Thermoelectric Industry Research Articles

Nitrogen mineralization in an Alfisol amended with thermoelectrical industry by-products

In thermoelectric industry, synthetic gypsum and coal ash are generated as industrial by-products. The objective of this work was to evaluate the effect of different mixtures of synthetic gypsum and coal ash on N mineralization in an Alfisol. Nitrogen mineralization was evaluated by soil incubations under controlled conditions and potential mineralization using the nonlinear first order kinetics model Nmt = N0 [1 - ℮(-k t )] , where Nmt is the mineral N accumulated at a specific time, N0 is the potentially mineralizable N, k is the mineralization rate, and finally t is the incubation time. Treatments consisted of different mixtures of synthetic gypsum, coal ash and urea (M1: 50% synthetic gypsum, 50% coal ash, M2: 50% synthetic gypsum, 35% coal ash, 15% urea, M3: 45% synthetic gypsum; 40% coal ash, 15% urea, M4: 65% synthetic gypsum, 20% coal ash, 15% urea, M5: 55% synthetic gypsum, 30% coal ash, 15% urea). Each mixture was applied to the soil at 2 t ha-1. The results shown the highest concentration (p < 0.05) of net mineral N (NMN) applying M3 (166.14 mg kg-1), while the lowest NMN (p < 0.05) was found applying M5 (98.30 mg kg-1). Treatment M1 presented the highest N0 value (579.0 mg kg-1) respect to treatments with urea in its composition, with exception of M3 (523.4 mg kg-1). Where the highest and lowest k were determined in M5 (k = 0.44990) and M3 (k = 0.04470), respectively. Mixtures of synthetic gypsum, coal ash and urea increased N mineralization over mixtures without urea. Respect N potential mineralization, in some cases N0 and k values would respond more to the fit of the mathematical model employed than to the biological process.

La(Fe, Si, Co)13/Cu conductive composites with tailoring thermal expansion

In this work, metal-matrix composites which possess tunable thermal expansion coefficients in combination with high electrical and thermal conductivities were successfully synthesized by a moderate temperature hot-pressing method. The composites are based on incorporating La(Fe, Si, Co)13, a material with a negative coefficient of thermal expansion, within a continuous Cu matrix. The La(Fe, Si, Co)13 enables us to tune the coefficient of thermal expansion in a predictable manner, while the Cu phase is responsible for the electrical and thermal conductivity properties. The resulting materials exhibit coefficients of thermal expansion which can be tuned between the value of pure Cu and La(Fe, Si, Co)13. Thus, by adjusting the relative amount of the two components, the materials can be designed with high electrical and thermal conductivities and tailoring coefficient of thermal expansion properties. This unique combination of electrical and thermal properties enables these Cu-based metal-matrix composites to be applied in the microelectronic, semiconductor and thermoelectric industries.

The Prevalence of Standard Large Modules in Thermoelectric Applications

The thermoelectric industry serves a broad range of applications using, mainly, a few standard module designs. This paper first briefly describes types of modules and two types of thermoelectric material used by the industry, after which the focus is on selected features of the standard designs and reasons for their prevalence. Whereas cost reduction and the need to maximize reliability drive the adoption of standard modules, other factors contribute to shaping the particular features of the standard thermoelectric cooling modules. These factors include the magnitude of heat loads, heat-sink performance, durability and performance expectations, and relative ease of manufacture. This discussion of the features and prevalence of standard modules relates to broader aspects of both the production and implementation of thermoelectric modules, and an estimate of current thermoelectric industry output is included.

Impact of ink synthesis on processing of inkjet-printed silicon nanoparticle thin films: A comparison of Rapid Thermal Annealing and photonic sintering

Inkjet printing has a high potential for cost reduction in solar cell and thermoelectric industry. This study demonstrates that silicon thin films can be produced by inkjet-printing of silicon nanoparticles followed by subsequent drying and annealing steps. Ink formulation is crucial for the sintering of the silicon nanoparticles and control of the microstructure at low temperature. Upon heating, the microstructure is modified from porous layer made of juxtaposed silicon nanoparticles to denser layer with coarser grains. This evolution is monitored by scanning electron microscopy and by micro-Raman spectroscopy, which offer a fast and precise characterization of the microstructure and chemical composition of thin films. Above a threshold temperature of 800°C cracks appear within thin film and substrate because of the stress induced by the oxidation of the surface. An innovative sintering method, photonic annealing, is studied in order to reduce both oxidation and stress in the thin films as well as reducing processing time. Evolution of the thermal conductivity is performed by micro-Raman spectroscopy and can be tailored in a large range between ~1 and ~100W·m−1·K−1 depending on the sintering method and atmosphere. Therefore control of the microstructure evolution with applied annealing process allows tailoring of both microstructure and thermal conductivity of the silicon thin films.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

Practical electrical contact resistance measurement method for bulk thermoelectric devices

