promising applications in propulsion and power generation. Despite intensive studies, the development of Marangoni rotors with high rotation output and fuel economy remains challenging. To address this challenge, we introduce an asymmetric porosity strategy to fabricate Marangoni rotor composed of thermoresponsive hydrogel and low surface tension anesthetic metabolite. Combining enhanced Marangoni propulsion of asymmetric porosity with drag reduction of well-designed profile, our rotor precedes previous studies in rotation output (~15 times) and fuel economy (~34% higher). Utilizing thermoresponsive hydrogel, the rotor realizes rapid refueling within 33 s. Moreover, iron-powder dopant further imparts the rotors with individual-specific locomotion in group under magnetic stimuli. Significantly, diverse functionalities including kinetic energy transmission, mini-generator and environmental remediation are demonstrated, which open new perspectives for designing miniaturized rotating machineries and inspire researchers in robotics, energy, and environment.

Profiling cross-sectional area of a radial rotating detonation combustor to increase pressure gain

The detonation wave(s) in a rotating detonation combustor (RDC) produce highly unsteady flow with varying supersonic and subsonic segments. The non-homogeneous RDC flow must be conditioned to improve its uniformity, which can increase the performance and operation of the downstream hardware for propulsion and power generation applications. In this study, the RDC channel and converging nozzle are combined into a single flow conditioning device, and Gradual to rapid (GTR), Linear, and Rapid to Gradual (RTG) strategies to profile the cross-sectional area of the combined channel are introduced. An inward flowing disk-RDC (D-RDC) operated on gaseous methane-oxygen is numerically investigated using a quasi-two-dimensional computational fluid dynamic (CFD) simulation with a curvilinear coordinate system. The study focuses on the combined channel to isolate the effects of area profiling and neglects radial to axial turning of the flow necessary to integrate it, for example, with an aerospike nozzle located downstream. Simulations show that the RTG area profile yields a higher performance compared to GTR and Linear cases. The RTG profile is also shown to improve pressure and temperature uniformity of the RDC flow at the throat. Results are analyzed to show that a rapid decrease in the cross-sectional area closer to the detonation for the RTG profile improves the stability of the detonation process and constrains the expansion of product gases behind detonation to orient the flow radially inwards. Therefore, profiling the cross-sectional area of an RDC can be vital in improving the operability and effective integration of the downstream hardware.

Synergistically Enhanced Thermoelectric and Mechanical Performance of Bi2te3 Via Industrial Scalable Hot Extrusion Method for Cooling and Power Generation Applications

Synergistically Enhanced Thermoelectric and Mechanical Performance of Bi2te3 Via Industrial Scalable Hot Extrusion Method for Cooling and Power Generation Applications

Magnetotelluric investigations over geothermal provinces of India: an overview

Magnetotelluric (MT) and audio-magnetotelluric (AMT) studies are sensitive to the geothermal fluids filling the faults and/ or fracture zones of the geothermal system. In India, MT/AMT studies have been carried out in NW Himalayas, central, eastern, and western India. In other areas, detailed MT/AMT studies need to be expedited. This review paper presents the art of geothermal exploration in India by using MT/AMT techniques and identifies potential zones that can be exploited for power generation and direct application. Reservoir characteristics, carbon emissions reduction methods, and levelised cost factor are also discussed.

High-Efficient Bladeless Expander Concept

Tesla bladeless expanders are promising in energy harvesting and small-scale power generation applications due to their lower cost and simplicity in design. Although such expanders exhibit very high rotor efficiency (analytical total to static efficiency ~ 90%), it shows poor performance when coupled with a stator (experimental total to static efficiency ~30%) due to losses present in the stator and stator-rotor interaction. This paper presents the design and experiment of a novel, high-efficient Tesla bladeless expander concept. The concept arises from the loss phenomena in the stator-rotor interaction in conventional bladeless expanders, which are among the main causes of the low performance. This concept is believed to bring the bladeless expanders to the same performances as the traditional ones with vanes, compared to which however the bladeless machines boast greater simplicity, robustness, and the absence of performance decay as the size decreases, competing even in the contexts for traditional turbomachinery. The high-efficient bladeless expander prototype with water as a working fluid is designed and developed, representing the similitude case for a liquid butane heat pump. The available isentropic power across the throttling process in the butane case is 3.3 kW @10000 rpm. The turbine consists of 24 nozzles and 150 disks separated by 0.1 mm spacers. The turbine shaft is connected to the high-speed electric generator. The performance test on the expander is carried out at rotational speeds ranging from 3000 rpm to 6200 rpm and with differential pressure across the expander up to 14 bar. Experimental ventilation loss is characterised and its effect on the performance of the expander is discussed. The preliminary results of the expander under investigation showed satisfactory production of power with an acceptable efficiency range. It is also shown that the present concept is promising and able to address the major i.e., stator-rotor interaction which is the major source of loss in the traditional bladeless expander.

Electrothermal System Design and Evaluation of Low EMI and Thermally Balanced 150 kW T-Type Traction Inverter

Power electronics switching devices utilized in traction, propulsion, and power generation applications require advanced thermal management systems and extensive electromagnetic interference filtering components. The traditional indirect cooling methods exhibit limited ability to target switching location hotspots, causing limited cooling capabilities and thermal imbalance. Additionally, they rely on metallic structures directly integrated with module base plates, allowing for an accentuation of common-mode noise. These effects present themselves concurrently, creating reliability concerns while requiring further noise filtering. This work demonstrates the integration of a nonmetallic jet impingement cooler for direct base plate thermal management of a 150 kW silicon-carbide inverter. The use of nonmetallic structures manufactured through additive techniques limits low-induction capacitance pathways by 99%, leading to a 25 dB reduction in common-mode noise. Impingement jets focused on module hotspots reduce maximum device temperatures and increase thermal uniformity. Finally, by attaching individual jet coolers to each power module, hydraulic circuit networks are used to demonstrate thermal balancing between power devices for optimal current sharing.

