COMMERCIALISING WAVE ENERGY

WAVE POWER: Water has long been used as a source of power. But using waves for the production of electricity is new. It has been discussed for the last hundred years, but only now is it starting to be commercialised. One of the players involved is the Danish company Wave Star Energy.

Managing director Per Resen Steenstrup has a strong determination to exploit wave power. His company is called Wave Star Energy, and over the next three years he expects to employ 12 engineers to develop a full-scale wave machine for electricity production.

Wave Star Energy was founded in 2003 with the aim of commercialising wave power. Per Resen Steenstrup has been interested in exploiting the energy in the sea for a long time, and now he has a serious opportunity to realise his ambition.

“It is very difficult to get started because even the simplest prototype must be extremely well constructed. When I began, I found a total lack of comparisons between different wave power systems. It seemed as if everyone before me had started up without building on existing knowledge. I learned from the experience of others and discovered the following essentials: the wave machine must be storm-proof, the technology simple and the price per kilowatt competitive with offshore wind power.”

Uninterrupted operation
Wave tank tests were carried out in a collaboration with Aalborg University. “That was in 2004,” says Per Resen Steenstrup, “and in 2005 we built a 1:10 scale prototype. It was made from standard components, so the construction time was unusually short for this industry where everyone prefers to start from scratch. The prototype was towed out to Nissum Bank on the west coast of Denmark, where it stands in two metres of water. The wave machine is 24 metres long with 20 floats on each side, which generate electricity from the upward pressure of the waves.

The floats are 1 metre in diameter, and can generate electricity from waves of just 10 cm in height. To function best the machine should be oriented so that the waves pass along its length. In a way you can compare it with a giant 40 cylinder engine. The prototype has been built in exactly the same way as the full scale 240 metre long Wave Star machine will be in the future.” The prototype has an output of 5.5 kW, sufficient to supply the electricity needs of two family homes.

“The wave machine has functioned without interruption since July 2006, and has operated for about 4,000 hours up to December 2006,” says Per Resen Steenstrup. “It is a major milestone that the machine has functioned for a period equivalent to the lifetime of a car. It has given us operational experience and lots of enthusiasm to continue. We are already building a 1:2 scale model of a 6 MW machine, which is the final objective. But initially we will test and document the production figures of the 1:2 scale model, which generates 500 kW. This will take place 2009/2010 in the North Sea 15 km offshore from Esbjerg on the west coast of Denmark. The wave machine will stand on piles which are driven about 10 metres into the seabed. If the waves become too high, an automatic security system will put the machine into “security mode”. We expect to market this 500 kW Wave Star model immediately thereafter,” says Per Resen Steenstrup.

Environmental benefit
Wave machines do no harm to the marine environment. In fact it has been found that the machine at Nissum Bank has actually attracted marine life. Norwegian lobsters have started to congregate around the piles on the seabed. On the underside of the wave machine, seaweed and other forms of marine vegetation have started to grow, thereby attracting many other forms of marine life. Wave Star has now employed an engineer to specifically document the environmentally friendly effects of wave machines.

Wave machines are being constructed for an operational lifetime of 50 years, explains Per Resen Steenstrup. “We expect the machines will need a major overhaul every 10 years. This will be done on land to avoid the expense of offshore activities. The depreciation period is estimated to be under 20 years.”

http://www.wavestarenergy.com