1,720,960 research outputs found
Artificial Intelligence Forecasting Techniques For Reducing Uncertainties In Renewable Energy Applications
Get PDFThe work presented in this thesis provides an integrated view and related insights for solar and wind farm operators and renewable energy regulators regarding factors influencing electricity production using those resources. The findings help production planning and grid stability improvements through better energy forecasting to reduce uncertainty.
With the high increase in energy demand expected in both the near and far future, generating energy from green sustainable resources has now become an imperative necessity. Renewable energy sources like wind and solar are among the most promising and environmentally-friendly energy generation options. However, wind and solar energy production are influenced by many variables which affect the reliability, stability, and economic benefits of wind and solar energy projects, therefore, forecasting the potential amount of energy from wind and solar resources is of great importance.
Hence, the objective of the work reported here was to explore the possibility of using artificial intelligence methods to accurately predict the generated renewable power from solar and wind farms based on the available data. Specifically, this thesis reports on the following results:
1. At first, solar photovoltaic (PV) energy forecasting was studied. Operators of grid-connected PV farms do not always have full sets of data available to them, especially over an extended period of time as required by key forecasting techniques such as multiple regression (MR) or artificial neural network (ANN). Therefore, the work reported here considered these two main approaches of building prediction models and compared their performance when utilizing structural, time-series, and hybrid methods for data input. Three years of PV power generation data (of an actual farm), as well as historical weather data (of the same location) with several key variables, were collected and utilized to build and test six prediction models. Models were built and designed to forecast the PV power for a 24-hour ahead horizon with 15 minutes resolutions. Results of comparative performance analysis show that different models have different prediction accuracy depending on the input method used to build the model: ANN models perform better than the MR regardless of the input method used. The hybrid input method results in better prediction accuracy for both MR and ANN techniques while using the time-series method results in the least accurate forecasting models. Furthermore, sensitivity analysis shows that poor data quality does impact forecasting accuracy negatively, especially for the structural approach.
2. Then, wind energy forecasting was studied utilizing three machine learning techniques namely Artificial Neural Network (ANN), Support vector machine (SVM), and k-nearest neighbors (K-NN). The three mentioned techniques were used to design, train and test wind energy, forecasting models. Later, a hybrid model was proposed based on these three techniques. Real data obtained from a 2MW grid-connected wind turbine has been used to train and validate the different machine learning techniques. To compare the accuracy of the models over different performance measures with different scales, a comparative evaluation method was devised and used. Results show that the ANN model has great performance in forecasting long-term wind energy, but in contrast, it has very poor short-term performance. SVM model shows better short-term forecasting performance than ANN but presents weak long-term forecasting abilities. K-NN model shows very good short-term forecasting abilities and fair long-term performance. The suggested hybrid model was able to forecast both long and short-term wind energy with very good performance. To that degree, the suggested model can help grid and wind farm operators to forecast the potential amount of wind energy for both long and short term with a good degree of certainty.
3. Finally, the effect of the input data resolution on the forecasting accuracy was studied for both wind and solar. So, datasets were collected from a 546 KWp grid-connected PV farm and a 2 MW wind turbine for one full year. This data was used to train and test Artificial Neural Network models to forecast day-ahead PV and wind energy utilizing time-series input data with 15, 30, and 60 minutes resolutions. The models were able to forecast the PV energy accurately, while the same models trained for wind showed poor performance. Higher input data resolutions lead to slightly better forecasting performance for the PV farm. Utilizing data with higher resolution can improve the forecast by 1-5%. While for wind energy forecasting, the resolution has very minor effects, the 30-minute resolution shows a bit better forecasting performance
Unraveling climate trends in the mediterranean : a hybrid machine learning and statistical approach
