Output Conversion Efficiency Research Articles

Experimental Investigation of the Output Performance of Compressed-Air-Powered Vehicles with a Pneumatic Motor

Compressed-air vehicles have the advantages of zero pollution and low cost. A compressed-air engine test bench is established in this study. The effects of rotational speed, torque, and regulated pressure on the power performance, economy, and energy conversion efficiency of the pneumatic motor are investigated. The differences in power output, compressed-air consumption rate, and energy conversion efficiency between forward and reverse rotation of the pneumatic motor are compared and analyzed. To effectively investigate the performance of a compressed-air vehicle under various road conditions, this study compares and analyzes the power performance, economy, and energy conversion efficiency of pneumatic motors under different road conditions. Experimental results show that the power output and energy conversion efficiency of the pneumatic motor in reverse rotation are less than those in forward rotation, indicating that the pneumatic motor has better power performance and higher efficiency with forward rotation than reverse rotation. The compressed-air consumption rate of the pneumatic motor with reverse rotation is higher than that with forward rotation, indicating that the pneumatic motor with forward rotation has better economic performance than with reverse rotation. The maximum power output and energy conversion efficiency of the pneumatic motor are about 1220 W and 13.23%, respectively.

Parametric study of cavity on the performance of a hydrogen-fueled micro planar combustor for thermophotovoltaic applications

In order to obtain high energy output power and energy conversion efficiency for micro-thermophotovoltaic system, a hydrogen-fueled micro planar combustor with cavity is designed in this work. Numerical investigations on the performance of micro-cylindrical combustors with and without cavity are executed under different cavity length, outlet size and solid wall materials. Results show that the micro planar combustor with cavity can obtain a higher and more uniform outer wall temperature comparing with the micro planar combustor without cavity. With the reduction of cavity length and outlet size, the energy output and energy conversion efficiency of MTPV is much higher, while the pressure loss becomes larger. Thus, the optimal dimensionless cavity length and outlet size is 3/9 and 5/7 × 1/3, respectively. Furthermore, with the optimal cavity length and outlet size, nickel is used as the solid wall material for higher energy conversion efficiency of MTPV system, which increases to 3.86% at the inlet velocity of 5 m/s. As a result, the micro planar combustor with cavity is more suitable in MTPV system for higher energy output and energy conversion efficiency.

Numerical investigations on the performance of a hydrogen-fueled micro planar combustor with tube outlet for thermophotovoltaic applications

As the practical application of the micro thermophotovoltaic system is limited by its low output power and energy conversion efficiency, optimizing the structure of micro combustor to enhance the thermal performance of micro combustors is an effective method. In this work, the tube outlet is proposed to enhance the heat transfer between the burned gas and combustor wall. A three-dimensional model including fluid flow, heat transfer and combustion is constructed to investigate effects of tube length, tube diameter and solid wall materials on the performance of a hydrogen-fueled micro planar combustor with tube outlet. The findings show that the tube outlet can effectively improve mean outer wall temperature and outer wall temperature uniformity of micro planar combustor, and the energy output and energy conversion efficiency of MTPV system, but the pressure loss is higher. The energy output and energy conversion efficiency of MTPV system is increased with the reduction of tube length and the increment of tube diameter, while the pressure loss is slowly decreased. Moreover, when nickel is used as the solid wall material, the energy output and energy conversion efficiency of MTPV system can reaches to 6.14 W and 3.54%, respectively.

