Browsing by Author "Justino, Paulo Alexandre"
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- Caraterização do recurso renovável offshore para o planeamento da instalação de sistemas de energias renováveis marinhas na costa portuguesaPublication . Simões, Teresa; Couto, António; Justino, Paulo Alexandre; Estanqueiro, AnaRESUMO: As energias renováveis marinhas (Offshore) apresentam um grande potencial de exploração em Portugal, por um lado devido à situação geográfica do país, com a sua área extensa de costa e uma das maiores zonas económicas exclusivas – e por outro, pelos indicadores de existência de elevado recurso energético, cujo estudo tem vindo a ser efetuado nos últimos anos. Não obstante esses estudos, persistem várias barreiras a ultrapassar para a disseminação das tecnologias de energias renováveis com maior aplicabilidade em Portugal – eólica offshore e ondas. Neste contexto, surgiu o projeto OffshorePlan - Planeamento da instalação de energias renováveis offshore em Portugal, no qual se desenvolveu uma metodologia de planeamento da instalação de sistemas de energias renováveis offshore – eólica offshore e ondas – onde se inclui o refinamento e a validação dos mapeamentos do potencial eólico e das ondas existentes. Neste trabalho apresentam-se as metodologias desenvolvidas para o mapeamento do recurso eólico offshore e das ondas, e a sua validação com dados experimentais obtidos com base em sensores LiDAR e bóias hidrográficas. Os resultados constituem atualmente os Atlas do potencial eólico offshore e de energia das ondas em Portugal.
- Energia solar no ambiente urbano: caso de estudo, desafios, abordagens e investigaçãoPublication . Viana, Susana; Simões, Teresa; Aelenei, Laura Elena; Justino, Paulo AlexandreRESUMO: O Município de Cascais tem vindo a empenhar-se na mitigação das alterações climáticas, na proteção do ambiente e renaturalização de florestas e espaços verdes, no aumento da recolha seletiva e melhoria de processos de tratamento de resíduos, na melhoria da mobilidade, apostando na mobilidade suave combinada com zonas intermodais de ligação a transportes públicos, como os comboios e a rede gratuita de autocarros municipais (Mobi Cascais) para residentes, trabalhadores e estudantes. Como forma de diminuir a sua pegada de carbono, o município pretende ainda apostar na geração de energia a partir de fontes renováveis, nomeadamente na integração de energia solar fotovoltaica em edifícios públicos e em edifícios geridos pela autarquia. Para atingir estes objetivos Cascais tornou-se um caso de estudo em dois projetos europeus, Re-Value e WeGenerate.
- Estimativa de potenciais técnicos de energia renovável em Portugal: eólico, solar fotovoltaico, solar concentrado, biomassa e oceanosPublication . Simoes, Sofia; Simões, Teresa; Barbosa, Juliana; Rodrigues, Carlos; Azevedo, Pedro; Cardoso, João P.; Facão, Jorge; Costa, Paula Silva; Justino, Paulo Alexandre; Gírio, Francisco; Reis, Alberto; Passarinho, Paula; Duarte, Luís C.; Moura, Patrícia; Abreu, Mariana; Estanqueiro, Ana; Couto, António; Oliveira, Paula; Quental, Lídia; Patinha, Pedro; Catarino, Justina; Picado, AnaExecutive Summary: There is a clear need to accelerate the energy transition, including the implementation of renewable electricity production plants, as well as the increase in consumption of other renewable energy carriers in buildings, industry, transport and other sectors. This work provides key information to make this transition possible, that is, the technical renewable energy potentials for Portugal. The aim is thus to contribute to policy support, as well as to decision-making by various Portuguese stakeholders (public and private) in the domains of energy, energy transition and greenhouse gases emissions mitigation. The work presents the technical renewable energy potentials for Portugal to: (i) decentralized solar photovoltaic (PV) plants in artificialized (or built-up) areas; (ii) centralized solar PV plants in non-artificialized (or natural) areas; (iii) concentrated solar power; (iv) onshore wind; (v) offshore wind (floating and fixed); (vi) bioenergy, and (vii) solar thermal. The wave energy primary energy resource potential is also presented (not the technical potential). The technical potential values of renewable energy sources (RES) presented are dynamic values, given the substantial uncertainty associated with their estimation. The study identifies technical RES potentials i.e., the technically viable energy generation