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

To exploit the high altitude wind energy, a concept of umbrella-ladder combination system, in which the polyethylene polymer transmission tethers play an important role, was proposed by a company. This paper studies the lightning impulse characteristics of polyethylene polymer transmission tethers. First the lightning environment characteristics are summarized, especially the potential of thundercloud can be 100MV and the maximum electric field strength of thundercloud reaches about 1000V/cm. The high altitude wind energy absorber will reach into the small lower positive charge region at the base of the thundercloud. Secondly, experiments are performed to get data of the lightning impulse breakdown voltages of the polyethylene polymer tethers with different pollution degree and different humidity degree, the lightning-withstand strength per unit length tether is tested as 250kV/m. Finally, the possibility the tether to triggers the lightning and causes a flashover along itself is discussed while the system is working.

Kite energy is radical advancement in wind power age. The innovation utilize the strong high-altitude wind of the lower atmosphere and proselytes it into power by methods of power kites. This paper shows the explanatory and numerical computational experiment to see the reaction of generator and inverter for high altitude wind energy utilizing parafoil kite. Here a methodological model of kite energy framework is presented. All numerical computational experiments are perceived in ANSYS Electronics Environment and MATLAB SIMULINK Environment. Also, the hardware setup of inverter integrated with high elevation wind energy system is presented in this experiment. The conduct of the kite is tested in Hmuifang village of Mizoram state.

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.

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

The power kite is a kind of high altitude wind energy (HAWE), which is a still untapped source of renewable energy and has received an increasing attention in the last decade. Automatic control of power kites is a key aspect of HAWE generators and it is a complex issue, since the system at hand is open-loop unstable, difficult to model and subject to significant external disturbances. In order to deal with this issue, a new kind of adaptive predictive functional controller (APFC) is presented in this paper. With subspace identification for predictive model of kites, the maximum generation controller is designed to control kites using PFC principles. The APFC, which is a combination of on-line identification, learning mechanism and predictive controller, is presented to solve the nonlinear real-time receding horizon optimization. The stability of control system is guaranteed by closed-loop subspace identification. The implementation of closed loop control system is given, and the proposed APFC approach for kite control results to be quite effective, as it is shown via numerical simulation tests.

High Altitude Wind Power (HAWP) can supply clean energy at low cost and high capacity factor than Conventional Wind Power (CWP) system. The concept of harvesting high altitude wind power using air-borne wind turbine-cum electric generator supported by light gas filled blimp/aerostat has been proposed in the paper. An air-borne wind turbine at high altitude extracts kinetic energy from high speed streamlined wind using buoyancy provided by the blimp. Using a suitable power electronic converter (PEC), harvested electrical power is transmitted to the ground by using a tether. Blimp is tethered to the ground and provides mechanical strength to hold the blimp and the same tether consisting of electrical conductors is used for transmitting the generated electrical power. The paper outlines major components used for harvesting high altitude wind power. Transmission of the electrical power at medium voltage DC reduces the transmission loss and volume of the conducting cable. The optimal transmission voltage level that gives minimum weight of the tether has been calculated for a given power level. The proposed HAWP system requires high power density PEC, which converts low voltage AC to medium voltage DC in an airborne unit and a ground based PEC that transforms medium voltage DC to distribution level grid voltage. An air-borne PEC converter consists of a rectifier and an isolated DC-DC converter that supports the unidirectional power flow. Further, the paper also proposes the ground based grid-side PEC for distributed grid interface. In addition, comparative study between conventional wind energy harvesting system and high altitude wind energy harvesting system shows that high altitude wind power is better in terms of capacity factor, Cost of Electricity (COE), ease of construction, and power density than conventional wind power generating system.

Kitenergy is an emerging technology in airborne wind energy (AWE) that captures high altitude wind energy (HAWE) by exploiting its controlled flight of tethered wings. Compared with its ground level counterparts, AWE has the advantages to harness wind energy with a higher efficiency and a more consistent behavior. Automatic control of the kite's airfoils is crucial to the proper running of kitenergy systems. In this paper, a control oriented model of a tethered kite system is developed step by step, and a simplified state-space model is established as a first attempt. Based on this model, a nonlinear model predictive controller (NMPC) is designed to track a pre-optimized figure-eight trajectory. The merits of the NMPC are validated by simulation studies on a practical-scale kitenergy system model.

The power kite is a kind of high altitude wind energy (HAWE), which has received an increasing attention in the last decade. The unique feature of the kite-based system is its structural simplicity coupled with the complexity in its modeling and control. Since the system is open-loop unstable, it is difficult to model and it subjects to significant external disturbances during operation. To address these challenges, nonlinear predictive functional controller (PFC) is presented in this paper. Firstly, a predictive model is established for the power kite using hybrid neural network, and then the PFC principles are applied for its controller design. With the neural network structure, the PFC integrates on-line identification, learning mechanism and predictive controller. A closed-loop control system is developed and implemented to improve the performance of the power kite. The effectiveness of the proposed approach has been illustrated by numerical simulation tests.