Real-time data-based performance analysis of a large-scale building applied PV system

Solar photovoltaic (PV) is one of the fastest-growing renewable technologies. Building applied photovoltaic systems can significantly help reduce the energy and environmental loads of buildings. This study analyzes the performance of a 425 kW building applied photovoltaic system by investigating important technical, economic, and environmental parameters. These analyses have been carried out with the help of year-long real-time performance data. The technical performance indicators examined in this study include direct current and alternating current power output, array yield, specific (final) yield, references yield, array losses, module and overall PV conversion efficiency, capacity factor, and performance ratio. The main strengths of the study include the large size of the BAPV system, and a comprehensive techno-economic and environmental analysis based upon real-time monitored data. The PV system has been found to annually produce 835.60 MWh and 814.88 MWh of DC and AC power output, respectively. The performance ratio varies from 74.03% in August to 84.62% in January with an annual figure of 78.09%. The annual capacity factor is determined to be 21.85%. For a project life of 25 years, the simple payback period and Net Present Value have been calculated to be 6.92 years and USD 866,565.24, respectively. Over the project lifetime, the savings of CO2, CH4 and N2O are calculated to be 15,666 tons, 483.75 kg, and 83.25 kg respectively.

Comparison of back conversion and power differential in extra-cavity multi-optical parametric oscillator using MgO:APLN

The extra-cavity multi-optical parametric oscillator (MOPO) using MgO-doped aperiodically poled lithium niobite (MgO:APLN) is a technique to generate multi-wavelength tunable laser output, in which the back conversion and power differential can reduce the output power and conversion efficiency. A comparison of the back conversion and power differential between the two methods is presented in this paper. One approach is to adjust the mirror transmittance to change the parametric light's power density involved in the oscillation. With 1.47 μm transmittance of 20 % and 3.30 μm transmittance of 60 %, the 3.30 μm output power is 0.95 W, the 3.84 μm output power is 0.94 W, and the power ratio is 1.01. The other approach is to add two electro-optical polarization mode converters (EO PC) to change the parametric light's polarization. When the electric fields of two EO PCs are 66 V/mm and 15 V/mm, the 3.30 μm and 3.84 μm output powers are 2.54 W and 2.49 W, the conversion efficiencies are 10.3 % and 10.0 %, and the power ratio is 1.02. The comparison results confirm that both methods have the capability of back conversion suppression and power differential reduction. Compared with the adjusting transmittance, adding EO PCs has higher output power and conversion efficiency, which is the first reported method for better balanced multi-wavelength laser output.

Comprehensive numerical investigations on the thermal performance of heat recirculating micro combustor with pin fins for micro-thermal voltaic system applications

Aiming at improving the relatively low energy output and energy conversion efficiency of the micro-thermal voltaic (MTPV) system, an innovative heat recirculating micro combustor with pin fins is designed. The effects of pin fins arrangement, hydrogen/air equivalent ratio on the energy output and performance of CHMC, HMCP and HMCI are compared and investigated. The result shows that when the Vin is 6 m/s and Φ is 1.0, the emitter power of CHMC is 72.76W, and that of HCMP and HCMI micro combustor are 75.99W and 76.35W. and the emitter efficiency of CHMC, HCMP and HCMI is 41.93%, 43.26% and 44.01%. HMCI has better energy output capability compared with CHMC and HMCP. Even though, HMCI brings a higher pressure drop, it is within the acceptable range. When the Vin is 6 m/s, the pressure drop from the pin fins only accounts for 26.4% of the total pressure drop for HMCI. Through the study of equivalent ratio, it is found that HMCI has good adaptability in different equivalent ratio range. This work provides new ideas for the development of MTPV system in the future.

Fabrication and synthesis of dye-sensitized solar cells (DSSC) using Pd doped ZnO photoanodes and extract of plant leaves as a natural dye

ABSTRACT A dye-sensitized solar cell (DSSC) is a photovoltaic-based electrical panel available in different colors. The working electrode of the cell consists of a Pd-doped ZnO nanocomposite. UV-Visible spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, Selected-area electron diffraction (SAED), Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscopy (TEM), Electrochemical Impedance Spectroscopy (EIS), and Incident Photon-to-Current Conversion Efficiency (IPEC) techniques characterized nanoparticles so synthesized. XRD results revealed that the hexagonal wurtzite phase of ZnO remains constant by doping with different molarity concentrations of Pd. The TEM result suggested that the particle featured a spherical shape with uniform distribution over the surface of ZnO. The effect of the thickness of semiconducting layers at the photoanode shows that photocurrent density stopped increasing and became constant for samples doped with 0.46 M Pd. On the other hand, the photocurrent density of the network cell gave a linear increase for samples doped with natural dye, contributing to the enhanced performance of the DSSC. It is about the thickness of the photoanode choice of chemical and natural dye that makes a difference with other solar cells synthesized by different methods. The electricity produced by our synthesized solar cell possibly allows us to harvest with a safe and power output conversion efficiency of 11.92% in real-time without interruption.

