Aerodynamic blockage and tip-loss effects in a multi-rotor vertical axis wind turbine system

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A novel multi-rotor system (MRS) has been proposed by Peter Jamieson. The design features a column of four 500kW Darrieus H-type vertical axis turbines atop each other, of high aspect ratio (5:1) and 45 degrees out of phase. 24 of these columns will be placed alongside each other, counter-rotating and in groups of four, with structural support between groups and around the whole system.The system may have many benefits. The out-of-phase VAWTs will smooth the torque experienced. For 96 turbines, only 24 generators will be required. Choosing symmetrical blades will allow VAWT units to rotate either direction simply by fitting upside-down. The counter-rotation will have energy production benefits from wake effects, and reduce the net torque on the overall system. The modular nature will ease production, and allow much of the turbine to continue operating should one turbine fail. Neither local nor global yawing will be present, and the system is expected to be floating on a tri-floater. The work of this PhD will be on blockage and tip loss effects. A power increase is expected from aerodynamic blockage effects, perhaps enhanced by the rotors of a VAWT passing the wind twice. It should also be enhanced by the support structure causing further flow concentration, as it is in-line with the rotors, rather than behind them like a HAWT MRS. A guideline on how best to optimise power enhancement will be produced.The high aspect ratio is likely to reduce tip loss significance, however there are additional complexities from the interaction of tip loss vortices from above/beneath and on one/two sides. Time permitting, wake effects may be briefly analysed.