The Ocean Grazer is a massive platform housing various renewable energy generator modules including wave, wind and solar that will be deployed in deep ocean waters. Its core technology, contributing about 80% of the energy generation, is a novel wave energy harvesting and storage device termed the multi-pump, multi-piston power take-off (MP2PTO) system. The MP2PTO system can adapt itself to extract energy in an efficient manner from wave heights varying between 1 and 12 meters and wave periods between 4 and 20 seconds. The Ocean Grazer is expected to have a combined average energy output of 260 GWh per year, enough to power approximately 70,000 households per device.

Since the availability of wave energy and energy demand are fluctuating over time, the Ocean Grazer’s MP2PTO system incorporates a large reservoir which can store 800 MWh of loss-free potential energy. Energy can be extracted from this reservoir by multiple hydroelectric turbines with short start-up times, so as to be able to potentially balance fluctuations between energy supply and demand, as well as provide a constant energy output over multiple days.

The Ocean Grazer structure itself will be made of concrete, protecting the system against ocean water and wind, while its massiveness will ensure stability even in the most extreme weather conditions. Similar to an iceberg, the core part of the Ocean Grazer structure will be situated well below the ocean surface such that the influence of ocean waves is minimized and the survivability of the structure is increased. The structure itself has a diameter of 435 meters and a height of 255 meters, of which 30 meters is situated above the ocean surface. 

In addition to the MP2PTO system, several other power take-off systems will be installed as well on the platform, including wind turbines and photovoltaic systems, which are all well-proven technologies. 

Ocean Grazer structure

The Ocean Grazer is a massive platform of which most is situated below the sea surface.

The MP2PTO system

The core innovation of the Ocean Grazer, the MP2PTO system, comprises a grid of interconnected floater elements (a floater blanket), with each floater being connected to a piston-type hydraulic pumping system (a multi-piston pump). Unlike conventional point-absorber systems, the floater blanket’s tightly-spaced interconnected floater elements can minimize radiation effects and hydrodynamic energy losses.

Each multi-piston pump is powered by one floater element to internally displace a column of working fluid between a lower and an upper reservoir, creating hydraulic head. Each floater element within the floater blanker can therefore gradually extract the energy from an incoming wave, so that all of the wave’s original energy will have been extracted by the time it exits the Ocean Grazer structure. Conditioned water is used as a working fluid within the internal hydraulic circuit, with enhanced lubrication properties to reduce the wear and corrosion of all internal components.

MP2PTO system

Schematic drawing of Ocean Grazer with the
multi-pump multi-piston power take-off system.