Fernando Ramos Martins

Effects of burning of biomass on satellite estimations of solar irradiation in Brazil

Abstract Atmospheric combustion products from forest fires in the Brazilian Amazon and ‘Cerrado’ regions during the dry season (July–October) induce systematic deviations on the routine satellite techniques for the assessment of solar energy resource information. This study, based on clear-sky days, has shown model overestimations of the incoming solar radiation as high as 44%. On the average, clear-sky model overestimation was four times larger than that found for clear-sky days in regions outside the biomass-burning season. A positive correlation between the combustion products of black carbon, total aerosols, CO, N 2 O, CH 4 , and the number of fire spots counted by the AVHRR sensor from the NOAA series satellites suggests a possible mechanism for the parameterization of these effects on the radiation transfer methods.

Comparative study of satellite and ground techniques for cloud cover determination

Abstract In this paper we compare cloud cover coefficient values derived from satellite images by using three different algorithms with cloud cover fraction obtained by automatic technique using a CCD sensor set on a ground platform. The main goal is to optimize the results obtained by each of the three satellite techniques when applied as input data for radiative transfer models. The satellite techniques are applied to generate clear and overcast composite images on the visible spectra (0.52–0.75pm), and the cloud cover coefficients are obtained from linear interpolation between clear and overcast conditions. The ground technique uses a CCD sensor adapted to a fisheye lens to derive cloud cover fraction in the visible range (0.4–0.7gm). We compared these techniques using data collected at the BSRN station of Floiianopolis (27° 28′S, 48° 29′W). The study encompasses the period from January/2002 to March/2002. The radiative transfer model has underestimated the incident global solar radiation by 25–32% when derived from cloud cover fractions obtained by the CCD sensor. When supplied with the cloud cover information derived from the satellite techniques the bias decrease to 3–7%. The reason for the underestimation is attributed to the fact that cloud cover fraction derived from the ground data does not bear information on cloud optical thickness.

O aproveitamento da energia eólica

Diversos estudos realizados nos ultimos anos tem apontado as implicacoes e impactos socio-ambientais do consumo de energia. As fontes renovaveis de energia sao apresentadas como a principal alternativa para atender as demandas da sociedade com relacao a qualidade e seguranca do atendimento da demanda de eletricidade com a reducao dos danos ambientais decorrentes do consumo de energia. Este artigo apresenta uma revisao dos conceitos fisicos relacionados ao emprego da energia cinetica dos ventos na geracao de eletricidade. Inicialmente, o artigo descreve a evolucao do aproveitamento da energia eolica, incluindo dados e informacoes sobre a situacao atual do uso desse recurso para geracao de energia eletrica. O artigo apresenta uma descricao dos aspectos dinâmicos dos ventos e circulacao atmosferica na Terra, incluindo a descricao dos fatores que influenciam a velocidade e direcao dos ventos nas proximidades da superficie de nosso planeta. A modelagem e previsao dos ventos sao discutidas apresentando os principais resultados obtidos com as metodologias empregadas no Brasil. Os aspectos relacionados a estimativa e previsao da potencia eolica sao abordados ressaltando a importância de uma base de dados de vento de qualidade para a determinacao da confiabilidade dos resultados fornecidos pelos modelos numericos.

Levantamento dos recursos de energia solar no Brasil com o emprego de satélite geoestacionário: o Projeto Swera

Solar radiation plays a chief role in many human activities like agriculture, architecture, energy planning and policies, etc. It constitutes a clean and renewable source of energy. For better knowledge of the availability of this source of energy, computational models can be used to obtain numeric solution of radiative transfer equations and to estimate the energy fluxes in the Earths atmosphere. This work reveals what is behind the satellite models and their use to derive the surface solar radiation, having the BRASIL-SR model as a case example. The BRASIL-SR model is currently being applied to map the solar energy potential for Latin America within the SWERA project (Solar and Wind Energy Resource Assessment). The Global Environment Facility (GEF) through a United Nations Environment Program grant supports this project.

The Impact of Haze on Performance Ratio and Short-Circuit Current of PV Systems in Singapore

The spectral content of sunlight directly affects the power output of solar photovoltaic (PV) devices. The extent of the effect of seasonal and weather-related spectral variations on the power output will depend largely on the semiconductor bandgap. In this study, haze, which is a common weather condition in many parts of the world, is found to affect the power output of PV systems. An analysis of a recent haze event in Singapore in mid-June 2013 reveals that haze has an impact on the performance ratios and short-circuit currents of PV systems. The performance ratio of amorphous silicon thin-film PV systems dropped during the haze event, while that of crystalline silicon wafer-based systems exhibited a slight increase. A detailed analysis showed that the main cause of the observed performance ratio variations was changes in the generated short-circuit currents, which were due to a red shift of the solar spectrum arriving in the module plane during the haze period. Therefore, PV systems with different semiconductor bandgaps were affected differently.

