1. Betz revisited Prof. Guy Houlsby Department of Engineering Science Oxford Tidal Energy Workshop sponsored by the Oxford Martin School 30 th March 2012

2. Classical Lanchester-Betz theory –An oversight –An additional calculation –Resolving these problems Betz for an open channel

7. Calculation Results

8. Optimal conditions as

11. PLAN view of channel

13. Conclusions Anomalies in the original Betz calculation can be resolved by treating it as the limiting case of a confined flow Efficiency can be calculated An “inner and outer” calculation is proposed for flow in a channel