Página 1 dos resultados de 114 itens digitais encontrados em 0.007 segundos

‣ Modelos de Previsão do Teor de Humidade de Combustíveis Florestais

Lopes, Sérgio Miguel Gomes
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
39.550127%
O teor de humidade de um combustível florestal reveste-se de enorme importância na problemática dos incêndios florestais devido à sua influência em vários aspetos, nomeadamente no risco, na ignição, na ocorrência, na propagação, na intensidade e na extinção de um incêndio florestal. No presente estudo apresentam-se resultados provenientes do programa de monitorização do teor de humidade de combustíveis florestais que se tem vindo a realizar, no centro de Portugal, desde 1986. Foi analisada a representatividade espacial e temporal do teor de humidade das espécies caracterizadas assim como a relação entre elas. Foi igualmente analisado o número de amostras necessárias para a sua correta caracterização assim como a comparação do teor de humidade determinado por secagem em estufa e do teor de humidade determinado pelo analisador rápido de humidade. Foi verificado que, quando o teor de humidade é reduzido, os resultados obtidos através do analisador rápido de humidade são bem correlacionáveis com o teor de humidade obtido por secagem em estufa. Devido à sua representatividade, os resultados obtidos no programa de monitorização da Lousã podem ser utilizados como indicadores do teor de humidade e do risco de incêndio de uma região mais vasta do território Português A modelação dos processos de adsorção e de dessorção e do teor de humidade de equilíbrio abaixo do ponto de saturação das fibras dos combustíveis florestais finos pode resultar em previsões mais precisas dos processos de secagem e humidificação. Com base em resultados laboratoriais e de campo realizados com agulhas mortas da espécie Pinus pinaster foram testados modelos de previsão das curvas de sorção e das isotérmicas do teor de humidade de equilíbrio. Os modelos apresentaram uma capacidade de previsão média a elevada para todos os casos testados. O melhor ajuste das curvas de sorção foi obtido através da aplicação dos modelos normalmente aplicados a produtos alimentares e agrícolas e para o teor de humidade de equilíbrio...

‣ Numerical simulation of a 200 kW downdraft gasifier using açaí seed (Euterpe oleracea Mart.) as fuel

Itai, Yuu; Rocha, Hendrick; Brasil, Augusto M.; Malico, Isabel
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Aula Formato: 11138 bytes; application/pdf
Português
Relevância na Pesquisa
38.62537%
In this work a thermochemical equilibrium model for downdraft gasifiers has been proposed. The model is similar and was compared to the model developed by Melgar et al. (2007). The properties such as efficiency of cold gas, LHV and temperature of an Amazonian biomass Euterpe olearacea Mart. was simulated. The numerical simulations aimed the maximization of H2 and CH4 in a gasification process. The model simulated numerically the influence of the gasifying relative fuel/air ratio and the biomass moisture content on the syngas composition. Two values of moisture content 33% and 37.5% were suggested for the gasification of açaí seed for the maximization of the H2 and CH4 concentrations in a range of the relative fuel/air ratio, Frg , between 2.5 and 6. The results also showed that to achieve the maximization of CH4 with Frg = 6 the reaction temperature drops up to 34%.

‣ Avaliação do teor de humidade da manta morta florestal através do Duff Moisture Meter 600

Castro, Sílvia Borges e
Fonte: Universidade de Trás-os-Montes e Alto Douro Publicador: Universidade de Trás-os-Montes e Alto Douro
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
49.370137%
Dissertação de Mestrado em Engenharia Florestal; A avaliação da humidade da manta morta florestal é importante, particularmente no âmbito do planeamento do fogo controlado e da avaliação da severidade ecológica de um incêndio. Este trabalho teve como objetivos a calibração do DMM600, aparelho utilizado para a medição do teor de humidade da manta morta florestal e a sua posterior aplicação ao mapeamento da distribuição espacial da humidade da manta morta. Para a calibração do DMM600 fez-se a medição da humidade do combustível com o aparelho diretamente no campo e procedeu-se à recolha de amostras para secagem na estufa. Através de análise de regressão desenvolveu-se uma equação para conversão dos valores de humidade expressos em percentagem do peso seco. O tipo de manta morta (de resinosas, de folhosas, ou mista) não influencia a relação entre as duas variáveis de humidade. Na segunda etapa deste trabalho procurou-se exemplificar uma potencial aplicação do DMM600. Mediu-se a humidade da manta morta em três povoamentos florestais de acordo com uma amostragem em grelha e, através do método de krigagem, obtiveram-se mapas da distribuição espacial da humidade, que permitem saber as zonas onde existe maior ou menor humidade e em função disso planear ações de fogo controlado...

