Integrating Wave and Wind Power

While Europe’s offshore wind sector has taken off, interest is resurging in marine energy. The UK’s Crown Estate took the major step this March, for example, of awarding leasing rights to 10 wave power projects to develop generation in Scotland’s Pentland Firth and Orkney waters of the North Sea.

Successful bidders were chosen from 40 bids, which comprised some 20 different marine energy firms and utilities. Among noteworthy projects were proposals to install three separate 50-MW wave farms by Pelamis Wave Power, E.ON, and ScottishPower. Aquamarine Power and SSE Renewables, meanwhile, have planned a 200-MW wave farm off the coast of Orkney, and the UK’s Marine Current Turbines said it wants to set up a 100-MW tidal energy farm off Brough Ness, on the southernmost tip of the Orkney Islands.

Meanwhile, Danish company Floating Power Plant this April introduced a novel approach to harness power offshore, which combines the best of wind and wave power. The company is in the process of completing a larger prototype of its Poseidon power plant in Lolland, Denmark—a 350-ton floating platform that will be outfitted with wind turbines.

The plant is based on a hydraulic power take-off system: The float absorbs inherent energy from waves and employs a piston pump (using water pressure to turn a turbine) to transform it into power. It also uses a patented anchor buoy system to ensure that waves always meet the front of the plant. The company says it plans to use three 1.5-MW or 2-MW “standard” offshore wind turbines—or possibly a single 5-MW turbine—to increase the amount of power generated from the seas. If it works out, the commercial version of the plant is expected to generate up to 50 GWh a year, depending on the waves and wind.

5. Flotsam and jetsam. Danish company Floating Power Plant has designed and is testing a 350–metric ton deep sea floating platform outfitted with 11-kW wind turbines to harness wave and wind power offshore. The company’s current demonstration platform at Nakskov Harbour will be followed by a commercial version, which the company says could generate some 50 GWh a year. Courtesy: Floating Power Plant

The current demonstration platform (Figure 5)—dubbed Poseidon 37—was launched at Nakskov Harbour, Denmark, in September 2008. Thirty-seven meters (m) wide, the entire platform is 25 m long and 6 m high. The devices that capture wave power beneath the surface are 6 m long and weigh 4.7 tons. This design follows three previous scale models, and in spring of 2010, it entered a high-profile second phase of testing at Onsevig that included cooperation from Danish research institutions. Once tests are completed next year, a massive, nearly 30,000–metric ton commercial version of the plant will be built.