High Altitude Wind Energy Research Articles

Optimization of Hybrid Energy Systems Based on MPC-LSTM-KAN: A Case Study of a High-Altitude Wind Energy Work Umbrella Control System

This paper presents an optimization method for hybrid energy systems based on Model Predictive Control (MPC), Long Short-Term Memory (LSTM) networks, and Kolmogorov–Arnold Networks (KANs). The proposed method is applied to a high-altitude wind energy work umbrella control system, where it aims to enhance the stability and efficiency of energy utilization. The work umbrella system integrates wind and solar energy sources, with energy stored in a battery and used to control the umbrella’s operations. The MPC framework is employed to optimize control actions by solving a finite-horizon optimization problem, ensuring the battery State of Charge (SOC) remains within an optimal range. The LSTM network provides accurate predictions of environmental conditions, including wind speed and solar irradiance, which are essential for MPC’s decision-making process. To address complex nonlinearities in the system, the KAN is utilized to model and approximate these dynamics, refining the LSTM predictions. The integration of these advanced control strategies enables the system to handle varying operational conditions and maintain optimal performance. The case study demonstrates the effectiveness of the MPC-LSTM-KAN approach, revealing improvements in the SOC stability, energy efficiency, and operational endurance of the high-altitude wind energy work umbrella system. The results indicate that this hybrid optimization method offers a robust solution for managing hybrid energy systems in dynamic environments.

Performance potential of fully-passive airborne wind energy system based on flapping airfoil

In the field of renewable energy, high-altitude wind energy emerges as a promising source, particularly at altitudes (>300 m) where conventional wind turbines cannot reach. Currently, the Airborne Wind Energy System (AWES) stands as the major technology for high-altitude wind energy harvesting, but confronts challenges including increasing performance enhancement, system robustness, and cost reduction. In response to these challenges, we developed a fully-passive AWES that employs a self-excited flapping airfoil to efficiently transfer wind energy to the ground. We study and optimize this fully-passive AWES with fluid-structure interaction method in a numerical wind tunnel, achieving a notable power coefficient of 1.17 and efficiency of 20 % with an average tether angle near 30°. We find that a thin airfoil with a slight camber near the leading edge outperforms other profiles. Increasing the pitching axis distance, the imbalance distance, the spring stiffness, and the pitching moment of inertia can improve the energy harvesting performance, but decreased the system robustness. We offer essential guidelines for setting initial parameters of the AWES, facilitating the design and deployment of this innovative technology. This work underscore that the fully-passive AWES is capable of realizing high-altitude wind energy harvesting with simplified structure and outstanding energy-harvesting performance.

Assessment of the Black Sea High-Altitude Wind Energy

Airborne wind energy systems (AWESs) represent a novel idea that aims to gather energy from stronger winds aloft while operating at altitudes above conventional wind turbines (WTs). For this study, we examined the wind resources at a height of 100 m available for traditional wind turbines with aerial wind energy technologies, in addition to the wind potential at higher altitudes up to 500 m. The considered period was 20 years from January 2002 to December 2020, and the data were extracted from the ERA5 reanalysis database. We studied the possibility of placing 500 kW and 5 MW airborne systems in the Black Sea and the Azov Sea and compared them with a conventional turbine. As expected, the western part of the Black Sea presented the best results, both for the 500 kW airborne system with an annual energy production (AEP) of 2.39 GWh and a capacity factor of 55%, and for the 5 MW airborne system, which has an annual electricity production of 15.81 GWh and a capacity factor of 36%. Better results were recorded for the Sea of Azov for both the 500 kW and the 5 MW airborne systems, with an AEP of 2.5 and 15.81 GWh and a capacity factor of 58% and 36%, respectively.

Fully-passive tethered flapping airfoil to harvest high-altitude wind energy

Airborne Wind Energy (AWE) system is an emerging technology aiming at harvesting high-altitude wind energy, which cannot be exploited by tower-mounted wind turbines. In the state-of-the-art AWE system, airborne actuators and ground-based drivers are necessary to control the posture and movements of the airborne component because it generates power through a complicated reciprocating motion. However, the control units required in the traditional AWE system inevitably introduce additional weight and decrease the system reliability, posing a challenge to designing a light airborne component with full automation. To address this issue, we developed a highly compact AWE system without any mechanical driver or control module. By adopting a biomimetic flapping airfoil, the new AWE system avoids the unnecessary power consumption of traditional design and yields consistent power output via a fully-passive flapping motion. Through a systematic optimization of structural parameters in a numerical wind tunnel, the fully-passive AWE system demonstrated efficient energy harvesting with a power coefficient of 0.825 and an efficiency of 18.9%. This advanced technology cannot only solve the fundamental issues that have persisted in the AWE system, but also offer a low-cost approach to enhance high-altitude wind power generation.

