A wave energy harvesting system based on the double-wing flywheel for unmanned surface vessels

Unmanned surface vessels (USVs) are increasingly used in environmental protection, safe search, rescue, and maritime investigations. These USVs are generally battery or diesel-powered for sailing, and the limited size of USVs results in a lower working life of USVs. This paper proposes a wave energy harvesting system for USVs based on a double-wing flywheel. This system is installed in the hull of the USV and converts the wave energy that causes the USV to vibrate into electrical power. The system can be divided into four modules: wave energy capture module, motion conversion module, electromagnetic transducer module, and circuit module. The wave energy capture module captures the mechanical energy of USV vibration caused by waves and the change of driving state and converts it into the mechanical energy of the mass block vibration. The motion conversion module uses a screw-nut mechanism and the double-wing flywheel mechanism to convert the reciprocating vibrations of the mass block into the relative one-way rotation of the magnet flywheel and the coil flywheel. The electromagnetic transducer module converts the mechanical energy of flywheels into electrical energy and transmits it to the circuit module. The circuit module rectifies the current and stores the electrical energy in a supercapacitor, eventually used to power various sensors. Simulations and experiments were conducted on the proposed wave energy harvesting system. MTS bench experiments confirm a 51.64% increase in energy harvesting power than an energy harvesting device without a mechanical motion rectifier (MMR). Data transfer experiments show that the system can capture wave energy to drive temperature and humidity sensors for data transmission. The results show that the energy harvesting system can be practically applied to USVs to improve their service life.