Solar energy budgets in central Amazonian ecosystems: a comparison between natural forest and bare soil areas

In order to estimate the deforestation consequences on the actual solar energy budget of the Central Amazon Region, two ecosystems of different characteristics were compared. The present conditions of the region were represented by a typical 'terra firme' forest cover located at INPA's Ducke Forest Reserve, where the measurements necessary to evaluate its solar energy balance were carried out. The second ecosystem, simulating a deforested area, was represented by an area about 1.0 ha without natural vegetation and situated in the same Reserve. In this area lysimeters were placed, two of them filled with yellow latosol and two others with quartzose sand soil. Both soils are representative soils in the region. Their water balances were taken into account as well as the other parameters necessary to compute the solar energy balances. The results showed that water loss by evaporation was about 41.8% of the total precipitation in the yellow latosol lysimeters and about 26.4% for the quartzose sand ones. For the forest cover it was estimated an evapotranspiration of 67.9% of the rainfall amount. In relation to solar energy balance calculated for the forest cover, it was found that 83.1% of the total energy incoming to this ecosystem was used by the evapotranspiration process, while the remaining of 16.9% can be taken as sensible heat. For bare soils, 55.1% and 31.8% of the total energy were used as latent heat by yellow latosol and quartzose sand soils, respectively. So, the remaining amounts of 44.9% and 68.2% were related to sensible heat and available to atmospheric air heating of these ecosystems. Such results suggest that a large deforestation of the Amazon Region would have direct consequences on their water and solar radiation balances, with an expected change on the actual climatic conditions of the region. © 1993.

The amount of solar energy made available for the production of a sabia (Mimosa caesalpinaefolia Benth.) seed has a determinating effect on its becoming dormant

The amount of solar energy made available for the production of a sabid seed varied as a function of the time of the year, the face of the plant in which, the position in the plant on which and the position in the pod in which it was produced.Variation in solar energy availability as a consequence of the time of the year was a direct consequence of latitude. At 21degrees5'22 S the highest amounts of Global Solar Radiation (GSR) reaching the site where the experiment was conducted took place during the months from November through February. During these months there were no marked differences between any two of the amounts of GSR reaching faces North (N), South (S), West (W) East (E). From February through November (period during which the sabid plants of this study flowered and the resulting seeds matured and were harvested) the total GSR's were the lowest and marked differences were found between faces N and S, with face N receiving much more GSR than face S. During that period, faces W and E received practically the same amount of GSR and it was much less than that received by face N and much more than the one received by face S.The amount of biological energy made available for the development of a seed seemed also to vary according to a dry matter partitioning strategy by the plant -the central third of the plant seemed to be the one receiving the highest amounts of energy, followed either by the upper or the lower third of the plant- it was not very clear which third of the plant immediately followed the central one. The partitioning of biological energy at the pod level also seemed to follow a strategy by which the central seeds would be the ones to receive more, followed by the proximal seeds and these by the distal ones.This availability of energy seemed to have a direct effect on seed size, weight and on the percentage of seeds which showed a degree of dormancy deep enough to prevent their germinating under the conditions of a standard germination test.The implications of these results for the improvement of methods for the overcoming of dormancy of sabia seeds are discussed.

The need of subsidy for the implementation of photovoltaic solar energy as supporting of decentralized electrical power generation in Brazil

The growing demand for electrical power and the limited capital invested to provide this power is forcing countries like Brazil to search for new alternatives for electrical power generation. The purpose of this paper is to present a technical and economic study on a 15 kW solar plant installed in an isolated community, highlighting the importance of the need for financial subsidy from the government. It evaluates the importance of parameters such as the annual interest rate, specific investment, the marginal cost of expanding the electrical power supply and the government subsidy on amortization time of capital invested. © 2012 Elsevier Ltd All rights reserved.

Analisys of thermal efficiency of a modified solar collector type evacuated tube

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Entransy and its utilization in problems of thermodynamics and heat transfer

The concept of entransy was recently proposed in terms of the analogy to the electric energy stored in a capacitor. The entransy of a system describes its heat transfer ability, as the exergy of a system quantifies its work production potential. Hence, the concept of entransy can be useful in problems where the heat transfer is the main objective, as for example, in systems collecting solar energy. This concept is quite recent and there are only a few works related to this topic. It is expected, however, that this approach will soon be used more often in the analysis of problems in thermodynamics and heat transfer. The objective of this work is to present a review of the concept of entransy in a systematic way, beginning with its definition, balance equations and a few examples of simple applications. It is hoped that this concept of entransy becomes a useful tool in the analysis and design of more efficient thermal systems. © 2012 Praise Worthy Prize S.r.l.- All rights reserved.

