Optimal scheduling of a renewable micro-grid in an isolated load area using mixed-integer linear programming

In the energy management of the isolated operation of small power system, the economic scheduling of the generation units is a crucial problem. Applying right timing can maximize the performance of the supply. The optimal operation of a wind turbine, a solar unit, a fuel cell and a storage battery is searched by a mixed-integer linear programming implemented in General Algebraic Modeling Systems (GAMS). A Virtual Power Producer (VPP) can optimal operate the generation units, assured the good functioning of equipment, including the maintenance, operation cost and the generation measurement and control. A central control at system allows a VPP to manage the optimal generation and their load control. The application of methodology to a real case study in Budapest Tech, demonstrates the effectiveness of this method to solve the optimal isolated dispatch of the DC micro-grid renewable energy park. The problem has been converged in 0.09 s and 30 iterations.

A probabilistic methodology for distributed generation location in isolated electrical service area

Distributed generation unlike centralized electrical generation aims to generate electrical energy on small scale as near as possible to load centers, interchanging electric power with the network. This work presents a probabilistic methodology conceived to assist the electric system planning engineers in the selection of the distributed generation location, taking into account the hourly load changes or the daily load cycle. The hourly load centers, for each of the different hourly load scenarios, are calculated deterministically. These location points, properly weighted according to their load magnitude, are used to calculate the best fit probability distribution. This distribution is used to determine the maximum likelihood perimeter of the area where each source distributed generation point should preferably be located by the planning engineers. This takes into account, for example, the availability and the cost of the land lots, which are factors of special relevance in urban areas, as well as several obstacles important for the final selection of the candidates of the distributed generation points. The proposed methodology has been applied to a real case, assuming three different bivariate probability distributions: the Gaussian distribution, a bivariate version of Freund’s exponential distribution and the Weibull probability distribution. The methodology algorithm has been programmed in MATLAB. Results are presented and discussed for the application of the methodology to a realistic case and demonstrate the ability of the proposed methodology for efficiently handling the determination of the best location of the distributed generation and their corresponding distribution networks.

