Wind, Volume 2, Issue 2 (June 2022) – 12 articles

This paper presents a study investigating the effects of surface roughness on airfoil performance and its consequences for wind turbine energy yield. This study examined 51 sets of experimental data across 16 airfoils to identify trends in roughened airfoil performance. The trends are used to formulate a novel ‘roughness evolution parameter’ that can be applied to airfoils with no roughened data available to predict the impact of roughness on performance. Blade element momentum theory is used to model the performance of the DTU 10 MW reference wind turbine, with uniformly roughened blades emulated using the roughness evolution parameter. An annual energy production loss between 0.6–9.6% is found for the DTU 10 MW turbine when considering a plausible range of values for the roughness evolution parameter derived from the experimental data. A framework has been developed to evaluate how the roughness evolution parameter changes over time, informed by observed changes in wind farm performance from previous studies. Full article

In the estimation of future investments in the offshore wind industry, the operation and maintenance (O&M) phase plays an important role. In the simulation of the O&M figures, the weather conditions should contain information about the waves’ main characteristics and the wind speed. As these parameters are correlated, they were simulated by using a multivariate approach, and thus by generating vectors of measurements. Four different stochastic weather time series generators were investigated: Markov chains (MC) of first and second order, vector autoregressive (VAR) models, and long short-term memory (LSTM) neural networks. The models were trained on a 40-year data set with 1 h resolution. Thereafter, the models simulated 25-year time series, which were analysed based on several time series metrics and criteria. The MC (especially the one of second order) and the VAR model were shown to be the ones capturing the characteristics of the original time series the best. The novelty of this paper lies in the application of LSTM models and multivariate higher-order MCs to generate offshore weather time series, and to compare their simulations to the ones of VAR models. Final recommendations for improving these models are provided as conclusion of this paper. Full article

Colombia has an energy matrix that is mostly hydroelectric and includes renewable energies such as wind power, which represents a minor contribution. The only operational wind farm is in the northern part of the country, where more projects will be implemented in the future in search of increasing the installed capacity and electricity generation. However, the wind potential and behavior of other areas of the national territory have been little reviewed. The most recommended method to characterize the potential in different areas of Colombia is to use real data, generating vertical extrapolations and respecting the good practices of the wind industry. The foregoing not only allows the generation of statistical and descriptive characterizations but also, together with the climatological, geographical, and technological variables (turbines), an estimate of the generable energy that can be obtained. In the described study, we applied specialized software to generate a rating matrix, from which it was possible to issue an opinion on five possible locations obtained from the theoretical development of micrositing, where 14 factors were reviewed. There is no published research of this nature for the country, so it is relevant in terms of novelty. Finally, it can be concluded that in Colombia, the wind potential should not be associated with a specific region, since there are data throughout the territory where this type of research can be replicated. Full article

Wind turbine drivetrains can be subjected to highly dynamic loading conditions caused by grid faults, power converter faults and dynamic wind excitations. These loading conditions can cause additional wear and possibly damage their components. Some of the most critical components in the mechanical drivetrain are its bearings. High-speed shaft bearings are especially prone to failure. Smearing is one possible damage pattern for these bearings. Previous studies observed a highly increased smearing risk caused by generator-induced torque excitations. In contrast, this study focuses on rotor-induced torque excitations and investigates the resulting smearing risk. The goal is to ascertain the general damage potential stemming from rotor-induced excitations for high-speed shaft bearings regarding smearing. To this end, a detailed bearing model was integrated into a validated multibody simulation of a research nacelle which was operated on a test bench. A smearing criterion was used to evaluate the smearing risk. Multiple sinusoidal rotor-induced torque excitations were investigated. The resulting smearing risk is highly dependent on the excitation amplitude and frequency, with higher amplitudes resulting in a greater smearing risk. Regarding frequency, only excitations with frequencies close to the system’s first torsional eigenfrequency result in a significantly increased smearing risk. In general, the determined amplitudes and frequencies of rotor-induced torque excitations, necessary to cause a significant increase in smearing risk, are unlikely to occur in the field and therefore are of lesser importance to the high-speed shaft bearings than generator-induced torque excitations. Full article

Renewable and local energy communities are viewed as a key component to the success of the energy transition. In this paper, we estimate wind power potential for such communities. Acquiring the most accurate weather data is important to support decision-making. We identify the most reliable publicly available wind speed data and demonstrate a case study for typical energy community scenarios such as a single commercial turbine at coastal and inland locations in Ireland. We describe our assessment methodology to evaluate the quality of the wind source data by comparing it with meteorological observations. We make recommendations on which publicly available wind data sources, such as reanalysis data sources (MERRA-2, ERA-5), PVGIS, and NEWA are best suited to support Renewable Energy Communities interested in exploring the possibilities of renewable wind energy. ERA5 is deemed to be the most suitable wind data source for these locations, while an anomaly is noted in the NEWA data. Full article

The need for energy and water security on islands has led to an increase in the use of wind power. However, the intermittent nature of wind generation means it needs to be coupled with a storage system. Motivated by this, two different models of surplus energy storage systems are investigated in this paper. In both models, renewable wind energy is provided by a wind farm. In the first model, a pumped hydro storage system (PHS) is used for surplus energy storage, while in the second scenario, a hybrid pumped hydrogen storage system (HPHS) is applied, consisting of a PHS and a hydrogen storage system. The goal of this study is to compare the single and the hybrid storage system to fulfill the energy requirements of the island’s electricity load and desalination demands for domestic and irrigation water. The cost of energy (COE) is 0.287 EUR/kWh for PHS and 0.360 EUR/kWh for HPHS, while the loss of load probability (LOLP) is 22.65% for PHS and 19.47% for HPHS. Sensitivity analysis shows that wind speed is the key parameter that most affects COE, cost of water (COW) and LOLP indices, while temperature affects the results the least. Full article

