© 2015 Ocean Harvesting Technologies AB
Wave power could provide 10-15% of the global demand for electricity. But there are technical challenges to solve before wave power can be produced at a competitive cost.
Waves move slowly and vary considerably in size. The peaks of captured power can be more than 30 times higher than the average. It is therefore challenging to build cost effective systems that can convert the irregular and power-ful movements of the waves into a smooth electrical output.
The power take-off (PTO) in a wave energy converter must use energy storage to smooth power in order to reduce cost and increase efficiency of components in the system. The PTO must also control the damping force applied to each buoy in every wave to increase the power capture and annual yield.
OHT offers wave power buoy developers a hub system with a central tower and a hydraulic power transmission system to collect the power from a large number of buoys. The captured power from the buoys is transfered to the tower through a hydraulic piping system in the form of high pressure fluid.
A hydraulic motor in the tower converts the hydraulic flow into mechanical power, which is then smoothed by a gravity storage technology and converted into a constant electric power output by a generator.
The hub system is based on a highly efficient power take-off (PTO) which integrates seamlessly with the buoys. A gear rack and variable hydraulic pump can be used in the buoy to provide the damping force control that is necessary to optimize power capture. The PTO enables energy storage over consecutive waves as well as detailed damping force control of buoys to optimize power capture.
The tower is a generic component based on wind power technology. Most wave power buoys can be designed to export a hydraulic flow to the collection system, instead of converting power to electricity directly on board. Read more
OHT´s patented gravity storage technology smoothes the captured power before electricity is generated in a very efficient way. Round trip efficiency of the gravity storage is > 95%.
A large weight is lifted with a rack and pinion drive inside a tower. A planetary gearbox with a floating ring gear connects the weight to the drive train and enables the generator to operate with constant speed and torque. The power output is constant and tuned to the sea state by changing the speed of the generator.
The gravity storage system provides a constant torque and pressure to the complete system, which reduces the cost and increases the efficiency of the power take-off compared to using hydraulic accumulators to smooth the captured power.