High altitude wind energy generation for stratospheric telecommunication balloons in real field

High altitude wind energy generation for stratospheric telecommunication balloons in real field

High altitude wind energy generation for stratospheric telecommunication balloons in real field

High altitude wind energy generation for stratospheric telecommunication balloons in real field

Comparison of the goodness-of-fit of intelligent-optimized wind speed distributions and calculation in high-altitude wind-energy potential assessment

Wind energy is an indispensable component of the power supply. To date, the majority of wind energy is generated based on the surface wind energy projects; however, it has a few technical limitations in satisfying the increasing power demand. Recently, more promising high-altitude wind energy projects (HAWEP) were started around the world using the emerging airborne wind power technology. This process technically requires the determination of high-altitude wind-energy potential for appropriately planning HAWEP. Nevertheless, most of the previous wind-energy potential assessment studies have considered only the wind energy close to the surface; few studies have focused on high-altitude wind energy. To bridge this gap, this study implements a comprehensive assessment of the high-altitude wind-energy potential of offshore China. The assessment applies the intelligent-optimized single and combined distributions to fit the high-altitude wind speed of 20 study sites and identifies the top-ranked distributions. Wind power density and available time are estimated and the general features of high-altitude wind-energy potential in the study area are discussed. The findings of this study can provide valuable suggestions for developing differentiated policies for HAWEP planning.

Analysis levelized cost of energy from the perspective of an power purchase agreements for airborne wind power technology

With the need to diversify the national electric matrix to expand the generation capacity, the searches for new technologies capable of contributing to supply the national demand are fundamental. In this sense, the development of wind energy technology, but specifically high-altitude wind energy using wired airfoils, is an attractive possibility, given the high national wind potential. This research aimed to analyze the cost models used in the literature to assess the leveled cost of energy (LCOE) from the perspective of an power purchase agreements (PPAs) and to simulate the leveled cost of energy for a wind farm with the innovative technology of wired airfoils. For this, we chose two cities Fortaleza (CE) and Florianópolis (SC) to carry out the simulations. The wind farms are identical, with the same number of wind turbines, the parameters that have been modified are, the amount of energy supplied by each of the scenarios, to visualize the influence of the capacity factor of each scenario within the real and nominal LCOE and the PPA real and nominal after 20 years of analysis. As wind energy is not a constant source of supply, the simulation considered the limits of energy delivery that are above or below the minimum limit of energy delivery. The results demonstrated economic viability in almost all scenarios, with greater attractiveness for scenarios with an increase in the capacity factor. When financial parameters such as federal and state charges are varied downwards, all scenarios investigated are attractive to development with an IRR greater than the reference value.

Aerostatic Way of Harvesting High Altitude Wind Energy

Renewable energy system in electrical power generation is one of important field of electrical engineering due to its source is natural, reusable and environmental pollution free and cost free. There are renewable energies such as wind, solar and so on. The wind is a free, clean, and inexhaustible energy source. It has served mankind well for many centuries by propelling ships and driving wind turbines to pump water. It has become one of the most attractive energy system in several decades due to rich availability. The important proposed contribution in this work is to enhance the efficiency of renewable energy using AEROSTATIC WAY OF HARVESTING WIND ENERGY that allows turbines to capture as much as possible wind by increase in the altitude at which is the turbine is placed. Which is done by attaching the turbine to aerostat and the aim of the study is to extract maximum energy of the turbine and transmit it to grid, storage device with suitable converters and controllers.

Modeling, parameterization and damping optimum-based control system design for an airborne wind energy ground station power plant

This paper presents the results of modeling and parameterization of the high-altitude wind energy system ground station power-plant equipped with a generator/motor unit as a primary power source tethered to the airborne module via a winch system, an ultracapacitor energy storage system, and grid inverter connected to the common direct-current link. Consequently, a suitable ground station power plant control strategy is designed, comprising the generator/motor speed control and cable tension control system, direct-current link power flow coordination control, and grid-side inverter control strategy. Control system design is exclusively based on the damping optimum criterion which provides a straightforward way of closed-loop damping tuning. The effectiveness of the proposed ground station control strategy is verified by means of comprehensive computer simulations. These have pointed out to precise coordination of the winch electrical servodrive with the airborne module-related rope force control system and sustained power production during the airborne module ascending phase in the presence of high-altitude wind disturbances, and continuous power delivery to the grid-side inverter, facilitated by the utilization of ultracapacitor energy storage. This indicates rather robust behavior of the overall ground station control system under anticipated external disturbance conditions.