‣ Influence of Fuel Moisture Content and Reactor Temperature on the Calorific Value of Syngas Resulted from Gasification of Oil Palm Fronds

Atnaw, Samson Mekbib; Sulaiman, Shaharin Anwar; Yusup, Suzana
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 20/01/2014 Português
Relevância na Pesquisa
59.24047%
Biomass wastes produced from oil palm mills and plantations include empty fruit bunches (EFBs), shells, fibers, trunks, and oil palm fronds (OPF). EFBs and shells are partially utilized as boiler fuel while the rest of the biomass materials like OPF have not been utilized for energy generation. No previous study has been reported on gasification of oil palm fronds (OPF) biomass for the production of fuel gas. In this paper, the effect of moisture content of fuel and reactor temperature on downdraft gasification of OPF was experimentally investigated using a lab scale gasifier of capacity 50 kW. In addition, results obtained from equilibrium model of gasification that was developed for facilitating the prediction of syngas composition are compared with experimental data. Comparison of simulation results for predicting calorific value of syngas with the experimental results showed a satisfactory agreement with a mean error of 0.1 MJ/Nm3. For a biomass moisture content of 29%, the resulting calorific value for the syngas was found to be only 2.63 MJ/Nm3, as compared to nearly double (4.95 MJ/Nm3) for biomass moisture content of 22%. A calorific value as high as 5.57 MJ/Nm3 was recorded for higher oxidation zone temperature values.

‣ Fuel moisture content enhances nonadditive effects of plant mixtures on flammability and fire behavior

Blauw, Luke G; Wensink, Niki; Bakker, Lisette; van Logtestijn, Richard S P; Aerts, Rien; Soudzilovskaia, Nadejda A; Cornelissen, J Hans C
Fonte: John Wiley & Sons, Ltd Publicador: John Wiley & Sons, Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
69.25898%
Fire behavior of plant mixtures includes a complex set of processes for which the interactive contributions of its drivers, such as plant identity and moisture, have not yet been unraveled fully. Plant flammability parameters of species mixtures can show substantial deviations of fire properties from those expected based on the component species when burnt alone; that is, there are nonadditive mixture effects. Here, we investigated how fuel moisture content affects nonadditive effects in fire behavior. We hypothesized that both the magnitude and variance of nonadditivity in flammability parameters are greater in moist than in dry fuel beds. We conducted a series of experimental burns in monocultures and 2-species mixtures with two ericaceous dwarf shrubs and two bryophyte species from temperate fire-prone heathlands. For a set of fire behavior parameters, we found that magnitude and variability of nonadditive effects are, on average, respectively 5.8 and 1.8 times larger in moist (30% MC) species mixtures compared to dry (10% MC) mixed fuel beds. In general, the moist mixtures caused negative nonadditive effects, but due to the larger variability these mixtures occasionally caused large positive nonadditive effects, while this did not occur in dry mixtures. Thus...

‣ China - Biomass Cogeneration Development Project : Fuel Supply Handbook for Biomass-Fired Power Projects

World Bank
Fonte: World Bank Publicador: World Bank
Português
Relevância na Pesquisa
48.968164%
This handbook provides an overview of the main topics that need consideration when managing the supply of biomass to large biomass power plants. It will help investors in China to develop, with assistance of local biomass supply experts, their own solutions. The focus is on biomass residues, in particular agricultural residues (mainly straw and stalks) and forestry residues (mainly residues from forestry operations). This handbook covers a wide range of topics related to biomass fuel supply risk in the planning and preparation stages for a biomass-fired power plant. Chapter two introduces the use of biomass as an energy source, including fuel selection considerations and the fuel standards and specifications required to match a particular fuel supply to a power generation system. Chapter three describes the use of biomass resource assessments at the project planning stage. Chapters four and five give insight into the biomass supply from straw and forestry residues, respectively. Finally, fuel supply management is covered in chapter six...

‣ Experimental development of a fire management model for Jarrah (Eucalyptus Marginata Donn ex Sm.) forest.

