SUMMARYThe suitable hybrid configuration of Darrieus lifttype and Savonius drag-type rotors for stand-alone wind turbine-generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up. Type A installs the Savonius rotor inside the Darrieus rotor and Type B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behavior of the system operated at the maximum power coefficient points show that Type A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational axis, is an effective way for stand-alone small-scale systems.

No abstract

13To attain the highest performance of energy supply systems, it is necessary to 14 rationally determine types, capacities, and numbers of equipment in consideration of 15 their operational strategies corresponding to seasonal and hourly variations in energy 16 demands. In the combinatorial optimization method based on the mixed-integer linear 17 programming (MILP), integer variables are used to express the selection, numbers, and 18 on/off status of operation of equipment, and the number of these variables increases 19 with those of equipment and periods for variations in energy demands, and affects the 20 computation efficiency significantly. In this paper, a MILP method utilizing the 21 hierarchical relationship between design and operation variables is proposed to solve the

No abstract

A suitable load control method for a constant tip speed ratio operation of stand-alone systems using vertical axis wind turbines with a self-starting capability is discussed from the viewpoint of its power generation capability and output fluctuations. This study takes up a stand-alone system with a straight-wing-type turbine, which is mainly operated at a constant tip speed ratio. Two types of load control methods are considered: Method-1 wherein the load torque is controlled in proportion to the square of the rotational speed and Method-2 that adopts a feedback control of the rotational speed in response to the inflow wind speed. The computational results using the dynamic simulation model show that the decrease in the output fluctuations from Method-1 to Method-2 is much larger than the increase in the power generation capability from Method-2 to Method-1. Therefore, it is concluded that Method-1 is the suitable load control method.