Wind Generation Facilities Research Articles

Quantifying Trailing Edge Flap Control Capability on Wind Turbines in a Controlled Environment

As wind turbine diameters continue to increase, the cyclic loading experienced by the turbine blade due to wind shear and yaw misalignment increases dramatically hindering the development of larger more efficient turbines. Based on current literature, controlling a section of the trailing edge of the turbine blade was found to reduce cyclic loading. To quantify the load control capability of a trailing edge flap (TEF), an experimental rig was designed to evaluate a TEF on a 3.5-m-diam wind turbine operating under different tip speed ratios, yaw angles, and blade pitch angles inside a large wind generation facility. The TEF was tested at two different spanwise locations and 0.82. The instrumented blade was capable of measuring rotor torque, flapwise/edgewise blade root bending moment, and normal force coefficient at two different spanwise locations and 0.82. The experimental results show that the use of a TEF was capable of manipulating the normal force coefficient by 40% and the flapwise bending moment by 20%. The relationship between the TEF angle and both blade bending moment and normal force coefficient was linear for all the cases tested. The results also show that when the TEF was centered at it could control the turbine loading more effectively. The results presented here prove that the TEF is capable of reducing cyclic loading on wind turbine blades.

Experimental load measurement on a yawed wind turbine and comparison to FAST

Current interest in unsteady aerodynamics of yawed turbines for wake redirection and cyclic load alleviation requires a clear understanding of turbine load fluctuation with azimuth position. To that end, an experimental 3.5 m diameter wind turbine rig was designed to measure rotor torque, flapwise/edgewise blade root bending moment, and normal force coefficient at r/R=0.66 and 0.82. The turbine was tested inside a large scale wind generation facility with a blockage ratio of 7%. Simultaneously and in time-resolved fashion, measurements were collected to produce phase-averaged performance parameters that are presented versus azimuth while the turbine is operating at different tip speed ratios and yaw angles. The NREL FAST code predictions were then compared to experimental data under the same conditions. It was found that in non-yawed conditions, FAST predictions were accurate but discrepancies start to emerge when the turbine is yawed and operating in dynamic stall conditions. In non-yawed cases, the discrepancy between experimental and FAST data is less than 7% when the flow is attached and increases to 22% when the flow is stalled. One of the main sources of discrepancy found is in the process of correcting the airfoil coefficients to account for 3D flow effects using AirfoilPrep.

In-Blade Measurements of Cyclic Loading on Yawed Turbines with Trailing Edge Flap

Wind turbines operate predominantly in relatively unsteady flow conditions and are typically misaligned with the incoming wind. Based on the literature review, controlling a section of the trailing edge of the turbine blade is found to reduce load fluctuations on wind turbine blades. Here, a detailed experimental setup describes a 3.5 m diameter wind turbine equipped with a trailing edge flap (TEF). The instrumentation of the compact blade was capable of measuring surface pressure and root bending moment, as well as controlling a TEF simultaneously and in time-resolved fashion. The blade is of constant pitch and chord of 178 mm while the TEF covers 20% of the chord and 22% of the 1.47 m aerodynamic blade span. The turbine was tested in a controlled wind generation facility large enough to house the turbine with less than 7% blockage. The wind turbine was tested for a range of tip speed ratios, blade pitch angles, flap angles and yaw cases. Although the turbine blade is capable of cyclically and dynamically change the blade pitch and flap angle, this paper only investigates constant pitch and flap angles. The results show that changes to the flap or pitch angle are capable of manipulating the coefficient of power, root bending moment and normal force coefficient. The results also show that the flap demonstrates similar control authority to that of the pitch system with the flap occupying just 4% of the blade surface area without reducing the power output of the turbine.

Wind turbine wake effect visualization and LiDAR measurement techniques

The expansion of wind energy development has resulted in larger wind farms and closer placement of turbines to utilize the space available. Each turbine produces a wake that affects downstream turbines, which causes issues such as production loss, blade loading, and fluctuating electrical output. To minimize this impact, the wake produced by turbines must first be understood. Experimental methods were used in the exploration of the wake effects of wind turbines. Smoke visualization inside the University of Waterloo Wind Generation Facility was used to determine the helical vortex wake distribution behind a 3.3 m diameter turbine as well as the tip vortex shedding from the blade. Wind Doppler Light Detection and Ranging (LiDAR) measurement devices were modified and used to measure wind turbine wake velocities. The University of Waterloo Wind Energy Group has a ZephIR z150 LiDAR to use in this study. The LiDAR was verified under normal operation for accuracy against a cup and vane anemometer. The LiDAR was then verified for accuracy and to determine the position of measurements after modifications necessary for future wake measurement experiments.

