A zoo of wave energy solutions

Despite 40 years of development, there is little convergence in wave energy systems. The current diversity limits further development, said Kim Nielsen during his ocean energy lecture yesterday.

(Image: Google, adaptation Jos Wassink)
(Image: Google, adaptation Jos Wassink)

The energy density of falling water in hydro-power inspired the Danish wave energy veteran Kim Nielsen to start developing wave energy solutions while he was a student. His bölgeenergimaskinar (wave energy machine) had a generator on the seabed connected to a floater which bopped up and down with passing waves. A scaled-up model with a six metre diameter worked well on the rugged Danish coast, but not for long. It had to be towed back due to a broken piston.

Grassroots development program

The Danish government had set up a grassroots development program in the late 1990s. It offered 10,000 euros to inventors who came up with a plausible idea to harvest wave energy (incoming energy is estimated as much as 40-80 kilowatt per meter coastline). The result was a series of prototypes with names like Wave Dragon, Floating Power Plant, Wave Plane, Wavestar and Pelamis.

An ocean energy websitetracks the different technologies, projects, and companies. It categorises the 'zoo of solutions' into three categories: the oscillating water column types, oscillating body types (such as Nielsen's first project) and overtopping devices.

But this wealth of ideas also has a drawback. Experts like Nielsen find it difficult to give a price per kilowatt-hour for wave energy because of the large variety in the systems. Investors face the same problem. They don't know which is best technology to for their money.

In comparison, in offshore wind energy a great convergence has taken place. One wind turbine looks very much like the next, at least superficially. At the same time, wind power has seen a dramatic drop in price per kilowatt-hour and growth in investments. Wave energy, on the other hand, is still very much in the prototype and demo phase and investments lag behind.

See also:

TU Delft page on Wave Energy.