EM - Escola de Minas

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Wave resource characterization through in-situ measurement followed by artificial neural networks' modeling.
(2018) Sánchez, Antonio Santos; Rodrigues, Diego Arruda; Fontes, Raony Maia; Martins, Márcio Fernandes; Kalid, Ricardo de Araújo; Torres, Ednildo Andrade
This research presents a mathematical model that uses artificial neural networks for the assessment of the wave energy potential of sites, based on data recorded by wave monitoring instrumentation. The model was implemented and validated in two different sites. The first one had a dataset from an upward-looking acoustic Doppler current profiler that recorded a hindcast during 2½ years. The second consisted in data from a buoy using motion sensors that recorded continuously during 23 years. For this second site, the performance of the neural network model was compared to that of the Nearshore Wave Prediction System (NWPS), which combines SWAN, Wavewatch III and other numerical models. For the 2½ years' hindcast, the error of the neural network was significant which suggests a better use for filling missing gaps within datasets than for resource assessment. Meanwhile the performance of the neural network trained with the 23 years' hindcast was satisfactory; better than the NWPS in terms of relative bias but worse in terms of scatter index. Therefore it is concluded that neural networks can make an optimal use of the data produced by wave monitoring instrumentation and are useful to characterize the wave energy resource of a coastal site.
Alternative biodiesel feedstock systems in the semi-arid region of Brazil : implications for ecosystem services.
(2017) Sánchez, Antonio Santos; Almeida, Mateus Bastos; Torres, Ednildo Andrade; Kalid, Ricardo de Araújo; Cohim, Eduardo; Gasparatos, Alexandros
The Northeast region of Brazil has low levels of human development and a marginal environment subject to chronic water scarcity. This paper assesses the potential impacts of bioenergy production from local varieties of castor oil plant and jatropha that could reduce the import of energy in the region, while developing its economy. Biodiesel systems based on these crops can be suitable for the Northeast region as they have low water needs, and are either indigenous or have shown excellent adaptation to the local climate. Apart from biodiesel production, the residue from their processing can be a valuable resource usable for biogas production and biofertilizers. Using the ecosystem services approach, five land management alternatives are compared: (i) Caatinga woodland (a type of dry savannah native to the region), (ii) a scheme of local jatropha varieties and vegetation for Caatinga forest restoration, (iii) a crop rotation scheme of castor oil plant and cowpeas, (iv) cowpea mono-cropping, and (v) pasture. Based on the analysis of secondary data, some provisioning and regulating services were assessed quantitatively, while others qualitatively. The results suggest that the conversion of (i) cowpea mono-cropping to a rotation of cowpeas and castor and (ii) degraded pastures to a jatropha-Caatinga forest restoration scheme can provide a bundle of provisioning, regulating and supporting ecosystem services. Feedstock for bioenergy is the most important ecosystem service derived from these multifunctional landscapes. In particular converting pasture to a jatropha-Caatinga forest restoration scheme could provide per hectare 0.7 t of oilseeds for biodiesel production and 1.8 GJ of usable energy, in the form of biogas from the residual seedcake. The castor-cowpea rotation scheme could provide per hectare 1.5 t of oilseeds for biodiesel production together with 2.2 GJ of usable biogas energy, per hectare.
Potencial energético das ondas na costa brasileira.
(2017) Sánchez, Antonio Santos; Rodrigues, Diego Arruda; Kalid, Ricardo de Araújo; Torres, Ednildo Andrade
Apresenta-se um modelo matemático em redes neurais para a avaliação do potencial de geração de energia elétrica mediante ondas. O objetivo é desenvolver um modelo confiável, capaz de avaliar de maneira precisa este recurso nos locais mais promissores da costa brasileira. Para validar o modelo, foi usada uma série de medições diretas, registradas durante 10 meses consecutivos por um perfilador acústico de ondas. O modelo conseguiu caracterizar o comportamento desta fonte renovável no local com um erro médio de 9,25%.
Waste bio-refineries for the cassava starch industry : new trends and review of alternatives.
(2017) Sánchez, Antonio Santos; Silva, Yuri Lopes; Kalid, Ricardo de Araújo; Cohim, Eduardo; Torres, Ednildo Andrade
The cassava starch industrial process generates very pollutant effluents that need to be treated before discharge. A series of successful experiences concerning the transformation of treatment ponds into covered lagoons have been conducted in the last years in Brazil, proving that the use of anaerobic digesters could make the worldwide cassava industry more profitable. The circular economy approach is used to add the balance of greenhouse gases, water and land use to the assessment of a set of waste-to-resource alternatives for this particular industrial process. The results point out to the convenience of upgrading the covered lagoon solution to a more complete waste bio-refinery that not only focus in electric power generation but also recovers process heat and biofertilizers as byproducts. Co-generation is very attractive for the resource recovery of this agricultural residue. It was also found that the higher efficiency that characterizes co-generation leads to the lowest level of greenhouse gases emissions.

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