An effective simulation model to predict and optimize the performance of single and double glaze flat-plate solar collector designs

This paper outlines and formulates a compact and effective simulation model, which predicts the performance of single and double glaze flat-plate collector. The model uses an elaborated iterative simulation algorithm and provides the collector top losses, the glass covers temperatures, the collector absorber temperature, the collector fluid outlet temperature, the system efficiency, and the thermal gain for any operational and environmental conditions. It is a numerical approach based on simultaneous guesses for the three temperatures, Tp plate collector temperature and the temperatures of the two glass covers Tg1, Tg2. A set of energy balance equations is developed which allows for structured iteration modes whose results converge very fast and provide the values of any quantity which concerns the steady state performance profile of any flat-plate collector design. Comparison of the results obtained by this model for flat-plate collectors, single or double glaze, with those obtained by using the Klein formula, as well as the results provided by other researchers, is presented

On the relationship factor between the PV module temperature and the solar radiation on it for various BIPV configurations

Temperatures of c-Si, pc-Si and a-Si PV modules making part of a roof in a building or hanging outside windows with various inclinations were measured with respect to the Intensity of the solar radiation on them under various environmental conditions. A relationship coefficient f was provided whose values are compared to those from a PV array operating in a free standing mode on a terrace. A theoretical model to predict f was elaborated. According to the analysis, the coefficient f takes higher values for PV modules embedded on a roof compared to the free standing PV array. The wind effect is much stronger for the free standing PV than for any BIPV configuration, either the PV is part of the roof, or placed upon the roof, or is placed outside a window like a shadow hanger. The f coefficient depends on various parameters such as angle of inclination, wind speed and direction, as well as solar radiation. For very low wind speeds the effect of the angle of inclination, β, of the PV module with respect to the horizontal on PV temperature is clear. As the wind speed increases, the heat transfer from the PV module shifts from natural flow to forced flow and this effect vanishes. The coefficient f values range from almost 0.01 m2°C/W for free standing PV arrays at strong wind speeds, vW>7m/s, up to around 0.05 m2°C/W for the case of flexible PV modules which make part of the roof in a BIPV system

Thermal modelling and experimental assessment of the dependence of PV module temperature on wind velocity and direction, module orientation and inclination

A theoretical and experimental analysis of PV module temperature under various environmental conditions is presented in relation to module inclination, wind velocity and direction. The present experimental study, makes use of hourly PV temperature data collected from a double-axis sun-tracking PV system and environmental parameters monitored for a period of one year. The f coefficient which relates the PV module temperature with the intensity of the global solar radiation on the PV plane and the ambient temperature, is assessed in relation to the angle of PV inclination, the wind velocity and the angle of incidence of the wind stream on the PV surface, either front or back. The f coefficient is evaluated both experimentally and theoretically through thermal modelling based on the energy balance equation. The simulation model developed in this study considers heat convection by natural and air forced flow, the flow pattern either laminar or turbulent, the relative geometry of the PV module with respect to the wind direction, and the radiated heat by the PV module. Various expressions for the forced heat convection coefficient available in the literature are tested within the thermal model with reference to the windward and leeward side of the PV module, and their applicability to PV thermal analysis is experimentally assessed in terms of the agreement shown with measured data. The values of the f coefficient provided by the simulation model lie very close to the experimental data for the entire range of PV inclination angles, wind velocities and wind directions tested

A cross-genus comparison of grazing pressure by two native marine herbivores on native, non-native naturalized, and non-native invasive Sargassum macroalgae

In marine systems, algal abundance and community composition is often heavily influenced by top-down control by herbivores. As a result, examining the extent to which native herbivores exert grazing pressure on non-native marine algae can provide valuable insight into mechanisms controlling invasion success. The purpose of this study was to examine the grazing preferences of two common intertidal and subtidal herbivores on three congeneric species of marine algae with unique colonization histories in San Diego, California, USA, to determine if grazing pressure, or lack thereof, may help explain invasion success. We provide evidence that neither native Sargassum agardhianum, nor non-native Sargassum horneri, are particularly palatable to purple urchins or black turban snails, but that non-native Sargassum muticum is consumed by both native herbivores. We also provide evidence that when given a choice of all three species neither herbivore exhibits a significant grazing preference for any algal species. We suggest that other mechanisms may determine the invasion success of the two non-native algal species and the overall distribution and abundance patterns of these species, and we discuss potential directions for future work

Stochastic prediction of hourly global solar radiation profiles

A stochastic prediction model of the hourly profile of the I(h;nj) for any day nj at a site is outlined. It requires 1,2,or 3 measurements of the global solar radiation in a day nj, uses a D.B. and gives I(h;nj) for the rest hours. The model is validated against solar measurements. Conclusions are deducted for the predictive power of the model developed in MATLAB. It provides I(h;nj) profile predictions very close to the measured values and offers itself as a promising tool for a predictive on-line daily load management