Advances in floating aerogenerators: Present status and future

High altitude winds are considered to be the most favorable source of renewable energy in the future. In this paper, review has been conducted on harnessing of high altitude wind energy via floating type aero-generators. This new generation of systems employs tethered wings, aircrafts, multi-copters, balloons in order to harness the higher atmospheric winds. A number of systems based on different concepts have been analyzed and tested from mid-seventies, with a rapid acceleration in last couple of years. This paper presents a comprehensive overview of different technologies that have been designed/ built to harvest the energy of high altitude winds, highlighting the accomplished results, technological issues and classification of such systems have been proposed on the basis of their working and design. Apart from the Airborne Wind Energy or High-Altitude Wind Energy based systems, a brief overview on offshore floating wind turbines have also been provided.

Freestanding Flag-Type Triboelectric Nanogenerator for Harvesting High-Altitude Wind Energy from Arbitrary Directions.

Wind energy at a high altitude is far more stable and stronger than that near the ground, but it is out of reach of the wind turbine. Herein, we develop an innovative freestanding woven triboelectric nanogenerator flag (WTENG-flag) that can harvest high-altitude wind energy from arbitrary directions. The wind-driven fluttering of the woven unit leads to the current generation by a coupled effect of contact electrification and electrostatic induction. Systematic study is conducted to optimize the structure/material parameters of the WTENG-flag to improve the power output. This 2D WTENG-flag can also be stacked in parallel connections in many layers for a linearly increased output. Finally, a self-powered high-altitude platform with temperature/humidity sensing/telecommunicating capability is demonstrated with the WTENG-flag as a power source. Due to the light weight, low cost, and easy scale-up, this WTENG-flag has great potential for applications in weather/environmental sensing/monitoring systems.

Spectrum analysis of wind profiling radar measurements

Unlike previous studies on wind turbulence spectrum in the planetary boundary layer, this investigation focuses on high-altitude (1–5 km) wind energy spectrum and turbulence spectrum under various weather conditions. A fast Fourier transform (FFT) is used to calculate the wind energy and turbulence spectrum density at high altitudes (1–5 km) based on wind profiling radar (WPR) measurements. The turbulence spectrum under stable weather conditions at high altitudes is expressed in powers within a frequency range of 2 × 10−5–10−3 s−1, and the slope b is between −0.82 and −1.04, indicating that the turbulence is in the transition from the energetic area to the inertial sub-range. The features of strong weather are reflected less obviously in the wind energy spectrum than in the turbulence spectrum, with peaks showing up at different heights in the latter spectrum. Cold windy weather appears over a period of 1.5 days in the turbulence spectrum. Wide-range rainstorms exhibit two or three peaks in the spectrum over a period of 15–20 h, while in severe convective weather conditions, there are two peaks at 13 and 9 h. The results indicate that spectrum analysis of wind profiling radar measurements can be used as a supplemental and helpful method for weather analysis.

Multi-mass dynamic model of a variable-length tether used in a high altitude wind energy system

This paper presents a multibody approach to dynamics modelling of a variable-length tether moving through air, in a system where an airborne module generates aerodynamic lift and uses the tether to cyclically drive the winch-generator unit fixed on the ground. The rope is modelled as a series of straight, massless, elastic segments with the rope mass fragments lumped to the segment joints. Individual segment length is constant, with the exception of segment being wound out from the winch, while the number of segments is variable. For the segment being wound out, a special modelling approach is derived. The forces acting on the rope are also concentrated at the joints, thus simplifying computations and facilitating rope aerodynamic drag modelling. The proposed tether dynamics model is integrated into the overall model of controlled power production system and verified by computer simulation. The model is compared with two simpler tether dynamics models also proposed in the paper.

Energy storage systems sizing study for a high-altitude wind energy application

As the ground-based wind-turbine systems have steadily reached their performance peak due to turbine blade size limitations, generator size constraints, high investment costs, and relatively unpredictable nature of near-surface winds, the possibility of harnessing the energy of steady, high-altitude/high-speed winds has become increasingly attractive within the last decade. However, due to the intermittent nature of power production of a considered high-altitude wind energy system utilizing an airborne module tethered to a ground station, sufficiently large energy storage is required in order to provide steady power supply to the electrical power grid. This paper focuses on the sizing of typical low-to-medium scale energy storage systems (up to 10 MW), such as those based on flywheels, compressed air, batteries and ultracapacitors, considering the intermittent power production cycle, airborne module altitude range and ground-station generator power ratings. The assessment results are summarized in terms of investment/running costs, storage system size, and durability, thus providing practical guidelines for the selection of appropriate energy storage system.