ABSTRACTAs thermoelectric (TE) element length decreases, the impact of contact resistance on TE device performance grows more significant. In fact, for a TE device containing 100-μm tall Bi2Te3TE elements, the figure of merit ratio (ZTDevice/ZTMaterial) drops from 0.9 to 0.5 as the contact resistivity increases from 5 x 10-07 to 5 x 10-06 Ω-cm2. To understand the effects of contact resistance on bulk TE device performance, a reliable experimental measurement method is needed. There are many popular methods to extract contact resistance such as Transmission Line Measurements (TLM) and Kelvin Cross Bridge Resistor method (KCBR), but they are only well-suited for measuring metal contacts on thin films and do not necessarily translate to measuring contact resistance on bulk thermoelectric materials. The authors present a new measurement technique that precisely measures contact resistance (on the order of 5 x 10-07 Ω-cm2) on bulk thermoelectric materials by processing stacks of bulk, metal-coated TE wafers using TE industry standard processes. One advantage of this technique is that it exploits realistic TE device manufacturing techniques and results in an almost device-like structure, therefore representing a realistic value for electrical contact resistance in a bulk TE device. Contact resistance measurements for metal contacts to n- and p-type Bi2Te3 alloys are presented and an estimate of the accuracy of the measurements is discussed.

Substrate effects on the thermoelectric properties of Co-sputtered Bi-Te thin films for micro-thermoelectric devices

Among the various thermoelectric materials, bismuth-tellurium (Bi-Te)-based materials are known to have excellent thermoelectric performance near room temperature and are widely used in the thermoelectric industry as thin films for thermoelectric coolers and generators. In this study, thermoelectric Bi-Te thin films, deposited on various substrates such as SiO2 wafers, glass, and sapphire, were fabricated by RF magnetron co-sputtering. The microstructural, electrical, and thermoelectric properties of n-type Bi-Te thin films were investigated. Based on the results of this study, we concluded that the surface roughness and the crystalline structure of the substrate influenced the grain size, crystallinity, and thermoelectric and electrical properties of the Bi-Te thin films. The Bi-Te film deposited on SiO2 had a power factor of 2.96 mW/K2·m without post-annealing. Previous studies have reported power factors of ∼3.0 mW/K2·m for n-type films after annealing.

Effect of temperature variation on the transport properties of fine-grained heavily doped n-type PbTe

The electrical conductivity, Seebeck coefficient, thermal conductivity, and figure-of-merit, which is a measure of the performance of the thermoelectric material, of heavily doped n-type PbTe single crystal and compacts of grain size in the range 10⩽ L⩽20 μm and very fine powder L ∼1 μm, are measured in the temperature range 300–750 K. Effect of the grain size on decreasing the lattice thermal conductivity λ L and the total thermal conductivity λ t, is demonstrated. A drop of 35% in λ L has been achieved at 750 K for the very fine powder. Also, the figure-of-merit Z of the very small grain size, L∼1 μm, n-type PbTe compacts improve by 9.41% at 750 K while the large grain size material, 10⩽ L⩽20 μm, achieve 7.35% increase in Z, at the same temperature, as compared with the single-crystal material. The result confirms that the very fine powder material is superior to large grain size or single-crystal material for thermoelectric power generation. This result is very important in the thermoelectric industry and related devices.

Sweden'S Water-Power Resources

DURING the War, sixty new power stations were built in Sweden, several of more than 40,000 kW. rating. The production of hydro-electric power in 1944 was 12,417 million kWh., and water-power plants now total about 2,500,000 kW. Further plants totalling about 600,000 kW. will be completed towards 1950, and works have been started for an additional 350,000 kW. The energy utilized in 1944 was 10,573 million kWh., of which 4,428 million kWh. were taken by the large industries for engine power, etc., while the electro-chemical and thermo-electric industries consumed 1,891 million kWh. About 1,040 million kWh. were used for traction purposes and 2,017 million kWh. for domestic purposes, etc. 1,093 million kWh. were used for electric steam-generation at night-time and during non-working hours.

The Adherence of Thick Silver Plate on Steel. II

A new, simple, sensitive and fast analytical method was developed to simultaneous quantification of Cd(II) and Pb(II) in cooling water by anodic square wave redissolution voltammetry (SWASV) using a modified carbon paste electrode composite with carbon black, resin functionalized with sulphonic group and paraffin. The experimental conditions such as supporting electrolyte (composition, pH and ionic strength) and SWASV parameters were optimized. The best conditions of Cd(II) and Pb(II) (higher peak current) were obtained in 0.1 mol L−1 BR buffer (pH 4.6) from -1.1 to 0.3 V, amplitude of 60 mV, frequency of 40 Hz, potential step of 5 mV, potential and deposition time of -1.1 V and 240 s, respectively. The analytical curve of Cd(II) and Pb were linear from 10 to 50 μg L-1 (R2=0.999) with quantification limit of 0.06 and 0.12 μg L-1, respectively. The method was successfully applied in cooling water from thermoelectric industry and the concentrations of Cd(II) and Pb(II) were 3.27 ± 0.30 and 2.80 ± 0.18 mg L-1, respectively. The method accuracy was evaluated through the comparison with the comparative method (SWV with Hanging Mercury Drop Electrode) and the relative error obtained was smaller than 9.8%.