BIOMASS BURNING CONTROLLED MODULATION OF THE SOLAR RADIATION IN BRAZIL

Atmospheric combustion products from forest fires in Brazil can affect routine satellite techniques for the assessment of solar energy resource information. The mean overes~ation of solar irradiance by BRASIL-SR clear sky model was up to 2.5 times larger than that found outside the region of biomass burnings. Within the region of biomass burnings the overestimation was over 5 times larger at the peak of the burning season when compared to the rest of the year. A positive correlation between combustion products and the number of fire spots counted by satellite technique suggests a possible method for the parameterization of these effects in radiation transfer models. 0 1999 COSPAR. Published by Elsevier Science Ltd. BACKGRO~ Satellite radiative transfer models employed for the study of the Earth’s radiative balance and for the evaluation of the solar energy resource in countries of the tropical belt must account for the influence of induced forest fires. This widely used processes of deforestation for farming and cattle growth introduces aerosols and gaseous combustion byproducts into the atmosphere. Whitlock and Tarpley (1996) have shown the influence on the pinker radiation transfer ~go~~rn by occurrences of forest fires in Africa between 1986 and 1987, Model ove~s~mations of as much as 120 W/m2 have been reported and linked to forest fires. A current estimation for the deforestation rate in the Brazilian Amazon region is 18,000 kn?/yr (http://www.inpe.br). The resulting total emission of particulate matter to the atmosphere from this source has been estimated at some 1014 g of particulate matter per year (Crutzen and Andreae, 1990; Ward et al., 1992). Black Carbon accounts for about 10% of this total anthropogenic release, and is of major concern for its distinctive low single scattering albedo. THE BRASIL-SR RADIATIVE TRANSFER MODEL The radiative transfer model BRASIL-SR was used in conjunction with ground radiation data from available sites in Brazil. The model, based on the IGMK (Stuhlmann, et al., 1990), assumes that clouds are the first order factor that modulates the solar radiation field in the atmosphere. The p~~ete~zation of the all-sky t~s~t~ce is made by the assumption that the upward flux rpr may be spfit into two independent con~bu~ons: one dete~nistic component corresponding to the cloud free sky conditions qc~earr = flra , Z, , 6, , p,); and another due to overcast conditions, which is nearly isotropic, cp clotir = gf I,, , 6). z, is the atmospheric transmittance, f3, is the solar zenith angle, Z,, is the radiation flux at the top of the atmosphere, 6 is the cloud optical thickness, and ps is the ground albedo. This component can be estimated on the basis of a known set of input atmospheric data. The stochastic nature of the all-sky solar radiation field is included in the model by defining a fractional cloud cover index, n,

A importância dos dados de cobertura de nuvens e de sua variabilidade: metodologias para aquisição de dados

such that cpr is linearly distibuted between these two extreme atmospheric conditions, ~)clea~r and g)cloudf :

Aplicações de redes neurais e previsões de disponibilidade de recursos energéticos solares

Este trabalho apresenta uma revisao dos aspectos ligados a influencia das nuvens sobre o clima como tambem seus impactos no desenvolvimento cientifico, tecnologico e economico de diversos setores da atividade humana. Conceitos basicos da fisica de nuvens sao discutidos. Tambem sao apresentadas as metodologias mais modernas para a determinacao da cobertura de nuvens a partir de medidas feitas na superficie e por satelite.

BRAZILIAN ATLAS FOR SOLAR ENERGY RESOURCE: SWERA RESULTS

This work aims at discussing the artificial neural networks (ANN) and some applications in renewable energy assessment. First, the paper describes the statistical relevance of this tool in different areas of knowledge and the main ANN concepts and configurations. Finally, the paper presents and discusses the use of ANN for the solar energy assessment in Brazil by using data collected in SONDA sites operated by the Center for Earth System Science of the Brazilian Institute for Space Research. The results show that ANN can provide reliable estimates with better performance than other statistical tools.

ESTUDO COMPARATIVO DA CONFIABILIDADE DE ESTIMATIVAS DE IRRADIAC ¸ ˜ AO SOLAR PARA O SUDESTE BRASILEIRO OBTIDAS A PARTIR DE DADOS DE SAT ´ ELITE E POR INTERPOLAC ¸ ˜ AO/EXTRAPOLAC ¸ ˜ AO DE DADOS DE SUPERFICIE

The solar energy assessment in SWERA project was prepared by using BRASIL-SR radiative transfer model and satellite database acquired from 1995 till 2005 – a full decade dataset. The annual and seasonal maps prepared were in 10X10km spatial resolution. In spite of the different climate characteristics along the Brazilian territory, one can observe that the annual average of daily solar irradiation is fairly uniform. The maximum daily global solar irradiation value (6.5 kWh/m2) occurs in the semi-arid climate area of Brazilian Northeastern region. The lowest daily global solar irradiation (4.25 kWh/m2) occurs on the shore of Southern region of Brazil. The Amazon region receives lower solar irradiation during the summer than the Southern region. The variation of the solar irradiation between winter and summer is smaller in the Northern region than in the Southern. The Central region of Brazil gets a larger incidence of solar radiation during the dry season when the precipitation is low and the number of clear sky days is larger.