Improvement of the thermal behaviour of gypsum blocks by the incorporation of microcapsules containing PCMS obtained by suspension polymerization with an optimal core/coating mass ratio

The feasibility of incorporating microcapsules containing Phase Change Materials (PCMs), previously obtained by a suspension polymerization process, in gypsum wallboards to increase the wall energy storage capacity was studied. Firstly, the energy storage capacity of the resulting microcapsules and the microencapsulation efficiency was maximized by studying the influence of the synthesis variable core/coating mass ratio on the suspension polymerization process. Results indicate that the higher paraffin wax to styrene monomer mass ratio, the lower microencapsulation efficiency. A mass ratio of Rubitherm® RT27 to styrene monomer equal 1.5 allowed to obtain microcapsules with the highest energy storage capacity and a good microencapsulation efficiency. It was also observed that the energy storage capacity is dependent on the particle size; the maximum capacity was obtained for a particle size of 500 μm. Finally, the thermal behaviour of three gypsum wallboards one without PCMs and the others doped with 4.7% and 7.5% by weight of microcapsules containing Rubitherm® RT27 at the optimal core/coating mass ratio was studied. Results showed that the higher the amount of microcapsules containing PCMs incorporated to the gypsum wallboard, the lower or higher the external wall temperature for heating or cooling process, respectively. Besides, the incorporation of the microcapsules to the wall increased the time required to achieve the final steady state, verifying that the material insulation capacity was enhanced by increasing PCMs content in the wall.     

Wastewater transformations and fertilizer value when co-digesting differing ratios of swine manure and used cooking grease in low-cost digesters

A nine-month co-digestion investigation was conducted in Costa Rica to optimize animal wastewater treatment, renewable energy production, and fertilizer creation using 12 Taiwanese-model, plug-flow digesters (250 L each) constructed of tubular polyethylene and PVC piping, operating without mechanical or heating components. The experiment tested three replications of four treatment groups: the control (T0), which contained only swine manure, and T2.5, T5, and T10, which contained 2.5%, 5%, and 10% used cooking grease (by volume) combined with swine manure.T2.5 had the greatest methane production (45 L d^?1), a 124% increase from the control. No adverse effects were observed from co-digesting 2.5% grease in terms of organic matter removal, pathogen reduction, grease removal, and pH. Chemical oxygen demand (COD) was reduced 94.7% to 1.96 g L^?1, fecal coliforms and Escherichia coli were reduced 99.2 and 97.1%, respectively, and grease removal was 99.9%. The average effluent pH (7.05) and alkalinity in T2.5 was within the optimal range for methanogens and increased significantly during the nine-month experiment, likely due to adaptation of the methanogenic organisms to the influent grease concentrations. Total nitrogen concentration decreased 34.0%, and NH₄-N increased 97.1% during digestion in T2.5, with no significant differences between T2.5 and T0. There was less phosphorus reduction with co-digestion, with 181 mg g^?1 of total phosphorus (TP) in T2.5 and only 90.6 mg g^?1 of TP in T0, resulting in lower N:P ratios in the grease treatment groups due to the greater concentration of phosphorus in the effluent.     

Analysis of Brazilian SHP policy and its regulation scenario

This article presents the main regulatory changes that occurred in the Brazilian power sector in 2009, along with the impacts these changes caused on the market, especially related to small hydropower (<30 MW). This study addresses regulatory issues based on inventory studies and records of basic projects, changes related to the compensation of the assured energy of SHPs in the Brazilian energy reallocation market, the socio-economic impact resulting from the construction of SHPs, SHPs in alternative resource auctions and finally the general outlook for the growth scenario for SHPs in Brazil according to the ten-year plan (2010–2019). The overall conclusions of this investigation were that the 2008/2009 biennium was a period of great changes in the regulation of small hydropower plants in Brazil, and the SHP market has shown maturity. Additionally, despite SHP being a type of technology that is completely dominated by domestic industry, in recent years, they have experienced policy disincentives caused by changes to rules that inhibit their growth.     

Design of pressure vessels using shape optimization: An integrated approach

Previous papers related to the optimization of pressure vessels have considered the optimization of the nozzle independently from the dished end. This approach generates problems such as thickness variation from nozzle to dished end (coupling cylindrical region) and, as a consequence, it reduces the optimality of the final result which may also be influenced by the boundary conditions. Thus, this work discusses shape optimization of axisymmetric pressure vessels considering an integrated approach in which the entire pressure vessel model is used in conjunction with a multi-objective function that aims to minimize the von-Mises mechanical stress from nozzle to head. Representative examples are examined and solutions obtained for the entire vessel considering temperature and pressure loading. It is noteworthy that different shapes from the usual ones are obtained. Even though such different shapes may not be profitable considering present manufacturing processes, they may be competitive for future manufacturing technologies, and contribute to a better understanding of the actual influence of shape in the behavior of pressure vessels.     

The influence of impurities on the acid-catalyzed reaction of glycerol with acetone

The acid-catalyzed reaction of glycerol with acetone was studied in the presence of impurities that might be present in the crude glycerin of biodiesel production. These are mainly methanol, water and sodium chloride, in different amounts. The results indicated that methanol has minor effect on the glycerol conversion, whereas the concomitant addition of water and sodium chloride produces a drastic decrease of the conversion. The nature of the acid catalyst also affects the conversion in the presence of impurities. Amberlyst-15™ acid resin is more sensible to the water content than zeolite Beta. The results of the glycerol adulteration with different contaminants were compared with the reaction using a crude glycerin from a Brazilian biodiesel industrial plant.     

