EOL - Artigos em revistas internacionais
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- Assessment of wind and solar PV local complementarity for the hybridization of the wind power plants installed in PortugalPublication . Couto, António; Estanqueiro, AnaABSTRACT: To decarbonize electrical power systems, it is essential to incorporate a high share of variable renewable energy sources while minimizing their costs. An important step towards this goal includes exploring the potential for the so-called hybrid renewable power plants through the combination of (existing) wind and solar power parks. Although that is not the usual approach in their design, hybrid power plants should take advantage of existing synergies, as generation complementarity among the renewable generation technologies, and benefit from using existing infrastructures and the same grid connection point. This investigation assesses the potential of existing Portuguese wind parks for hybridization with solar power photovoltaic generation. Correlation and energy metrics for assessing the complementarity at hourly and daily periods are applied to quantify existing synergies. Results show a high potential for hybrid power plants: levels of complementarity between wind and solar resources are globally high thus allowing to increase the share of variable renewable energy sources with minimal energy curtailment, when compared with scenarios of overplanting additional wind power capacity. The highest and most consistent levels of complementarity are found in the interior regions of central and northern Portugal. The research shows that Portugal has privileged weather conditions that allow the concept of hybrid power plants to be largely explored and extended on a large and efficient scale. This outcome, which may be replicated for other countries, is an important contribution to increasing the penetration of renewable energy in electrical power systems while minimizing the overall costs of renewable energy.
- Currents of ChangesPublication . Holttinen, Hannele; Orths, Antje; Eriksen, Peter Børre; Hidalgo, Jorge; Estanqueiro, Ana; Groome, Frank; Coughlan, Yvonne; Neumann, Hendrik; Lange, Bernhard; Hulle, Frans van; Dudurych, IvanThe Power Systems in Denmark, Portugal, Spain, Ireland, and Germany have some of the highest wind penetrations in the world, as shown in Table 1. The management of the different power systems to date,with increasing amounts of wind energy, has been successful.There have been no reported incidents in which wind has directly or indirectly been a major factor causing operational problems on the system. In some areas with high wind penetration, however, the transmission system operator (TSO) had to increase remedial actions signifi cantly in order to decrease the loading of system assets during times of high wind power infeed. In some areas, the risk of faults may have increased. Higher targets for wind power will mean even higher penetration levels locally and high penetration levels in larger power systems. There are a number of issues that will require active management in the near future; in some cases, such management is needed today. In this article, the situations of five countries with high wind penetration are briefl y presented, with special emphasis given to their future needs with respect to accommodating targeted wind power amounts. The final section provides an overview of offshore grid developments and plans in Europe.
- A cyclic time-dependent Markov process to model daily patterns in wind turbine power productionPublication . Scholz, Teresa; Lopes, Vitor V.; Estanqueiro, AnaWind energy is becoming a top contributor to the renewable energy mix, which raises potential reliability issues for the grid due to the fluctuating nature of its source. To achieve an adequate reserve commitment which mitigates wind integration costs as well as to promote market participation, it is necessary to provide models that can capture daily patterns in wind power production. This paper presents a cyclic inhomogeneous Markov process, which is based on a three-dimensional state-space partition of the wind power, speed and direction variables. Each transition probability is a time-dependent function, expressed as a Bernstein polynomial. The model parameters are estimated by solving a constrained optimization problem: The objective function combines two maximum likelihood estimators, one to ensure that the Markov process long-term behavior reproduces the data accurately and, another to capture daily fluctuations. The paper presents a convex formulation for the overall optimization problem and demonstrates its applicability through the analysis of a case-study. The proposed model is capable of reproducing the diurnal patterns of a three-year dataset collected from a wind turbine located in a mountainous region in Portugal. In addition, it is shown how to compute persistence statistics directly from the Markov process transition matrices. Based on the case-study, the power production persistence through the daily cycle is analysed and discussed.
- Design of a new urban wind turbine airfoil using a pressure-load inverse methodPublication . Henriques, J.C.C.; Silva, F. Marques da; Estanqueiro, Ana; Gato, L.M.C.This paper presents the design methodology of a new wind turbine airfoil that achieves high performance in urban environment by increasing the maximum lift. For this purpose, an inverse method was applied to obtain a new wind turbine blade section with constant pressure-load along the chord, at the design inlet angle. In comparison with conventional blade section designs, the new airfoil has increased maximum lift, reduced leading edge suction peak and controlled soft-stall behaviour, due to a reduction of the adverse pressure gradient on the suction side. Wind tunnel experimental results confirmed the computational results.
- A Dynamic Wind Generation Model for Power Systems StudiesPublication . Estanqueiro, AnaIn this paper, a wind park dynamic model is presented together with a base methodology for its application to power system studies. This detailed wind generation model addresses the wind turbine components and phenomena more relevant to characterize the power quality of a grid connected wind park, as well as the wind park response to the grid fast perturbations, e.g., low voltage ride through fault. The developed model was applied to the operating conditions of the selected sets of wind turbine experimental benchmark data from Azores and Alsvik wind parks, both for steady and transient operation of the grid. The results show a fairly good agreement in the relevant range of frequencies and indicate the model may be used as a tool for power system studies.
