Simplified Tidal Barrage for Small-Scale Applications

The performance of a tidal barrage with no gates and continuous flow through its turbines has been investigated by simulation. Double-effect generation could be achieved with an axial-flow turbine that reverses direction after each half of the tidal cycle. Such a system might be attractive for unmanned operation in remote areas, perhaps on a smaller scale than for conventional barrage systems. Predictions have been made about the energy obtainable from such a system, and the conditions necessary to maximize energy capture have been determined. A mathematical model of a high specific speed turbine, incorporated into the prediction procedures, allowed the behavior of the system under varying tidal range (and hence varying head) to be examined. Differential heads across the turbine are somewhat less than those achievable with a gated barrage, and performance is correspondingly affected in very small tidal ranges. Variable-speed turbine operation was found to be beneficial in these circumstances. Overall levels of predicted output were very encouraging and compare surprisingly well with conventional barrage schemes. The concept would seem to merit further investigation.