The development of thermoelectric power generation system utilizing heat of municipal solid waste is presented. The design method is based on one-dimensional, steady state model taking account of radiation heat transmission from combustion gas to channel wall embedded thermoelectric modules. A middle scale incinerator system of 200ton/day in process and of 2300kcal/kg in enthalpy is selected to be applied with a thermoelectric power generation system as an example. Because of low heat transfer performance, the energy conversion efficiency is estimated to be 3.6-6%. On the basis of a small scale experiment for real incinerator, technological problems to the way for practical thermoelectric power generation system utilizing heat of municipal solid waste are discussed.
A considerable stimulus in the study of applications of the large scale thermoelectric generator of low-grade heat is being afforded by the needs for the energy saving and the environmentally friendly energy resources. From the view point, the author has turned his attention to thermoelectric conversion of low-grade waste heat and its efficient use in the production of hydrogen gas. Hydrogen gas can readily be produced by the electrolysis of water and the low voltage, high d. c. current output of a thermoelectric generator provides an ideal source of electric power. These considerations have resulted in the construction of a prototype laboratory scale solid polymer electrolyte (SPE) electrolysis plant combined with a 100W (e) thermoelectric generator powered by low grade waste heat. The system is currently being evaluated and preliminary results are reported in this paper.
At the Electrotechnical Laboratory the PIES (Pulverized and Intermixed Elements Sintering) method has been investigated in order to prepare mechanically strong and cost efficient materials and Ruthenium Sesquisilicide has been investigated in order to obtain high thermoelectric figure of merit above 1300K. The figure of merit values of p-type bismuth telluride based materials prepared by PIES method were the same as those of the commercial materials. In order to synthesize functionally graded thermoelectric materials by PIES method the temperature dependence of electrical properties of materials with different composition were clarified. Experiments on 10 doping elements were performed and we determined that phosphorous was the best candidate for n-type dopant which could achieve the optimum doping level.
Thermo-electric phenomena have been rigorously analysed by using Boltzmann equation. From the analysis, it is concluded that Ioffe's theory of Peltier cooling is the limitted theory of our theory. In this paper, some conclusions on the operation of Peltier cooling system which can be introduced from our theory are shown.
In order to investigate a possibility to tailor the system's band gap of the quaternary alloyed Pb-, Sr-chalcogenide compounds, we theoretically study the electronic structures and their characteristics based on the semi-empirical band calculation and the coherent potential approximation (CPA) approach. The calculated energy gap of both the ordered alloy system and the random system is greatly influenced by the presence of Pb. And for the ordered system, the atomic arrangement around Pb atoms causes the change of the energy gap.
Single crystals of p-type PbTe were prepared by Bridgman method, where either Ag2Te or PbI2 was doped as the source material of silver and iodine. The carrier concentration and Hall mobility were measured from 77 to 300K. The hole concentration was successfully controlled in the range from 2.0×1018 to 9.0×1018cm-3 and from 3.5×1017 to 4.5×1019cm-3 by doping 100 to 1000molppm Ag2Te and 100 to 650molpm PbI2 respectively. The Hall mobility at carrier concentration p>1018cm-3 indicated that the dominant scattering mechanism is phonon scattering at 77-300K. The temperature dependence of the hole mobility at p<1018cm-3 showed an irregular behavior, which was explained on the basis in the overlapped valence bands with light and heavy holes, respectively.
