Fishing Boat Becomes Wave Power Plant

Is it possible for a redundant fishing vessel to be used as a power plant? Absolutely. The first vessel of its kind is now anchored offshore in the Stadthavet area west of Ålesund, Norway.

"In principle, it works almost like a bicycle pump," says engineer and Project Manager Edgar Kvernevik of Kvernevik Engineering.

For the last two years his company has been working with Geir Arne Solheim, the founder of Havkraft and the man who came up with the idea, to develop and build the wave power plant now installed in a former trawler.

The makers installed four large chambers in the vessel's bow. As the waves strike the vessel, the water level in the chambers rises. This creates an increase in air pressure which in turn drives four turbines – one for each chamber. The pitch of the vessel also contributes by generating additional air pressure in the chambers when the wave height is large. The design of the chambers is such that they work in response to different wave heights, which means that the energy is exploited very effectively.

"The plant thus produces electricity with the help of what is called a fluctuating water column," explains Kvernevik, who has spent much of his working life designing and building vessels. "All we have to do is to let the vessel swing at anchor in a part of the ocean with sufficient wave energy. Everything is designed to be remotely-controlled from onshore."

The fluctuating water column concept is a tried and trusted approach. However, installing a wave energy plant inside a fishing vessel is novel.

"This floating power plant has also been equipped with a special anchoring system which means that it is always facing into the incoming waves," explains Kvernevik. "This ensures that the plant is in the optimal position at all times."

One of the organizations contributing to the project is Marintek, which has developed a mathematical model and run a number of simulations of the plant. This has provided developers with a better overall picture of how much energy can be extracted from the waves. The project has advanced on the basis of analyses, model experiments and full-scale simulations.

The nominal capacity of the plant is 4 x 50kW – 200kW in total. Marintek's computations indicate that the plant is capable of producing 320,000 kWh per year.

Even though the principle behind the plant is simple, there is a lot of advanced engineering installed on board. None of the moving parts are in direct contact with salt water. In fact, the only moving parts are the turbines, which are installed above the vessel's deck. 

The vessel is currently located offshore Stadtlandet, in an area where the company Stadt Wind has a renewable energy testing license.

A study of an offshore wind farm (the 1080MW Stadtwind project, involving floating wind turbines) was previously carried out in the same area. The Norwegian Water Resources and Energy Directorate (NVE) subsequently declared the area as one of the few in Norway suitable for the installation of floating offshore wind farms. 

The annual average wind speed measured in the area is 11 m/s, which is higher than any other location in Norway, including the North Sea. This indicates that the area is clearly well suited to the exploitation of renewable energy from wind and waves, which is interesting because in the long-term, the project plans to look into the possibility of combining floating wave power plants with wind turbines.

"We see this project as a three-stage rocket," says Kvernevik. "The first stage is to test the model we have just built to make sure that electricity generation can be carried out as planned. Next, a hydrogen production plant will be installed on board the vessel so that the electricity generated can be stored in the form of hydrogen gas. We have high hopes that hydrogen will be the car fuel of the future. Our aim is to work with others to produce hydrogen at a competitive price – based on an infinite resource and involving no harmful emissions.

"The plan is then to construct a plant with a nominal capacity of 1000kW (1MW). We will do this by installing five production modules similar to the current plant either on a larger vessel or a custom-built barge. Finally, we will build a semi-submersible platform designed to carry a 4MW wave power plant with a 6MW wind turbine installed on top," he says.