a new wave energy converter ...... looking for investors
Francis J.M. Farley
A flexible air tight bag V1, entirely under water, is inflated with compressed air. It is held down by a ballast weight which roughly balances its buoyancy. At the top the bag is attached to a float which heaves in the waves. This excites a much larger resonant oscillation of the ballast. The bag is alternately squeezed and expanded and pumps air through a reversible flow turbine into a fixed volume V2 on the float. V1 and V2 are sealed and inflated with compressed air. No water can get at the turbine.
The float is bell-shaped. The water trapped inside heaves with the float, adding inertia and lengthening the heave period. Any air trapped inside vents to atmoaphere through a small tube (not shown)
In 1975 Budal & Falnes showed that a small heaving float can capture power over a frontage equal to the wavelength/(2 pi). But in the open ocean there is no fixed reference for the float to work against and perhaps drive a pump or turbine. Many solutions have been tried, pumps connected to the sea floor, horizontal plates which move less, counter-moving masses with different resonances; all eventually abandoned, too expensive or too delicate. WAVEBELL does not need a reference: the ballast hanging below the flexible air bag has its own motion separate from the float and this (miraculously) generates the power by pumping air.
NO MECHANICAL MOVING PARTS !! No levers, links, hinges; no pistons, no sliding seals, no flaps, no one-way valves. No limit stops, nothing to break, nothing to lubricate. The only moving parts are the turbine (a standard component) and the flexible bag. The life of the flexible bag needs to be studied but potential manufacturers are optimistic.
There are two coupled resonances, the float with its natural heave period, and the bag/ballast combination with its own period. So the capture width covers a wide range of wave periods with two peaks, both reaching the theoretical value of wavelength/(2 pi)
(see graph below)
British patent GB 2522074 is granted. International patents pending.
For more information and detailed calculations contact
Capture width in metres versus wave period in seconds
Very wide band response due to the two coupled resonances