Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>For the last 20 years, solar collectors have been developing rapidly in the use of energy in buildings. Under experimental conditions, the solar energy utilization efficiency (SEUE) of flat plate solar collectors (FPSC) can reach more than 80%, but the engineering application of SEUE is low, and even the collector heating cannot meet the design requirements. In this paper, based on the existing thermal performance of FPSC, the influence of ambient meteorological parameters and hot water system operation parameters on SEUE is studied using experimental tests and analytical calculations. The results reflected that the collectors connected to the auxiliary heaters will affect SEUE, with series-connected systems having greater SEUE than parallel-connected systems. When the solar radiation intensity was low, the SEUE of parallel-connected systems was more likely to be negative. Under calculated conditions, when the water inlet temperature was 20, 30, 40, and 50 °C, the SEUE of the collector was 0%, and the corresponding solar radiation intensity was 113, 184, 225, and 328 W/m<jats:sup>2</jats:sup>, respectively. Reducing the average water temperature of the collector can reduce the heat loss in the energy conversion process between the collector and the air and increase the SEUE. When the solar radiation intensity was 500 W/m<jats:sup>2</jats:sup>, the collector inlet temperature decreases from 50 °C to 30 °C, and the SEUE increased from 20.9% to 38.5%. The research results can provide a parameter basis for the design of the FPSC system, especially the connection mode of collector and auxiliary heat device, and the design of system water temperature.</jats:p>

<jats:title>Abstract</jats:title><jats:p>With the growing contribution of wind power to the electric energy supply, fluctuation in available wind energy might increasingly become part of public debate. Fluctuation influences energy prices and might lead to acceptance problems. As a first step to gauge potential communication strategies, we investigated in an experimental study if acceptance is influenced by being made aware of fluctuation. Participants either answered questions on acceptance before or after judging fluctuation and predictability for 30 days of wind energy input. To test for potentially biased cognition, we additionally checked if judgments were affected by whether or not it was transparent that the graphs showed wind energy input. Mean acceptance did not differ between the groups. Directing attention to the fluctuation of power generated by wind does not have an impact on acceptance. Additionally, presence or absence of labels on the graphs and thus knowing that the graphs depicted wind energy supply, did not affect fluctuation and predictability ratings.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Hot water supply is a daily necessity for various purposes ranging from industrial to domestic usage. However, the availability of hot water supply is dependent on reliable energy systems to heat the water. The load shedding plan declared the energy crisis in South Africa. Therefore, exploring alternative energy methods for hot water supply is critical, especially renewable energy resources. The use of natural resources such as solar energy to heat water is highly impacted or limited by the resources and environmental conditions existing at the area of interest. The use of the solar water heating system based on Bellville; South Africa was the undertaken study. This study reports on the experimental investigation that was conducted on a 50 L water geyser, which was solar-based. The test rig that was constructed and tested was an active solar water heating system. It was tested over a period of 10 days under the environmental conditions experienced in mid-winter season of South Africa. A 20 tubed evacuated tube collector unit was used, and it was found that in mid-winter of the highest water temperature that the system could reach was above 65 °C and the lowest was 30 °C. Intriguing outputs were found in the study which revealed that, on the days that yield the highest solar irradiation did not necessarily produce the hottest water temperature. Therefore, scrutinizing the impact of other parameters that contributed to the overall water temperature output was necessary. From the tests it was observed that the wind velocity together with other environmental parameters effectively had an impact on the water temperature yield by an evacuated tube system.</jats:p>

<jats:title>Abstract</jats:title><jats:p>While desalination of water is energy intensive, traditional use of fossil fuels makes it not only costly, but also unsustainable and environmentally unfriendly; utilization of solar energy for desalination is therefore highly encouraged. This paper presents a study on the technical performance of a solar desalination unit located in Tehran city. The process is modeled using standard energy equations and performance indices are defined. The model simulation results are compared with experimental data from laboratory tests. This study observed that there is good agreement between the experimental data and the model simulation results. It is observed that the maximum solar radiation intensity is found in June and the highest evaporation rate in this month is about <jats:inline-formula><jats:alternatives><jats:tex-math>$$5\times {10}^{-3}\,{\mathrm{m}}^{3}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mspace /> <mml:msup> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> </mml:msup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>. It is found that the treatment efficacy of the plant decreases with increasing depth of wastewater. Performance of the desalination unit is found to be satisfactory.</jats:p>