Aren’t all parasail systems governed by the Cosine-cubed law? At a tether angle of 30°, the power losses are 35% due to this law. I believe that this value should be reflected in the formula for tether tension where the area is not the true area of the parasail, but the subtended area due to the angle of the parasail to the horizontal. This loss is considerably more than the possible losses due to wake separation.
To avoid these losses, would it not be advantageous to launch the parasail system from a high tower so that the tether is approximately horizontal? This tower could be a light weight system, supported by guy wires. At the top of the tower there would be a transfer pulley, which will direct the tether tension to a ground-based generator.
Advantages:
- All parasails are at a higher elevation, and so the average wind velocity is greater.
- Parasails will not fall to the ground if the wind stops blowing.
- Land area around the base of the tower can be used for other purposes.
- When not in use, the parasails can be stored vertically.
- Launching and landing the system is easier.
Disadvantages:
- Additional costs.
- Small efficiency loss due to the transfer pulley.
- For changes in wind direction, the transfer pulley must be re-oriented. (The present system has even more problems if the wind direction changes.)