Consequences of Magnetic Properties in Stainless Steel for a High-efficiency Wave Power Generator

Abstract: A new kind of wave power generator is being developed at KTH Royal Institute of Technology which potentially can reach an efficiency of 98 %. However, this generator’s small air gap sets strict requirements on the stiffness of the structure to withstand the large magnetic forces. The structure, therefore, need to be both stiff and non-magnetic. To tackle that problem austenitic stainless steel will be used. Then again, austenitic stainless steel tends to become slightly magnetic because of impurities and mechanical stress. The purpose of this report is to study the magnetic properties of the austenitic stainless steel and observe how mechanical stress can change their properties. Moreover, economic and environmental aspects considering the use and production of the steel are studied. Two experiments were applied to measure the magnetic properties, using an LCR-meter and an electrical circuit with a current amplifier. Both methods showed that mechanical stress will result in changing the magnetic property of austenitic stainless steel. Some steel types were less affected by the mechanical stress applied leading to the conclusion that they are more effective when placed near the generator’s air gap. Regarding sustainable development, it is uncertain to determine the impact the generator has on the environment, mainly because of the steel types manufacturing process is unknown. On the contrary, the maintenance costs of the generator are predicted to be low and if the prototype fulfills the efficiency expectations it will have a huge impact on the future of wave power technology.