Determinação da eficiência de um coletor solar plano com aletas de vidro

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Análise numérica da convecção natural em dispositivos solar integrados coletor-tanque

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação da eficiência térmica de um coletor solar tipo tubo evacuado modificado

Pós-graduação em Engenharia Mecânica - FEB

Análise numérica de uma geometria de coletor solar para sistemas de aquecimento de água

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Feasibility of solar heating systems composed of recyclable packaging for low-income rural communities

Solar heaters are an appropriate technology in tropical and sub-tropical climates to heat bath water by solar energy. Low-cost solar heaters meet the demand of low-income rural communities which currently do not have access to this technology. Current research analyzes the economic viability of solar heaters, built with recyclable materials, to reduce electric energy bill. A solar heating system was built consisting of recyclable materials in accordance with the manuals provided by the Secretariat of Environment of the state of Paraná (SEMA). Duration of use of electric showers by families of rural properties was determined to calculate expenses and billing of electricity. Simulation and material costs showed that the system was feasible. Commercial solar heaters could be replaced at a cost of R$ 22.61 per month during 13 months.

Estimativa da radiação solar global diária em função do potencial de energia solar na superfície do solo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estimativa do fluxo de calor latente pelo balanço de energia em cultivo protegido de pimentão

O objetivo deste trabalho foi caracterizar e relacionar a radiação líquida com o calor latente equivalente, em mm de água, nos cultivos protegido e de campo, na cultura de pimentão. O experimento foi feito em Botucatu, SP. A estimativa do fluxo de calor latente foi feita pelo método do balanço de energia, por meio da razão de Bowen. Foram feitas medidas instantâneas da radiação líquida (Rn), dos fluxos convectivos de calor latente (LE) e sensível (H), do fluxo de calor no solo (G), e dos gradientes psicrométricos sobre a cultura. O cultivo protegido, apesar de receber menor quantidade de radiação solar global, foi mais eficiente na conversão da radiação líquida disponível em matéria seca total e na produtividade de frutos. No balanço de energia, o cultivo protegido apresentou razões G/Rn e LE/Rn inferiores e H/Rn superior, com um fluxo de calor latente, equivalente em milímetros, 45,43% menor que no cultivo no campo. Apresentou, ainda, menor quantidade de radiação líquida disponível e menores perdas de energia, mostrando-se mais eficiente no uso da água.

Degradation of [D-Leu]-Microcystin-LR by solar heterogeneous photocatalysis (TiO2)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Simulation of the energy performance of maize production integrated to pig farming

Foi avaliado o desempenho energético da suinocultura integrada à produção de milho em grão em sistema de plantio direto mecanizado. Nesta concepção de integração proposta, os dejetos suínos são utilizados como fertilizantes na produção de milho. O sistema foi delimitado envolvendo as atividades associadas ao manejo dos suínos e de produção do milho (manejo do solo, cultivo e colheita). O período de análise considerado foi de um ano, o que possibilita a produção de três lotes de suínos e duas safras de milho. Para avaliar o desempenho energético, foram criados três indicadores: eficiência energética, eficiência de uso de fontes não renováveis e o custo de energia não renovável para a produção de proteína. As entradas energéticas são compostas pelos insumos e pela infraestrutura, utilizados na criação dos suínos e na produção de milho, e pela radiação solar incidente no agrossistema. Já as saídas são representadas pelos seus produtos (suínos terminados e o milho). Os resultados obtidos nas simulações apontam que a integração melhora o desempenho energético das granjas suinícolas, aumentando a eficiência energética (186%) e a eficiência não renovável (352%), além de reduzir o custo de energia não renovável para a produção de proteína (‑58%).

A software to process daily solar radiation data

This work presents one software developed to process solar radiation data. This software can be used in meteorological and climatic stations, and also as a support for solar radiation measurements in researches of solar energy availability allowing data quality control, statistical calculations and validation of models, as well as ease interchanging of data. (C) 1999 Elsevier B.V. Ltd. All rights reserved.