Pb1-xSnxTe (0≤x≤0.25) doped with different amount of PbI2 ranging from 0 to 0.4wt% were prepared by stirring melt mixtures and unidirectional solidifying using PbTe and SnTe. The thermal conductivity of the Pb0.75Sn0.25Te doped with 0.04wt% PbI2 reduced to 18.0mW/cmK, which is 18% lower than that of the melt grown PbTe, as a resultant of the reduction of the phonon component κph. The electron density of an n-type Pb0.95Sn0.05Te doped with 0.4wt% of PbI2 decreased along the growth direction from 3.18×1020cm-3 to 2.60×1017cm-3, which confirms FGM structure. The n-type sintered Pb0.95Sn0.05Te specimens were prepared by the hot-pressing technique using the melt-grown ingot. The thermal conductivity of the sintered specimens was 16.4mW/cmK, which was 12% lower than that of an n-type sintered PbTe. It is found that the carrier scattering mechanism of the sintered specimens are remarkably different from that of the melt-grown ones. The resistivity of an n-type melt-grown PbTe had a hysteretic temperature dependence up to 800K due to evaporation of Te and ambient Ar pressure, which indicates that the change of the thermoelectric properties occurs during practical operation.
The magnetic field dependences of the thermoelectric effect, the magnetoresistance, the thermal conductivity and the transverse Nernst-Ettingshausen effect are investigated on Bi88Sb12 alloy single crystals. The Seebeck effect under the magnetic field along the temperature gradient is the longitudinal Nernst-Ettingshausen effect. The longitudinal and transverse Nernst-Ettingshausen effects (LNE and THE respectively) have been measured with the magnetic field up to 1.2T and at the temperature of 100K to 300K. Two configurations, Bz//c-axis and Bz⊥ c-axis, have been used. The Seebeck coefficient of the minus sign increases in the absolute value as the temperature is lowered. By the application of the magnetic field, the coefficient very much increases in the minus sense. The increase of the resistivity by the magnetic field is more drastic compared to the increase of Seebeck effect. The magnetic field dependence of the thermal conductivity κ is minor compared to the Seebeck effect S and the magnetoresistivity ρB. The figure of merit Z (=S2/ρBκ) is calculated by using the measured values of S, ρB and κ. Z value without the field changes from 5×10-4K-1 at 300K to 4×10-3K-1 at 110K. By applying the field of 1.2T, Z-value increase about 20-30% above about 160K, while decreases down to 5×10-4K-1 at 110K. The addition of an appropriate impurity such as Te should improve the Z under the magnetic field. The merit of the TNE effect for the thermomagnetic application is mentioned.
Iron disilici de FeSi2 is the most hopeful Thermoelectric Semiconductor, because both the components Fe and Si are deposited in plenty, the thermoelectric properties of FeSi2 devices can readily be designed by controlled doping, and so on. Sintered bodies of Fe1-xMnxSi2 (0≤x≤0.10) and Fe1-yCoySi2 (0≤y≤0.10) were prepared by the ceramic techniques, which are suitable for mass-production, and the roasting, sintering and annealing conditions in the sintering were investigated. For completely semiconducting specimens, the resistivity ρ and thermoelectric power Q were measured in the temperature range from 100 to 1400K in an argon atmosphere. The electrical resistivity ρ of Fe1-xMnxSi2 (x=0.03 and x=0.06) indicated the relationship ρ=ρoexp[(Ea+Eh)/(kT)] in the temperature range from 150 to 600K, where Ea and Eh are the activation energy of the acceptor and the hopping energy, respectively. The Hall mobility μH showed the relationship μH=μoexp[-Eh/(kT)] in the temperature range from 150 to 250K. The electrical conduction mechanism of Fe1-xMnxSi2 is qualitatively explained on the basis of the small polaron model.
Far-infrared (F-IR) reflection spectra were measured for n-type Bi0.88Sb0.12, p-type (Bi0.25Sb0.75)2Te3, n-type Bi2(Se0.2Te0.8)3 and n-type Bi2(Se0.05Te0.95)3, and dispersion parameters, plasma frequency and damping factor were determined. For electrical conductivity, carrier density and mobility calculated from those dispersion parameters, good agreement was obtained with those from electrical measurements.