achievable from a specific technology, considering the primary energy resource available and the geographic, environmental and land use limitations. RES economic potentials represent the fraction of RES technical potential that is economically viable, but they are not presented in this work. Likewise, this report does not address market potential, that translate the capacity and energy generation that the market effectively manages to implement. The presented RES technical potentials include the total capacity currently installed in the country. The technical potentials are estimated mostly for mainland Portugal, in most cases with a spatial disaggregation of at least NUT2 and sometimes for NUT5 and/or type of building. Despite adopting an approach based on a territorial analysis in which some areas of the country are excluded, this potential does not correspond to the work done in mapping less-sensitive areas towards future definition of RES “Go-To Areas”. The decentralized solar PV potential in artificialized areas is divided into 6 area types: industrial areas; commercial buildings; residential and mixed-use buildings; villas; health, education, cultural, tourist and military buildings, and other land uses (including parking lots and patios, ports, waste and wastewater treatment infrastructure, sports facilities, among others). It is estimated a technical potential of 23.33 GW that could generate up to 36.84 TWh/year. This potential is distributed throughout the entire territory of mainland Portugal but is higher in the North and Center regions. The RES technical potential for centralized solar PV was estimated as a range of values that translate the uncertainty associated with using different levels of concern in excluding certain areas in which solar PV can be deployed (for example to safeguard ecosystems, water resources, agriculture or archaeological heritage). The centralized solar PV potential varies between 168.82 GW and 45.63 GW. The maximum threshold of installed capacity could generate 278.11 TWh/year of electricity. The value is high and reflects on the one hand, the excellence of the solar resource throughout the country, and on the other, the large size of the considered areas. The CSP potential is 62.6 GW with a corresponding electrical production potential of 183.61 TWh/year. It is mainly located in the Alentejo region, although other areas have also been identified in other regions of the country. The wind onshore technical potential is 15.7 GW, that could generate 37.13 TWh/year, taking into account the safeguarding of various areas for the protection of ecosystems and also social acceptability issues. In the case of offshore wind and considering a capacity density of 4 MW/km2 for floating offshore and 5.5 MW/km2 for fixed offshore, a total of 36 GW and 2 GW are obtained, respectively. This capacity could generate up to 126.14 TWh/year (floating offshore) or 6.31 TWh/year (fixed offshore). The solar thermal energy potential focused residential and service buildings (such as nursing homes, barracks, etc., tourism, hospitals, indoor swimming pools and other sports facilities). The potential is of 0.95 GWt and 0.95 TWh/year for service buildings, 7.26 GWt and 5.84 TWh/year for residential buildings. For industry there is a potential of 1.06 GWt, which could generate up to 1.15 TWh/year for applications up to 160 ºC. The total technical potential of solar thermal is 9.25 GWt and 7.93 TWh/year of thermal energy generated, with a substantial weight of residential buildings in the total value. Potential values are disaggregated by NUTS III and type of building. In terms of biomass and bioenergy potential, annual values of forest biomass, agricultural biomass, agro-industrial waste, urban waste and wastewater treatment are estimated, totaling around 58 TWh/year. Regarding the production of biofuels (HVO and FAME) it is estimated that the annual production of domestic used oils and other similar residues is 1.4 TWh/year. The use of oils from food crops such as soybean, sunflower and rapeseed is limited by European (and national) policy guidelines and is 2.1 TWh/year. Regarding wave energy, the resource potential is estimated between 1.4 GW for 80 m bathymetry and 4.8 for 20 m bathymetry. There are substantial uncertainties associated with the presented values, inherent to the methodological approach considered. Nevertheless, these estimates are a valuable starting point to be refined and improved in subsequent updates.