Burrows, Neil D
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD)
Português
Relevância na Pesquisa
39.315935%
Accumulations of flammable fuel and seasonal hot, dry weather has ensured that fire is an important environmental factor which has shaped jarrah forest ecosystems of south-west Western Australia. Today, fire impacts on all aspects of jarrah forest management, including timber and water production, recreation and wildlife conservation. Fire management involves controlling destructive wildfires and applying prescribed fires over a wide range of burning conditions to achieve a variety of protection, production and conservation objectives. A sound scientific understanding of the behaviour, physical impacts and long term ecological and commercial effects of fire is essential to planning and implementing fire regimes and suppression activities pertinent to current and foreseeable management. Existing forest fire behaviour guides developed in the 1960s from small low intensity experimental fires set under mild conditions perform adequately over the low fire intensity range, but are deficient at predicting the behaviour of moderate and high intensity fires burning under warm, dry conditions. Another shortcoming is that they do not attempt to predict physical impacts of fire which give rise to ecological responses or commercial losses. This thesis describes laboratory and field experiments designed to model the behaviour and some important physical impacts of fire in jarrah forest over a wide range of potential burning conditions. Fire behaviour and fire impact models were developed for a standardjarrah. forest fuel type; the structure...

‣ Advanced Biofuel Technologies : Status and Barriers

Cheng, Jay J.; Timilsina, Govinda R.
Fonte: Banco Mundial Publicador: Banco Mundial
Tipo: Publications & Research :: Policy Research Working Paper
Português
Relevância na Pesquisa
38.648308%
Large-scale production of crop based (first generation) biofuels may not be feasible without adversely affecting global food supply or encroaching on other important land uses. Because alternatives to liquid fossil fuels are important to develop in order to address greenhouse gas mitigation and other energy policy objectives, the potential for increased use of advanced (non-crop, second generation) biofuel production technologies has significant policy relevance. This study reviews the current status of several advanced biofuel technologies. Technically, it would be possible to produce a large portion of transportation fuels using advanced biofuel technologies, specifically those that can be grown using a small portion of the world's land area (for example, microalgae), or those grown on arable lands without affecting food supply (for example, agricultural residues). However, serious technical barriers limit the near-term commercial application of advanced biofuels technologies. Key technical barriers include low conversion efficiency from biomass to fuel...

‣ A simple method for assessing fuel moisture content and fire danger rating

Sharples, J.J.; McRae, R.H.D.; Weber, R.O.; Gill, A Malcom
Fonte: Modelling and Simulation Society of Australia and New Zealand Inc. Publicador: Modelling and Simulation Society of Australia and New Zealand Inc.
Tipo: Conference paper
Português
Relevância na Pesquisa
58.41397%
The flammability of wildland vegetation is strongly dependent upon the moisture content of fine dead fuels. Consequently, assessing the moisture content of these fuels to within a reasonable degree of accuracy is an important part of wildland fire managem

‣ Estimation of live fuel moisture content from MODIS images for fire risk assessment

Yebra, Marta; Chuvieco, Emelio; Riano, David
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
99.24047%
This paper presents a method to estimate fuel moisture content (FMC) of Mediterranean vegetation species from satellite images in the context of fire risk assessment. The relationship between satellite images and field collected FMC data was based on two

‣ A simple index for assessing fuel moisture content

Sharples, J.J.; McRae, R.H.D.; Weber, R.O.; Gill, A Malcom
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
69.167534%
Assessing fuel moisture content to within a reasonable degree of accuracy is an important part of wildland fire management. In this paper we introduce a fuel moisture index that provides a simple and intuitive method for assessing fuel moisture content. T

‣ Generation of Species-Specific Look-Up Table for Fuel Moisture Content Assessment

Yebra, Marta; Chuvieco, Emelio
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
68.44538%
This study involved the generation of a species-specific Look-Up Table (LUT) for the retrieval of Fuel Moisture Content (FMC) in natural areas dominated by Quercus ilex (Holm oak). Parameter combinations observed in drying Q. ilex samples were used as inp

‣ Linking ecological information and radiative transfer models to estimate fuel moisture content in the Mediterranean region of Spain: Solving the ill-posed inverse problem

Yebra, Marta; Chuvieco, Emelio
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
68.44538%
Live fuel moisture content (FMC) is a key factor required to evaluate fire risk and its operative and accurate estimation is essential for allocating pre-fire resources as a part of fire prevention. This paper presents an operative and accurate procedure

‣ Laboratory Measurements of Plant Drying: Implications to Estimate Moisture Content from Radiative Transfer Models in Two Temperate Species