Optimização do tratamento por lamas activadas do efluente líquido da Mundotêxtil

A Mundotêxtil foi fundada em 1975 tendo iniciado a sua actividade na área comercial de produtos têxteis. Actualmente é o maior produtor nacional de atoalhados de felpo e emprega 575 colaboradores. Como resultado do seu crescimento e sobretudo da actividade de tingimento de fio e felpo, as necessidades de água são consideráveis e o volume de efluentes gerados nos processos industriais é cada vez maior a empresa avançou com a construção de uma estação de tratamento por lamas activadas, colocando-a em funcionamento em Setembro de 2004. Inicialmente surgiram dificuldades para a remoção da cor e da concentração da Carência Química de Oxigénio (CQO) de modo a cumprir os limites máximos de emissão permitidos nas normas de descarga no rio Ave e no Decreto-Lei nº 236/98, de 1 de Agosto. Com a descarga de parte dos efluentes no SIDVA e a utilização de um coagulante adicionado ao reactor o tratamento passou a apresentar melhores resultados. O intuito deste trabalho é o de apresentar soluções de modo a optimizar o funcionamento do tratamento biológico da Mundotêxtil. A optimização pode começar na concepção dos produtos, pode incidir no processo de fabrico para além de poder ser efectuada no seio da estação de tratamento biológico. Foi efectuado um estudo do tratamento biológico por lamas activadas no Laboratório de Tecnologia Química Profª Doutora Lída de Vasconcelos, laboratório tecnológico do Instituto Superior de Engenharia do Porto (ISEP) que decorreu nos meses de Maio, Junho e Julho de 2010. O estudo laboratorial foi efectuado para três situações distintas: 1) tratamento do efluente bruto sem qualquer tipo de pré-tratamento (ensaios 1 a 3); 2) tratamento do efluente bruto submetido a pré-tratamento com coagulante Ambifloc BIO MD (ensaios 4 e 5) e 3) tratamento com adição de fungos ao tanque de arejamento (ensaio 6). Foram utilizadas duas instalações de tratamento alimentadas a partir do mesmo tanque de alimentação. Os dois sistemas eram idênticos, diferiram nos caudais de alimentação de efluente que foram alterados ao longo do estudo. O efluente a tratar foi fornecido pela empresa Mundotêxtil, sendo recolhido por diversas vezes ao longo dos ensaios. Este efluente foi retirado após o pré-tratamento da empresa, ou seja este efluente é o mesmo que alimenta o tratamento biológico da Mundotêxtil. Devido a este facto o efluente usado no estudo laboratorial teve uma variabilidade no período em que decorreu o estudo, nomeadamente em termos de concentração de CQO e cor. A relação entre a Carência Bioquímica (CBO5) e a CQO situouse entre 0,47 e 0,63 o que traduz que está dentro dos valores típicos para um efluente têxtil. Os melhores resultados globais de remoção de CQO foram obtidos no ensaio 5 e estiveram compreendidos entre 73,2% e 77,5% para o ensaio 5.1 e entre 62,9 e 73,2% para o ensaio 5.2. Neste ensaio foi utilizado o coagulante. Todos os valores de concentração de CQO obtidos nos efluentes dos decantadores para os ensaios 2, 5 e 6 são inferiores aos valores limite de descarga definidos nas normas de descarga no rio Ave e o Decreto-Lei 236/98. Os valores de concentração de Sólidos Suspensos Totais (SST), pH, fósforo, CBO5 e cor nos decantadores cumpriram os limites de descarga definidos nas normas de descarga no rio Ave e no Decreto-Lei nº 236/98 em todos os ensaios. Os parâmetros cinéticos obtidos para os ensaios com descorante são os que melhor se ajustam ao projecto de uma instalação de tratamento biológico por lamas activadas do efluente da Mundotêxtil. Os valores obtidos, após ajuste, são os seguintes: k=0,015 L/(mgSSV*d); Sn=12 mg/L; a=0,7982 kgO2/kgCBO5; b=0,0233 [kgO2/(kgSSV*d); y=0,2253 kgSSV/kgCBO5; kd=0,0036 kgSSV/(kgSSV*d. Com base nos parâmetros cinéticos obtiveram-se os seguintes resultados para o projecto de uma estação de tratamento biológico por lamas activadas: · Tempo de retenção hidráulica no reactor de 1,79 d, · Volume do reactor igual a 3643 m3 · Consumo de oxigénio no reactor de 604 kg/d · Razão de recirculação igual a 0,8 · Volume total do decantador secundário igual a 540 m3 · Diâmetro do decantador secundário igual a 15 m A quantidade de oxigénio necessário é baixa e o valor mais adequado deverá ser da ordem de 1200 kg/d. Também foi efectuada uma análise aos produtos químicos consumidos pela empresa na área das tinturarias com a finalidade de identificar as substâncias com uma maior influência potencial no funcionamento da Estação de Tratamento Biológico. O encolante CB, Cera Têxtil P Líquida, Perfemina P-12, Meropan DPE-P, Meropan BRE-P, Indimina STS e Benzym TEC são os produtos químicos que têm uma influência potencial mais significativa na qualidade dos efluentes. Devido ao facto das temperaturas do efluente alimentado ao tratamento biológico da Mundotêxtil oscilarem entre 35 ºC e 43ºC efectuou-se um estudo às necessidades de água quente das tinturarias e por outro lado à capacidade de aquecimento dos efluentes disponíveis. Actualmente a racionalização dos consumos de água é cada vez mais premente, por isso também é apresentado neste trabalho um estudo para a substituição das máquinas convencionais das tinturarias com uma relação de banho 1:10 por máquinas de banho curto (1:6,5). Verifica-se a redução de consumos de 40% de água, 52% de energia eléctrica, 35% de produtos químicos, 51% das necessidades de vapor e por consequência um aumento da produtividade. A empresa pode reduzir os consumos de água em cerca de 280.000 m3/ano. A utilização do pré-tratamento com o coagulante permitirá baixar a concentração da CQO e reduzir a cor à entrada do reactor tratamento biológico. Deste modo é possível manter um tratamento eficiente à saída do tratamento biológico nas situações de descarga de cores carregadas e carga orgânica elevada. Com este conjunto de soluções, quer sejam aplicadas na totalidade ou não, a empresa Mundotêxtil pode enfrentar o futuro com mais confiança podendo estar preparada para fazer face à escassez de água e custos cada vez maiores da energia. Por outro lado pode tratar os seus efluentes a custos menores. A substituição das máquinas de tingimento por máquinas com relação de banho mais baixa (banho curto) implica investimentos elevados mas estes investimentos são necessários não só por motivos ambientais mas também devido à grande competitividade dos mercados.

