Systematic comprehensive techno-economic assessment of solar cooling technologies using location-specific climate data

A methodology for assessing solar cooling technologies is proposed. The method takes into account location specific boundary conditions such as the cooling demand time series, solar resource availability, climatic conditions, component cost and component performance characteristics. This methodology evaluates the techno-economic performance of the solar collector/chiller system. We demonstrate the method by systematic evaluation of 25 feasible combinations of solar energy collection and cooling technologies. The comparison includes solar thermal and solar electric cooling options and is extended to solar cooling through concentrated solar power plants. Solar cooling technologies are compared on an economic and overall system efficiency perspective. This analysis has implication for the importance of solar load fraction and storage size in the design of solar cooling systems. We also stress the importance of studying the relation between cooling demand and solar resource availability, it was found that overlooking this relation might lead to overestimations of the potential of a solar cooling system in the range of 22% to over 100% of the actual potential.     

Thermal buckling behavior of two-dimensional imperfect functionally graded microscale-tapered porous beam

This article presents a study on the thermal buckling behavior of two-dimensional functionally graded microbeams made of porous materials. The material composition varies along thickness and length of the microbeam based on the power law distribution. The microbeam is modeled within the framework of Euler–Bernoulli beam theory. The microbeam is considered having variable material composition along thickness. The equations are derived using the modified couple stress theory and the solving process is based on the generalized differential quadrature method. The validity of the results is shown through comparison of the results with the results of other published research.     

Performance assessment of a solar hydrogen and electricity production plant using high temperature PEM electrolyzer and energy storage

This paper investigates the performance of a high temperature Polymer Electrolyte Membrane (PEM) electrolyzer integrated with concentrating solar power (CSP) plant and thermal energy storage (TES) to produce hydrogen and electricity, concurrently. A finite-time-thermodynamic analysis is conducted to evaluate the performance of a PEM system integrated with a Rankine cycle based on the concept of exergy. The effects of solar intensity, electrolyzer current density and working temperature on the performance of the overall system are identified. A TES subsystem is utilized to facilitate continuous generation of hydrogen and electricity. The hydrogen and electricity generation efficiency and the exergy efficiency of the integrated system are 20.1% and 41.25%, respectively. When TES system supplies the required energy, the overall energy and exergy efficiencies decrease to 23.1% and 45%, respectively. The integration of PEM electrolyzer enhances the exergy efficiency of the Rankine cycle, considerably. However, it causes almost 5% exergy destruction in the integrated system due to conversion of electrical energy to hydrogen energy. Also, it is concluded that increase of working pressure and membrane thickness leads to higher cell voltage and lower electrolyzer efficiency. The results indicate that the integrated system is a promising technology to enhance the performance of concentrating solar power plants.     

Emission of phthalates from PVC and other materials

The main objective of this study was to generate quantitative and qualitative emission data on phthalates from different materials. To achieve this the existing (Chamber for Laboratory Investigations of Materials, Pollution and Air Quality) Climpaq-based procedure for simplified measurements of emissions of plasticizer from PVC and other plasticized materials was modified. It was applied to a range of products. Some of them were suspected of contributing to the indoor concentration of plasticizers. The emissions from PVC flooring, polyolefine flooring, a refrigerator list, two electric cables, PVC skirting and floor wax were studied in separate Climpaqs. The emission from the PVC flooring in the Climpaq was compared with results from the ultra-small chamber Field and Laboratory Emission Cell (FLEC). Sampling and analysis methods were optimized to measure plasticizers. Samples were taken in exhaust air from the chambers after 6, 35, 62, 105, and 150 days from the start of the experiment. PVC flooring was tested for an additional 100 days. Polyolefine covered with wax resulted in an air concentration of 22 microg/m3 of dibutylphthalate (DBP), which is two orders of magnitude larger than any other materials, but did not emit di(2-ethylhexyl)phthalate (DEHP). The other materials resulted in max concentration of approximately 1 microg/m3 of DEHP and low emissions of DBP. The concentration of DEHP in each chamber increased slowly to a rather stable level which was reached after 150 days. DBP concentrations in the chambers with PVC skirting, PVC flooring, polyolefine and floor wax reached their quasi-static equilibrium after 60 days. The modified method did not create sufficient data for the calculation of emission rates. Adsorption of emission on chamber surfaces made it impossible to use the first part of the experiment for emission rate calculation. When the concentration had stabilized, it was found to be almost identical and independent of chamber and ventilation rate. Emission rates were reduced at high concentrations probably because the concentration in the material was near equilibrium with the concentration in the chamber air.     

Dynamic analysis of a nonlinear pressure regulator using bondgraph simulation technique

The dynamics of a direct pressure regulator valve have been studied through bondgraph simulation technique. The governing equations of the system have been derived from the obtained model. While solving the system equations numerically, various pressure-flow characteristics across the regulator ports and the orifices are taken into consideration. The simulation study identifies some critical parameters, which have significant effect on the transient response of the system. The simulation results are determined using the MATLAB-SIMULINK environment. The main novelty of this work is to present an analytic solution in analyzing a nonlinear complex system with interaction of several energy domains. The other conventional attempts employed before this solution resulted to inaccurate simulation results which can not predict the dynamical response of the system. Numerical results implied to the good accuracy of the bondgraph study, while comparing with experimental results.     