Clustering and dispatching hydro, wind, and photovoltaic power resources with multiobjective optimization of power generation fluctuations: A case study in southwestern China

Hydropower can be used to smooth out the output fluctuations from power systems including wind and solar sources. This paper proposes a double-layer model for coordinating the operations of cascaded hydropower and neighboring wind and photovoltaic (PV) facilities. In a local complementary model, hydropower with less regulating ability (local complementary hydropower, LCH) is dispatched to alleviate short-term fluctuations (i.e., hourly variations), whereas in the global one, hydropower with greater regulating capacity (global complementary hydropower, GCH) is operated to alleviate long-term fluctuations (i.e., intraday peak-valley differences). The results of a case study of a hydro-wind-PV cluster project in southwestern China show that most (90%) short-term fluctuations can be smoothed by LCH with a minimum impact on the capacity factor (−0.02). In contrast, alleviation of long-term fluctuations can be achieved with GCH, but this causes a large capacity factor reduction (−0.25). The discharge fluctuation of GCH is notably lower (70–75%) than that of LCH. In this system (which includes 5200 MW wind and 1400 MW PV), the output fluctuations can be eliminated if hydropower capacity reaches 2200 MW. These findings demonstrate that clustering of hydropower cascades with wind and solar generation facilities is a promising avenue for the decarbonization of electricity systems.

Flexibility Provisions From a Fast Charging Facility Equipped With DERs for Wind Integrated Grids

This paper presents a new mathematical model to design a fast charging facility (FCF) with distributed energy resources (DERs) to provide flexibility services in wind integrated power grids. Two different ownership structures of the FCF and wind generation facility (WGF) are considered. The DER options considered for FCF design are solar photovoltaic (PV) units and battery energy storage systems. The effects of wind power uncertainty on power system operations are mitigated through the designed FCF with DERs via the upward and downward flexibility provisions. Monte Carlo simulations are used to simulate the uncertainties in PV and wind generation, and market price. Studies considering an 18 MW WGF and the National Household Travel Survey 2009 data are presented to demonstrate the effectiveness of the flexibility provisions from the proposed design of FCF with DERs.

On intermediate-scale open-sea experiments on floating offshore structures: Feasibility and application on a spar support for offshore wind turbines

Experimental investigation of floating structures represents the most direct way for achieving their dynamic identification and it is particularly valuable for relatively new concepts, such as floating supports for offshore wind turbines, in order to fully understand their dynamic behaviour. Traditional experimental campaigns on floating structures are carried out at small scale, in indoor laboratories, equipped with wave and wind generation facilities. This article presents the results of an open-sea experimental activity on a 1:30 scale model of the OC3-Hywind spar, in parked rotor conditions, carried out at the Natural Ocean Engineering Laboratory (NOEL) of Reggio Calabria (Italy). The aim of the experiment is two-fold. Firstly, it aims to assess the feasibility of low-cost, intermediate-scale, open-sea activities on offshore structures, which are proposed to substitute or complement the traditional indoor activities in ocean basins. Secondly, it provides useful experimental data on damping properties of spar support structures for offshore wind turbines, with respect to heave, roll and pitch degrees of freedom. It is proven that the proposed approach may overcome some limitations of traditional small-scale activities, namely high costs and small scale, and allows to enhance the fidelity of the experimental data currently available in literature for spar floating supports for offshore wind turbines.

Local government climate change mitigation and adaptation ranking assessment

Climate change awareness in local areas is critical, and this study assessed levels of mitigation and adaptation of local government areas (LGAs), across the rural/urban State of Tasmania. Fourteen indicators were developed in the sectors of energy, transport, awareness, and physical carbon sinks, and allocated quantitative parameters for ranking. Results were mapped using geographical information systems software. Higher energy results occurred on the two large northern islands both with solar and wind generation facilities, and around some cities with energy efficient street lighting systems. Highest transport scores occurred in the remote west, and around most cities, but mostly not in agricultural areas. Higher awareness levels and overall scores were found around city areas. Higher physical scores resulted from community tree plantings and carbon sequestering vegetation. This study shows how geographic trend mapping can improve understanding of spatial differences in climate change mitigation and adaptation, to improve prioritised allocation of assistance policy.

Optimal over installation of wind generation facilities

This paper evaluates the economic benefits to over-installing turbines on capacity-constrained wind farm sites in order to capture more energy at low wind speeds. Although this implies curtailment at high wind speeds, we show that over installing generation facilities can increase returns to investors and reduce system costs. A detailed model-based analysis is developed using British data, with variations in the range of over installation, the renewable policy support systems (fixed feed-in tariffs or green certificate premia to wholesale energy prices) and the extent of replacement of fossil generation in the technology mix with wind. In the cases of premia to market prices, we use agent-based, computational learning and risk simulation to model market prices. Not only is over installation beneficial under fixed feed-in tariffs, but is more so under premia to market prices and increasingly so as wind replaces fossil generation.

The Effect of Hydro Power on the Optimal Distribution of Wind and Solar Generation Facilities in a Simplified Highly Renewable European Power System

We investigate the optimal distribution of wind and photovoltaic generation facilities in Europe. For this purpose, feed-in data covering Europe for the renewable sources wind, photovoltaics and hydro are used. Together with historical load data and a transmission model, a simplified European power system is simulated. The results show that wind should be placed in countries on the shores of the North-Sea while the picture for PV is complex: A band from Germany to Italy over Switzerland is optimal. Furthermore, we show that hydro power has little influence on the optimal distribution.