- Frequency and Stochastic Domain Models for Two Geometries of the IPS Wave Power BuoyPublication . Cândido, J.; Justino, Paulo Alexandre; Henriques, J.C.C.Frequency-domain analysis is applied to a geometry of the original IPS buoy device concept. The analysis is particularly useful in the early development stages to establish the response of power take-off mechanism characteristic parameters to different frequencies of the wave spectrum. Optimal mechanical damping and spring coefficients are computed for some parameters restrictions. Absorbed power, capture width and other variables, such as relative displacement,are computed for regular waves and these optimal mechanical coefficients. A stochastic model is developed in order to evaluate the IPS buoy behaviour for irregular waves’ conditions. This allows defining probability density functions for parameters that characterize the device’s behaviour. Assuming that the overall system behaviour is linear and that the surface elevation for irregular waves may be regarded as a stochastic process with a Gaussian probability density function, the variables that define the system behaviour, such as bodies’ displacements and velocities, will also hold a Gaussian probability density function. The average power extraction is computed for different sea state conditions.Aiming to enhance the device’s hydrodynamic performance, a new non-axisymmetric IPS geometry is conceived. Using the stochastic modelling approach, the device’s behaviour is studied for several wave directions and compared to the axisymmetric configuration’s behaviour.
- Frequency-domain and stochastic model for an articulated wave power devicePublication . Cândido, J.; Justino, Paulo AlexandreTo have the first look into device performance, analytical and numerical tools must be used. Assuming that the wave power system hydrodynamics has a linear behaviour, diffraction and radiation coefficients can be computed. If the power take-off equipment may be, for the first approach, regarded as holding a linear behaviour then overall (i.e. hydrodynamic plus mechanical) device performance can be studied for regular waves. In this study a frequency-domain model describes the articulated system behaviour for regular waves. For this paper a stochastic model is found for an articulated wave power device, and probability density functions are defined for the relevant parameters that characterize the wave power system behaviour. For these parameters and for different sea states the probability density functions are found. The articulated system is characterized by these probability density functions. Also, average values for capture width are obtained for these sea state conditions.
- Hydrodynamics of triangular-grid arrays of floating point-absorber wave energy converters with inter-body and bottom slack-mooring connectionsPublication . Vicente, Pedro C.; Falcão, António F. de O.; Gato, L.M.C.; Justino, Paulo AlexandreIt may be convenient that dense arrays of floating point absorbers are spread-moored to the sea bottom through only some of their elements (possibly located in the periphery), while the other array elements are prevented from drifting and colliding with each other by connections to adjacent elements. An array of identical floating point absorbers located at the grid points of an equilateral triangular grid is considered in the paper. A spread set of slack-mooring lines connect the peripheric floaters to the bottom. A weight is located at the centre of each triangle whose function is to pull the three floaters towards each other and keep the inter-body moorings lines under tension. The whole system – buoys, moorings and power take-off systems – is assumed linear, so that a frequency domain analysis may be employed. Equations are presented for a set of three identical point absorbers. This is then extended to more complex equilateral triangular grid arrays. Results from numerical simulations, with regular and irregular waves, are presented for the motions and power absorption of hemispherical converters in arrays of three and seven elements and different mooring and PTO parameters, and wave incidence angles. Comparisons are given with the unmoored and independently-moored buoy situations.
- Impact of the wave/wind induced oscillations on the power performance of the WindFloat wind turbinePublication . Couto, António; Justino, Paulo Alexandre; Simões, Teresa; Estanqueiro, AnaABSTRACT: The main objective of this work is the characterization of the wave/wind induced oscillations on the power performance of the wind turbine operating on a WindFloat floating system. To assess the potential impact on the wind turbine power performance induced by these oscillations, the nacelle movements of the WindFloat wind turbine were monitored using accelerometer sensors synchronized with : 1) metocean data measured with a buoy; 2) wind turbine power data installed in the WindFloat floating system; and 3) wind speed data gathered from a nacelle-mounted LiDAR. Based on this data, a clustering analysis approach is proposed. No meaningful relationship between the ocean parameters and the nacelle movements or the wind power production could be established. The obtained results suggest that the dynamic adaptation of the drive train (mainly due to wind turbine torque control) to a fast oscillating (primary energy) moving force is the source of the largest oscillations in the nacelle of the WindFloat wind turbine. Nevertheless, results suggest that the wind/wave induced oscillations and their impact on the power performance of the WindFloat wind turbine is low considering its nominal capacity. Outcomes of this work were extremely relevant to demonstrate the stability of the WindFloat system, and, consequently, also important for the development of the floating wind offshore industry (and other technologies).