Jurdao, Sara; Yebra, Marta; Oliva, Patricia; Chuvieco, Emelio
Fonte: American Society for Photogrammetry and Remote Sensing Publicador: American Society for Photogrammetry and Remote Sensing
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
58.101763%
The estimation of live fuel moisture content (LFMC) is necessary for fire danger assessment. Several studies have successfully used satellite imagery to estimate LFMC, both using empirical and simulation approaches (Yebra et al., 2013). The latter are bas

‣ Data assimilation of dead fuel moisture observations from remote automated weather stations

Vejmelka, Martin; Kochanski, Adam K.; Mandel, Jan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/06/2014 Português
Relevância na Pesquisa
59.784487%
Fuel moisture has a major influence on the behavior of wildland fires and is an important underlying factor in fire risk assessment. We propose a method to assimilate dead fuel moisture content observations from remote automated weather stations (RAWS) into a time-lag fuel moisture model. RAWS are spatially sparse and a mechanism is needed to estimate fuel moisture content at locations potentially distant from observational stations. This is arranged using a trend surface model (TSM), which allows us to account for the effects of topography and atmospheric state on the spatial variability of fuel moisture content. At each location of interest, the TSM provides a pseudo-observation, which is assimilated via Kalman filtering. The method is tested with the time-lag fuel moisture model in the coupled weather-fire code WRF-SFIRE on 10-hr fuel moisture content observations from Colorado RAWS in 2013. We show using leave-one-out testing that the TSM compares favorably with inverse squared distance interpolation as used in the Wildland Fire Assessment System. Finally, we demonstrate that the data assimilation method is able to improve fuel moisture content estimates in unobserved fuel classes.; Comment: 28 pages

‣ Estimation of Vegetation Water Content with MODIS data and Radiative Transfer Simulation

Zarco-Tejada, Pablo J.; Ustin, S. L.
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Comunicación de congreso Formato: 56684 bytes; application/pdf
Português
Relevância na Pesquisa
58.073613%
In Proceedings of the First International Sysmposium on Recent Advances in Quantitative Remote Sensing, Valencia, Spain, 16-20 September, 2002; Radiative-transfer physically-based studies have previously demonstrated the relationship between leaf water content and leaf-level reflectance in the near-infrared spectral region. The successful scaling up of such methods to the canopy level requires modeling the effect of canopy structure and viewing geometry on reflectance bands and optical indices used for estimation of water content, such as NDWI and SRWI. This study conducts a radiative transfer simulation, linking leaf and canopy models, to study the effects of leaf structure, dry matter content, leaf area index, and the viewing geometry, on the estimation of leaf equivalent water thickness from canopy-level reflectance. The applicability of radiative transfer model inversion methods to MODIS is studied, investigating its spectral capability for water content estimation. A field sampling campaign was undertaken for analysis of leaf water content from leaf samples in 10 study sites of chaparral vegetation in California, USA, between March and June 2000. MODIS reflectance data were processed from the same period for equivalent water thickness estimation by model inversion linking the PROSPECT leaf model and SAILH canopy reflectance model. MODIS reflectance and viewing geometry values obtained from MOD09A1 product...

‣ Estimation of fuel moisture content by inversion of radiative transfer models to simulate equivalent water thickness and dry matter content: Analysis at leaf and canopy level

Riaño, D.; Vaughan, P; Chuvieco, E.; Zarco-Tejada, Pablo J.; Ustin, S. L.
Fonte: Institute of Electrical and Electronics Engineers Publicador: Institute of Electrical and Electronics Engineers
Tipo: Artículo Formato: 4085 bytes; image/gif
Português
Relevância na Pesquisa
99.09561%
Fire danger models identify fuel moisture content (FMC) of live vegetation as a critical variable, since it affects fire ignition and propagation. FMC can be calculated by dividing equivalent water thickness (EWT) by dry matter content (DM). The “leaf optical properties spectra” (PROSPECT) model was inverted to estimate EWT and DM separately using the Leaf Optical Properties Experiment (LOPEX) database, based on 490 measurements of leaf optical and biochemical properties. DM estimations were poor when leaf samples were fresh ( 2 = 0 38). Results of a sensitivity analysis conducted on the spectral response of samples demonstrated that water absorption masks the effects of DM on the spectral response. This causes a poor estimation of FMC ( 2 = 033), even though EWT estimation was good ( 2 = 094). However, DM of dry samples was accurately estimated ( 2 = 0 84), since no water was present. FMC estimation in fresh leaf material improved considerably ( 2 = 089) by accounting for DM in fresh samples ( 2 = 071), when a constant species-dependent DM value is used. A similar approach was taken on a canopy level by linking the PROSPECT leaf model with the Lillesaeter infinitive reflectance canopy model using data from laboratory measurements under controlled conditions. As expected...