Effect of Ni on Pt/C and PtSn/C prepared by the Pechini method

Different compositions of Pt, PtNi, PtSn, and PtSnNi electrocatalysts supported on carbon Vulcan XC-72 were prepared through thermal decomposition of polymeric precursors. The nanoparticles were characterized by morphological and structural analyses (XRD, TEM, and EDX). XRD results revealed a face-centered cubic structure for platinum, and there was evidence that Ni and Sn atoms are incorporated into the Pt structure. The electrochemical investigation was carried out in slightly acidic medium (H₂SO₄ 0.05 mol L⁻¹), in the absence and in the presence of ethanol. Addition of Ni to Pt/C and PtSn/C catalysts significantly shifted the onset of ethanol and CO oxidations toward lower potentials, thus enhancing the catalytic activity, especially in the case of the ternary PtSnNi/C composition. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed for determination of acetaldehyde and acetic acid as the reaction products, as detected by HPLC analysis. Due to the high concentration of ethanol employed in the electrolysis experiments (1.0 mol L⁻¹), no formation of CO₂ was observed.     

Energy efficiency actions related to the rollout of smart meters for small consumers, application to the Austrian system

Smart meters (SM) may provide large benefits to all stakeholders by providing the information required to implement certain sets of demand response actions. Benefits produced by SM related actions depend on the features of these actions, the system and the targeted consumer group.We first lay out an analytical framework to analyze the application of Demand Response (DR) actions. Based on this framework, we describe a way to determine the response of domestic load in a system to the implementation of DR actions. We propose determining the overall change in the consumption behavior of domestic load based on previously obtained estimates of the peak load and overall consumption reduction for different types of consumers in different types of systems resulting from the application of each set of actions. We have carried out a comprehensive literature review to provide here such estimates.We apply the analytical framework and methodology developed to characterize the reaction of consumers in the Austrian system to different SM related actions. Finally, we provide guidelines on which DR actions to implement in this system and how to implement them. The use of advanced indirect feedback on consumption behavior, critical peak prices and simple time-of-use tariffs is advocated.     

Non-catalytic production of fatty acid ethyl esters from soybean oil with supercritical ethanol in a two-step process using a microtube reactor

This work reports the production of fatty acid ethyl esters (FAEE) from the transesterification of soybean oil in supercritical ethanol in a continuous catalyst-free process using different reactor configurations. Experiments were performed in a microtube reactor with experimental simulation of two reactors operated in series and a reactor with recycle, both configurations at a constant temperature of 573 K, pressure of 20 MPa and oil to ethanol mass ratio of 1:1. Results show that the configurations studied with intermediate separation of glycerol afford higher conversions of vegetable oil to its fatty acid ethyl ester derivatives when compared to the one-step reaction, with relatively low decomposition of fatty acids (<3.0 wt%).     

Evaluation of the impact of access to electricity: A comparative analysis of South Africa,China, India and Brazil

Most developing countries include rural electrification programs in their efforts to improve social conditions. There are, however, several obstacles to the evaluation of such programs and therefore of their social, economic, environmental and energy impacts on the target population, particularly on impoverished communities located in remote areas. Evaluation of the efficacy of public policies aimed at rural electrification in South Africa, China, India and Brazil enables such actions to be quantified and re-considered so as to bolster the sustainability of their planning and implementation and also so as to enable comprehension of the significance of access to electricity in relation to other aspects of the drive to improve living standards. The provision of electric energy amounts to more than access to a public service and should be considered an essential right, in a context of social equity and justice, which permits social integration and the access to other equally essential services.     

Experimental thermal–hydraulic evaluation of CuO nanofluids in microchannels at various concentrations with and without suspension enhancers

This experimental study focuses on the effect of two important factors on the heat transfer and flow properties of copper oxide (CuO)/water nanofluids in a parallel microchannel flow configuration. The first factor considered is the solid media (CuO) concentration. In this investigation, concentration values of 0.005%, 0.01%, and 0.1% by volume were tested. The second factor is the use of a surfactant, cetyltrimethylammonium bromide (CTAB), as a suspension enhancer. All together, these two factors led to a total of six types of nanofluids, which were tested in addition to pure water, the reference fluid. The experimental setup allowed for the determination of the hydrodynamic and thermal performance of each nanofluid. In addition, a selection of the nanofluids were characterized by the use of scanning transmission electron microscopy (STEM) and Dynamic Light Scattering (DLS) techniques. The DLS transient settling measurements showed that for a nanofluid with a concentration of 0.1% by volume, the nanoparticle dispersion and suspension is negatively affected unless a surfactant is used. Hydrodynamic losses, which were evaluated by comparing the effect of the imposed pressure drop on the mass flow rate, were not meaningfully affected by the composition of the nanofluids tested. The measurements also showed that nanofluids containing a surfactant generally provided a modest increase in heat transfer rate when compared with tests performed using pure water. The largest increase was about 17% for a fluid with a concentration of 0.01% by volume. Consequently, the gains in heat transfer do not appear to be accompanied by a significant pumping power penalty. The results of this study suggest that the use of a surfactant is essential in maintaining a proper suspension of nanoparticles in the fluid, especially at higher concentrations.