Innovation in renewable electricity generation

The Ocean Harvester is a point absorber based on a patented mechanical power takeoff (transmission) using a counterweight for power smoothing. The power takeoff greatly improves energy capture, efficiency and utilization rate in wave power systems. Approx. 65% utilization can be achieved in good wave conditions with only 5% spill of energy (EMEC wave data used as reference). 

Key advantages

The key technical and cost related advantages of the Ocean Harvester are its:

• Efficient energy capture with the use of a winch system. Energy is absorbed throughout the full rise of each wave (end limits of winch drums never reached). Self adjusting to changing tide levels.
 
• Power smoothing using mechanical power takeoff (PTO) with a counterweight enables peak energy from the waves to be intermediately stored and utilized without the need to oversize components in PTO and power electronics. Mechanical components are much more efficient in terms of processing the highly fluctuating energy from ocean waves compared to hydraulic components.
 
• Power generation with the use of a conventional generator running at a continuous and high speed. Power smoothing in the PTO reduces the working range of the generator which greatly improves efficiency and utilization rate. Compliant to the grid requirements on electrical quality. 
  
  
• Survivability: Winch systems reduce structural strain (end limits never reached). Counterweight limits the mechanical peak loads/torque in the system in all wave conditions. Power takeoff can be disengaged to put the wave energy converter in standby/failsafe mode to survive the roughest sea states. Position moorings (secondary moorings) are used to secure station keeping.
  
  

Power smoothing

The mechanical power smoothing technology developed by OHT is a novel and highly efficient solution with suitable and sufficient power smoothing capabilities for a wave spectrum. OHT´s PTO technology can be engineered for most point absorbers and can as a standalone unit offer the following advantages:

• Converts the slow and highly fluctuating wave motion into a uni-directional rotation with smooth torque and speed, suitable for a conventional high speed generator and for the grid connection in terms of power quality.
  
  
• Approx. 65% utilization rate with only 5% spill of energy is achievable (EMEC wave data used as reference).
  
  
• A mechanical transmission system with approx. 75% calculated average efficiency, including energy storage.
  
  
• Sufficient storage capacity to smooth power over several following waves, which is needed to create a stable power output from a wave spectrum with constantly changing wave sizes.

Commercial objective

Our objective is that the Ocean Harvester Wave Energy Converter will be competitive to offshore wind power in the short term and to conventional power production such as nuclear, coal and hydro power in the longer term.