On the way to harness high-altitude wind power: Defining the operational asset for an airship wind generator

The utilization of high-altitude wind energy potential is a very attractive challenge. This is mainly due to the perspective of producing a large amount of electricity from a renewable source without using land, and having a very low visibility impact. The wind flow on the upper levels of the surface boundary layer is characterized by good power with low variability of wind conditions.Many innovative wind energy conversion flying devices are currently under development for this purpose. The technological solutions can be grouped in:•land installed generators (such as kite systems);•airship flying generators that can produce electricity far from the ground and are tethered by control wires, also used for the power transmission.Flying generators could prove more problematic in maintaining flying conditions due to their heavier weight, but they have the advantage that they can be moved to different locations with less intervention on the ground.Another important characteristic that the airship wind generator has, is the possibility of changing its height of operation very quickly and simply by using control cables.In this study, the operational scenario of the possible application of an innovative airship wind generator is studied and discussed. The possibility of adjusting the height of operation was analysed, and a methodology for choosing the optimal operating level was developed and applied to real test cases. Numerical and experimental techniques used to assess the characteristics of high-altitude winds, were also considered.Remotely sensed wind data obtained from a monostatic phased-array Doppler Sonic Detection and Ranging (SODAR) system were used to validate and tune the CFD model in one of the real-test cases investigated.

Estimating the spatial distribution of high altitude wind energy potential in Southeast Europe

High altitude winds are considered to be, together with solar energy, the most promising renewable energy source in the future. Till date, there are no yet solutions available on the market but various concepts for utilizing high altitude winds are under research and are expected to be fully operational within next few years.In this paper, the potential of high altitude wind energy will be investigated for the SEE (Southeast Europe) region and mapped using available data and technologies. The data available from NCEP/DOE analysis will be used in terms of obtaining the high altitude wind speeds for the span of 30 years, from 1980 to 2010, which are then processed for easier visualization. The obtained data is plotted against the available geographic data which could limit the positioning of the system (settlements, traffic…). The result of this work will display the “optimal” locations for these kinds of facilities for the Southeast Europe region. Such map could be beneficial for all future plans of utilizing this high altitude winds as a power source.

Harvesting high altitude wind energy for power production: The concept based on Magnus’ effect

High altitude winds are considered to be, together with solar energy, the most promising renewable energy source in the future. The concepts based on kites or airfoils are already under development. In this paper the concept of transforming kinetic energy of high altitude winds to mechanical energy by exploiting Magnus effect on airborne rotating cylinders is presented, together with corresponding two-dimensional per-module aerodynamic and process dynamics analysis. The concept is based on a rotating airborne cylinder connected to the ground station with a tether cable which is used for mechanical energy transfer. Performed studies have shown the positive correlation between the wind speed and mechanical energy output. The main conclusion of this work is that the presented concept is feasible for power production.

Analysis on lightning triggering possibility along transmission tethers of high altitude wind energy exploitation system

Recently a new concept of umbrella–ladder combination system to exploit the high altitude wind energy has been proposed. In this system the polyethylene polymer transmission tether plays an important role as the connection between the high altitude wind power absorber and the ground station. To make the concept practical, whether the tether would lead lightning to the ground station is one of the key issues. In this paper, the possibility of the polyethylene polymer transmission tether triggering lightning is studied. Firstly, the lightning environment characteristics are summarized, especially the possible potential distribution and electric field distribution. The charge structure of the thundercloud and the lightning activities which may affect the high altitude wind energy absorber are described. Secondly, the ways of the tether triggering lightning under thunderstorm in static electric field produced by charge accumulated in thundercloud and in impulsive electric field produced by lightning are analyzed. The lightning impulse characteristic of the tether and the influence factors on it are obtained through experiment and the result shows that the critical lightning impulsive breakdown electric field is about 300kV/m. Therefore there is a great possibility that the tether triggering lightning. Finally the simple lightning protection for the system is discussed.

High-Altitude Wind Energy for Sustainable Marine Transportation

This paper investigates the use of a controlled tethered wing, or kite, for naval transportation. Linked to a boat by light composite-fiber lines, the kite is able to fly between 200 and 600 m above the sea and to generate high traction forces. A mechatronic system named Kite Steering Unit (KSU) that is installed on the boat controls the kite and converts the line speed and force into electricity. Different from previous works, the boat is also equipped with electric propellers so that naval propulsion can be achieved both directly, i.e., through the towing forces exerted by the lines, and indirectly, i.e., through the electricity generated by the KSU that is fed to the electric propellers via a battery pack. The optimal system operating conditions that maximize the boat speed for the given wind characteristics are computed. Then, a model predictive controller is designed, and numerical simulations with a realistic model are carried out to assess the performance of the control system against the optimal operating conditions. The results indicate that, with this system, a completely green naval transportation system can be obtained, regardless of the wind direction.