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[en] Highlights: ► A new TEG test measurement system with the PLC has been carried out. ► A new SCADA program has been written and tested for the test measurement system. ► An operator panel has been used for monitoring to the instant TEG data. ► All of the measurement data of TEG have been aggregated in the system. - Abstract: In this study, a new test measurement system and supervisory control and data acquisition application with programmable logic controller has been carried out to be enable the collection of the data of thermoelectric generator for the usage of thermoelectric modules as thermoelectric generator. During the production of the electric energy from the thermoelectric generator, the temperatures of the surfaces of the thermoelectric generator, current–voltage values obtained from output of the thermoelectric generator, hot and cold flows have been measured by the newly established system instantly. All these data have been monitored continuously from the computer and recorded by a supervisory control and data acquisition program. At the same time, in environments where there was no computer, an operator panel with the ability to communicate with the programmable logic controller has been added for the monitoring of the instant thermoelectric generator data. All of the measurement data of the thermoelectric generator have been aggregated in the new test measurement and supervisory control and data acquisition system. The setup test measurement system has been implemented on the thermoelectric generator system with about 10 W. Thermoelectric generators, Altec-GM-1 brand-coded have been examined by the new proposed test measurement system and the values of maximum power and thermoelectric generator efficiency were calculated by the programmable logic controller. When the obtained results were compared with the datasheets, the relative error for the maximum power was around 4% and the value for efficiency was below 3%.
[en] It is well known that components with dissimilar compatibility factors cannot be combined by segmentation into an efficient thermoelectric generator, since each component needs a unique optimal current density. Based on the complex variable method, the thermal-electric field within a bi-layered thermoelectric composite has been analyzed, and the field distributions have been obtained in closed-form. Our analysis shows that current refraction occurs at the interface, both the refraction angle and current density vary with the incidence angle. Further analysis proves that the current densities in two components can be adjusted independently by adjusting the incidence current density and incidence angle, thus the optimal current density can be matched in both components, and the conversion efficiency can be significantly increased. These results point to a new route for high efficiency thermoelectric composites. (paper)
[en] Highlights: • Nominal power density of TEGs with non-constant cross sections pins is analyzed. • An analytical model of nominal power density (NPD) is developed. • Influences of shape parameter on NPD for different geometric pins are investigated. • Effects of dimensionless efficiency and the temperature ratio on NPD are examined. - Abstract: The investigation of the geometric structure of TEG (thermoelectric generator) pins is essential, as their geometry determines the performance of devices. In this study, nominal power density (NPD) is used to find a better geometric structure of thermoelectric pins of TEGs, since a comparison of maximum dimensionless efficiencies for different geometric pins cannot be used to identify the optimum geometry. The influence of shape parameter on NPD for TEG pins in linear, quadratic and exponential cross-sectional functions is studied. The NPD decreases when the shape parameter increases for different geometric pins, while the maximum values of NPD are the same. Then, the effects of dimensionless efficiency and the temperature ratio on the NPD are analyzed. The NPD decreases with the increase in dimensionless efficiency and temperature ratio. Pins with linear variation in cross section have the highest NPD among the three geometries of pins evaluated
[en] Highlights: • The efficiency of the MNITG at arbitrary power is analytically derived. • A universal bound on the efficiency of the MNITG with broken time-reversal symmetry and the arbitrary power is obtained. • Some system-specific characteristics are discussed and uncovered. • The broken time-reversal symmetry provides the physically allowed degrees of freedom for tuning the performance of heat devices. - Abstract: We investigate the performance at arbitrary power of minimally nonlinear irreversible thermoelectric generators (MNITGs) with broken time-reversal symmetry within linear irreversible thermodynamics, and the efficiency of MNITGs at arbitrary power is analytically derived. Furthermore, a universal bound on the efficiency of thermoelectric generators (TGs) with broken time-reversal symmetry and the arbitrary power is obtained. Some system-specific characteristics are discussed and uncovered. A large efficiency at arbitrary power can also be achieved via the cooperative mechanism between the system parameters. Our results indicate that the broken time-reversal symmetry provides the physically allowed degrees of freedom for tuning the performance of thermoelectric devices, and the physical trade-off region between the efficiency and the power output can also offer the appropriate space for optimizing the performance of TGs.
