Search results for "IRRADIANCE"
showing 10 items of 152 documents
Sensitivity of scope modelled GPP and fluorescence for different plant functional types
2014
This study addresses the question which factors are responsible for reported positive correlations between solar induced fluorescence (SIF) and gross primary production (GPP). A sensitivity analysis of the model SCOPE, which simulates photosynthesis, fluorescence emission and radiative transfer in canopies, has been carried out for four different plant functional types (PFT): tropical rainforest, C4 crops, C3 crops, and tundra, located in distinct climate zones: tropical everwet (Af), tropical with seasonal drought (savannah, Aw), temperate (Cf), and continental tundra (Dfd). Literature values for structural and physiological parameters and climate reanalysis data were used as input. The ef…
Climate change and Ecotone boundaries: Insights from a cellular automata ecohydrology model in a Mediterranean catchment with topography controlled v…
2014
Abstract Regions of vegetation transitions (ecotones) are known to be highly sensitive to climate fluctuations. In this study, the Cellular-Automata Tree Grass Shrub Simulator (CATGraSS) has been modified, calibrated and used with downscaled future climate scenarios to examine the role of climate change on vegetation patterns in a steep mountainous catchment (1.3 km2) located in Sicily, Italy. In the catchment, north-facing slopes are mostly covered by trees and grass, and south-facing slopes by Indian Fig opuntia and grass, with grasses dominating as elevation grows. CATGraSS simulates solar radiation, evapotranspiration, and soil moisture in space and time. Each model cell can hold a sing…
Assessment of the Usability and Accuracy of Two-Diode Models for Photovoltaic Modules
2017
Many diode-based equivalent circuits for simulating the electrical behaviour of photovoltaic (PV) cells and panels are reported in the scientific literature. Two-diode equivalent circuits, which require more complex procedures to calculate the seven model parameters, are less numerous. The model parameters are generally calculated using the data extracted from the datasheets issued by the PV panel manufactures and adopting simplifying hypotheses and numerical solving techniques. A criterion for rating both the usability and accuracy of two-diode models is proposed in this paper with the aim of supporting researchers and designers, working in the area of PV systems, to select and use a model…
A Criterion for Rating the Usability and Accuracy of the One-Diode Models for Photovoltaic Modules
2016
In selecting a mathematical model for simulating physical behaviours, it is important to reach an acceptable compromise between analytical complexity and achievable precision. With the aim of helping researchers and designers working in the area of photovoltaic systems to make a choice among the numerous diode-based models, a criterion for rating both the usability and accuracy of one-diode models is proposed in this paper. A three-level rating scale, which considers the ease of finding the data used by the analytical procedure, the simplicity of the mathematical tools needed to perform calculations and the accuracy achieved in calculating the current and power, is used. The proposed criter…
Assessment of the Usability and Accuracy of the Simplified One-Diode Models for Photovoltaic Modules
2016
Models for photovoltaic (PV) cells and panels, based on the diode equivalent circuit, have been widely used because they are effective tools for system design. Many authors have presented simplified one-diode models whose three or four parameters are calculated using the data extracted from the datasheets issued by PV panel manufactures and adopting some simplifying hypotheses and numerical solving techniques. Sometimes it may be difficult to make a choice among so many models. To help researchers and designers working in the area of photovoltaic systems in selecting the model that is fit for purpose, a criterion for rating both the usability and accuracy of simplified one-diode models is p…
Effect of light intensity, light duration and photoperiods in the performance of an outdoor photobioreactor for urban wastewater treatment
2019
[EN] A series of eight experiments were carried out to analyse the effects of light intensity, light duration and photoperiods on a microalgae culture for treating AnMBR effluent at an outdoor photobioreactor (PBR) plant. Improved performance was achieved in terms of nutrient recovery rates, biomass productivity and effluent nutrient concentrations at a higher net photon flux. However, the higher irradiance was also responsible for lower biomass productivity:light irradiance ratios. None of the experiments with different lighting regimes and the same net photon flux showed any significant differences. The data obtained suggest that microalgae performance in this system did not depend on the…
Effect of the relative optical air mass and the clearness index on solar erythemal UV irradiance
2014
This paper analyses the effects of the clearness index (Kt) and the relative optical air mass (mr) on erythemal UV irradiance (UVER). The UVER measurements were made in Valencia (Spain) from 6:00 am to 6:00 pm between June 2003 and December 2012 and (140,000 data points). Firstly, two models were used to calculate values for the erythemal ultraviolet irradiance clearness index (KtUVER) as a function of the global irradiance clearness index (Kt). Secondly, a potential regression model to measure the KtUVER as a function of the relative optical air mass was studied. The coefficients of this regression were evaluated for clear and cloudy days, as well as for days with high and low ozone levels…
Analysis of spectral irradiance distribution for PV applications at high latitude
2020
The spectral distribution of global tilted irradiance measured in Grimstad, Norway, is analyzed in terms of the average photon energy ( $APE$ ) blue fraction ( $BF$ ) and useful fraction ( $UF$ ). The results based on eight months of recorded data show a general shift of the $APE,\ BF$ , and $UF$ values to higher values than reference AM1.5G spectrum, with 1.63 eV, 0.45, and 0.88 being the average indices, respectively. The statistical coefficient of variation ( $CV$ ) is used to determine the variation of indices. The $CV$ for $APE,\ BF$ , and $UF$ are calculated to be 20.1%, 26.1%, and 25.7%, respectively confirming the earlier findings on $APE$ being a more accurate index for the quantif…
Test of the European Joint Research Centre performance model for c-Si PV modules
2012
The performance of ten c-Si PV modules is studied at different levels of illumination and module temperatures and is modeled in terms of relative efficiency with respect to Standard Testing Conditions (STC). A recently proposed model is tested in Nordic conditions for generic mono- and mc-Si devices with screen-printed cells as well as for some high-efficiency cell designs. Two of the modules are field aged. Averaged model coefficients are derived and compared to values found in the literature. Irradiance and module temperatures measured in 2011 are then used to estimate the expected annual energy yields. The measured yields equal the predicted ones within 1.6% (mean bias error −1.0%) which…
Growth and survival of European whitefish larvae under enhanced UV-B irradiance
2004
Two laboratory rearing experiments with newly hatched European whitefish Coregonus lavaretus larvae were performed to study the effects of UV-B (280–315 nm) radiation on their survival and growth. The results indicate that under normal circumstances in Finnish lakes, enhanced UV irradiance will not be a threat to the survival of newly hatched European whitefish larvae.