- Modelling of the IPS buoy wave energy converter including the effect of non-uniform tube cross-sectionPublication . Falcão, António F. de O.; Cândido, José J.; Justino, Paulo Alexandre; Henriques, João C. C.An important class of floating wave energy converters (that includes the IPS buoy, the Wavebob and the PowerBuoy) comprehends devices in which the energy is converted from the relative (essentially heaving) motion between two bodies oscillating differently. The paper considers the case of the IPS buoy, consisting of a floater rigidly connected to a fully submerged vertical (acceleration) tube open at both ends. The tube contains a piston whose motion relative to the floater-tube system (motion originated by wave action on the floater and by the inertia of the water enclosed in the tube) drives a power take-off mechanism (PTO) (assumed to be a linear damper). To solve the problem of the end-stops, the central part of the tube, along which the piston slides, bells out at either end to limit the stroke of the piston. The use of a hydraulic turbine inside the tube is examined as an alternative to the piston. A frequency domain analysis of the device in regular waves is developed, combined with a one-dimensional unsteady flow model inside the tube (whose cross-section is in general nonuniform). Numerical results are presented for a cylindrical buoy in regular waves, including the optimization of the acceleration tube geometry and PTO damping coefficient for several wave periods.
- Modelling, control and Pontryagin Maximum Principle for a two-body wave energy devicePublication . Justino, Paulo Alexandre; Cândido, J.Frequency domain analysis is applied to a wave energy device composed by two coaxial axisymmetric bodies. For each frequency optimal damping coefficient values which maximize absorbed power are obtained. Several displacement amplitude restriction scenarios are considered. A stochastic model to describe the device’s behaviour in irregular waves is developed. Optimal mechanical damping and spring coefficients are computed. Considering different sea state conditions, probability density functions are defined for relevant parameters and time averaged absorbed power values are obtained.A time domain model is also developed for the device. A non-linear power take-off mechanism configuration, consisting in a hydraulic circuit with low-pressure and high-pressure gas accumulators, is devised. Time averaged absorbed power is maximized in terms of characteristic mechanism parameter. A sub-optimal method of phase control by latching is applied to the device in order to improve its performance. Analytical development of Pontryagin Maximum Principle is used to establish an algorithm for device’s control.
- Non-linear Slack-Mooring Modelling of a Floating Two-Body Wave Energy ConverterPublication . Vicente, Pedro C.; Falcão, António F. de O.; Justino, Paulo AlexandreMost floating oscillating-body wave energy converters that have been proposed and developed so far are two-body systems where the power is extracted from the relative translational motion between the two bodies. As any floating device, floating point absorbers are subject to drift forces due to waves, currents and wind, and therefore need to be kept in place by a proper mooring system. The mooring cables can be approximately modelled as catenary lines in a quasi-static analysis. The use of a time-domain analysis allows for nonlinear mooring forces of slack chain cables to be considered. Numerical results for motion, mooring tensions and absorbed power are presented for a two body system consisting of a hemispherical floater and a submerged body and slack bottom moorings, for regular and irregular waves. Comparisons are given with the unmoored two-body heaving system, the moored heaving twobody system and with the simplified one body linear PTO model. Results show the possibility of occurrence of low-frequency horizontal oscillations of large amplitude, and non linear motions, even for regular waves. Some differences are seen in comparison with the simplified one body model and with the heave two-body system. The moorings were found not to affect very significantly the power absorbed.