By Tyler Seed

While much attention on renewables in recent years has focussed on solar and wind technologies, awareness has been growing around the enormous energy generating potential of the Earth's oceans. A 2005 report from the Electric Power Research Institute stated that wave power properly and effectively harnessed, would likely have minimal environmental impact, and be much less visible on the landscape, than competing technologies. At the same time, waves possess the advantage of being more predictable than either wind or solar, which in principle makes ocean power a more reliable source of energy.

The rapidly expanding field of wave power is rife with innovation and an extraordinarily diverse range of approaches. Several technologies have been, and are being, developed and tested in coastal regions around the world. So far however, technical challenges involved in engineering a sufficiently inexpensive, efficient and reliable method of extracting this energy have proven difficult enough that as yet there is no agreed upon 'best way' to do it.

Among the significant difficulties facing engineers of commercially viable wave power have been durability in storms, and low generating capacity factors resulting from the difficulties of extracting a steady load from constantly shifting wave motions. Irregular and alternating wave motions lead to large variations of the power produced, severely limiting the power output of many Wave Energy Converters (WEC).

Mikael Sidenmark, founder of Ocean Harvesting Technologies, and the inventor of the Ocean Harvester (pictured above), has developed a method of generating electricity from waves that offers compelling and cost-efficient solutions to these problems.

As Sidenmark explains:

A buoy follows the wave motions at the surface. When the wave rises, a drum inside the buoy is rotated by a mooring line wound around it, converting vertical motion into a rotation. This is a very efficient way of extracting energy from waves that is independent of the wave sizes and has been used in earlier technologies.
What is unique with the Ocean Harvester is the way a counterweight is used to achieve a leveled and controlled load on the generator. As a result, excess energy from larger waves can be accumulated and used to compensate for shortage from smaller waves. In combination with the flexible mooring, this also composes a simple and efficient storm protection system.
Together, these characteristics result in an exceptionally high capacity factor.
The system should produce a consistent level of power throughout the wave motion, over changing wave sizes, and even in storms. Besides generating efficiently and evenly, the simplicity of its design will allow the Ocean Harvester to be easily protected in rough conditions, and make its manufacture impressively cost-efficient.

Ocean Harvesting Technologies is currently planning a two-year scale model testing period, slated to begin in March 2009 in the coastal Blekinge region of Sweden, on the Baltic Sea. The company expects the Ocean Harvester to enter the commercial market in 2013.

The AquaBuOY
Image source: Finavera
Institutions across Sweden are researching further possibilities of wave energy. Among those with notable programs are Uppsala University, Blekinge Institute of Technology (BTH) (where wave power research initiated with the Ocean Harvester in February 2008), and at Chalmers University of Technology, where researchers were involved in pioneering the AquaBuoy, a concept now being tested on a commercial scale.

Read more about innovations in wave energy in the Worldchanging archives:

Wave Energy (2005)

The Wave Hub (2006)

Biomimetic Ocean Power (2006)

Graphic Series: Earthly Ideas, Week 10: Ocean Power (2008)

Tyler Seed is completing a Masters' degree in Sustainability at Blekinge Institute of Technology in Karlskrona, Sweden