Savonius AWE kite?

[PierreB]

@PierreB

In this paper, see the “Figure 5 – Streamlines around turbine with no gap (left) and with a gap (right)”, and the corresponding text pages 4 and 5 (just below the Figure 5):

Blackwell et. Al. from Sandia laboratories [6] were testing 15 two and three buckets configurations. They were changing the non dimensional gap size and the orientation for the three buckets configuration. Yet they used only circular sections.They found that except starting the two buckets configurations showed better performance, 0.24-0.28 power coefficient at 1 unit speed ratio (tangential velocity over wind speed).The three buckets configurations reached to only 0.14-0.16 power coefficient for the same speed ratio. The latter configuration performed as reported in fig. 3 but the two buckets with an opening is almost double in efficiency.

The correct reference is [5] and is linked below the reference quote:

5. Blackwell B. F., Sheldahl R.E. and Feltz L.V. Wind Tunnel Performance data for two and three bucket Savonius Rotors, SAND76-0131, Sandia National Laboratories.

SAND-76-0131.pdf

@PierreB

The latter configuration performed as reported in fig. 3 but the two buckets with an opening is almost double in efficiency.

The difference of efficiency between two and three buckets seems to be much larger than the difference from gap (opening) and no gap.

Indeed the Figure 39 (a) page 84 represents max Cp of 0.22 with no gap (s/d = 0), a little less with gap (s/d = 0.2), and 0.24 with gap (s/d = 0.1 to 0.15).