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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] 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: ► 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] A simple model has been presented for the conduction of current between adjacent electrodes separated by an insulating wall and duct filled with conducting hot gases. Analytical expressions and calculations have been made for plasma initiated and insulator initiated breakdowns for the conditions prevailing in a typical open cycle MHD generator. The relative importance of the two types of breakdowns has also been evaluated. (author)
[en] Highlights: • We realized and characterized a new small thermoelectric generator. • The device supplies, for sufficient long time, an output voltage higher than 200 mV. • The complete power conditioning and control module has been realized. • The device is able to power autonomous sensors in remote environmental sites. • The device has been tested in real environmental conditions. - Abstract: A small thermoelectric generator to power autonomous sensors in remote environmental sites is studied, designed, realized, characterized, and tested. The thermoelectric phenomena, applied to our device, are theoretically introduced and experimentally verified by directly measuring the physical quantities when the thermoelectric generator operates in working conditions. The device is then tested under different external conditions, showing that it is able to supply, for sufficient long time, an output voltage higher than 200 mV and an output power on the order of 10 mW when a temperature difference higher than 10 K and a load resistance close to the internal resistance are considered. Furthermore we developed a devoted power conditioning circuit in order to usefully manage the output voltage. Finally, we tested the device in real operative conditions
[en] Physical factors affecting the efficiency of segmented generator thermoelements are analyzed. The optimal control theory are used for development of a sufficiently precise method for a computerize design of generator modules of segmented thermoelements. The optimal thermoelectric parameters of BiTe-based materials for single- and double-segmented thermoelements are determined. The experimental generator samples have been made of such materials and their characteristics measured. The efficiency of modules of double-segmented legs has been found to be about 7.5% and exceed the power efficiency of homogeneous material generators.
[en] Finitely segmented, Faraday-type and combustion gas driven MHD generators have been considered. Accounting for the finite electrode segmentation effect and the nonuniformity of gas in the channel an expression has been derived for the gas dynamic drop for a turbulent boundary layer. Combining the electrical sheath drop, discussed in brief, with the gas dynamic drop, the electrode voltage drop has been evaluated for two experimental runs of MHD generators. The computed results are compared and found to be in good agreement with other evaluations. (author)
[en] End effects phenomena in a Faraday type generator with diverging electrode walls for two types of velocity profiles - one with a source velocity and the other with a fully developed velocity - are discussed. The electric potential is determined numerically using the successive overrelaxation method in polar coordinates. It is found that the viscous forces increase the end losses and create current concentrations on the electrodes even at far distances from the entrance. (author)
[en] Highlights: • Analytic model of temperature relaxation in segmented thermoelectric generators. • Equivalent figure of merit for series thermoelectric configuration. • Numerical simulations corroborate analytic results. - Abstract: We study the physical processes at work at the interface of two thermoelectric generators (TEGs) thermally and electrically connected in series. We show and explain how these processes impact on the system’s performance: the derivation of the equivalent electrical series resistance yields a term whose physical meaning is thoroughly discussed. We demonstrate that this term must exist as a consequence of thermal continuity at the interface, since it is related to the variation of the junction temperature between the two TEGs associated in series as the electrical current varies. We then derive an expression for the equivalent series figure of merit. Finally we highlight the strong thermal/electrical symmetry between the parallel and series configurations and we compare our derivation with recent published results for the parallel configuration