Участник:Эйхер/Песочница: различия между версиями
Содержимое удалено Содержимое добавлено
Эйхер (обсуждение | вклад) |
Эйхер (обсуждение | вклад) |
||
Строка 114:
It was shown by Ganuaa ''et al'' that with 100% efficiencies (i.e. no losses in the drivetrain, on the wind turbine or on the propeller) and with no drag other than associated with energy harvesting (e. g. no aerodynamic drag besides the drag of the wind turbine) there no upper limit to the speed for such vehicle neither when travelling upwind nor when travelling downwind (regardless of how small the speed of the wind is). In practice, however, losses in the system and aerodynamic drag of the vehicle's hull limit the maximum speed that can be obtained for a given wind speed.
In both cases the two media travel in the same direction relative to the vehicle - backwards. In the case of going upwind the air is travelling faster than the Earth and in the case of going downwind faster than wind the Earth is travelling faster relative to the vehicle. For a given force imparted by a medium to the vehicle the power delivered to or gained from the meduim is directly proportional to the velocity of the medium relative to the vehicle. Therefore, in accordance with the law of conservation of energy, in order to sustain the motion the vehicle must harvest the power from the medium that moves faster relative to the vehicle and to deliver power to the slower medium.
So the rotor is used to harvest the power from the air when the vehicle goes upwind, acting as a wind turbine and driving the wheels. In such case the rotor feels drag force imparted on it by the air and impedes the motion of the vehicle, while the wheels driven by the turbine propel the vehicle overcoming both the drag felt by the turbine and the drag felt by the hull.
| |||