Measurement of Ultrafine Particles: A Comparison of Two Handheld Condensation Particle Counters

The objective of this study was to compare two real-time condensation particle counters for measurement of number concentrations of ultrafine particles (UFPs). The comparison is based on the data from side-by-side measurements conducted in several locations, both indoors and outdoors. CPC 3007 and P-Trak? 8525 manufactured by TSI (instruments A and B, respectively) were used simultaneously. They measure particles in sizes from 0.01 to greater than 1 μ m and 0.02 to greater than 1 μ m, respectively. The results reveal a good correlation between the two instruments. The ratios of measured aerosol concentrations varied from 0.81 to 1.17, which implies that in all data sets the difference between the two instruments was less than ± 20%. About 63% of the results were in the range of ± 10%, and about 44% showed differences less than ± 5%. The maximum particle concentration detected by instrument A was approximately 105,000 particles cm ^{? 3} and the minimum was about 230 particles cm ^{? 3} . Because of the lower particle size threshold for instrument A, it was expected that this instrument should never show concentrations lower than those detected by instrument B. This was the case in most of the measurement series. The results revealed that the concentration of UFPs changes rapidly, especially in the presence of a local UFP source. A sampling interval of 1 min is sufficient to provide substantial information about the change in concentration level.     

Optimizing the mechanical properties of TiO2/PA12 nano-composites fabricated by SLS 3D printing

In this paper, the selective laser sintering process was used to fabricate the TiO₂/PA12 nano-composite parts by considering the parameters of laser power, scanning speed, and TiO₂ content. The response surface methodology was used to improve the mechanical properties of TiO₂/PA12 nano-composite parts. The fracture surface characteristics of the specimens were examined using the scanning and transmission electron microscopy. The results indicated that the increase in laser power from 10 to 15 W improved the tensile strength, modulus, and impact strength of the nano-composite parts because of the fine dispersion of TiO₂ nano-particles. An increase in the scanning speed from 2000 to 3000 mm/s resulted in the reduction of tensile strength and modulus due to lower heat input and consequently incomplete densification of polyamide-12. In addition, the increase of TiO₂ content up to 5 wt% can improve the tensile strength, modulus, and impact strength, but requires increasing the laser power. However, the mechanical properties of the nano-composite parts were enhanced simultaneously at laser power of 12.4 W, scanning speed of 2000 mm/s and TiO₂ content of 1.9 wt%. Moreover, the addition of TiO₂ up to 5 wt% showed a slight influence on thermal stability and crystallinity of the sintered specimens.     

From microstructure to mechanical properties of compatibilized polylactide/thermoplastic starch blends

Bio‐degradable polymer blends of polylactic acid/thermoplastic starch (PLA/TPS) were prepared via direct melt blending varying order of mixing of ingredients fed into the extruder. The effect of interface interactions between PLA and TPS in the presence of maleic anhydride (MA) compatibilizer on the microstructure and mechanical properties was then investigated. The prepared PLA/TPS blends were characterized by scanning electron microscopy, differential scanning calorimetry (DSC), tensile, and rheological measurements. Morphology of PLA/TPS shows that the introduction of MA into the polymer matrix increases the presence of TPS at the interface region. DSC results revealed the reduction of glass transition temperature of PLA with contributions from both TPS and MA. The crystallization temperature was decreased by the addition of MA leading to reduction of overall crystallization of PLA/TPS blend. The mechanical measurements show that increasing MA content up to 2 wt % enhances the modulus of PLA/TPS more than 45% compared to the corresponding blends free of MA compatibilizer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44734.     

Properties of films and fibers obtained from Lewis acid-base complexed nylon 6,6

A nylon 6,6 complex with GaCl₃ in nitromethane (4-5 wt% nylon 6,6) was prepared at 50-70 °C over 24 h for the purpose of disrupting the interchain hydrogen bonding between nylon 6,6 chains, resulting in amorphous nylon 6,6, and increasing the draw ratio for improving the performance of nylon 6,6 fibers. After drawing, complexed films and fibers were soaked in water to remove GaCl₃ and regenerate pure nylon 6,6 films and fibers. FTIR, SEM, DSC, TGA, and mechanical properties were used for characterization of the regenerated nylon 6,6 films and fibers. The amorphous complexed nylon 6,6 can be stretched to high draw ratios at low strain rates, due to the absence of hydrogen bonding and crystallinity in these complexed samples. Draw ratios of 7-13 can be achieved for complexed fibers, under low strain rate stretching. This study indicates that nylon 6,6 fibers made from the GaCl₃ complexed state, using a high molecular weight polymer, can reach initial moduli up to 13 GPa, compared to initial moduli of 6 GPa for commercial nylon 6,6 fibers. Lewis acid-base complexation of polyamides provides a way to temporarily suppress hydrogen bonding, potentially increasing orientation while drawing, and following regeneration of hydrogen bonding in the drawn state, to impart higher performance to their fibers.