A simple, sail based vertical axis wind turbine design, viewed from above.
Diagram showing approximate status of sails throughout the cycle.
When on the upwind side, the sails produce a lift force as well as a drag force (albeit the drag force is smaller than on the downwind side). This is why my turbine uses sails as opposed to flat blades.
As far as I am aware, this is the only vertical axis sail based design in which the sails extract useful energy from the wind at all points around the circle, as shown by the arrows above. Even when the sails are moving into the wind, some of the wind's energy is being used to move them around the circle. A sail attached to the central tower would be used to orientate the device into the wind at all times (the cogs attached to the central tower would then orientate each blade so they are always facing the wind as in the diagram above).
By using large sails a huge amount of energy will be captured from the wind, and by using eight sails, there will be virtually no 'space' through which the wind can get through without affecting the sails. If you look at the three sails on the left hand side, energy that is not utilised by the first sail (as not all the energy in the wind can be removed from it, otherwise the sail would be motionless) is used by the sail behind it, and so on. As the first sail on the left hand side (bottom left) moves upwards, the wind that is above it which still has some energy left will act on the second sail (left hand), as well as any wind that has managed to get past the first sail and hit the second one, etc.etc.
When I initially came up with the idea above, many years ago, I had no idea if it was possible to produce this sort of sail position. As luck would have it, a few simple experiments with a very small scale model (about 1 foot across), using toothed gears, proved that it was possible to produce the desired rotation of the sails using a two to one gear ratio, as shown above. This would use chains on a real life model, to reduce friction. (These would be housed inside some sort of bodywork to protect them from the elements.)
As the diagram above elegantly shows, the sails are at all times pointing towards the right hand 'dead' point. This is the point that they are being continually pushed away from when on the bottom half of their path, and continually pushed towards when on the top half.
The diagram above shows more positions of the sails as they move around their path, I am sure some sort of CAD modelling program could be used to show the net forces all the way round the circle, at all times (except for the right hand 'dead' point) the sails are producing some degree of force in their direction of travel, unlike all other sail based VAWT designs that I have seen so far.