Design of high-performance photovoltaic-thermoelectric hybrid systems using multi-objective genetic algorithm

Hybrid systems which integrate photovoltaic (PV) and thermoelectric generator (TEG) can improve the utilization of solar energy. In this study, a multi-objective genetic algorithm (MOGA) is adopted to maximize the output power and conversion efficiency for the PV-TEG system, where the CFD model is coupled in the optimization procedure and the penalty function is employed to ensure the appropriate operating temperature. Meanwhile, two geometric parameters along with two boundary conditions are selected as the design variables, while the effects of three cooling conditions are also discussed. Compared with the PV only system, the output power of the PV-TEG system is improved by up to 11.52% with the conversion efficiency also improved by 44.97%. At the same solar concentration condition, the optimal PV-TEG system could increase the output power by 36%. Based on the analysis of optimal solutions, it is demonstrated that the adopted TEG contributes significantly to the output power, while a better cooling condition also has a positive effect on the comprehensive performances. Furthermore, a multiple-criteria decision-making approach is applied to balance output power and conversion efficiency. Compared with the maximum efficiency solution, the best compromise solution increases output power by 120.02% and decreases the efficiency only by 14.83%.

High performance of Bi2Te3-based thermoelectric generator owing to pressure in fabrication process

A Bi2Te3-based thermoelectric generator (TEG) is known to be the leading technology in low-temperature heat energy recovery. In its fabricating process, the thermoelectric (TE) materials should be heated over the melting temperature of tin solder, but the unmatched thermal expansion between p-type and n-type TE materials will lead to considerable interfacial resistivity, resulting in the sharp decrease of the output power and conversion efficiency. Here, we introduce the pressure to suppress interfacial resistance of Bi2Te3-based TEGs. The theoretical model governing the pressure and interfacial resistivity is built based on the equations of thermal-electric-elastic coupling, and the explicit expressions for maximum output power and conversion efficiency are derived when considering interfacial resistivity. With the guidance of theoretical and simulation results, the average interfacial resistivity of 10 μΩ·cm2 is measured in a Bi2Te3-based TEG, while the conversion efficiency is increased by 44% from the commercial devices. Besides, the stress caused by suitable pressure force is less than the allowable stress of Bi2Te3-based TE materials. These findings provide strong support for the fabrication of high-performance TEGs.

Band gap tunning to enhance photovoltaic response in NaNbO3-based bulk ferroelectrics

The observation of anomalous photovoltaic effect and switchable photocurrent in ferroelectrics receive extensive attention for its great advantages in next-generation high-performance photovoltaic devices, but the key factor, the wide band gap results in low photocurrent output and photoelectric conversion efficiency. Focusing on narrowing band gap to improve photovoltaic performance in NaNbO3, in this work, we fabricated the NaNbO3 and 0.8NaNbO3-0.2La(Mn0.5Ni0.5)O3 (abbreviated as 0.2NLMNO) ferroelectric ceramics through a solid state method. The optical absorption spectra reveal the band gap of ceramics reduce from 3.42 eV to 2.11 eV and the light absorption in visible region is significantly enhanced. A higher symmetry of crystal structure and great reduced resistance of grain and grain boundary induced by introducing La(Mn0.5Ni0.5)O3. What's more, the photocurrent density of 0.2NLMNO improves approximately 10 times larger than that of pure ferroelectric NaNbO3, it is expected to explore a new ferroelectric material with photovoltaic effect.

