Glassceramic materials of pyroxene composition synthesized on a large solar furnace

Synthesis peculiarities of glassceramic material of pyroxene composition on the basis of the pyroxene wastes of Ingichinsk (Samarkand region) ore deposit are investigated. The synthesis process is carried out in the Large Solar Furnace. It is revealed that, if the flux density is 300–400 W/cm², homogenous castings can be produced. Molten material sintering under 900–1100°C makes it possible to synthesize glassceramic of pyroxene composition with high mechanical properties.     

Concentration of the solar radiation in a solar furnace

Energy concentration in a solar furnace is greatly influenced by the optical accuracy of the reflecting surface of the mirror. The highest density of a heat flux on the heating surface of a specimen is determined by its concentration and by the reflectivity of the mirror.

Since the apparent diameter of the moon is almost equal to that of the sun and the illumination of the moon may be adapted to the photographic determination of flux density, the rate of energy concentration in the authors' solar furnace was studied by the moon's image projected upon the heating zone in place of that of the sun.

As a result, about 300 watts per cm was obtained as the highest possible density of the heat flux in this solar furnace. This figure also agreed with the results of an optical analysis based on the practical finishing of the present mirror surface. With a heat flux of 300 watts per sq cm, in accordance with Stefan-Boltzmann's law of radiation, the highest temperature attainable is estimated to be approximately 2700°K. Besides the above, in actual experiment, approximately 2300°C was obtained in observing the melting points of binary mixtures, e.g., MgO---CoO and MgO---Cr₂O₃. Thus, the above-mentioned three approaches to the problem are in fairly good agreement.     

Phase formation in ceramic materials that contain a cordierite glass synthesized by means of a large solar furnace

We investigate how to synthesize materials with a prescribed phase composition for creating porous ceramics, and the results of the investigation are presented. It is shown that, if synthesized cordierite glass, mineral raw material, and waste products are used as an initial material, it becomes possible to synthesize porous ceramic of different phase compositions: mullite-cordierite, mullite-cordierite-corundum, and cordierite-corundum.     

Features of zirconium carbonitride synthesis in a large solar furnace

It is shown that zirconium carbonitride can be synthesized by concentrated solar energy generated in large solar furnace.     

Creating melting furnaces based on the large solar furnace

The results of numerical-experimental investigations to determine the optimal parameters of melting furnaces of the “rotor” and “ladle” types intended for melting, synthesis, and thermotreatment of refractory materials in the optical scheme of the Large Solar Furnace (LSF) are presented.     

Studying refractoriness of silicon-carbide materials fabricated in a big solar furnace

The dependence of the refractoriness value of a silicon-carbide material on the phase component ratio in it has been obtained. We demonstrate the possibility of determining the refractoriness value and/or the relative phase content in silicon-carbide materials by the procedure proposed using the refractoriness value-phase composition curve.     

The influence of radiation absorption on solar pond stability

This paper presents a study of the gravitational stability of a salty layer of a fluid subject to an adverse temperature gradient as a result of heat absorption. This is intended to model solar ponds where an artificial gradient of salt concentration in water is used to prevent convective motions induced by the absorption of solar radiation. The stability of the Boussinesq approximation of the Navier-Stokes equations is analysed for perturbations of a certain kind imposed on the stationary solution. The marginal states for the onset of convection are obtained using a Galerkin method based on a weak formulation of the governing equations. The analysis considers solar energy absorption in the layer and assumes prescribed heat flux values as boundary conditions for the temperature equation. Results are compared with those obtained earlier by different authors for a layer of fluid, heated from below, with linear profiles of both salt concentration and temperature.     

Trends of solar radiation effects on the temperature of vertical surfaces of a modern terrace house

This is a study done to investigate the effects of solar radiation on the wall surface temperature of a modern terrace house. It involves the analysis of the thermal fluctuations of common building materials used for walls or vertical surface areas such as the bricks, glass of the window, and metal doors. A thermal imager and data logging system was used in collecting the data for the Southeast and Northwest façades of the house. The imager gave resourceful data on the thermal heat trend of the walls and their surface temperature. The results show that a lighter wall surface color reduces the temperature of the surface. Furthermore, the bricks, which have a higher density hence a higher absorptivity due to their high capacity for storage of heat, decrease the flow of heat. However, the use of tinted glass on windows increases the surface temperature of the glass area of the wall surface. The metal also shows a high similarity with glass in terms of its thermal performance. In conclusion, the types of material used on wall surfaces have a significant impact on the wall temperature.     

All solution processed tandem polymer solar cells based on thermocleavable materials

Multilayer tandem polymer solar cells were prepared by solution processing using thermocleavable polymer materials that allow for conversion to an insoluble state through a short thermal treatment. The problems associated with solubility during application of subsequent layers in the stack were efficiently solved. Devices comprised a transparent front cathode based on solution processed zinc oxide nanoparticles, a large band gap active layer based on a bulk heterojunction between zinc oxide and poly(3-carboxydithiophene) (P3CT) followed by a layer of PEDOT:PSS processed from water. The second cell in the stack employed a zinc oxide front cathode processed on top of the PEDOT:PSS layer from an organic solvent, a low band gap active layer based on a bulk heterojunction between zinc oxide and the novel poly(carboxyterthiophene-co-diphenylthienopyrazine) (P3CTTP) followed by a layer of PEDOT:PSS again processed from water and finally a printed silver electrode. The devices were prepared without the use of fullerenes and vacuum steps and employ only thermal treatments and orthogonal solvents. The devices exhibited operational stability in air without any form of encapsulation.     