Many residential houses in Japan have hip roofs with pitches ranging from 20° to 30°. Recently, roof-mounted photovoltaic (PV) panels have become popular all over the world for environmental conservation. The design of PV systems in Japan is usually based on the Japanese Industrial Standard (JIS) C 8955 (2017). However, the standard does not provide wind force coefficients for PV panels installed near roof edges (up to 0.3 m from the edge) because flow separation at the roof edges causes large up-lift forces on such panels. In this paper, we investigated the wind force coefficients for designing PV panels installed on hip roofs of rectangular and L-shaped low-rise buildings. The roof pitch was set to 25° as a typical value. Rectangular panels were installed almost over the whole roof, including the edge zones. Because the thickness of PV panels and the distance between PV panels and the roof are both as small as several centimeters, it is difficult to make wind tunnel models of PV systems with the same geometric scale as that for buildings. We focused on a numerical simulation using the unsteady Bernoulli equation to estimate the pressures in the space between PV panels and the roof. In the simulation, we used the time histories of wind pressure coefficients on the bare roof, which were measured in a turbulent boundary layer. We propose installing PV panels with small gaps between them along their short sides. The gaps may reduce the wind loads not only on the PV panels but also on the roofing due to pressure equalization. We discuss the optimum gap width from the viewpoint of wind load reduction. Full article

Certain wind turbine maintenance tasks require specialist equipment, such as a large crane for heavy lift operations. Equipment hire often has a lead time of several weeks but equipment use is restricted by future weather conditions through wind speed safety limits, necessitating an assessment of future weather conditions. This paper sets out a methodology for producing subseasonal-to-seasonal (up to 6 weeks ahead) forecasts that are site- and task-specific. Forecasts are shown to improve on climatology at all sites, with fair skill out to six weeks for both variability and weather window forecasts. For the case of crane hire, a cost-loss model identifies the range of electricity prices where the hiring decision is sensitive to the forecasts. While there is little difference in the hiring decision made by the proposed forecasts and the climatology benchmark at most electricity prices, the repair cost per turbine is reduced at lower electricity prices. Full article

This paper is aimed at improving the maintenance and end-of-life steps in the associated Life Cycle Assessment (LCA) of barge-type floating wind turbines to reduce their environmental impact. Maintenance and end-of-life steps are given special attention since these phases have received only cursory focus in previous LCA studies. Different maintenance and end-of-life scenarios have been considered in the analysis. From the LCA results, it has been found that by applying on-site and onshore maintenance strategies, the lifetime of the turbine can be extended. Four alternative scenarios for the end-of-life step have been examined: mechanical recycling, mechanical-incineration, incineration processes, and landfill. The environmental impacts of these scenarios are evaluated using the LCA methodology. The investigation showed that the lowest environmental impacts correspond to the onshore maintenance and the mechanical recycling scenarios. These CO₂ emissions of these scenarios are 13.68 g CO₂ eq/kWh and 0.107 g CO₂ eq/kWh, respectively. Full article

This paper investigated the development of a hybrid model for wind speed forecast, ranging from 1 to 46 days, in the northeast of Brazil. The prediction system was linked to the widely used numerical weather prediction from the ECMWF global ensemble forecast, with neural networks (NNs) trained using local measurements. The focus of this study was on the post-processing of NNs, in terms of data structure, dimensionality, architecture, training strategy, and validation. Multilayer perceptron NNs were constructed using the following inputs: wind components, temperature, humidity, and atmospheric pressure information from ECMWF, as well as latitude, longitude, sin/cos of time, and forecast lead time. The main NN output consisted of the residue of wind speed, i.e., the difference between the arithmetic ensemble mean, derived from ECMWF, and the observations. By preserving the simplicity and small dimension of the NN model, it was possible to build an ensemble of NNs (20 members) that significantly improved the forecasts. The original ECMWF bias of −0.3 to −1.4 m/s has been corrected to values between −0.1 and 0.1 m/s, while also reducing the RMSE in 10 to 30%. The operational implementation is discussed, and a detailed evaluation shows the considerable generalization capability and robustness of the forecast system, with low computational cost. Full article

It has been stated that by 2030, South Korea will have increased their capacity for wind power from 124 MW to 12 GW. According to official statements, offshore wind turbines will provide most of this wind energy. In order to determine the costs for an offshore wind energy production site, an economic analysis was performed in Incheon, South Korea, and the levelized cost of energy (LCoE) value was calculated at 129.97 USD per MWh, and the net present value and the internal rate of return were also calculated. Various scenarios were tested, and it was proven that minimum or no governmental support can lead to economically problematic projects. Is zero subsidy the future of the offshore wind industry? Full article

Onshore wind energy has been one of the most promising new renewable energy sources in the Northeast region of Brazil. This technology has generated long-term energy without serious socio-environmental impacts for some and, therefore, has been considered clean, renewable, and sustainable. However, given its spatial complexity, water scarcity, and social poverty of indigenous populations, the development of wind energy in vulnerable areas of this region raises socio-ecological concerns. Hence, studies of sustainability challenges are essential. The aim of this article is to systematically review the main multidimensional sustainability challenges of studies on onshore wind power generation, resulting in a quick scoping review of the literature. The study highlighted the promise of onshore wind generation in the current period of climatic and socio-ecological crises, but also highlighted some resulting socio-ecological problems, such as: deforestation for the construction of wind farms, expropriation of subsistence arable land, generation of turbine noise, insignificant employment, maintenance of inequalities, rural–city migration, extinction of cultural traditions, and food insecurity. This review offers an overview of wind energy generation, aiming to inform society and decision makers about the nature of challenges that lead to unsustainability arising from wind energy technology. Full article