4,842 research outputs found
Predicting the energy output of wind farms based on weather data: important variables and their correlation
Pre-print available at: http://arxiv.org/abs/1109.1922Wind energy plays an increasing role in the supply of energy world wide. The energy output of a wind farm is highly dependent on the weather conditions present at its site. If the output can be predicted more accurately, energy suppliers can coordinate the collaborative production of different energy sources more efficiently to avoid costly overproduction. In this paper, we take a computer science perspective on energy prediction based on weather data and analyze the important parameters as well as their correlation on the energy output. To deal with the interaction of the different parameters, we use symbolic regression based on the genetic programming tool DataModeler. Our studies are carried out on publicly available weather and energy data for a wind farm in Australia. We report on the correlation of the different variables for the energy output. The model obtained for energy prediction gives a very reliable prediction of the energy output for newly supplied weather data. © 2012 Elsevier Ltd.Ekaterina Vladislavleva, Tobias Friedrich, Frank Neumann, Markus Wagne
Multi-objective constrained optimization for energy applications via tree ensembles
Energy systems optimization problems are complex due to strongly non-linear system behavior and multiple competing objectives, e.g. economic gain vs. environmental impact. Moreover, a large number of input variables and different variable types, e.g. continuous and categorical, are challenges commonly present in real-world applications. In some cases, proposed optimal solutions need to obey explicit input constraints related to physical properties or safety-critical operating conditions. This paper proposes a novel data-driven strategy using tree ensembles for constrained multi-objective optimization of black-box problems with heterogeneous variable spaces for which underlying system dynamics are either too complex to model or unknown. In an extensive case study comprised of synthetic benchmarks and relevant energy applications we demonstrate the competitive performance and sampling efficiency of the proposed algorithm compared to other state-of-the-art tools, making it a useful all-in-one solution for real-world applications with limited evaluation budgets
Improving prediction intervals using measured solar power with a multi-objective approach
Prediction Intervals are pairs of lower and upper bounds on point forecasts and are useful to take into account the uncertainty on predictions. This article studies the influence of using measured solar power, available at prediction time, on the quality of prediction intervals. While previous studies have suggested that using measured variables can improve point forecasts, not much research has been done on the usefulness of that additional information, so that prediction intervals with less uncertainty can be obtained. With this aim, a multi-objective particle swarm optimization method was used to train neural networks whose outputs are the interval bounds. The inputs to the network used measured solar power in addition to hourly meteorological forecasts. This study was carried out on data from three different locations and for five forecast horizons, from 1 to 5 h. The results were compared with two benchmark methods (quantile regression and quantile regression forests). The Wilcoxon test was used to assess statistical significance. The results show that using measured power reduces the uncertainty associated to the prediction intervals, but mainly for the short forecasting horizonsThis work was funded by the Spanish Ministry of Science under contract ENE2014-56126-C2-2-R (AOPRIN-SOL project)
A hybrid ensemble method with negative correlation learning for regression
Hybrid ensemble, an essential branch of ensembles, has flourished in numerous
machine learning problems, especially regression. Several studies have
confirmed the importance of diversity; however, previous ensembles only
consider diversity in the sub-model training stage, with limited improvement
compared to single models. In contrast, this study selects and weights
sub-models from a heterogeneous model pool automatically. It solves an
optimization problem using an interior-point filtering linear-search algorithm.
This optimization problem innovatively incorporates negative correlation
learning as a penalty term, with which a diverse model subset can be selected.
Experimental results show some meaningful points. Model pool construction
requires different classes of models, with all possible parameter sets for each
class as sub-models. The best sub-models from each class are selected to
construct an NCL-based ensemble, which is far more better than the average of
the sub-models. Furthermore, comparing with classical constant and non-constant
weighting methods, NCL-based ensemble has a significant advantage in several
prediction metrics. In practice, it is difficult to conclude the optimal
sub-model for a dataset prior due to the model uncertainty. However, our method
would achieve comparable accuracy as the potential optimal sub-models on RMSE
metric. In conclusion, the value of this study lies in its ease of use and
effectiveness, allowing the hybrid ensemble to embrace both diversity and
accuracy.Comment: 37 pages, 14 figures, 11 table
Wind Power Forecasting Methods Based on Deep Learning: A Survey
Accurate wind power forecasting in wind farm can effectively reduce the enormous impact on grid operation safety when high permeability intermittent power supply is connected to the power grid. Aiming to provide reference strategies for relevant researchers as well as practical applications, this paper attempts to provide the literature investigation and methods analysis of deep learning, enforcement learning and transfer learning in wind speed and wind power forecasting modeling. Usually, wind speed and wind power forecasting around a wind farm requires the calculation of the next moment of the definite state, which is usually achieved based on the state of the atmosphere that encompasses nearby atmospheric pressure, temperature, roughness, and obstacles. As an effective method of high-dimensional feature extraction, deep neural network can theoretically deal with arbitrary nonlinear transformation through proper structural design, such as adding noise to outputs, evolutionary learning used to optimize hidden layer weights, optimize the objective function so as to save information that can improve the output accuracy while filter out the irrelevant or less affected information for forecasting. The establishment of high-precision wind speed and wind power forecasting models is always a challenge due to the randomness, instantaneity and seasonal characteristics
Parallel multi-level genetic ensemble for numerical weather prediction enhancement
The need for reliable predictions in environmental modelling is well-known. Particularly, the predicted weather and meteorological information about the future atmospheric state is crucial and necessary for almost all other areas of environmental modelling. Additionally, right decisions to prevent damages and save lives could be taken depending on a reliable meteorological prediction process. Lack and uncertainty of input data and parameters constitute the main source of errors for most of these models. In recent years, evolutionary optimization methods have become popular to solve the input parameter problem of environmental models. We propose a new parallel meteorological prediction scheme that uses evolutionary optimization methods based on Multi-Chromosome Genetic Algorithm to enhance the quality of weather forecasts by focusing on the calibration of input parameters. This new scheme is parallelized and executed on a HPC environment in order to reduce the time needed to obtain the final prediction. The new approach is called Multi-Level Genetic Ensemble (M-Level G-Ensemble) and it has been tested using historical data of a well-known weather catastrophe: Hurricane Katrina that occurred in 2005 in the Gulf of Mexico. Results obtained with our approach provide both significant improvements in weather prediction and a significant reduction in the execution time. © 2012 Published by Elsevier Ltd
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