Wind Turbine Ice Throw Hazard

F2E Figure1Experiences and Recent Developments in Germany

Ice throw from wind turbines is a serious environmental hazard. Experience in Germany may serve as a contribution to future standardisation of ice throw from wind turbines. No national or international standards exist, but they are urgently needed. The aim of this article is to give an overview of the critical points which should be assessed in a future guideline.

By Thomas Hahm and Nicole Stoffels, F2E Fluid & Energy Engineering, Germany

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Wind–Tidal Energy Storage

wind tidal storage fig 1An Integrated Energy Storage System

Wind speed is unpredictable and variable such that the power output from wind turbines often does not coincide with demands from the national grid. In the UK, constraint payments are made to wind farm owners when the turbines are shut down because of lack of demand for their power. Clearly the wind farm owner would wish to sell any energy generated whatever the demand and also be able to deliver higher power if necessary on demand. Here a novel wind–tidal integrated storage power generation system is described that addresses these issues.

By Mike Lewis, RGL Associates, UK

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A Wind Turbine Inside a Wind Turbine

Mucsy Figure 1v2Using Pneumatic Power to Generate Wind Energy

Over 60 years ago a 100kW test wind turbine was built with pneumatic power transmission in southern England (Figure 1), based on a design patented by M. Andreau. Test results from the turbine showed a lower energy extraction than was obtained by wind turbines with conventional mechanical power transmission, and therefore the pneumatic power transmission was abandoned, without attempting to improve it. Our team has re-investigated this type of transmission, and following a number of patented innovations we have been able to considerably improve on the previous results. We are now hoping to upscale our working models for field testing.

By Dr Endre Mucsy, Hungary

Below we discuss the differences between conventional and pneumatic turbine types and their resulting properties. Why was the potential of pneumatic power transmission underestimated and abandoned? What design changes did we make to improve the efficiency of the pneumatic turbine, and how have we tested them? Finally, how much energy is there in the wind and what proportion can be utilised?

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NGC StanGear

NGC Figure1A Serialised and Standardised Product Platform for Wind Drives

NGC StanGear is a serialised product platform based on an application database, standardisation, and a modularisation concept for wind gearboxes. The approach of NGC is based on its experience of over 50,000 NGC main gearboxes supplied to the market worldwide as well as a comprehensive data analysis of the turbine and gearbox market. The database includes operational parameters for different power classes. From the technology side, the different materials, manufacturing methods and design features have also been considered.

By Dr-Ing. Valentin Meimann, Mr Yizhong Sun, Mr Sudong Li, Mr Aimin He and Dr-Ing. Jianhui Gou, Germany and China

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Analysing the Lifetime of a Wind Turbine

Holzmuller 1bOperation Beyond Design Life

According to IEC 61400 [1], the lifetime of a wind turbine is a minimum of 20 years . However, differences between the design loads and the actual loads on site can lead to the possibility of operating the wind energy converter (WEC) longer than the design life. Using an aeroelastic simulation the individual overall lifetime can be calculated for each main component.

By Jürgen Holzmüller, President, 8.2 Group, Germany

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Edgewise Vibration and Wind Turbine Blade Failure

Investigating the Causes and Mitigating the Risks

EV Figure 1Edgewise vibration (EV) is an aeroelastic resonant phenomenon induced by the wind that can occur when a wind turbine is parked with a brake applied or idling (e.g. not producing power). While EV is an infrequent event, the authors have conducted several blade failure investigations that identified EV as the mechanism of failure. The investigations involved blades designed and manufactured by multiple entities, with blade lengths ranging from approximately 40 metres to more than 80 metres. This range encompasses most utility-scale blade lengths currently in production. EV is a specific case of vortex-induced vibration, where shed vortices in fluid flow around a structure impart forces to the structure, resulting in oscillatory motion. EV is characterised by increasing blade deflections (Figure 1), primarily in the edgewise direction, that (for the context of this article) results in blade damage.

By M. Malkin, Principal Engineer, and D. Griffin, Senior Principal Engineer, DNV GL, USA

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Service Life of Blade Bearings

Problems Faced in Service Life Estimation of Blade Bearings

Schwack Figure1The blade bearings of wind turbines allow the required oscillation to control the loads and power of the wind turbine. The pitch system brings the blade to the desired position by adapting the aerodynamic angle of attack. The pitch bearing, which is connected to the blade and the hub of the turbine, is subjected to high axial forces and bending moments. The conditions of these bearings are unique and most standards to estimate bearing service life are designed for rotating bearings and do not consider the oscillation. This article gives a brief overview of the current problems of blade bearings. The article focuses on the tribological challenges like fatigue life calculation of oscillating bearings, different wear damage modes like false brinelling and fretting wear, grease lubrication and the contact conditions occurring under different operating environments.

By Fabian Schwack and Prof. Dr.-Ing. Gerhard Poll, Institute of Machine Design and Tribology, Germany

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