Evaluation of energy recovery potential of solar thermoelectric generators using a three-dimensional transient numerical model

The solar thermoelectric generator (STEG) is regarded as a promising energy conversion technology to convert solar heat into electricity. Considering the real solar irradiance, impedance matching, and interface contacts, a comprehensive three-dimensional transient thermal-electric numerical model for the STEG is established to evaluate its dynamic response and energy recovery potential. The transient performance prediction of the STEG during the whole daytime is completed for the first time. Due to the temperature limitation of thermoelectric materials, the allowable concentration ratio for the Bi2Te3-based STEG is 150 suns, corresponding to the average daytime output power of 13.16 W and the average daytime conversion efficiency of 6.15%. Dynamic responses of output voltage and conversion efficiency present the same changing trend as solar irradiance. However, the steady-state numerical model underestimates the output power by 6.91% and overestimates the conversion efficiency by 1.85%, due to the ignorance of thermal inertia during thermal diffusion. The established transient model can predict more reasonable results and is well verified via transient experiments. It is obtained that the STEG can produce 491.4 kJ of electricity a day and 49.79 kW h a year, and the theoretical cost-recovery cycle for the cost of the thermoelectric generator module is 1.61 years.

Research on the output characteristics of laser wireless power transmission system with nonuniform laser irradiation

Laser wireless power transmission (LWPT), which can realize long-range power transmission, has been received widespread attention in recent years. The influence of high-power laser nonuniform irradiation on the output power and conversion efficiency of photocells has attracted much attention. This article conducted simulations and experiments on nonuniform irradiation with a constant power density and on nonuniform irradiation with constant incident power. The current I, voltage V, output power PL, conversion efficiency ηL, internal resistance R0, and maximum power point resistance RLmax of a 1 cm × 1 cm single-junction gallium arsenide photocell under nonuniform irradiation were studied. Under the condition of nonuniform irradiation with a constant laser power density, the conversion efficiency of the photocell remained constant, but R0 increased nonlinearly from 0.5 to 5 Ω. The ηL decreased from 45% to 5% when the load resistance is constant. Under the condition of nonuniform irradiation with constant laser power, the photoelectric conversion efficiency and R0 changed little, and the ηL remained about 45%, for it is not affected by nonuniform irradiation. The output characteristics of the photocells under uniform irradiation were also studied, and the results were consistent with the above conclusions. When the photocells with constant temperature were irradiated in-homogeneously, it was also revealed that the internal resistance increased and that the conversion efficiency decreased due to the irradiation power variation. The empirical formula was derived through circuit transformation and curve fitting.

Global sensitivity analysis of photovoltaic cell parameters based on credibility variance

Photovoltaic cells can directly convert solar energy into electrical energy, which is environmentally friendly and has a wide range of applications. In practical engineering, the uncertainty of photovoltaic cell parameters has an important impact on cell performance. In order to study the influence of parameter uncertainty on the output performance of photovoltaic cells, a photovoltaic cell model is established and five parameters are selected: irradiation intensity, photovoltaic cell surface temperature, temperature coefficient, equivalent series resistance and equivalent parallel resistance. The influence of these parameters on the output power and conversion efficiency of photovoltaic cells is studied by using the global sensitivity analysis method based on fuzzy theory. The principal and total global sensitivity indexes describing the influence of each parameter on the output performance were therefore calculated and ranked. The key parameters influencing the performance of photovoltaic cells were determined to be related to cell surface temperature and equivalent parallel resistance. In actual production and life, the output performance of photovoltaic cells can be improved by controlling these two factors. The results of this study can help to guide the performance analysis and parameter optimization of photovoltaic cells, accelerating the development and improving the adoption of photovoltaic systems.

