Antonia Sonia Alves Cardoso Diniz

Resumo A deposição de sujidades tem impacto significativo no desempenho de módulos fotovoltaicos (FV). Visando aprimorar técnicas que possam contribuir para o maior rendimento da tecnologia FV, esforços têm sido realizados para identificação e quantificação das perdas por sujidades em diferentes regiões sobre influência de diferentes zonas climáticas. Normalmente, esta análise baseia-se na utilização de parâmetros elétricos e térmicos medidos em estações de monitoramento de sujidade, comparados com variáveis meteorológicas medidas na mesma localidade. Porém, novas técnicas têm sido estudadas como alternativa para quantificar as perdas de desempenho de módulos FV devido a deposição de sujidade, tornando, em algumas vezes, o processo menos dispendioso e mais prático. Neste cenário, este trabalho tem como objetivo apresentar uma metodologia para quantificar as taxas de sujidade para módulos fotovoltaicos de filme fino e silício cristalino, considerando dados de densidade gravimétrica. Para isso, cupons foram colocados em uma área externa próxima as estações de sujidade instaladas no laboratório GREEN PUC Minas em Belo Horizonte/MG. A densidade gravimétrica da sujidade (g/m2) foi medida em intervalos de sete dias, e a taxa de sujidade (SRatio) foi estimada usando o modelo proposto por Coello e Boyle (2018) e Hegazy (2001). Essa taxa de sujidade (SRatio) estimada foi comparada com a taxa de sujidade identificada a partir de dados coletados das estações de monitoramento de sujidade disponibilizada por Costa (2018). Além disso, imagens foram tiradas dos cupons utilizando microscópio de sujidade, seguindo metodologia Figgis (2017).

Resumo O acúmulo de sujidades sobre módulos fotovoltaicos (FV), seja poeira, pólen, dejetos de pássaros, sujeiras, ou outros contaminantes, causa significativo impacto no desempenho destes dispositivos. As perdas por sujidade em módulos fotovoltaicos são denominadas taxas de sujidades (SRatio), normalmente, mensuradas através de parâmetros elétricos e térmicos de módulos fotovoltaicos utilizados em estação de monitoramento de sujidade ou sistemas fotovoltaicos. Porém, devido às dificuldades em se obter dados contínuos e de longos períodos (considerando sazonalidade das estações do ano e interanuais) seja de estações ou sistemas FV, pesquisas têm sido realizadas em vários países com o objetivo de identificar a relação entre as variáveis meteorológicas e de materiais particulados (PM) com o processo de deposição de sujidade em módulos fotovoltaicos. Dessa forma, esse trabalho tem como objetivo avaliar o comportamento das variáveis meteorológicas e das taxas de sujidade obtidas através de dados de estação de sujidade de silício policristalino instalada na cidade de Belo Horizonte/MG.

Photovoltaic solar energy systems is a renewable source that has raised great worldwide interest in recent decades. However, in Brazil still, the cost of photovoltaic (PV) systems is still high, and the current public policies are incipient. From 2014 to 2019, an average growth of 203% per year was observed in the installed PV power systems in Brazil. Such performance can also be justified by a greater understanding of externalities, i.e., external positive and negative impacts inherent to the generation of electric energy. The objective is to understand the economic effects of photovoltaic externalities from different perspectives. The following externalities were studied: air pollution; energy quality; construction element; thermal load and real estate valuation, and all of them were analyzed for the Brazilian scenario. The results indicated that the externality of air pollution, which has impacts on health, estimated from the society perspective, could be worth, at least, 4.12% of the price of the energy generated by PV systems. The losses avoided and the voltage profile, energy quality parameters, may account to 12.61% of the electricity price for utilities, and from the consumer perspective, the externality real estate value may be around 79.44% of the price of the electricity generated by photovoltaic systems. The results of this study indicate that the externalities were, for the most part, positive for PV electric energy generating systems. Thus, considering externalities, it is intended to further understand their relationship with the expansion of the distributed generation of electric energy with PV systems in Brazil.

This paper examines the performance of solar photovoltaic generators on roofs of residential buildings. The primary focus is the loss of performance due to temperature increase as function of roof material and the distance from the photovoltaic (PV) generator to the roof. A heat transfer model has been developed to predict PV module temperature, and the equations of the model were solved using the Engineering Equation Solver (EES) software. The research modeling correlates the distance of the solar generator to the roof and the roofing material with the temperature variations in the PV generator. There are many models to predict PV module temperature, but this study refines the prediction by the distance from PV module to roof and the roofing material as variables. Optimal combinations of distance and materials that minimize the heating loss in the solar generator leading to increased electrical power generation. Results show an average error of 3%–4% from the temperature predicted by the model to the temperature measured under experimental conditions in Belo Horizonte, Brazil. The minimum roof-module separation required to ensure minimal PV performance loss from heating from the roof is ∼10 cm for red ceramic and cement fiber roofs. For galvanized steel, the optimal distance is between 20 cm and 30 cm. Cement fiber shows the best predicted and measured characteristics for PV-panel roof mounting among the 3-common commercial roofs evaluated in these studies. These investigations were based on roof installations and local materials in Belo Horizonte, Brazil.

The cleaning of PV-module glass to remove soiling and other contaminants can alter the surface physical and optical properties. To assess the impacts of mechanical cleaning, we examined the effects of several PV-cleaning processes used in Brazil PV installation. Specifically, we evaluated modules and module glass covers that were exposed to natural soiling during a 90-day period and cleaned twice daily. With this accelerated timeframe, a controlled artificial soiling method was used to mimic the local soiling conditions. The surface roughness, optical transmittance, and PV-panel short-circuit current (I sc ) were measured at regular intervals during the cleaning processes. The cleaning techniques included water spraying, compressed air, brushes with various bristles used in the field (thick nylon, soft-thin nylon, silicone foam) with water, polyurethane sponge with water, and abrasive synthetic resin sponge with water, and rubber squeegee to remove the water. For this region in Minas Gerais, Brazil, (characterized by moderate soiling conditions during the dry season), the water-only and compressed-air techniques provided the best results, with minimal detected damage to the surfaces and changes in the measured I sc after the 90-day period of experiment. The methods using the synthetic brushes were the most harmful to the glasses. For situations of higher dirt adhesion (e.g., caking) or thicker soiling layers on the module glass, the methods with a nylon brush and polyurethane bushing were more effective.