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[en] Transparent covers used in solar collectors collect both solar radiation and dirt from the environment. The dirt collected reduces the amount of useful incident solar radiation that would have been transmitted into system. Samples of ordinary glass used as transparent covers in solar devices at Sokoto Energy Research Centre were exposed to the weather for a period of one year. Cleaning was done on daily, weekly, bi-monthly and monthly basis. A sample was left uncleaned throughout the period. Using the measured average daily transmittance for all seasons as a constant for such glass covers in Sokoto showed that varying the cost/wash/collector for a collector of one-square metre receiver area from =N=0.50 to =N=50.00, would vary the frequency of washing the collector covers from 160 down to 25 times annually respectively. Cost of washing per annum would also vary from 79.90 Naira to 834.46 Naira
[en] A solar collector system is a possible method using solar energy to deflect Earth-threatening near-Earth objects. We investigate the dynamics and control of a solar collector system including a main collector (MC) and secondary collector (SC). The MC is used to collect the sunlight to its focal point, where the SC is placed and directs the collected light to an asteroid. Both the relative position and attitude of the two collectors should be accurately controlled to achieve the desired optical path. First, the dynamical equation of the relative motion of the two collectors in the vicinity of the asteroid is modeled. Secondly, the nonlinear sliding-mode method is employed to design a control law to achieve the desired configuration of the two collectors. Finally, the deflection capability of this solar collector system is compared with those of the gravitational tractor and solar sail gravitational tractor. The results show that the solar collector is much more efficient with respect to deflection capability.
[en] The performance of conventional box type solar cookers can be improved by better designs of cooking vessels with proper understanding of the heat flow to the material to be cooked. An attempt has been made in this article to arrive at a mathematical model to understand the heat flow process to the cooking vessel and thereby to the food material. The mathematical model considers a double glazed hot box type solar cooker loaded with two different types of vessels, kept either on the floor of the cooker or on lugs. The performance of the cooking vessel with a central cylindrical cavity is compared with that of a conventional cylindrical cooking vessel. It is found from the experiments and modeling that the cooking vessel with a central cylindrical cavity on lugs results in a higher temperature of the thermic fluid than that of a conventional vessel on the floor or on lugs. The average improvement of performance of the vessel with a central cylindrical cavity kept on lugs is found to be 5.9% and 2.4% more than that of a conventional cylindrical vessel on the floor and on lugs, respectively
[en] A Life Cycle Assessment (LCA) is a tool for analysing and estimating the total influence on the environment during the complete life cycle of a certain product. The assessment can bring valuable information about the production processes, the use of materials, the use and the disposal of the product. This information can be used to determine, how to improve the product environmentally. The LCA information can also be used as a comparative study to determine which of two products are environmentally preferably. LCA''s on solar collectors are interesting because solar energy systems are introduced to encourage a sustainable development, hence it follows that the systems themselves should be based on a sustainable technology. The collector should produce as much energy as possible during its lifetime, but it is also important that it is produced in an environmentally friendly way, that it can be disposed properly after use and so on. (orig.) 2 refs
[en] Kapton (polypyromellitimide) is used in space applications as an insulator, thermal blanket layer, substrate for solar cell arrays, and surface coatings. This report describes laboratory tests of kapton materials to investigate the erosion damage caused by simulated space radiation on those polymers. The tests were carried out at the McMaster University Tandem Accelerator Laboratory using protons and alpha particles at various energies, approach angles, and fluences. Samples tested were 7-millimeter squares 0.1 millimeter thick. Damage to specimens was measured by a weight loss technique. Results are presented and compared to those obtained using Monte Carlo simulation
[en] Our previous article (Part I) discussed the theoretical and experimental study of the performance boost obtained by a cooking vessel with central cylindrical cavity on lugs when compared to that of a conventional cylindrical vessel on floor/lugs. This article compares the performance of the cooking vessel with depressed lid on lugs with that of the conventional vessel on lugs. A mathematical model is presented to understand the heat flow process to the cooking vessel and, thereby, to the food material. It is found from the experiments that the cooking vessel with depressed lid results in higher temperature of the thermic fluid loaded in the cooking vessel compared to that of the thermic fluid kept in the conventional vessel when both are placed on lugs. Similar results were obtained by modeling the process mathematically. The average improvement of performance of the vessel with depressed lid is found to be 8.4% better than the conventional cylindrical vessel
[en] Full text: We created multifunctional metal surfaces by producing a hieratical nano- and micro-structures with femtosecond laser pulses on titanium, platinum and brass. The multifunctional surfaces exhibit excellent broadband light absorption, superhydrophobicity, and self-cleaning effects. The creation of these multifunctional surfaces is inspired by biological surfaces of Lotus leaves and blue Morpho butterfly wings. The enhanced absorption is useful whenever light collection is needed, such as in sensors and solar energy absorbers. The self-cleaning effect will improve the performance of the devices and minimize the maintenance. This surface should also possess other highly desirable functionalities such as anti-corrosion, anti-icing, anti-biofouling, and self-sanitation, since these properties are directly related to superhydrophobicity. (author)
[en] The possible energy characteristics of the LSF (large solar furnace with a capacity 1000 kW) based on numerical calculations are analyzed. The technical characteristics of the LSF are presented. The energy characteristics of the total system with different inaccuracies of the reflecting surfaces, energy contributions of certain shelves and groups of heliostats, and the contributions of certain heliostats and shapes of their focal spot are determined. Empirical formulas are proposed to describe the obtained numerical results. The problem of implementing the possible energy modes of the LSF with and/or without the inclusion of certain shelves and groups of heliostats is analyzed. The problem of a change in the energy density distribution in the focal spot of the LSF during the day is considered.