Modelling load and vibrations due to iced turbine operation

Wind energy in icing and low-temperature climate has a huge growth potential, but rotor icing effects on turbine dynamics and lifetime are not well known and simulations with iced rotor are not required in current IEC 61400-1 turbine design standard. In this article, simulations with iced rotor are compared to measured mechanical loads. The dynamic behaviour of the wind turbine was simulated with FLEX5 aeroelastic code for Senvion MM92 2 MW wind turbine. Simulations with typical iced airfoil lift and drag coefficients, aerodynamic and mass imbalances for iced rotor were performed and compared to measured iced turbine loads. Resulting iced turbine simulation parameters can be used in defining new design load cases for cold climate turbines. The most representative simulation parameter combination was achieved with a symmetric aerodynamic penalty applied on all blades and an asymmetric rotor mass imbalance of 166 kg ice load on two blades and 83 kg ice load on one blade

An invitation to market design

Market design seeks to translate economic theory and analysis into practical solutions to real-world problems. By redesigning both the rules that guide market transactions and the infrastructure that enables those transactions to take place, market designers can address a broad range of market failures. In this paper, we illustrate the process and power of market design through three examples: the design of medical residency matching programmes; a scrip system to allocate food donations to food banks; and the recent 'Incentive Auction' that reallocated wireless spectrum from television broadcasters to telecoms. Our lead examples show how effective market design can encourage participation, reduce gaming, and aggregate information, in order to improve liquidity, efficiency, and equity in markets. We also discuss a number of fruitful applications of market design in other areas of economic and public policy