‣ Water content estimation in vegetation with MODIS reflectance data and model inversion methods

Zarco-Tejada, Pablo J.; Rueda, C. A.; Ustin, S. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 4085 bytes; image/gif
Português
Relevância na Pesquisa
58.786997%
Statistical and radiative-transfer physically based studies have previously demonstrated the relationship between leaf water content and leaf-level reflectance in the near-infrared spectral region. The successful scaling up of such methods to the canopy level requires modeling the effect of canopy structure and viewing geometry on reflectance bands and optical indices used for estimation of water content, such as normalized difference water index (NDWI), simple ratio water index (SRWI) and plant water index (PWI). This study conducts a radiative transfer simulation, linking leaf and canopy models, to study the effects of leaf structure, dry matter content, leaf area index (LAI), and the viewing geometry, on the estimation of leaf equivalent water thickness from canopy-level reflectance. The applicability of radiative transfer model inversion methods to MODIS is studied, investigating its spectral capability for water content estimation. A modeling study is conducted, simulating leaf and canopy MODIS-equivalent synthetic spectra with random input variables to test different inversion assumptions. A field sampling campaign to assess the investigated simulation methods was undertaken for analysis of leaf water content from leaf samples in 10 study sites of chaparral vegetation in California...

‣ A Biomass Fuel Assessment for Duke University’s Chilled Water Plant #2

Crowley, Richard
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project Formato: 798502 bytes; application/pdf
Português
Relevância na Pesquisa
48.45598%
This Masters Project identifies the University’s biomass fuelshed and locates potential supply sources and probable fuel quantities. An Excel workbook couples user-defined transportation, processing, collection and handling, and purchase premium expenses within fuel classes to establish probable purchase costs for each supply source. Results are optimized for a lowest cost fuel mix to meet modeled plant demand based on user defined plant parameters. Finally, total biomass fuel costs are compared to fossil options to determine if biomass is a financially justifiable fuel for Duke to pursue. The results of this study indicate that the university fuelshed likely contains supply for more than 4 times the steam plants fuel requirements. The cost per million British thermal units combusted within the fuelshed is highly variable, ranging from approximately $1.01 for construction / demolition material to over $29 for forest thinnings. Several fuel classes are more economic than current prices for natural gas, ranging from less than a quarter to three quarters of the price of natural gas. The preliminary assessments of purchasing biomass fuel for use in the plant resulted in costs significantly lower than natural gas, and even potentially lower than coal. It is anticipated that the annual fuel costs for a biomass plant could be met for around $2.25 million based on plant parameters modeled and the estimated biomass characteristics (collection...

‣ INFLUÊNCIA DA ÉPOCA DE ESTOCAGEM NA QUALIDADE DA BIOMASSA FLORESTAL PARA A GERAÇÃO DE ENERGIA; Influence of the storage season over the quality of wood fuel

Brand, Martha Andreia; Universidade do Estado de Santa Catarina; Brito, José Otávio; Escola Superior de Agricultura Luiz de Queiroz; Quirino, Waldir Ferreira; IBAMA; de Muniz, Graciela Inês Bolzon
Fonte: FUPEF DO PARANÁ Publicador: FUPEF DO PARANÁ
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 14/05/2012 Português
Relevância na Pesquisa
39.088774%
This study aimed to determine the optimal storage season for improving the quality of forest biomass for energy generation. The experiment was carried out in Lages, Brazil, between October 2003 and February 2005. 4 lots of Pinus taeda and Eucalyptus dunnii logs were stocked, in piles, with samples collected from the freshly harvested material, with two, four and six months of storage. The lot 1 was stored between October (2003) and May (2004), lot 2 (January-August (2004)), lot 3 (May-November (2204)) and 4 (August (2004)-February (2005)). The evaluated properties were as follows: moisture content on wet basis, gross and net calorific value. The storage season had influence on the biomass quality, with changes in moisture content and net calorific value. For both species, the best storage season was between August and February (lot 4) and from October to May (lot 1), with the greatest loss of moisture and higher energy savings. Therefore, forest biomass harvested in late winter or early spring, which remained in storage during the summer up to early winter had a better energy quality.; Este trabalho objetivou determinar a época de estocagem ideal para a melhoria da qualidade da biomassa florestal para geração de energia. O experimento foi realizado em Lages...