Analyzing the Impacts of Wind Generation on Distribution System Performance

Increasing wind power generation affects performance of existing power system in terms of power losses, voltage regulation and short circuit levels. Jhimpir wind generation having 49.5 MW capacity is connected to 132kV network of Hyderabd Electric Supply Company (HESCO) to meet its energy demand. Distribution network of HESCO is modelled and simulated using Power system Simulator – Siemens Network Calculator (PSS SINCAL) as simulation platform. Simulation results are compared to observe impacts of wind integration to existing power system network. Simulation results indicate reduction of power losses from 15.26 to 14.79MW as a result of wind integration to existing HESCO network. Reduction in power losses is mainly caused by changed current flows in lines. Reduction in current also reduce line drops resulting in improved bus voltages. Short circuit level is slightly increased for all buses due to network modification. Increase in short circuit level is highest near the wind generation as Zorlu grid shows 13.02% increase. 66kV network shows small increase in short circuit level due to its long distance from wind generation facility. Use of real network data for this research work identifies possible protection issues alongwith the reduction in power losses and voltage drop. Each system network has separate network parameters and will have different response to any network change. Hence a simulation analysis is important to ensure maximum benefits from renewable energy sources and their integration with existing power system network

Optimal Oversizing of Wind Generation Facilities

This paper evaluates the economic benefits to over-installing turbines on wind farm sites in order to capture more energy at low wind speeds. Although this implies curtailment at high wind speeds, we show that oversizing generation facilities can increase returns to investors and reduce system costs. A detailed model-based analysis is developed using British and Irish data, with variations in the range of oversizing, the renewable policy support systems (fixed feed-in tariffs or green certificate premia to wholesale energy prices) and the extent of replacement of fossil generation in the technology mix with wind. In the cases of premia to market prices, we use agent-based, computational learning and risk simulation to model market prices. Not only is oversizing beneficial under fixed feed-in tariffs, but is more so under premia to market prices and increasingly so as wind replaces fossil generation. We suggest policy makers should provide positive support to oversizing.

Calculation of Probabilistic Available Transfer Capability in Wind Power Integrated System

As the number of wind generation facilities in the power system is fast increasing, the research on available transfer capability (ATC) calculation with wind farms has great significance to system operation. With consideration of the uncertainty of the wind powers output, this paper proposes a probability computing method to study the ATC in wind power integrated system. This computing method of ATC is evaluated on non-sequential Monte Carlo simulation, and the ATC of every system state in random sampling is calculated by interior point method. The result shows that the model and algorithm is correct and effective.

Models for Change

Not much more than a decade ago, the desired action for a wind generation facility was to shut down or disconnect electrically in the event of a disruption on the bulk electric system. This, of course, was a reflection of the novelty that was wind generation at the time, as well as prudent engineering judgment, as the loss of a small amount of generation-the wind plants that were in service at the time-posed little risk to system reliability.

Managing Wind-based Electricity Generation with Storage and Transmission Capacity

The electricity industry is currently considering co-locating wind generation and electricity storage facilities. This configuration would allow wind-farms to: (i) store wind generation that exceeds transmission capacity; (ii) time-shift sales of generated power to periods of more favorable prices (i.e., from night to day); and (iii) buy power from the market for future resale. We model this problem --- managing a wind-storage system with limited transmission capacity and the option of buying from the market --- as a finite-horizon Markov decision process that assumes uncertain wind and stochastic prices that can be negative, and apply it to wind and price models calibrated to data. Past literature on wind-storage systems either assumes deterministic wind and price dynamics, based on a single joint historical path, or neglects some relevant market or operational features, such as negative prices (a unique feature of the electricity markets) or the buying option. We find that storage can significantly increase the value of wind generators (typically by more than 30%), but using a deterministic sample path approach could misvalue storage by ±50 %. Likewise, ignoring negative prices could be detrimental when negative prices occur at least 5% of the time (with a loss of about 5%), and omitting the buying option could result in a much larger loss of value (of about 17% when negative prices occur 5% of the time), an observation for which we provide theoretical support. We also find that known static threshold heuristic policies can be more than 30% suboptimal, while a state-dependent multi-threshold heuristic policy that we develop is near optimal (being less than 0.05% suboptimal for many scenarios), even when negative prices are prevalent.

Making connections [wind generation facilities

Large-scale wind generation facilities have become a very visible component of the interconnected power grid in many options of the United States. Only a decade ago, wind generation facilities were viewed by most power engineers as a novelty, and by simple engineering judgement, it could be safely concluded that the effects of these unique but smaller facilities on system reliability would be negligible. Now, with individual wind generation facilities approaching the output rating of conventional power plants, a deeper understanding of their potential impacts on the interaction with the bulk electric power system is needed.