Matlab simulink modeling of photovoltaic cells for understanding shadow effect

Irradiation is the main component for producing the electricity from solar energy. When obstacles come in between the sun and the PV cell then it doesn’t get sufficient irradiance to produce enough electricity. Shadowing has a great impact on photovoltaic cell. The main fuel of PV cell is solar radiation. Using solar radiation, a photovoltaic cell produces electricity. The shadow on a PV cell decreases the output of the photovoltaic cell. It has been already shown in different papers that shadow effect decreases the output of the PV cell. There are different kinds of shadow effects which are observed, some minimize the PV cell output and some reduce the output to zero. There are different types of shadow based on their effects on the photovoltaic cell. The shadow has also effects depending on whether the PV cells are connected in series connection or in parallel connection. In series when one cell is out of order then the whole series of the PV cells will not work but in parallel connection if one cell is damaged, the others will work because they work independently. According to the output requirement the arrangement of the PV cells are made in series or parallel. Simulink modeling is made for series and parallel connection between two PV cells and the shadow effect is analyzed on one of the PV cells. Using SIMULINK, the shadowing is simulated on the two PV cells, where in one system they are in series and in another system they are in parallel. Slowly the irradiance is decreased to simulate the shadow effect. Simulation of the shadow effect gives an idea about the output of the PV cell system when system has shadow on the PV cells. Here the shadow effect on the two PV cells using series and parallel combinations are simulated and analyzed for understanding the effects on output.

Um café pela natureza, qual a melhor opção

O café é originário das florestas tropicais da Etiópia e do Sudão, crescendo sobre uma canópia diversa. Devido ao facto de haver uma tendência para o desaparecimento do sombreamento tradicional e consequente perda de biodiversidade, os sistemas de certificação oferecem a oportunidade de aproximar objectivos económicos, sociais e ambientais de modo a beneficiar os agricultores. Este estudo tem como objectivo dar a conhecer a todos os intervenientes da cadeia de custódia, principalmente aos consumidores, qual a certificação que podem optar por se a sua principal preocupação quando tomam um café for a natureza. Caracterizou-se o valor ecológico do sistema de produção sustentável e do sistema convencional. Analisaram-se e comparam-se os diferentes critérios ambientais dos sistemas de certificação, através da construção de uma matriz. Os resultados sugerem que a certificação que melhor responde ao pretendido é a Rainforest Alliance, no entanto, a dupla ou tripla certificação parecem ser também boas opções. ABSTRACT; Coffee originates in Ethiopia and Sudan’s ram forests, growing above a diverse canephora. Due to the fact that there is a tendency to the vanishing of traditional shadowing and consequent loss of biodiversity, certification schemes offer the opportunity of bringing together economical, social and environmental goals allowing benefits to farmers. This study aims to bring cognizance to every intervenient of the custody chain, mainly to consumers, which certification scheme to choose if their major concern when drinking a coffee is nature. The ecological value of sustainable production system has been characterized as well as the conventional system. Different environmental criteria of certification schemes have been analysed and compared trough the construction of an evaluation template. Results suggest that the certification that better suits the desired goal is the Rainforest Alliance, but double or triple certification also appear as options that might be followed.

Cross-shore transport in a daily varying upwelling regime: A case study of barnacle larvae on the southwestern Iberian coast.

With favored offshore and downstream advection, the question of which physical mechanism may promote onshore transport of larvae in upwelling systems is of central interest. We have conducted a semi-realistic high resolution (0.25 km) numerical study of Lagrangian transports across the inner-shelf under upwelling-favorable wind forcing conditions, focusing on the shelf area of the Southwestern Portuguese coast, in the lee of Cape Sines. We add our findings to several years of biological observations of C. montagui, a planktonic species with higher recruitment during the upwelling peak timely with the daylight flood. Simulations cover a fifteen days period during the summer of 2006. We focused on Spring and Neap tide periods and observed upfront differences between simulations and the in situ observa- tions. However, the model is capable of representing the main dynamics of the region, namely the re- petitive character of the inner-shelf currents. We find that the cross-shore flow varies significantly in the daily cycle, and locally within a scale of a few kilometers in association with local topography and the presence of the cape. We consider the region immediately in the lee of the cape to be an upwelling shadow where the larvae became retained, and found that tidally tied migration proves beneficial for successful recruitment during the spring tides period. Our work suggested that the wind is not the only mechanism responsible for the daily variability of the cross-shore exchange. However, its sharp reversal at midday is critical for the advection of larvae towards the coast.