A dialytic battery (DB) with ion-exchange membranes can convert the mixing free energy into the electric energy. The solar membrane cell (SMC) which was proposed by one of the present authors consists of DB and a solar still. The seawater is separated into the fresh water and the concentrated seawater by flowing through the solar still. Therefore, in order to seek a feasibility of SMC it needs to make a performance test of DB at higher concentration than the seawater. In the present study, an experimental study has been made on the concentration dependence of the DB-performance. The dialytic battery constructed consists of 101 compartments and has an effective area of 475cm2 per a sheet of ion-exchange menbrane. The carbon plate electrodes were used, which would produce not only an electric power, but also useful materials such as Cl2-, H2-gas as a result of the electrode reaction. The saline water concentration cc ranged from 3.5-17wt%. The open circuit potential decreased from 9 to 7V with increasing cc. The power output, however, increased considerably with the increase in cc due to the decrease in the internal resistance: The maximum power of about 1100mW was obtained at the concentration of 17wt%. The Weinstein-Leitz model has been modified so as to be applicable to the present case. An good agreement was obtained between the calculated and the measured.
The electric properties of the oxide superconductors of the RBa2Cu3O6+x family are determined by the stoichiometry and ordering of oxygen in their CuOX planes. These O atoms are also very mobile even at room temperature and below, as demonstrated by the change of the electric properties of O deficient samples with aging at room temperature. Detailed information on the atomic mobility can be obtained by anelastic relaxation experiments (acoustic absorption), and here is made a short review of the main results obtained by this technique on the mobility of O in RBa2Cu3O6+X. Three elastic energy loss peaks as a function of temperature are attributed to jumps of O in different environments. The O atoms near a O vacancy in the OI domains (x=1) can jump with an activation energy of 1.1eV, those in the OII domains (x=0.5) or in disordered chains cause a separate relaxation process with a similar activation energy (-1.2eV). The isolated O atoms are much more mobile, and they are supposed to be the cause of a relaxation process with an activation energy of only 0.1eV in the highly O deficient samples. The apparent contrast between such a high mobility and the slow time constants for reaching equilibrium in O deficient samples is discussed.
The coil system designed to free from the magnetic force and to confine the high β plasma is proposed. We carry out the calculation of the magnetic field for the proposed coil by using the Biot-Savart law. It is noted that no or very weak magnetic fields are appeared in the central region of the proposed coil, while the strong magnetic field localizes at the outside of this region, being satisfied the requirement of confining the high β plasma. The simplified model is considered in order to reduce the cpu time for the computation. From the results of the computation, it is shown that the proposed coil is able to be replaced by the simplified model.
Collisions of drops in polydisperse sprays moving in a gaseous host medium influence the drop size distribution in the spray. Such collisions may either lead to stable coalescence of the colliding drops or to the formation of satellite droplets for certain geometric and kinetic conditions of the collision. This latter process still is not very well understood, and the present paper presents data on the number of satellete droplets produced by the collision as a function of the relevant parameters of the collision. Deeper insight into the processes of satellite formation is provided by a photographic documentation of the collisions. Two different liquids (propanol-2 and n-hexadecane) are investigated. It is shown that, at given kinetic conditions, for a certain value of the collision parameter, a maximum number of satellites is formed. Larger and smaller collision parameters lead to a smaller number of satellites. Furhter investigations will involve other drop sizes and collisions of drops of different diameter. These results will support modelling of spray flows.
Hardness is defined as a scale to evaluate the resistance of an object against the force of an impression. Throughout their long history, hardness tests have acquired more and more applications in line with growing attention to the mechanical properties of industrial materials. The more advanced the materials, the greater accuracy is required when testing their hardness, attracting attention to a broader range of parameters which includes the geometry of indenters, loading conditions, and methods for measuring impressions. The purposes of hardness tests have also expanded to include the evaluation of material strength and microstructural changes as a factor of hardness and to guarantee product quality. The level of quality control required for hardness testing machines is highly dependent on their applications. Given this complicated situations, this paper deals with some basics for effectively using the scale of hardness.