Exergoeconomic and enviroeconomic evaluations of conventional solar still using PCM and electric heater powered by solar energy: an experimental study.

Solar stills are used in distant and arid areas to convert brackish or salty water into potable water fit for human use in a simple, affordable, and effective manner. Even when PCM materials are used, typical solar systems still have minimal production per day. In this study, experimental tests were carried out in order to increase the performance of a single-slope solar still combined with PCM material (paraffin wax) and a solar-powered electric heater. Two identical single-slope solar stills were designed, fabricated, and tested under the same climatic conditions during the summer and spring seasons of 2021 in Al-Arish, Egypt. The first is a conventional solar still (CVSS), and the other is also a conventional still but with PCM and an electric heater (CVSSWPCM). Several parameters were measured during the experiments, including sun intensity, meteorological aspects, cumulative freshwater production, average glass, and water temperatures and PCM temperature. The improved solar still was evaluated at different operating temperatures and was compared to the conventional traditional one. There were four cases studied: one case without a heater (paraffin wax only) and three other cases with a heater operating at 58 °C, 60 °C, and 65 °C, respectively. The experimental results revealed that activating the heater inside the paraffin wax increased daily production (i) in the spring by 2.38, 2.66, and 3.1 times and (ii) and in the summer by 2.2, 2.39, and 2.67 times at the three above-mentioned temperatures respectively (when compared to the traditional still). In addition, the maximum rate of daily freshwater production was achieved at paraffin wax temperature of 65 °C in both spring and summer (Case 5). Finally, the economic evaluation of the modified solar still was carried out according to cost per litre. The modified solar still with a heater operating at 65 °C has a higher exergoeconomic value than the traditional one. The maximum CO2 mitigation in cases 1 and 5 was approximately 28 tons and 160 tons, respectively.

Mechanically Robust, Stretchable Solar Absorbers with Submicron-Thick Multilayer Sheets for Wearable and Energy Applications.

A facile method to fabricate a mechanically robust, stretchable solar absorber for stretchable heat generation and an enhanced thermoelectric generator (TEG) is demonstrated. This strategy is very simple: it uses a multilayer film made of titanium and magnesium fluoride optimized by a two-dimensional finite element frequency-domain simulation, followed by the application of mechanical stresses such as bending and stretching to the film. This process produces many microsized sheets with submicron thickness (∼500 nm), showing great adhesion to any substrates such as fabrics and polydimethylsiloxane. It exhibits a quite high light absorption of approximately 85% over a wavelength range of 0.2-4.0 µm. Under 1 sun illumination, the solar absorber on various stretchable substrates increased the substrate temperature to approximately 60 °C, irrespective of various mechanical stresses such as bending, stretching, rubbing, and even washing. The TEG with the absorber on the top surface also showed an enhanced output power of 60%, compared with that without the absorber. With an incident solar radiation flux of 38.3 kW/m2, the output power significantly increased to 24 mW/cm2 because of the increase in the surface temperature to 141 °C.

Eficiência de sistema de aquecimento auxiliar para aviários, com base nos índices de conforto térmico / Auxiliary heating system efficiency for poultry housing, based on thermal indexes

Este trabalho teve como objetivo avaliar protótipos de aquecedor solar para pintinhos com 1,0; 1,5 e 2,0 m de diâmetro (tratamentos AQ1, AQ2 e AQ3, respectivamente) com base nos índices de conforto térmico no município de Marechal Candido Rondon, Paraná. Valores de temperatura de globo negro, bulbo seco, bulbo úmido e velocidade do vento foram registrados acima do dissipador e nas condições externas. Os dados foram coletados a cada duas horas, entre 08h00min e 16h00min durante o período experimental. Com base em valores horários por aquecedor, o Índice de Temperatura e Umidade (ITU) e o Índice de Temperatura Globo Umidade (ITGU) não apresentaram resultados que diferenciassem entre os coletores avaliados. A maior Carga Térmica de Radiação (CTR) foi observada para AQ1 e AQ2 às 14 h. Quando se comparam os aquecedores, independente do horário de observação, verifica-se que os maiores valores de ITU e ITGU ocorreram para AQ1 e AQ3 e a CTR para AQ1. O horário para o qual foram observados os maiores valores destes índices foi às 14 h. Concluiu-se que o sistema de aquecimento pode se constituir uma alternativa para uso em aviários já que propicia condições de conforto térmico semelhante aos sistemas empregados comercialmente.

This study had as objective to evaluate prototypes of solar heater for broiler chicken with diameter of 1.0; 1.5 and 2.0 m (treatments AQ1, AQ2 and AQ3, respectively) based on the thermal comfort indexes in Marechal Candido Rondon, Paraná State, Brazil. The values of black globe temperature, dry bulb, wet bulb and wind speed were registered above the heater and in the external conditions. Data were collected each two hours, between 8:00 AM and 4:00 PM during the experimental period. Based on hourly values for heater, the Temperature and Humidity Index (THI) and the Black Globe Humidity Index (BGHI) didn't present results that differentiated the appraised heaters. The highest value of Thermal Heat Load (THL) was observed for AQ1 and AQ2 at 2:00 PM. When the heaters are compared, independent of the observation schedule, was verified that the largest values of THI and BGHI occurred for AQ1 and AQ3 and CTR for AQ1. The time which were observed the largest values of these indexes was 2:00 PM. It was concluded that the heating system can be constituted an alternative for use in aviaries considering that provide similar conditions of thermal comfort that the commercial systems.