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[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 chances of the title systems on the Dutch market are discussed. It appears that the most important growth for solar thermal energy systems will first be realized in utility buildings. 5 ills
[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 simulator has been designed and constructed for indoor testing for solar collectors. The simulator consists of 45 halogen lamps. Each lamp has a rated power of a 300 watts. The lamps in ten rows where each row consists of 4 to 5 lamps. The lamps occupied area 6 m2. Dimmers are used to control the amount of lamp intensities. The spacing between the lamps and the collector is about 150 cm. The intensities of the lamps are measured using a pyranometer. The intensity contours or mappings for minimum and maximum average pyranometer readings about 280 to 640 W/m2 are produced, with errors are about of 3.16 % to 4.5 %. (Author)
[en] In this paper, we study a collector, made by cheap local materials (wood, aluminium, etc.), and prepared in the carpenteries, and in the mechanic work rooms with a simple technology. The efficiency of our collector is compared with several variants made in other countries. (author). 9 refs, 6 figs, 2 tabs
[en] Highlights: ► Analysis of processing parameters is presented to Fresnel lens solar collector. ► Orthogonal array, variance analysis, and response surface methodology are employed. ► Best combination of processing parameters is searched by optimization methods. ► Confirmation experiment was conducted to validate the results. - Abstract: This study analyzed and evaluated important parameters in fabrication of Fresnel lens solar collector (melt temperature, mold temperature, packing pressure, and injection speed) based on its two qualities (ratio of power efficiency and percentage error of groove filling ratio). To design the experiment effectively, Taguchi method was applied. The experimental results were analyzed by analysis of variance (ANOVA) in order to derive the significant parameters affecting each quality. Relationships among significant parameters and each quality were established using the response surface methodology (RSM). Two equations were integrated to derive a fitness function, which was optimized by two popular optimization methods – particle swarm optimization (PSO) and genetic algorithm (GA). Optimization results from both methods were chosen based on the highest fitness value. The results showed that with the optimal combination (270 °C, 100 °C, 1040.4 bar, and 60 mm/s for melt temperature, mold temperature, packing pressure, and injection speed, respectively), a high ratio of conversion efficiency and a low percentage error of groove filling ratio could be successfully derived. Confirmation experiment was conducted to validate the results.
[en] Lithuania is situated between 54-56 deg. of Northern Latitudes, which it is the same as UK, Southern Denmarks and Southern Sweden. Climate conditions in Lithuania are comparable, or even better, than in neighboring countries. Trying to get into the market with the products, made somewhere out of Lithuania, did not let us to come even to theoretical economical efficiency of the systems, and only the local production of solar collectors and accumulating tanks, gave positive results. Domestic hot water systems (DHWS) with the new collectors and storage tanks, showed rather good approximate figures of the system efficiency. The payback of such solar DHWS, in comparison with electricity, is in average 8.5 years. (au)
[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)