Slow Chat II

[PierreB]

@dougselsam

and only now generating an independently-verified power curve, seems like an oxymoron. Normally, a power curve is a first step for any new wind energy system.

Hi Doug, you are never happy. However, we will have to be content with it. I very much doubt that more radical news could arise in this field which is getting tired.

@dougselsam

Power a house

My advice: buy a classic wind turbine rather than an AWES. The first works, the second does not work, whatever the theoretical improvements.

Betz limit and power available in the wind

The Betz limit takes account of energy extraction slowing the wind, whereby a lot of the wind goes around the rotor disc, just as we avoid going into a store if the prices are too high. And even the air that has had energy extracted must still be left with some energy in order to leave the volumetric region of energy extraction, to allow more wind to enter.

Here we are talking about the 4/27 limit, applicable to an AWES in pumping mode, and which is 4 times lower than the Betz limit (16/27). See also what I say about a tether-aligned (not crosswind) parachute in pumping mode and with a high Cd:

Betz limit and power available in the wind

In two steps: Betz limit 16/27 is 4 times the limit in pumping mode which is given for 4/27. The paper details the reasons. I see a simple reason: the swept area, in pumping mode, is dragging at 1/3 wind speed which is reel-out speed, keeping 2/3 wind speed. So the force (measured by the square of wind speed) becomes 2²/3² = 4/9. Power is force x reel-out speed: 4/9 x 1/3 = 4/27. The parachute takes the whole area of power available in the wind, if we do not take into account wind deflections…

@dougselsam

Seems to me the number of non-flying ship sails, (or at least the amount of proposals and renderings), greatly outnumbers the number of kites pulling ships.

I am thinking of boats rather than ships.