Analysis Of Energy Conversion Efficiency Research Articles

Furfural Influences Hydrogen Evolution and Energy Conversion in Photo-Fermentation by Rhodobacter capsulatus

Furfural, as a typical byproduct produced during the hydrolysis of lignocellulose biomass, is harmful to the photo fermentation hydrogen production. In this work, the effects of furfural on the photo fermentation hydrogen production by Rhodobacter capsulatus using glucose as substrate were investigated. The characteristics of cell growth, hydrogen production, and fermentation end-products with the addition of different concentrations of furfural (0–20 mM) were studied. The results showed that furfural negatively affected the maximum hydrogen production rate and total hydrogen yield. The maximum hydrogen yield of 2.59 ± 0.13 mol-H2/mol-glucose was obtained without furfural. However, 5 mM furfural showed a 40% increase in cell concentration. Furfural in high concentrations can favor the overproduction and accumulation of inhibitive end-products. Further analysis of energy conversion efficiency showed that most of the energy in the substrate was underused and unconverted when the furfural concentration was high. The maximum glucose consumption (93%) was achieved without furfural, while it dramatically declined to 7% with 20 mM furfural addition. The index of half-maximal inhibitory concentration was calculated as 13.40 mM. Moreover, the possible metabolic pathway of furfural and glucose was discussed.

Numerical analysis of energy conversion efficiency and thermal reliability of novel, unileg segmented thermoelectric generation systems

Despite their great potential to recover waste heat, thermoelectric generators (TEGs) find limited usage since thermoelectric materials are only efficient within a limited temperature range. Using multiple materials in segmented TEGs can significantly enhance the overall energy conversion efficiency. However, thermal reliability is questionable in these systems especially at elevated temperatures and in annular configurations. This study explores the feasibility of utilizing unileg (single material) segmented TEG configuration as a remedy for the thermal stress problem. This study introduces the concept of unileg, segmented thermoelectric configurations (flat and annular) for the first time, and three-dimensional finite element simulations are conducted to investigate the thermoelectric performance and thermal reliability analysis in comparison with the conventional unicouple (dual material) systems. Results indicate that thermal stresses are significantly lowered in unileg systems compared to the unicouple configuration. In addition to the enhanced thermal reliability, power generation and thermoelectric conversion efficiency are higher in unileg systems since the material with higher performance is used solely eliminating the need of poorly performing, second thermoelectric leg material.

Dynamic Characteristics of Downhole Bit Load and Analysis of Conversion Efficiency of Drill String Vibration Energy

The longitudinal vibration of the drill pipe contains considerable energy which can be used to improve the rock-breaking efficiency during drilling. It is very important to the development of drilling speed-up tools to have a comprehensive understanding of the energy conversion efficiency of downhole drill string vibration. In this paper, the characteristics of downhole bit load and longitudinal vibration of drill string under different conditions were studied in the experiment, and the analysis method of energy conversion efficiency from drill string vibration to spring potential energy was proposed. The experimental analysis showed that the fluctuation of the downhole bit load was reduced by 10%–90% after the spring was installed in the bottom hole assembly. The rotation rate and the spring elastic stiffness had a significant and positive influence on the fluctuation amplitude of the downhole bit load. Meanwhile, the longitudinal vibration amplitude and acceleration of the drill string peaked at the elastic stiffness of 1 kN/mm. The closer the spring position to the drill bit was, the more severe the longitudinal vibration of the drill string above the spring component was. The bit load and the rotation rate had a positive influence on the severity of longitudinal vibration. The analysis of energy conversion efficiency showed that the available mechanical energy range of the longitudinal vibration of the drill pipe was about 200–420 kW. The work power of the drill string vibration to the spring component increased sharply and then decreased with the increasing of elastic stiffness. The energy conversion efficiency came to the optimal value when the elastic stiffness was between 1 kN/mm and 2 kN/mm. Increasing the rotation rate, keeping the bit load below 134.5 kN and installing the spring component near the drill bit are beneficial for improving the energy conversion efficiency of drill string vibration. This paper reveals the main factors affecting the energy conversion efficiency of drill string vibration and their influencing laws, and determines the range of WOB, rotation speed, spring position and stiffness to obtain the best energy conversion efficiency.

Mathematical modeling and analysis of energy conversion efficiency of particle jet accelerating nozzle

The impact kinetic energy of particle jet determines rock-breaking effect and velocity, and as acceleration device of particle jet, the energy conversion efficiency of nozzle determines rock-breaking efficiency. According to three different types of nozzles of the straight-taper nozzle, the pressure drop model and energy conversion efficiency of particle jet was established, and the energy conversion efficiency under different type nozzles was studied. And then, the acceleration ability of different nozzles for was analyzed with simulation. The results of model calculation and simulation show that constant-acceleration nozzle has the best acceleration ability and energy conversion efficiency. The rock-breaking experiment was carried out with the adopted nozzle, and comparison analysis between experimental results and numerical calculation prove that the applicability of mathematical model.

Analysis of Energy Conversion Efficiency of a Capacitor-Based Pulsed-Power System for Railgun Experiments

To analyze the stored-to-kinetic energy conversion efficiency, a transient electric-circuit model for a railgun system is built using the electrical circuit analysis software SIMPLORER in this paper, and the electric parameters of the model are defined with measurement values of the actual system. Many results of simulations and experiments are also presented, and the results show that the equivalent series resistance of the coaxial cables and the rail resistance are major factors on the energy conversion efficiency. In the end, some methods are proposed to improve energy conversion efficiency of the pulsed-power supply system.

Analysis of Energy Conversion Efficiency in Parallel and Series Hybrid Powertrains

The aim of this paper is to present a simulation and analytical analysis of the energy conversion efficiency in parallel and series hybrid powertrains. The analytical approach is based on the energy balance equations, whereas the simulation approach is based on an accurate and fast forward-facing simulation model for simulating parallel and series hybrid powertrains. A very good agreement between simulation and analytical results gives confidence pertaining to the accuracy of the performed analysis and confirms the validity of the analytical framework. Thus, combined simulation and analytical analysis enables deep insight into the energy conversion phenomena in hybrid powertrains and reveals the advantages and disadvantages of both hybrid concepts running under different operating conditions. It is obvious from the presented results that the parallel hybrid powertrain features better fuel economy than the series one for the applied test cycles, whereas both hybrid powertrain concepts feature the best fuel economy at light-duty application.

Analysis of Energy Conversion Efficiency with an Empirical Model in Dye-Sensitized Nanocrystalline Solar Cells

Current-voltage characteristics were formulated on the basis of the clear dependence of open-circuit voltages and fill factors on short-circuit current densities found in dye-sensitized nanocrystalline solar cells of 2-4%efficiency. A survey of the highest efficiency cells has demonstrated applicability of this model to these cells as well, and made clear the necessary conditions for these efficiencies. An estimation of a theoretical maximum efficiency in dye-sensitized TiO 2 solar cells of the I - /I - 3 redox couple has revealed that 13% efficiency is attainable with improvement of short-circuit current density. Nonnegligible influences of drift current and trap states on energy conversion processes are suggested.