Get PDFThis study presents a comprehensive spatiotemporal analysis of sea surface temperatures (SST) and surface air temperatures (TAS) across 15 Mediterranean coastal stations, leveraging centennial-scale data to analyze regional climate dynamics. The modeling framework integrates three sequential phases: data preprocessing, statistical analysis, and advanced machine learning techniques, creating a robust analytical pipeline. The data preprocessing phase harmonizes diverse datasets, addresses missing values, and applies transformations to ensure analytical consistency. The statistical modeling employs the Pettitt test for change point detection and linear trend analysis to unveil underlying patterns. The machine learning phase utilizes K-means clustering for climate regime classification and implements tailored Convolutional Neural Networks (CNNs) for cluster-specific future climate anomaly projections. Results unveil a marked anthropogenic climate signal, with contemporary observations consistently surpassing historical baselines. Breakpoint analyses and linear trend assessments reveal heterogeneous climatic shifts, with pronounced warming in the northern Mediterranean. Notably, Nice and Ajaccio exhibit the highest SST increases (0.0119 and 0.0113 °C/decade, respectively), contrasting with more modest trends in Alexandria (0.0052 °C/decade) and Antalya (0.0047 °C/decade) in the eastern Mediterranean. The application of clustering and CNN projections provides granular insights into differential warming trajectories. By 2050, cooler
northwestern Mediterranean zones are projected to experience dramatic SST anomalies of approximately 3 °C above the
average, with corresponding TAS increases of 2.5 °C. In contrast, warmer eastern and southern regions display more sub-dued warming patterns, with projected SST and TAS increases of 1.5–2.5 °C by mid-century. This research’s importance is highlighted by its potential to inform tailored adaptation strategies and contribute to the theoretical understanding of climate dynamics, advancing climate modeling and analysis efforts
Evaluating neural network and linear regression photovoltaic power forecasting models based on different input methods
Get PDFAs Photovoltaic (PV) energy is impacted by various weather variables such as solar radiation and
temperature, one of the key challenges facing solar energy forecasting is choosing the right inputs
to achieve the most accurate prediction. Weather datasets, past power data sets, or both sets can be
utilized to build different forecasting models. However, operators of grid-connected PV farms do not
always have full sets of data available to them especially over an extended period of time as required
by key techniques such as multiple regression (MR) or artificial neural network (ANN). Therefore,
the research reported here considered these two main approaches of building prediction models and
compared their performance when utilizing structural, time-series, and hybrid methods for data input.
Three years of PV power generation data (of an actual farm) as well as historical weather data (of the
same location) with several key variables were collected and utilized to build and test six prediction
models. Models were built and designed to forecast the PV power for a 24-hour ahead horizon with
15 min resolutions. Results of comparative performance analysis show that different models have
different prediction accuracy depending on the input method used to build the model: ANN models
perform better than the MR regardless of the input method used. The hybrid input method results
in better prediction accuracy for both MR and ANN techniques, while using the time-series method
results in the least accurate forecasting models. Furthermore, sensitivity analysis shows that poor data
quality does impact forecasting accuracy negatively especially for the structural approach
Adaptive machine learning for forecasting in wind energy : A dynamic, multi-algorithmic approach for short and long-term predictions
Get PDFThis study elucidates the formulation and validation of a dynamic hybrid model for wind energy forecasting, with a particular emphasis on its capability for both short-term and long-term predictive accuracy. The model is predicated on the assimilation of time-series data from past wind energy generation and employs a triad of machine learning algorithms: Artificial Neural Network (ANN), Support Vector Machine (SVM), and K-Nearest Neighbors (K-NN). Empirical data, harvested from a 2 MW grid-connected wind turbine, served as the basis for the training and validation phases. A comparative evaluation methodology was devised to scrutinize the performance of each constituent algorithm across a diverse array of metrics. This evaluation framework facilitated the identification of individual algorithmic limitations, which were subsequently mitigated through the implementation of a dynamic switching mechanism within the hybrid model. This innovative feature enables the model to adaptively select the most efficacious forecasting technique based on historical performance data. The hybrid model demonstrated superior forecasting accuracy in both, short-term energy forecasts at 15-min intervals over a day, and in broad, long-term. It recorded a Normalized Mean Absolute Error (NMAE) of 5.54 %, which is notably lower than the NMAE range of 5.65 %–9.22 % observed in other tested models, and significantly better than the average NMAE found in the literature, which spans from 6.73 % to 10.07 %. Such versatility renders it invaluable for grid operators and wind farm management, aiding in both operational and strategic planning. The study’s findings not only contribute to the existing body of knowledge in renewable energy forecasting but also suggest the hybrid model’s broader applicability in various other predictive analytics domains
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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