High altitude wind energy (HAWE) is a new field of renewable energy that has received an increasing attention during the last decade. Many solutions were proposed to harness this energy including the usage of kites, which were for a long time considered as child-toys. An overview on HAWE and its exploitation technologies is presented, followed by focusing on the the kite-based systems. Proposed structures and scenarios are presented, discussed and compared.

Electrical field distribution along the insulator surface is considered one of the important parameters for the performance evaluation of outdoor insulators. In this paper numerical simulations were carried out to investigate the electric field and potential distribution along silicone rubber insulators under various polluted and dry band conditions. Simulations were performed using commercially available simulation package Comsol Multiphysics based on the finite element method. Various pollution severity levels were simulated by changing the conductivity of pollution layer. Dry bands of 2 cm width were inserted at the high voltage end, ground end, middle part, shed, sheath, and at the junction of shed and sheath to investigate the effect of dry band location and width on electric field and potential distribution. Partial pollution conditions were simulated by applying pollution layer on the top and bottom surface respectively. It was observed from the simulation results that electric field intensity was higher at the metal electrode ends and at the junction of dry bands. Simulation results showed that potential distribution is nonlinear in the case of clean and partially polluted insulator and linear for uniform pollution layer. Dry band formation effect both potential and electric field distribution. Power dissipated along the insulator surface and the resultant heat generation was also studied. The results of this study could be useful in the selection of polymeric insulators for contaminated environments.

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

High altitude wind energy (HAWE) is a new field of renewable energy that has received an increasing attention during the last decade. Many solutions were proposed to harvest this energy including the usage of kites and wings. In this paper, a novel wind power system based on a tethered wing is presented. An observer-based control strategy that avoids the need for precise knowledge of the dynamic model is then applied. Numerical simulations show the performance of the proposed control scheme which is validated in real time on an indoor experimental set-up of Gipsa-lab control system department.

Fostering of high altitude wind energy (HAWE) resources above 200 meters is a recent promising technology that seeks to capture the strong wind currents at high elevations. Among the many concepts of airborne wind energy (AWE) generators, the soft-kite pumping-cycle (PC) concept promises to provide a very lightweight, high power density, and cost-effective solution. In this study, the impact of the load-cycle on the lifetime of the machine-side converter (MSC) is examined. By employing a physics-of-failure estimation approach, the main pumping-cycles and the machine speed-reversal were identified as the primary adverse influencers of the IGBT and diode solder joints. Whereas, wind speeds around 12 m/s contribute the most to the predicted degradation. To fulfill the thermal limitations and the lifetime requirements of the application, an optimum converter dimension is found using linear scaling of the semiconductors chip-area and the heatsink thermal impedances. With the generation (reel-out) phase power defined as the base value, the results suggest that the converter needs to be scaled by at least 150 % to meet the thermal constraints, and by 350 % to approach the target lifetime of ten years.

This paper presents a simple concept of harvesting high altitude wind power using air-borne wind turbine-cum-electric generators supported by light gas filled blimp/aerostat. Air-borne wind turbine at high altitude extracts kinetic energy from high speed streamlined wind using buoyancy provided by the blimp. Using a suitable power electronic converter (PEC), extracted electrical power is sent to the ground using a tether. Blimp is tethered to the ground and the same tether is used for electricity transmission as well. This paper outlines major components used for harvesting high altitude wind power. Transmission of power at medium voltage DC reduces the transmission loss and volume of the conducting cable. The optimal transmission voltage level is determined that gives minimum weight of the tether for a given power level and proposes a simple and high power density power electronic converter, which converts low voltage AC to medium voltage DC in an air-borne unit. Simulation results obtained prove efficient power conversion using the proposed power electronic converter. In addition, comparative study between conventional wind energy harvesting system and high altitude wind energy harvesting system shows high altitude wind power is better in terms of capacity factor, cost of electricity (COE), ease of construction and power density than conventional wind power generating system.

High altitude wind power (HAWP) generating system poses several benefits over conventional wind power (CWP) generating system. An air-borne electric generator is held at high altitude above the ground surface with buoyancy provided by light gas filled blimp/aerostat. In order to minimize the size of the blimp and to reduce the number of electric components in the air-borne system, generation of electrical power is carried out at three phase medium voltage AC (MV-AC) and transmitted to the ground station (without any power conversion) using electromechanical tethers. Thus, transmitted power is interfaced into the distribution level grid at 415 V and 50 Hz. This paper evaluates possible power electronic converter (PEC) topologies that can be used to convert variable voltage and variable frequency three phase medium voltage AC power into constant frequency distribution level grid voltage. Three different PEC topologies are proposed that allow generation and grid side current control and generation side maximum power point tracking (MPPT) control. In addition, the proposed PECs provide step down of voltage and electrical isolation with the distribution grid. Suitable active and passive components are selected for 100 kW HAWP system and overall semiconductor losses are evaluated. The converters are simulated using computer software programs PSIM-9 and MATLAB. The converter that exhibits good efficiency, easy control of generation and grid side current as well as facilitates MPPT control of HAWP generation side is selected for grid interface of isolated HAWP system.