Transient and steady state simulation studies and experiments for the performance of c-Si and pc-Si PV cells in high illumination levels

A set of experiments was carried out to study the Voc, isc and the PV cell temperature time profile Tc(t) of a c-Si and a pc-Si cells. The analysis of the transient performance for Voc, isc and the cell temperature Tc(t) , vs time at different illumination levels was tried. A prediction model for the PV cell temperature, Tc, is developed and the results are compared with measured values. The same is tried for the prediction of Voc. The predicted Voc values by this model are compared to measured ones

Future sea-level rise drives rocky intertidal habitat loss and benthic community change

Abstract: Rocky intertidal ecosystems may be particularly susceptible to sea-level rise impacts but few studies have explored community scale response to future sea-level scenarios. Combining remote-sensing with large-area imaging, we quantify habitat extent and describe biological community structure at two rocky intertidal study locations in California. We then estimate changes in habitat area and community composition under a range of sea-level rise scenarios using a model-based approach. Our results suggest that future sea-level rise will significantly reduce rocky intertidal area at our study locations, leading to an overall decrease in benthic habitat and a reduction in overall invertebrate abundances, but increased densities of certain taxa. These results suggest that sea-level rise may fundamentally alter the structure and function of rocky intertidal systems. As large scale environmental changes such as sea-level rise accelerate in the next century, more extensive spatially-explicit monitoring at ecologically relevant scales will be needed to visualize and quantify the impacts to biological systems

The effect of mergers on US bank risk in the short run and in the long run

We examine changes in risk following US bank mergers in the period 1981-2014. Short-run (two-year) increases in acquirer risk following mergers occur only in the first few mergers undertaken by the same acquirer, not in the later ones. They occur only in the stocks’ sensitivity to banking industry risk and not in bank-specific risk. The equity volatility of acquirers does not increase, but diversification benefits are entirely dissipated. Using a new approach to measure the long-run effect we find that these results persist, consistent with banks maintaining a constant level of total equity risk in the long run. We measure the loss of diversification of the US bank industry associated with mergers and find it to be 40% of the risk level in 1981. Almost all of this occurred prior to 2004. In addition, there has been a large increase in correlations between the largest banks, much of which has come from sources other than mergers

PV module temperature prediction at any environmental conditions and mounting configurations

Photovoltaic (PV) module temperature is known to significantly affect its power output and efficiency, while it has been shown to depend mainly on the ambient temperature, the solar irradiance incident on the PV plane and the wind speed, while to a lesser extent on the wind incidence angle and various other environmental parameters as well as PV module structural characteristics, module type, etc. The mounting configuration has been shown to play a significant role in the PV temperature developed and the power output. This paper presents an algorithmic approach for the prediction of PV module temperature at any environmental conditions based on the energy balance equation taking into account PV orientation, windward and leeward side, heat convection by natural and air forced flow, heat conduction and the radiated heat by the PV module. The results are compared to measured data under various outdoor conditions of ambient temperature, solar irradiance and wind speed. In addition, the predicted PV temperature is compared to predicted values from existing models. The robustness of the simulation algorithm developed in the prediction of PV module temperature is presented and its clear advantage over empirical models, which are fine tuned for the exact experimental conditions and/or experimental set ups under which they were developed, is illustrated. Furthermore, the coefficient f which relates the PV module temperature with the solar irradiance on the PV plane and the ambient temperature is examined for various configurations of free-standing fixed and sun-tracking PV system as well as building integrated photovoltaic (BIPV), illustrating essential differences in this and in the temperature developed in the PV module

The contribution of X-linked coding variation to severe developmental disorders

Over 130 X-linked genes have been robustly associated with developmental disorders, and X-linked causes have been hypothesised to underlie the higher developmental disorder rates in males. Here, we evaluate the burden of X-linked coding variation in 11,044 developmental disorder patients, and find a similar rate of X-linked causes in males and females (6.0% and 6.9%, respectively), indicating that such variants do not account for the 1.4-fold male bias. We develop an improved strategy to detect X-linked developmental disorders and identify 23 significant genes, all of which were previously known, consistent with our inference that the vast majority of the X-linked burden is in known developmental disorder-associated genes. Importantly, we estimate that, in male probands, only 13% of inherited rare missense variants in known developmental disorder-associated genes are likely to be pathogenic. Our results demonstrate that statistical analysis of large datasets can refine our understanding of modes of inheritance for individual X-linked disorders. Developmental disorders (DDs) are more prevalent in males, thought to be due to X-linked genetic variation. Here, the authors investigate the burden of X-linked coding variants in 11,044 DD patients, showing that this contributes to similar to 6% of both male and female cases and therefore does not solely explain male bias in DDs.Peer reviewe