Durban-based mechanical engineering draughtsperson Doug Da Costa has developed and patented a near-shore wave power generator that collects wave energy from its entire surface and from every wave travelling through it, which it converts into electricity.

Many other devices currently under development collect energy from a single point, making them less efficient, says Da Costa, who is the managing member of Spring Master.

A unique aspect of the device is that all the equipment, including the hydraulic systems and electrical generators/switchgear, are housed inside the sealed pontoons, protecting them from harsh sea conditions.

The first full-scale prototype device, approximately 30 m wide and 110 m long, is expected to produce between 1 MW and 1,5 MW of power, depending on its location.

Locations will have to be granted by government, as certain areas are allocated for different uses.

Da Costa says a 1:50 scale model has been tested at the Council for Scientific and Industrial Research's (CSIR's) marine engineering research centre, at Stellenbosch, and hasproved that the concept works.

"We were able to take somemeasurements of linear deflections of the torque tubes against eachwave size, but the scale was too small to conduct meaningful tests.

"Weare very grateful to the CSIR for using its research funding toconduct the tests and are delighted that it has now installed abigger wave generator facility tank that will enable us to test a 1:10 scale model. We have applied to the Indusrial Development Corporation and the Innovation Fund for further development funding, and both have informed us that they will give us an answer this month.

"Ifwe can test the 1:10 scale and it is successful, we will be able tobring on board a commercial partner to inject funds into the project."

The device consists of two parallel pontoons about 3,5 m indiameter, between which are pivoted floating torque tubes with shaftsoperating actuator arms. These operate hydraulic cylinders pumping oilinto a hydraulic system, which operates hydraulic motors drivingelectric generators.

Moored at 20 m to 30 m sea depth, thedevice, like others, is connected to the shore by an electrical cable,which makes the efficiency of wave power collected the crucial factorin determining cost effectiveness.

Da Costa, who developed the wave power generator with his sons, Carl and Adrian, says the family has already held discussions with Eskom, which hasindicated that it will be happy to look at the device on a commercialbasis and motivate for capital expenditure once a 1:10 scale modelhas proved its effectiveness.

Adrian Da Costa says that once independent power producers come on board, they will also be in themarket for the device, as they will be able to sell power generatedfrom ocean waves to Eskom, a common practice in the US and the EuropeanUnion.

The device can also be used simultaneously todesalinate sea water, with the added advantage that the salt can bepumped straight back into the ocean, without polluting the land, says Adrian Da Costa. He adds that 25-million litres of sea water a day could be pumped intoa desalination plant, which would convert about one-third of this intofresh water.

Doug Da Costa says that, if only 10% of South Africa's 2 800-km coastline was used to generate wave power, it could generate approximately 8 400 MW, based on an average wave intensity of 2,5 kW/m wave crest, which is equivalent to three coal power stations. Eskom's current nominal capacity is 42 00 MW.

He estimates that it will take about five years to put all the infrastructure in place, but says individual modules could be rolled out much sooner.