Wave power

The Australian-based wave energy company Oceanlinx is to supply up to 2.7MW of electricity to the island of Maui, Hawaii from a system it has developed that extracts energy from ocean waves and converts it into electricity. 

Three of the company's floating wave energy converter (WECs) will be installed about a kilometre off the north coast of Maui, due north of the Pauwela lighthouse. A sub-sea cable will run from the WEC array along the sea-bed with a shore crossing in to the east of Maliko Bay, where it will feed into a substation on the Maui Electric Company grid.

The floating wave energy converter (WEC) itself combines an oscillating water column with Oceanlinx's own patented turbine technology.

Most turbines are designed to function for gas or liquid flowing in one direction and at constant velocity with the blades designed to take advantage of the optimal 'angle of attack'. However, when the flow is not always from the same direction or a constant velocity, traditional turbines become ineffective.

Previous attempts to address this difficulty have mostly resulted in turbines with varying degrees of efficiency. The Oceanlinx turbine, however, uses a different method - variable pitch blades which, with the slower rotational speed and higher torque of the turbine, improve efficiency and reliability.

The WEC itself uses a transducer to identify the height, duration and shape of each wave entering its capture chamber. The signal from the transducer is sent to a programmable logic controller which then adjusts various parameters of the turbine in real time, such as blade angle and speed.

Once deployed off the coast of Maui, the three units could provide clean, renewable energy for more than 4000 homes and save 9000 tonnes of CO₂ from the atmosphere each year on a like-for-like comparison with coal-generated power.

The unit’s performance has been independently verified by a number of parties including Rockwell, the University of New South Wales and the UK wave power consultancy Oxford Oceanics. Oceanlinx also has further project developments and contracts in Europe, Africa and Australia.

Hawaii state has mandated that 20 per cent of electricity should come from renewable sources by 2020, and Maui has a head start, with nearly 10 per cent of its electricity already coming from renewables.