A Solvothermal Synthetic Environmental Design for High‐Performance SnSe‐Based Thermoelectric Materials

AbstractSnSe is challenging to use in thermoelectric devices due to difficulties in simultaneously optimizing its thermoelectric and mechanical properties. Here, the authors show a unique solvothermal synthetic environmental design to fabricate super‐large and micro/nanoporous Sn0.965Se microplates by using CrCl3. Cl− ions to trigger Sn‐vacancy formation and optimize the hole concentration to ≈3 × 1019 cm−3, while the as‐formed Cr(OH)3 colloidal precipitations act as “templates” to achieve micro/nanoporous features, leading to low lattice thermal conductivity of ≈0.2 W m−1 K−1 in the as‐sintered polycrystal, contributing to a high ZT of ≈2.4 at 823 K and an average ZT of ≈1.1. Of particular note, the polycrystal exhibits high hardness (≈2.26 GPa) and compression strength (≈109 MPa), strengthened by grain refinement and vacancy‐induced lattice distortions and dislocations; while a single‐leg device provides a stable output power (>100 mW) and conversion efficiency of ≈10% by a temperature difference of 425 K, indicating great potential for applying to practical thermoelectric devices.

An Energy Harvester Coupled with a Triboelectric Mechanism and Electrostatic Mechanism for Biomechanical Energy Harvesting.

Energy-harvesting devices based on a single energy conversion mechanism generally have a low output and low conversion efficiency. To solve this problem, an energy harvester coupled with a triboelectric mechanism and electrostatic mechanism for biomechanical energy harvesting is presented. The output performances of the device coupled with a triboelectric mechanism and electrostatic mechanism were systematically studied through principle analysis, simulation, and experimental demonstration. Experiments showed that the output performance of the device was greatly improved by coupling the electrostatic induction mechanisms, and a sustainable and enhanced peak power of approximately 289 μW was produced when the external impedance was 100 MΩ, which gave over a 46-fold enhancement to the conventional single triboelectric conversion mechanism. Moreover, it showed higher resolution for motion states compared with the conventional triboelectric nanogenerator, and can precisely and constantly monitor and distinguish various motion states, including stepping, walking, running, and jumping. Furthermore, it can charge a capacitor of 10 μF to 3 V within 2 min and light up 16 LEDs. On this basis, a self-powered access control system, based on gait recognition, was successfully demonstrated. This work proposes a novel and cost-effective method for biomechanical energy harvesting, which provides a more convenient choice for human motion status monitoring and can be widely used in personnel identification systems.

High thermoelectric performance of PNP abrupt heterostructures by independent regulation of the electrical conductivity and Seebeck coefficient

Improving thermoelectric conversion efficiency is a hotspot in the current field of thermoelectricity. In this work, a novel scheme for the PI-Bi0.5Sb1.5Te3/N-Bi2Te2.97Se0.03/PII-Bi0.5Sb1.5Te3 abrupt heterostructure vertical to temperature gradient is presented, resulting in theoretical results of high output power and conversion efficiency. Under the effect of temperature gradient, the hole concentrations in the PNP heterostructure change linearly and the build-in voltages also vary. As a result, the PNP heterostructure can possess the amplifying characteristic of the bipolar transistor, namely, the forward conduction occurs at the cold end in PI-N junction and the reverse bias occurs at the hot end in N-PII junction. The calculation results show that the optimal output power can reach 48.38 mW and conversion efficiency can reach 14.56% at ΔT = 50 K. This work offers a new idea and method for the realization and application of high-performance thermoelectric materials.

Efficient Lasing Through Raman-Assisted Four-Wave Mixing With Intrinsic Weak Spectral Broadening Characteristics

Narrow linewidth nonlinear frequency conversion has attracted numerous research attentions. In this manuscript, we demonstrate efficient frequency conversion with weak spectral broadening characteristics through Raman-assisted four-wave mixing (FWM) process in birefringent phosphosilicate fiber. The output power of the generated Stokes light reaches 12.05 W, with a conversion efficiency of 67.4%. Compared to previously reported FWM-based fiber lasers with output power and conversion efficiency below watt level and 50% respectively, our result shows significant improvement. Besides, benefiting from the strict phase match requirement of FWM process, this laser system has unique advantages in suppressing spectral broadening, the output linewidth of which is less than half of the conventional Raman fiber laser under same power level. Furtherly, we propose a power balance model to describe the power evolution characteristics of the Raman-assisted FWM process, proving the advantage of phosphosilicate fiber in improving the conversion efficiency of FWM process. This work gives a reference for efficient narrow linewidth frequency conversion or amplification.

