Experimental investigation of cavity flow under building integrated photovoltaic panels using thermography and particle image velocimetry

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.An extensive experimental investigation demonstrates the impact of cavity airflow underneath photovoltaic (PV) panels integrated in the roof assemblies of buildings. The benefit of underside ventilation is seen in terms of an increased efficiency of photovoltaic panels due to lowering their operating temperature, resulting in less turn-off times as well as an improved hygrothermal and durability behavior of the panels. We perform an extensive measurement campaign of the surface temperature using infrared thermography and of the airflow using particle image velocimetry. A novel setup was developed consisting of a building model with a mock PV panel and a solar simulator placed inside a large-scale atmospheric wind tunnel. A solar simulator is positioned in the tunnel to provide a range of various radiation intensities over the panels and the approaching upstream wind is well controlled in the wind tunnel. The top surface temperatures and air speeds above and below the panel are monitored simultaneously. It is shown that, in general, the airflow within the cavity is faster compared to the free upstream air velocity, resulting in an increased heat exchange between the PV and the air cavity and a reduction of the PV surface temperatures. A stepped open arrangement of panels is shown to be more effective in reducing the surface temperatures comparing to a flat arrangement. The results also show the presence of different interacting flow phenomena: natural convection due to irradiation, forced convection due to the upstream wind, cavity ventilation and surface convection, as well as the presence of complex 3D flows patterns (e.g. lateral eddies), which contribute to a highly non-uniform surface temperature distribution over the PV modules.dc201

Symmetric Vlasov-type antenna for High Power Microwave applications

We present a novel Vlasov-type antenna operating at 2.5 GHz and composed of a circular waveguide with a double bevel-cut. Simulation results show that the proposed antenna is capable of providing a wider emission angle if compared to standard Vlasov configurations, while still maintaining an adequate gain level. For this reason, it could be of interest for those High-Power Microwave (HPM) applications in which a larger area need to be covered by the EM field

Habitat quality affects the condition of Luciobarbus sclateri in the Guadiamar River (SW Iberian Peninsula): Effects of disturbances by the toxic spill of the Aznalcóllar mine

This study analyzes the somatic condition of southern Iberian barbel Luciobarbus sclateri (Günther, 1868) in the Guadiamar River (SW Iberian Peninsula). This river was seriously affected by a toxic spill of about 4 million cubic meters of acidic water and 2 million cubic meters of mud rich in heavy metals. Once the spill removal works concluded, sites affected and unaffected by the accident were sampled to study its effects on the fish fauna. The ecological variables registered were related to water quality, physical state of reaches, ecological quality, resources exploited by fish, and potential intra-specific interactions. From an initial 15 ecological variables, seasonal water flow and pH explained most of the variation in barbel condition. This study shows that the Guadiamar River, 56 months after the accident, is still undergoing a recovery process where, beyond ecological variables, proximity to the affected area is the most influential factor for fish condition. © 2012 Springer Science+Business Media B.V

Factors affecting milking speed in Murciano-Granadina breed goats

[EN] Milk flow during the first minute of milking was analyzed using data from 1,132 Murciano-Granadina breed goats belonging to 17 herds. During the individual lactations, 2 test days were scheduled for recording several milk flow traits, total milk, milk composition (fat and protein percentages), and somatic cell count. Average lag time from teatcup attachment to arrival of milk at the milk claw (TO) was 4.9 s and at the milk meter (T1) was 15.8 s. Average milk flow after 30 s (MF0.5) was 0.29 kg/30 s (0 to 1.1 kg/30 s) and milk flow at 60 s or milking speed (MF1) was 0.67 kg/min (0.1 to 2.1 kg/min). Repeatabilities of T0, T1, MF0.5, and MF1 were 0.45, 0.58, 0.62, and 0.68, respectively. The MF1 showed high phenotypic correlation with T1 (-0.63) and MF0.5 (0.90), medium values with T0 (-0.42) and total milk (0.22), and very low values (-0.04 to -0.12) with fat, protein, and somatic cell count. We found no differences between flows during the first 3 lactations, with a reduction as the lactation number increased. Months in milk since parturition affected MF1, being highest in the first 3 mo (0.67-0.71 kg/ min) and decreasing until the end of lactation (0.58 kg/ min). The effect of herd-test day was significant for all traits. Inclusion of all these effects for the analysis of milk flow traits is considered necessary.This work was funded by the Spanish INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain) through European FEDER funds (the project RTA2010 0132 led by E. A. Gomez and the scholarship FPI-INIA2011 042 attained by E. Blasco).Blasco, E.; Gómez, E.; Vicente Martín, C.; Vidal, G.; Peris Ribera, CJ. (2016). Factors affecting milking speed in Murciano-Granadina breed goats. Journal of Dairy Science. 99(12):10102-10108. https://doi.org/10.3168/jds.2016-10869S1010210108991