- Experience and challenges with short-term balancing in european systems with large share of wind powerPublication . Soder, Lennart; Abildgaard, Hans; Estanqueiro, Ana; Hamon, Camile; Holttinen, Hannele; Lannoye, E.; Gomez-Lázaro, E.; O'Malley, Mark; Zimmermann, UweThe amount of wind power in the world is quickly increasing. The background for this development is improved technology, decreased costs for the units, and increased concern regarding environmental problems of competing technologies such as fossil fuels. Some areas are starting to experience very high penetration levels of wind and there have been many instances when wind power has exceeded 50% of the electrical energy production in some balancing areas. The aims of this paper are to show the increased need for balancing, caused by wind power in the minutes to hourly time scale, and to show how this balancing has been performed in some systems when the wind share was higher than 50%. Experience has shown that this is possible, but that there are some challenges that have to be solved as the amount of wind power increases.
- Exploring wind and solar PV generation complementarity to meet electricity demandPublication . Couto, António; Estanqueiro, AnaABSTRACT: Understanding the spatiotemporal complementarity of wind and solar power generation and their combined capability to meet the demand of electricity is a crucial step towards increasing their share in power systems without neglecting neither the security of supply nor the overall cost efficiency of the power system operation. This work proposes a methodology to exploit the complementarity of the wind and solar primary resources and electricity demand in planning the expansion of electric power systems. Scenarios that exploit the strategic combined deployment of wind and solar power against scenarios based only on the development of an individual renewable power source are compared and analysed. For each scenario of the power system development, the characterization of the additional power capacity, typical daily profile, extreme values, and energy deficit are assessed. The method is applied to a Portuguese case study and results show that coupled scenarios based on the strategic combined development of wind and solar generation provide a more sustainable way to increase the share of variable renewables into the power system (up to 68% for an annual energy exceedance of 10% for the renewable generation) when compared to scenarios based on an individual renewable power source. Combined development also enables to reduce the overall variability and extreme values of a power system net load.
- A GIS methodology for planning sustainable renewable energy deployment in PortugalPublication . Costa, Paula Silva; Simões, Teresa; Estanqueiro, AnaABSTRACT: A Geographical Information System (GIS) methodology was developed to identify and characterize suitable areas for deploying renewable energy projects. The methodology enables to compute the sustainable renewable energy potential in an area under study and can be implemented for different spatial scales, ranging from local to national levels, while operating with different restriction layers. This GIS-based method has been successfully applied to wind energy deployment studies in Continental Portugal and other foreign countries (e.g. Venezuela, Mozambique among others). Results from several development plans using this methodology enable to conclude it is an adequate tool for planning sustainable renewable energy deployment both for onshore and offshore regions.
- High resolution forecasts of wind in rough orography and in coastal conditionsPublication . Miranda, Pedro; Costa, Paula Silva; Antunes, C.; Ferreira, João P.; Valente, A.; Rodrigues, Álvaro; Estanqueiro, AnaThe increase of the share of wind energy in total electrical power requires the development of reliable forecasts of wind power at different time scales, from minutes to days, on a regional and national basis. That development is multidisciplinary, involving meteorological and engineering components. In the present stage, though, it is thought that for time scales beyond 3 hours, the largest improvements are expected from the meteorological side, if meteorological forecasts are able to deal with mesoscale flow. In this paper three case studies of mesoscale modeling are analyzed and compared against wind observations in sites selected for their high potential for wind energy. Two cases deal with flow in the Islands of Madeira and San Jorge (Azores), characterized by rough orography, where measurements were made at the top of elevated plateaus. In these two cases, the large scale flow is obtained from ECMWF analysis and the mesoscale flow is computed, for one summer and one winter month, with two mesoscale models at resolutions between 6 and 0.5 km. In the third case, one full year of simulationis Continental Portugal is performed at resolutions between 27 and 3km, using boundary conditions from the NCEP/NCAR reanalysis and the MM5 model. Results indicate the interest of high horizontal resolution for wind forecasts in complex terrain but also some difficulties in the representation of boundary layer effects in conditions of large thermal forcing.
- How to Prepare a Power System for 15% Wind Energy Penetration: the Portuguese Case StudyPublication . Estanqueiro, Ana; Castro, Rui; Flores, Pedro; Ricardo, João; Pinto, Medeiro; Rodrigues, Reis; Lopes, J. PeçasThe 2001/77/CE Renewable Energies European Directive together with Kyoto Protocol ratification supported by a government vision and strong objective on the reduction of external oil dependence put Portugal in the front line to achieve one of the highest wind energy penetrations within 10 years$1 (B time. This paper gives a summarized overview of the Portuguese technical approaches and methodologies followed in order to plan and accommodate the ambitious wind power goals to 2010/2013, preserving the overall quality of the power system.