The use of organic solid waste for energy generation has become a promising and sustainable solution to address environmental issues, particularly those related to fossil fuel consumption. Producing energy from forest biomass offers a viable and eco-friendly alternative, aiming to reduce greenhouse gas (GHG) emissions. A key factor for the sustainable production and supply of bioenergy is the abundant availability of suitable raw materials. Among these, forestry pruning waste stands out as a significant resource, often poorly managed and improperly disposed of. An environmentally responsible way to utilize these residues is through incineration, using the resulting hot gases from combustion for energy generation. The primary goal of this study was to quantify the energy generation potential from the forestry pruning waste of UFPR. To achieve this, the organic waste from UFPR was chemically characterized through Proximate Analysis, along with determining the higher heating value and moisture content. A mathematical model was developed to quantify the generation of electrical energy, simulating the steady-state operation of the incineration system. Additionally, a mathematical model of the Rankine cycle plant was created to predict the necessary thermal exchange areas in the plant. The analyses of the collected samples showed heterogeneity, with low ash content at 0.76% and moisture content ranging from 10.67% to 16.80%, but an average high higher heating value of 19.39 MJ.kg-1. The mathematical model predicted that these residues could be sustainably used for electricity generation, with a power output of 54.28 kW. The chemical analysis results led to optimization in the thermal exchange areas of the Rankine cycle plant, facilitating the efficient utilization of hot gases produced from the incineration of these forestry residues.
Nitrogen thin film evaporation is a novel technique applied to cryopreservation, which aims to improve the preservation of biological samples at ultra-low temperatures. Cryopreservation is a critical process used in various fields, including biomedical research, regenerative medicine, and the storage of genetic materials. Traditional cryopreservation methods often suffer from sample damage caused by ice crystal formation and chemical toxicity associated with conventional cryoprotectants. This study developed an experimental apparatus comprising a vacuum chamber and two cryocauteries. The sample is stored in a polydimethylsiloxane-based composite reservoir between two copper plates with a nickel microporous outer surface. This system is suspended inside the chamber, and nitrogen jets promote evaporation. Chamber pressure and sample temperatures are recorded during the experiments. Tests were performed using dimethyl sulfoxide, glycerol and sucrose solutions in phosphate-buffered saline at different concentrations and volumes to evaluate vitrification and cooling rates. Effects of volume and concentration were evaluated, and it was found that vitrification success is directly related to the cryoprotective agent concentration used. In addition, no significant impact on the visual appearance of the samples related to vitrification regarding the sample geometry was observed. The copper foam porous surface resulted in the highest cooling rate, which is associated with the properties of the foam, such as its high thermal conductivity.
Higher concentrations of greenhouse gases, resulting from anthropogenic actions associated with energy generation, are one of the causes of climate change. In view of this, several efforts have been undertaken in the search for more sustainable alternatives, and photovoltaic (PV) technology has stood out among the different possibilities. However, PV generation is highly sensitive to future climate variability, which is a source of uncertainty that can complicate energy planning and compromise the viability of systems. This theme has received attention from the academic community, but some challenges to mapping and identifying the relevant literature have been encountered. Therefore, this study was conducted to analyze and identify relevant aspects of international scientific production focused on the impacts of climate change on the potential of photovoltaic production, CC-PVP, through bibliometric techniques. For this purpose, 3900 articles from the Web of Science and Scopus databases, published between 1960 and 2021, were retrieved and analyzed through a bibliometric approach, using the SciMAT v1.1.04 tool. Among the results obtained, it is worth pointing out that the CC-PVP research field has moderate maturity, and it is concentrated in the areas of energy, fuels, and technology, as well as environmental sciences and meteorology. It was concluded that key themes revolve around global energy, forecasting photovoltaic energy production, and electrical energy consumption, especially concerning climate change. Furthermore, it was found that researchers from China, North America, and Australia contribute significantly to this area compared to researchers from other countries.
This work consists of a comparative study between two standing wave thermoacoustic engines that differ in the geometry of their resonant chambers, but hold the same internal elements and operate at the same fundamental frequency and boundary conditions. One of the engines consists of a straight tube of circular cross-section as its main part that defines a resonant acoustic waveguide, while the other one consists of, in addition to a similar straight tube, also a conical bulb connected to one of its ends acting as a coupled Helmholtz resonator. According to the literature, the Helmholtz cavity causes a higher pitch quality in the first harmonic mode, which is of greatest interest from the energetic point of view. The main objective of this work is to verify and evaluate such an effect on the engine performance so that to explore its optimization by means of frequency and geometric. Both engines are simulated in the DeltaEC software. DeltaEC, however, does not include harmonics other than the fundamental one. Understanding of the influence of higher acoustic modes may lead to a better management of the thermoacoustic engine configuration towards higher thermal efficiencies.
This study is motivated by the production of synthesis gas (syngas) from gasification of refused-derived fuel (RDF) in thermochemical reactors. For this purpose, a reactor with a circulating fluidized bed transforms RDF into synthesis gas at temperatures around 850°C. The syngas consists of a biphasic mixture, containing fuel gas and solid particles that are dragged during the gasification process. The gas flows into an axial cyclone positioned inside the upper part of the reactor, so that non-gasified particulates, inert residues and particles from the bed can be removed. Due to the size and density of the solid particles and the residence time inside the thermochemical reactor, the cyclone must be designed to clean the gas, improving its quality and reducing costs with scrubbers. Therefore, in this study, a vertical cylindrical reactor with 10.57 m height and 0.95 m diameter was modeled computationally, with an axial cyclone inside measuring 9.3 m in height and 0.6 m in the largest diameter region. The model does not consider thermochemical reactions inside the reactor. For the solid phase, 0.425 m³ of 100 mesh sand particles with a constant density equal to 1500 kg/m³ were considered. For the gas phase an air flow of 800 kg/h at 500°C was adopted. Numerical-computational models were solved using the ANSYS® software, based on the classical equations of mass conservation, momentum and energy. The k-omega SST turbulence model has been applied. From the analysis of pressure gradient, velocity profiles and the particulate removal rate in the cyclone, the cyclone efficiency and the pressure drop were determined. An efficiency of 99.83% in the cleaning process carried out by the axial cyclone was observed. The obtained results also allowed analyze the distribution of particles inside the reactor and their passage in the axial cyclone.