PAH air pollution at a Portuguese urban area: carcinogenic risks and sources identification

This study aimed to characterize air pollution and the associated carcinogenic risks of polycyclic aromatic hydrocarbon (PAHs) at an urban site, to identify possible emission sources of PAHs using several statistical methodologies, and to analyze the influence of other air pollutants and meteorological variables on PAH concentrations.The air quality and meteorological data were collected in Oporto, the second largest city of Portugal. Eighteen PAHs (the 16 PAHs considered by United States Environment Protection Agency (USEPA) as priority pollutants, dibenzo[a,l]pyrene, and benzo[j]fluoranthene) were collected daily for 24 h in air (gas phase and in particles) during 40 consecutive days in November and December 2008 by constant low-flow samplers and using polytetrafluoroethylene (PTFE) membrane filters for particulate (PM10 and PM2.5 bound) PAHs and pre-cleaned polyurethane foam plugs for gaseous compounds. The other monitored air pollutants were SO2, PM10, NO2, CO, and O3; the meteorological variables were temperature, relative humidity, wind speed, total precipitation, and solar radiation. Benzo[a]pyrene reached a mean concentration of 2.02 ngm−3, surpassing the EU annual limit value. The target carcinogenic risks were equal than the health-based guideline level set by USEPA (10−6) at the studied site, with the cancer risks of eight PAHs reaching senior levels of 9.98×10−7 in PM10 and 1.06×10−6 in air. The applied statistical methods, correlation matrix, cluster analysis, and principal component analysis, were in agreement in the grouping of the PAHs. The groups were formed according to their chemical structure (number of rings), phase distribution, and emission sources. PAH diagnostic ratios were also calculated to evaluate the main emission sources. Diesel vehicular emissions were the major source of PAHs at the studied site. Besides that source, emissions from residential heating and oil refinery were identified to contribute to PAH levels at the respective area. Additionally, principal component regression indicated that SO2, NO2, PM10, CO, and solar radiation had positive correlation with PAHs concentrations, while O3, temperature, relative humidity, and wind speed were negatively correlated.

BANMAC: an opportunistic MAC protocol for reliable communications in body area networks

We consider reliable communications in Body Area Networks (BAN), where a set of nodes placed on human body are connected using wireless links. In order to keep the Specific Absorption Rate (SAR) as low as possible for health safety reasons, these networks operate in low transmit power regime, which however, is known to be error prone. It has been observed that the fluctuations of the Received Signal Strength (RSS) at the nodes of a BAN on a moving person show certain regularities and that the magnitude of these fluctuations are significant (5 - 20 dB). In this paper, we present BANMAC, a MAC protocol that monitors and predicts the channel fluctuations and schedules transmissions opportunistically when the RSS is likely to be higher. The MAC protocol is capable of providing differentiated service and resolves co-channel interference in the event of multiple co-located BANs in a vicinity. We report the design and implementation details of BANMAC integrated with the IEEE 802.15.4 protocol stack. We present experimental data which show that the packet loss rate (PLR) of BANMAC is significantly lower as compared to that of the IEEE 802.15.4 MAC. For comparable PLR, the power consumption of BANMAC is also significantly lower than that of the IEEE 802.15.4. For co-located networks, the convergence time to find a conflict-free channel allocation was approximately 1 s for the centralized coordination mechanism and was approximately 4 s for the distributed coordination mechanism.

Opportunistic packet scheduling in body area networks

Significant research efforts are being devoted to Body Area Networks (BAN) due to their potential for revolutionizing healthcare practices. Energy-efficiency and communication reliability are critically important for these networks. In an experimental study with three different mote platforms, we show that changes in human body shadowing as well as those in the relative distance and orientation of nodes caused by the common human body movements can result in significant fluctuations in the received signal strength within a BAN. Furthermore, regular movements, such as walking, typically manifest in approximately periodic variations in signal strength. We present an algorithm that predicts the signal strength peaks and evaluate it on real-world data. We present the design of an opportunistic MAC protocol, named BANMAC, that takes advantage of the periodic fluctuations of the signal strength to achieve high reliability even with low transmission power.

A multi-objective approach for the motion planning of redundant manipulators

Kinematic redundancy occurs when a manipulator possesses more degrees of freedom than those required to execute a given task. Several kinematic techniques for redundant manipulators control the gripper through the pseudo-inverse of the Jacobian, but lead to a kind of chaotic inner motion with unpredictable arm configurations. Such algorithms are not easy to adapt to optimization schemes and, moreover, often there are multiple optimization objectives that can conflict between them. Unlike single optimization, where one attempts to find the best solution, in multi-objective optimization there is no single solution that is optimum with respect to all indices. Therefore, trajectory planning of redundant robots remains an important area of research and more efficient optimization algorithms are needed. This paper presents a new technique to solve the inverse kinematics of redundant manipulators, using a multi-objective genetic algorithm. This scheme combines the closed-loop pseudo-inverse method with a multi-objective genetic algorithm to control the joint positions. Simulations for manipulators with three or four rotational joints, considering the optimization of two objectives in a workspace without and with obstacles are developed. The results reveal that it is possible to choose several solutions from the Pareto optimal front according to the importance of each individual objective.