Digital pyrometry in a solar furnace

The brightness temperature and emissivity measurements of an irradiated specimen at the focal point of a solar furnace have been performed by the use of a brightness pyrometer to which an electrical recorder, an oscilloscope and Polaroid camera were attached previously. The use of such a photographic method gave reading errors as ±2K at 3000°C and ±15K at 2000°C.

Therefore, a digital computer system has been coupled with the brightness pyrometer in order to give the higher accuracy in brightness and true temperature measurements and to process a large amount of data. The system consists of A/D converter, central processing unit, graphic display and other transfer units. After an analog signal from the brightness pyrometer was amplified by a dc amplifier, the signal converted into digital form was operated by the digital computer. Conversion errors in the data processing were found to be ±1K at 3000°C and ±7K at 2000°C respectively. The freezing point data by the new system on refractory oxides such as ZrO₂ and Y₂O₃ were presented.     

Application of functional ceramics synthesized in a large solar furnace for the synthesis of complex compounds

In this paper, we considered the peculiarities of functional ceramics synthesized in a large solar furnace generating high-density impulses in the far IR region with a steep pulse rise. We showed the effectiveness of pulsed radiation in the IR region in the synthesis technology of complex compounds.     

Influence of thermal ageing on the stability of polymer bulk heterojunction solar cells

A new approach is presented in order to improve the thermal stability of polymer: [6-6]-phenyl C₆₁ butyric acid methyl ester (PCBM) bulk heterojunction solar cells. The central idea in this approach is the use of a polymer with high glass transition temperature (T_g), well above the normal operating temperatures of the devices. In this paper, a PPV-derivative with a T_g of 150 °C was used as an electron donor and the thermal stability of the obtained solar cells was compared with solar cells based on the reference material poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) with a T_g of 45 °C. The use of the material with higher glass transition temperature resulted in a significant improvement of the thermal stability of the photovoltaic parameters. Furthermore, a systematic transmission electron microscope (TEM) study demonstrates that the better thermal stability of performance coincides with a more stable active layer morphology. Both improvements are attributed to the reduced free movement of the electron donor material (PCBM) within the active layer of the solar cell.     

A guidance system for a solar furnace

A guidance system for a solar furnace is described. The system will automatically track the sun about any two orthogonal axes. A single photosensitive detector is used in conjunction with a rotating shutter to generate an a-c error signal. The amplitude of the error signal is dependent upon the radial displacement of the solar image from the optic axis. The phase of the error signal is dependent upon the angular position of the image. The error signal is amplified and used to operate two motors which direct the seeking system so that the optical axis is pointed toward the sun.     

Working experience with a foundry solar furnace

Literature reveals that a low order priority has been given to foundry applications of the solar furnace for temperatures upto about 1000°C. In the present work, the performance of a solar furnace capable of melting small quantities of foundry-grade metals and alloys had been studied under various conditions. Crucibles of different materials and shapes were tried and the effect of having different heat-shield materials was also studied. Al---bronze crucible with cavity, and well-polished stainless stell heat-shield were found to be most effective in enhancing the efficiency of the furnace. Many important industrial applications of the present solar furnace, such as the recovery of metallic zinc from slags, had also been realised.     

An inter-laboratory stability study of roll-to-roll coated flexible polymer solar modules

A large number of flexible polymer solar modules comprising 16 serially connected individual cells was prepared at the experimental workshop at Risø DTU. The photoactive layer was prepared from several varieties of P3HT (Merck, Plextronics, BASF and Risø DTU) and two varieties of ZnO (nanoparticulate, thin film) were employed as electron transport layers. The devices were all tested at Risø DTU and the functional devices were subjected to an inter-laboratory study involving the performance and the stability of modules over time in the dark, under light soaking and outdoor conditions. 24 laboratories from 10 countries and across four different continents were involved in the studies. The reported results allowed for analysis of the variability between different groups in performing lifetime studies as well as performing a comparison of different testing procedures. These studies constitute the first steps toward establishing standard procedures for an OPV lifetime characterization.     

Modification of aluminum alloys in a solar furnace

The processes of the modification of the D16 aluminum alloy at the focus of a solar furnace are studied experimentally. The surface heat treatment at the solar furnace focus was performed without melting the surface. The experiment showed that the grain size decreases from 10 to 3 microns with the exposure of the specimens at the focal spot for 35 seconds, and small regions with the grain size 0.3 micron appear. Grains of dimension 0.3 micron are observed with the exposure of the specimen at the solar furnace focus for 40 seconds, and the microhardness is H _v = 74.8 kg/mm². The repeat measurement of the microhardness after 40 days corresponds to H _v = 104.8 kg/mm², i.e., the microhardness after modification in the solar furnace and natural aging increases by 16%.