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This study quantifies spatial and temporal patterns in snow water equivalent (SWE), chemistry, and water isotopes associated with snowpack shading due to aspect and vegetation in the Valles Caldera National Preserve, New Mexico. Depth, density, stratigraphy, temperature, and snow chemistry, isotope, and biogeochemical nutrient samples were collected and analyzed from five snowpit locations on approximate monthly intervals between January-April 2007. SWE showed little variability between sites in January (~10mm) but differences expanded to 84mm (30%) by max accumulation in open sites and 153mm (45%) between all sites. Sulfate varied by 22% (10.6-13.5 microeq/L), Cl- by 35% (17.4-26.9 microeq/L), and d18O by 17% (-16.3 to -13.5), with SWE exhibiting inverse correlations with d18O (r2=0.96), SO42- (r2=0.75), and Cl- (r2=0.60) at max accumulation. Regression relationships suggest variability in SWE and solutes/water isotopes are primarily driven by sublimation. Mass balance techniques estimate sublimation ranges from 1-16% between topographically- and non-shaded open sites.

A Solar Radiation Concentrating System for generation of high temperature heat for a solar oven was developed and evaluated at the University of KwaZulu-Natal, Westville Campus, Durban - South Africa. The system concentrates direct solar radiation on a small area receiver which absorbs the radiation and converts it into thermal energy that may be stored and used for several applications where food preparation and water pasteurization is the priority. The concentrator, area 2.2 m², is a half satellite communication dish covered with trapezoidal acrylic mirror tiles. The receiver/absorber is a spiral coil of blackened stainless steel pipe. Oil is circulated as heat transfer fluid. To determine the optimal dimension and position of the receiver, two experimental methods were used: (1) The tiles were scanned using a vertical, self adjusting laser beam to get a distribution of reflected radiation across the focal volume. (2) A thin, blackened stainless steel plate was placed at appropriate distances in the focal volume, and temperature distribution scanned using a temperature gun. The latter method proved to be the more useful. Results of the analysis of system performance showed that the system has the capability to produce high temperatures for domestic purposes. The efficiency of the system is about 35 %. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

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4th International Conference on Advances in Experimental Structural Engineering, Ispra, Lombardy, Italy, June 29-30, 2011

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Various solar energy technologies are being developed to harness the available environmentally friendly and sustainable solar radiation. New ways of utilizing this "free" power for different energy consuming processes continue to be created. In this thesis, a multi-stage solar energy concentrating system has been developed and its feasibility as a radiation source for polymer processing has been explored. The solar energy concentrator (SEC) facility comprises a modified Cassegrainian configuration combined with auxiliary imaging and non-imaging optics, serving as an alternative energy source for polymer joining, ageing and adhesive curing. Modeling and improvement of various aspects of the operation and performance of the SEC facility have been implemented. Optical ray tracing models of the Cassegrainian concentrator with various conventional imaging components and nonimaging concentrators have been created to optimize the optical layout and system efficiency. On their basis, combined 3D ray tracing computer models integrated with the mechanical components have been developed to simulate the entire SEC facility and predict the image size, location and orientation. Additionally, the energy transfer, radiation absorption and heat generation and transfer in the irradiated polymer have been modeled in order to study the radiation-polymer interaction. One novel contribution of this research is the enhancement of the image forming concentrator with non-imaging cone-like concentrators (conical and compound parabolic concentrator (CPC)), utilizing their inherent disadvantage of excessive length. Compared to the refractive type means of transmitting concentrated solar radiation, the truncated cone and CPC concentrators have been found more efficient enhancing further the concentration and widening the utilized spectral range. The experimental studies have demonstrated that transparent and colored, similar and dissimilar polymers can be successfully joined using the SEC facility. The especially developed through-transmission technique removes the need to use a special absorbing medium of the radiant energy required by current advanced welding techniques. The tensile strengths of the joints achieved are comparable to those achieved for similar polymers with other advanced plastic joining methods. The results from the polymer ageing experiments have shown that ultraaccelerated exposure to concentrated sunlight can be performed with the SEC facility without introducing spurious failure mechanisms. Based on the preliminary investigation on adhesive curing utilizing concentrated solar radiation, it has been concluded that with carefully chosen light-curing adhesives solar radiation can be a useful radiation source for adhesive curing.