The utilization bound of non-preemptive rate-monotonic scheduling in controller area networks is 25%

Consider a distributed computer system comprising many computer nodes, each interconnected with a controller area network (CAN) bus. We prove that if priorities to message streams are assigned using rate-monotonic (RM) and if the requested capacity of the CAN bus does not exceed 25% then all deadlines are met.

Damage evaluation of drilled carbon/epoxy laminates based on area assessment methods

The characteristics of carbon fibre reinforced laminates had widened their use, from aerospace to domestic appliances. A common characteristic is the need of drilling for assembly purposes. It is known that a drilling process that reduces the drill thrust force can decrease the risk of delamination. In this work, delamination assessment methods based on radiographic data are compared and correlated with mechanical test results (bearing test).

A sensitivity study of the WRF model in wind simulation for an area of high wind energy

The performance of the Weather Research and Forecast (WRF) model in wind simulation was evaluated under different numerical and physical options for an area of Portugal, located in complex terrain and characterized by its significant wind energy resource. The grid nudging and integration time of the simulations were the tested numerical options. Since the goal is to simulate the near-surface wind, the physical parameterization schemes regarding the boundary layer were the ones under evaluation. Also, the influences of the local terrain complexity and simulation domain resolution on the model results were also studied. Data from three wind measuring stations located within the chosen area were compared with the model results, in terms of Root Mean Square Error, Standard Deviation Error and Bias. Wind speed histograms, occurrences and energy wind roses were also used for model evaluation. Globally, the model accurately reproduced the local wind regime, despite a significant underestimation of the wind speed. The wind direction is reasonably simulated by the model especially in wind regimes where there is a clear dominant sector, but in the presence of low wind speeds the characterization of the wind direction (observed and simulated) is very subjective and led to higher deviations between simulations and observations. Within the tested options, results show that the use of grid nudging in simulations that should not exceed an integration time of 2 days is the best numerical configuration, and the parameterization set composed by the physical schemes MM5–Yonsei University–Noah are the most suitable for this site. Results were poorer in sites with higher terrain complexity, mainly due to limitations of the terrain data supplied to the model. The increase of the simulation domain resolution alone is not enough to significantly improve the model performance. Results suggest that error minimization in the wind simulation can be achieved by testing and choosing a suitable numerical and physical configuration for the region of interest together with the use of high resolution terrain data, if available.

Forest fires occurrences and burned area in mainland Portugal: preliminary assessment to a fifteen years period

Portugal, as well as the Mediterranean basin, is favorable to the occurrence of forest fires. In this work a statistical analysis was carried out based on the official information, considering the forest fires occurrences and the corresponding burned area for each of the districts of the mainland Portugal, between 1996 and 2010. Concerning to the forest fires occurrence it was possible to identify three main regions in mainland Portugal, while the burned area can be characterized in two main regions. Associations between districts and years are different in the two approaches. The results obtained provide a synthetic analysis of the phenomenon of forest fires in continental Portugal, based on all the official information available to date.

Characterization of soils in an area of prescribed fire

The prescribed fire is a technique that is often used, it has several advantages. Pedological and hydropedological techniques were tested to assess the prescribed fire changes may cause in soils. This work was performed in Tresminas area (Vila Pouca de Aguiar, Northern Portugal), during February and March 2011. In the present study we applied several techniques. For the field sampling was followed the ISO 10381-1[1], ISO 10381-2[2], and FAO rules [3], as well as were used a grid with 17 points for measuring the soil parameters. During the fire, we have tried to check, with the assistance of the Portuguese Forestry Authority, some important parameters such as, the propagation speed, the size of the flame front and the intensity of energy emitted per unit area. Before the fire, was collected carefully soil disturbed and undisturbed samples for laboratory analysis, and measured soil water content; we also have placed four sets of thermocouples for measuring soil temperature. After the fire, were collected the thermocouples and new soil samples; the water content were measured in the soil and collected ashes. In the laboratory, after preparing and sieving the samples, were determined the soil particle size. The soil pH and electrical conductivity in water was also determined. The total carbon (TC) and inorganic carbon (IC)[4] was measured by a Shimadzu TOC-Vcsn. The water content in soil has not varied significantly before and after the fire, as well as soil pH and soil electrical conductivity. The TC and IC did not change, which was expected, since the fire not overcome the 200° C. Through the various parameters, we determined that the prescribed fire didn’t affect the soil. The low temperature of the fire and its rapid implementation that lead to the possible adverse effects caused by the wild fire didn’t occurred.