Modified Perturb and Observe Approach in MPPT for a Standalone Photovoltaic System

This paper proposes a modified perturb and observe algorithm approach to increase the output power of an independent photovoltaic system. Today, photovoltaic application as renewable energy power plant has been prevalent. This popularity is because photovoltaic power plants are easy to apply on-grid and off-grid schemes. In standalone power generation applications, the increased photovoltaic output power is of great help to users as it contributes to increasing overall system efficiency. The perturb and observe algorithm has been known as a reliable and inexpensive method. However, the performance still needs to be improved. Therefore, this study proposes a modified perturb and observe algorithm approach. The research results show the superiority of the proposed method.

Effect of associated gas utilization on the creep life of gas turbines employed for power generation application

Utilizing associated gas (A-Gas) in gas turbines for power generation applications would greatly solve some of the acute power challenges Nigeria is faced with over the years. However, utilizing A-Gas to generate a given power demand, would necessitate the engine fired with associated gas to consume more fuel; thereby causing the engine to operate at elevated turbine entry temperatures, which may affect the creep life of the turbines. This study investigates the effect of associated gas utilization on the creep life of gas turbines. GasTurb details 5.1 was employed to model the A-Gas fuel, while GasTurb 11 was used to model and simulate the performance of the aero-derivative gas turbine engine fired with natural gas and associated gas separately. The input and output gas path parameters obtained from GasTurb simulations which include mass flow rate, Pressure ratio, turbine entry temperature, engine rotational speed, power output etc. were used as input to size the HP turbine Blade. Larson Miller parameter and blade metal temperatures obtained for different sections of the blade were used to estimate the time to failure of the HP turbine blade for the two conditions (blade of engine fired with natural gas and A-gas separately) investigated. The results show that the estimated time to failure of the HP turbine blades for engine fired with natural gas is 49,821.4 h as against 33,158 h for the one operated with A-Gas fuel.

Biomimetic and Constructal Design of Alveolus-Inspired Extended Surfaces for Heat Dispersion

Biomimetics is a school of design based on taking inspiration from nature to solve complex problems. This is done with the assumption that the natural world already has solutions to many engineering problems that have been refined through trial and error—an example of the constructal law. In this study, biomimicry is used to investigate the impact of the shape of an extended surface for mixed convection cooling within the context of the cavity problem. This is a simplified two-dimensional case that aims to develop new heat dispersal ideas for use in electronics, power generation, and industrial applications. A numerical model is developed and solved using ANSYS Fluent and the results were examined for varying Reynolds, Rayleigh, and Richardson numbers with the goal of maximizing heat transfer. The results show that the alveolus-inspired fin design provides better heat transfer compared with the design based on a rectangular fin in a cavity.

Controlled growth of Ag-ZnO thin films by thermal evaporation technique for optimized thermoelectric power generation

This manuscript is described the facile and cost-effective growth of silver Zinc Oxide (Ag-ZnO) thin films by simple thermal evaporation method for thermoelectric power generation applications. Growth of samples is started by making pellets of pure silver (Ag) and zinc (Zn) powders which are composed of 1:1 ration and evaporated in vacuum tube furnace. The other growth parameters are fixed as; evaporation time (45 min), evaporation temperature (1010 0C) and oxygen flow rate (60 sccm). Five samples are prepared at different source to substrate distances (6.5–8.5 in.) and post deposition annealing of all samples is carried out at 800 °C using semi-programable muffle furnace. Prepared thin films are analyzed using X-Ray Diffraction (XRD), Raman spectroscopy, Scanning Electron Microscope (SEM) and Seebeck measurements to study the impact of various source to substrate distances on the structural morphological and thermoelectric behavior of Ag-ZnO nanocomposite thin films. The obtained results are revealed that different source to substrate distances strongly influence the structural, morphological, and thermoelectric behavior of prepared thin films. Optimal values for electrical conductivity, Seebeck coefficient and powerful factor of synthesized thin films are calculated as 3.05 × 103 S/m, 645 µV/°C and 1.27 × 10−3 Wm−1 oC−2 respectively at source to substrate distance of 7.0 in.

Open-Circuit Fault Diagnosis Method for Grid-Connected Bidirectional T-Type Converter Based on Geometrical Similarity Measurement

Grid-connected bidirectional T-type converter (GBTC) is widely used in power generation, vehicle-to-grid, and other applications because of its bidirectional energy flow and superior performance. However, transistor open-circuit fault can cause serious output harmonics and even system outage. In this work, a novel open-circuit fault diagnosis method is proposed based on geometrical similarity measurement, which is suitable for the rectifier state and inverter state of the GBTC. Under healthy and faulty conditions, current paths and distortions are deeply analyzed. To evaluate the distortions, reference geometry vectors and current geometry vectors constructed from the grid angle and normalized currents are studied. Geometry features including vector triangle area, structural similarity, and contour similarity are used to measure the similarities among the vectors and carry out fault detection, fault phase location, and fault transistor location, respectively. Reasonable diagnostic thresholds are designed, and no additional sensor is needed. The robustness and effectiveness of the method are verified by experiment results.