First principles study of monolayer Sb2S2Te and a mathematical model of a thin-film thermoelectric generator with maximum power point tracing

The result of the structural, electronic and thermoelectric performance of monolayer Sb2S2Te, which is a bran-new material, is calculated by using the method of full-potential linearized augmented plane-wave (FP-LAPW), and the exchange-correlation potential selected in this paper is generalized gradient approximation (GGA) scheme. There are no negative frequencies in the calculated phonon spectra, which demonstrates that dynamics of monolayer Sb2S2Te is stable in theory. The average value of lattice thermal conductivity (κl) is smaller than that of other thermoelectric (TE) materials, and monolayer Sb2S2Te has larger figure of merit (ZT) comparing with other well-known materials. According to the TE parameters (Seebeck coefficient S, electrical conductivity σ, electronic thermal conductivity κe and lattice thermal conductivity κl) of monolayer Sb2S2Te, an idealized model of thermoelectric generator (TEG) and a realistic model of maximum power point tracking (MPPT) are built. In addition, this paper studies the influence of different temperature zones, different temperature differences, cross sectional area, height and the number of P–N junction on output power and conversion efficiency of TEG. The results of physical calculation and simulation models show that the conversion efficiency of TEG of monolayer Sb2S2Te is larger than or close to that of other well-known materials, and the tracking accuracy of MPPT proposed in this paper is higher than or close to that of other researches.

Hybrid Energy‐Harvesting System by a Coupling of Triboelectric and Thermoelectric Generator

Triboelectric nanogenerator (TENG) is considered as one of the critical parts for the construction of Internet of Things (IoTs) by harvesting distributed energy. However, its high alternating current voltage output characteristic is not suitable for directly driving electronics and the undesirable heat generated during friction will cause friction of dielectric layer and energy loss. Herein, an energy‐harvesting device is designed, which includes an adaptive rotating triboelectric nanogenerator (AR‐TENG) coupling of a thermoelectric generator (ThEG) and a matching transformers circuit. The AR‐TENG is beneficial to reduce the friction by dielectric layer's inherent elasticity and the ThEG can reuse the inevitable heat with Seebeck effect. Besides, the maximal output conversion efficiency of the designed transformers circuit for AR‐TENG is enhanced up to 96.4%. Therefore, the energy storage velocity of the whole device charging supercapacitor is improved almost by 28 times than that of alone AR‐TENG. This finding not only provides a strategy to improve the energy‐harvesting efficiency of TENG, but also offers a wide application for TENG in IoTs.

Energy Conversion Efficiency of Thermoelectric Power Generators With Cylindrical Legs

Abstract Thermoelectric power generators (TEGs) have been attracted increasing attention due to their capability of converting waste heat into useful electric energy without hazardous emissions. Many theoretical models to conduct their performance analysis are developed based on the generalized heat transport theory. However, most of them are assumed that the TEGs are thermally isolate from the surroundings except for the heat exchange at hot and cold reservoirs. This paper develops a theoretical model to study the performance of TEGs with cylindrical legs, and the influence of convective heat loss between lateral surfaces of legs and ambient environment is considered. Analytical solutions for temperature distribution inside the TEG, power output and energy conversion efficiency are obtained by using eigenfunction expansion method. A new dimensionless impact factor H is introduced to capture the convective heat effect, and the maximum energy conversion efficiency can be evaluated by the figure of merit, impact factor H and temperature ratio of heat sink to hot source for a well-designed TEG. There exists an optimal leg’s height for maximum energy conversion efficiency when the convective heat loss on lateral surfaces of thermoelectric legs and electrode thermal resistance are considered. The conclusions provided in this paper will be very helpful in the designing of high-performance TEG devices.