Measurements of environmental background radiation in the surrounding area of a coal-fired power plant

Certain materials used and produced in a wide range of non-nuclear industries contain enhanced activity concentrations of natural radionuclides. In particular, electricity production from coal is one of the major sources of increased exposure to man from enhanced naturally occurring materials. Over the past decades there has been some discussion about the elevated natural background radiation in the area near coal-fired power plants due to high uranium and thorium content present in coal. This work describes the methodology developed to assess the radiological impact due to natural radiation background increasing levels, potentially originated by a coal-fired power plant’s operation. Gamma radiation measurements have been done with two different instruments: a scintillometer (SPP2 NF, Saphymo) and a gamma ray spectrometer with energy discrimination (Falcon 5000, Canberra). A total of 40 relevant sampling points were established at locations within 20 km from the power plant: 15 urban and 25 suburban measured stations. The highest values were measured at the sampling points near to the power plant and those located in the area within the 6 and 20 km from the stacks. This may be explained by the presence of a huge coal pile (1.3 million tons) located near the stacks contributing to the dispersion of unburned coal and, on the other hand, the height of the stacks (225 m) which may influence ash’s dispersion up to a distance of 20 km. In situ gamma radiation measurements with energy discrimination identified natural emitting nuclides as well as their decay products (212Pb, 214Pb, 226Ra 232Th, 228Ac, 234Th 234Pa, 235U, etc.). This work has been primarily done to in order to assess the impact of a coal-fired power plant operation on the background radiation level in the surrounding area. According to the results, an increase or at least an influence has been identified both qualitatively and quantitatively.

Ultrafine Particles in Ambient Air of an Urban Area: Dose Implications for Elderly

Due to their detrimental effects on human health, the scientific interest in ultrafine particles (UFP) has been increasing, but available information is far from comprehensive. Compared to the remaining population, the elderly are potentially highly susceptible to the effects of outdoor air pollution. Thus, this study aimed to (1) determine the levels of outdoor pollutants in an urban area with emphasis on UFP concentrations and (2) estimate the respective dose rates of exposure for elderly populations. UFP were continuously measured over 3 weeks at 3 sites in north Portugal: 2 urban (U1 and U2) and 1 rural used as reference (R1). Meteorological parameters and outdoor pollutants including particulate matter (PM10), ozone (O3), nitric oxide (NO), and nitrogen dioxide (NO2) were also measured. The dose rates of inhalation exposure to UFP were estimated for three different elderly age categories: 64–70, 71–80, and >81 years. Over the sampling period levels of PM10, O3 and NO2 were in compliance with European legislation. Mean UFP were 1.7 × 104 and 1.2 × 104 particles/cm3 at U1 and U2, respectively, whereas at rural site levels were 20–70% lower (mean of 1 ×104 particles/cm3). Vehicular traffic and local emissions were the predominant identified sources of UFP at urban sites. In addition, results of correlation analysis showed that UFP were meteorologically dependent. Exposure dose rates were 1.2- to 1.4-fold higher at urban than reference sites with the highest levels noted for adults at 71–80 yr, attributed mainly to higher inhalation rates.

Cloud-assisted Wireless Body Area Networks

Wireless Body Area Networks (WBANs) have emerged as a promising technology for medical and non-medical applications. WBANs consist of a number of miniaturized, portable, and autonomous sensor nodes that are used for long-term health monitoring of patients. These sensor nodes continuously collect information of patients, which are used for ubiquitous health monitoring. In addition, WBANs may be used for managing catastrophic events and increasing the effectiveness and performance of rescue forces. The huge amount of data collected by WBAN nodes demands scalable, on-demand, powerful, and secure storage and processing infrastructure. Cloud computing is expected to play a significant role in achieving the aforementioned objectives. The cloud computing environment links different devices ranging from miniaturized sensor nodes to high-performance supercomputers for delivering people-centric and context-centric services to the individuals and industries. The possible integration of WBANs with cloud computing (WBAN-cloud) will introduce viable and hybrid platform that must be able to process the huge amount of data collected from multiple WBANs. This WBAN-cloud will enable users (including physicians and nurses) to globally access the processing and storage infrastructure at competitive costs. Because WBANs forward useful and life-critical information to the cloud – which may operate in distributed and hostile environments, novel security mechanisms are required to prevent malicious interactions to the storage infrastructure. Both the cloud providers and the users must take strong security measures to protect the storage infrastructure.