Improved wave power yields more energy
Wave power is a huge unexploited source of renewable energy. Uppsala University is conducting research on wave energy in a facility off the west coast of Sweden near Lysekil. In his dissertation Jens Engström has shown how the facility’s present units can be improved to convert even more wave energy into electricity.
In recent years research on ways to convert waves into energy has taken off, largely due to the growing environmental debate and the insight that the dominating energy sources are finite. Several projects, both private and university-based, are now taking the final steps toward developing full-scale wave power arrays and commercialization. The world’s seas present a renewable source of energy on the order of a terawatt from surface waves, which is estimated to play a significant role in meeting the growing energy needs of the future.
In 2002 the Division of Electricity at Uppsala University started to develop a wave power concept. The concept was called the Lysekil Project and is based on a direct-drive linear generator connected via a line to a buoy on the surface of the sea. In 2006 the first test facility was set up just outside of Lysekil. Since then eight more units (L2-L9) have been deployed, along with an underwater relay plant, and electricity has been delivered on shore.
Jens Engström’s dissertation is part of the research project and focuses on the transport of energy in the ocean waves and increasing the energy conversion efficiency between the waves and the buoy. The latter part involves coupled equations for both wave/buoy interaction as well as electromagnetic equations to describe the generator and the electrical circuit.
One major objective of the dissertation has been to increase the energy absorption of the unit. The results of the research have led to a conceptual two-body point absorption model based on the Lysekil unit, a concept in which a sphere with neutral buoyancy is placed between the buoy on the surface and the generator on the sea floor. The purpose of the extra body is that its own mass and hydrodynamic inertia will increase the inertia of the system and thereby affect the natural oscillation period.
The findings show that the system’s natural oscillating period can be adapted to typical Swedish climate periods. Simulations with the two-body model show that the system finds resonance and dramatically boosts the conversion of energy, with up to 80-percent energy conversion in the two-body system.
These findings present an enhanced way to calculate the transport of energy in ocean waves in the coastal zone and indicate a way to dramatically increase the energy conversion efficiency of the existing Lysekil concept.
More information about the Lysekil Project.
Linda Koffmar