[en] Highlights: ► Thermodynamic analysis of thermoelectric power generator is carried out. ► The influence of the slope parameter on the efficiency is formulated. ► The efficiency of thermoelectric generator is influenced by the slope parameter. ► The power generation by the device reduces with slope parameter. ► Increasing external load resistance decreases the efficiency. - Abstract: Thermoelectric power generators are one of the promising clean energy resources with the cost effective operation despite the low device efficiency. Investigation into device efficiency improvement is necessary for the practical applications. Consequently, in the present study, a theoretical analysis of thermoelectric power generator is carried out and influence of thermoelectric leg geometry on the device efficiency and the power generation is formulated. The geometric configuration of the legs in the device is associated with the shape parameter and incorporated in the analysis. The influence of the shape parameter on the device efficiency and power generation is examined for various temperature and external load resistance ratios. It is found that increasing or decreasing of the shape parameter (μ) has a favorable effect on the device efficiency; however, the shape parameter (μ) has an adverse effect on the thermoelectric power generation.
[en] Highlights: • We analyze the practical performance of TEMs to meet specific requirements. • The influence of different input power sources are discussed. • The step-change phenomena of thermoelectric cooling are found and discussed. • The influence ratio of hot side heat exchanger and input power source is compared. - Abstract: The practical operating conditions of thermoelectric products, such as the input power source and the thermal resistance of hot side heat exchanger, are different from the theoretical study. Thus the equations, which are used to estimate the practical maximum cooling performance just according to the datum in datasheet of commercial thermoelectric module (TEM), are given. The nested loop method is adopted to solve the numerical model. This study provides a method to choose a suitable TEM for thermoelectric product to meet the application requirement. It finds that the minimum cold side temperature increase and the voltage for achieving the minimum cold side temperature step decrease with the increase of thermal resistance of hot side heat exchanger, respectively. The maximum temperature difference increase and the voltage for achieving the maximum temperature difference step increase with the increase of thermal resistance of hot side heat exchanger, respectively. According to the dimension, three kinds of thermoelectric module, bulk TEM, miniature TEM and micro TEM, are studied. The novel scale effect are discovered by comparing these TEMs. It found that the step-change phenomenon become more and more obvious with the decrease of the dimension of thermoelectric module. The influence ratio of thermal resistance of hot side heat exchanger on the maximum cooling performance increases and the influence ratio of input power source decreases from macro to micro, respectively. It forecasts that there exists a critical value for the dimension of thermoelectric module, when the dimension of thermoelectric module is smaller than this critical value, the maximum voltage or current of thermoelectric module is constant and does not change with the thermal resistance of hot side heat exchanger
[en] In this paper we analyze the thermodynamic efficiency expected for a fully dissipative thermoelectric generator (TEG) operating under stationary conditions at a finite rate. Although a finite-time thermodynamic analysis of TEGs has been aimed at since long time, no complete theory is available yet. The state of the art of theory is reviewed, and a simple expression for the maximum achievable efficiency of TEGs operating under fully irreversible conditions is obtained. This also sets a reference efficiency for forthcoming studies of nonstationary operation of TEGs.
[en] A parametric analysis is presented for the performance of a thermoelectric generator based on its operating conditions. The mathematical model, consisting of non linear equations, is made dimensionless to allow the characteristic parameters to be evidenced. The proposed parameterization lends generality to the results obtained. In particular the relationships have been investigated between the temperature difference inside the thermoelectric cell and that on the outside of the generator, and the effect of the outer thermal resistances of the generator on the working conditions. These parameters have a significant effect on the efficiency and therefore on the optimization of the operating conditions of the thermoelectric generator.
[en] Performance evaluation of a direct carbon fuel cell (DCFC) was conducted according to coals and a graphite particle. Several fuel properties such as thermal reactivity, textural structure, gas adsorption characteristic, and functional groups on the surface of fuels were investigated and their effects on electrochemistry were discussed. The strong carbon structure inside of fuels led the rapid potential decreasing in high current density region, because it caused small surface area and low pore volume. The functional groups on the surface were related to the low current density region. The maximum current density and power density of fuels were affected by the total carbon content in fuels. The effect of operating conditions such as stirring rate and operating temperature was investigated in this study
[en] Direct charge nuclear battery has a low efficiency in converting decay energy into electrical power. In order to improve its efficiency, a theoretical model of direct charge nuclear battery is built in this paper, based on its structure and working principle. Formulas for calculating its output power and efficiency are presented. Compared with the experimental results, the error of the max theoretical output power calculated by simplified theoretical model is about 4%. Voltage-current characteristic of simplified theoretical model is well in line with experiment conducted by others. (authors)