Hydrodynamic Performance And Bench Test Of A Wave Energy Conversion Based On Floating Breakwater

As an abundant renewable energy,wave energy has attracted extensive study over the world due to its wide distribution and high power density.Simultaneously,floating breakwater is widely applied due to its low construction and maintenance cost,insensitivity to geological conditions,and flexibility.Since wave energy has high power density,the impact of water wave on the breakwater can also cause immense environmental loads and serious structural damage.It is,therefore,consequential to reinforce the hydrodynamic performance of and reduce the damage to floating breakwaters.On the other hand,the R&D expense of wave energy converters(WECs)can be very high,which somewhat hind the commercial application of WECs.When a WEC absorbs wave power,it at the same time reduces the wave energy passing through it.This fact puts forward a suggestion to make the floating breakwater and WECs a hybrid system,which can both absorb extra wave power for further use and protect breakwaters.In this thesis,a WEC that inserts a linear generator into a floating flap is designed based on the analysis the dynamic characteristics of existing floating breakwaters wave energy system.The PTO(power take off)system is protected by the shell of the float from harsh marine environment to extend its working life.A series study is carried out.First,the AQWA software that based on the Boundary Element Method(BEM)is used calculate the hydrodynamic coefficients and motion response of the float.An experimental WEC model and a bench system are designed to carry out the design and test of the build-in power generation module.This paper focuses on the mechanical performance of the linear generator module.Because the bench test that based on dynamic simulation test system can verify the power generation performance of the built-in power generation module of the WEC under the premise of saving the experimental cost,and can provide theoretical support for the application in the actual sea state,this paper developed a motion simulation test bench for the experimental sea conditions,simulating the pitch motion of the WEC in the wave.Through the bench experiment,different mechanical parameters(air gap,resistance)and the motion parameters(period and motion amplitude)of the pitch motion simulation platform are combined to obtain the motion response and output power of the built-in power generation module.At the same time,based on the linear damping assumption,the solution method of PTO damping is derived to analyze the effective PTO damping and total damping under different working conditions,and the mechanical efficiency of the PTO system is obtained.Finally,the power generation performance of the floating breakwater wave energy convertion system is predicted according to the efficiency and capture width ratio of the WEC and the average mechanical efficiency of the generator obtained by the bench experiment under pratical operating sea conditions.