Air bags for the 'Clam' wave energy device

The Lancaster Flexible Bag and the Sea Energy Associates Clam utilise a rubber-coated corded material as the primary water/air interface. In both cases air, at slightly more than atmospheric pressure, is held partially under water. As peaks and troughs in the waves approach these bags, the air is forced to leave and then re-enter the bags and, in so doing, passes through a turbine where its energy is extracted and ultimately converted to electricity. These flexible rubber bags permit reasonably good matching of the device to the incoming wave energy and hance promote efficient energy capture. To ensure a life of several years the bag must remain buckle and kink-free throughout its operational range of volumes and pressures. A two-ply cross-corded arrangement is described with the angle between the cords chosen to provide anisotrophy in the elasticity and strength of the bag. By judicious choice of this angle the differing vertical and horizontal requirements of the fabric can be satisifed. (A)