To counteract one of the most urgent environmental issues in the Baltic Sea; eutrophication, excessive algal blooms and hypoxia, a proposal to use wave energy to pump oxygen-rich surface water towards the sea bottom is investigated. Proposals have suggested that 100 kg of oxygen per second is needed to oxygenate bottom water and enhance binding of phosphorus to bottom sediments.
This corresponds to 10 000 m3/s of oxygen-rich surface water. This thesis investigates a wave-powered device to facilitate this oxygen ux. Results give expected water flow rates between 0.15 – 0.40 m3/s and meter breakwater.The mean specic wave power for the analyzed wave data is calculated to be between 3 – 4 kW/m wavecrest and the median to 1 kW/m.
This study indicate, however, that the energy uxes in the BalticProper are signicantly higher. The study gives that the wave climate of the Baltic Sea is suffciently intense to facilitate vertical pumping with a feasible number of breakwaters. A full-scale implementation in the Baltic Sea would require some 300 to 1 200 oating breakwaters of a length of 50 m each. The total cost is roughly estimated to 170 – 680 million EURO. The study also concludes that the interleaving of surface water should be constrained to a relatively small vertical distance from the outlet depth(20 – 30 m) and not stir up deep water to the surface.
Wave modelling for the proposed pilot location Kanholmsfjärden indicate that this bay is not large enough to permanently produce a favorable wave climate. It is, however, still an interesting location consistently to its vicinity to Stockholm and relatively long measurement series.
Author: Carstens, Christoffer