Power Take Off System

A few weeks ago I made comment about a schematic diagram that CWE attached to the end of their quarterly report.  There was no accompanying description of the diagram.  I suggested it was a "teaser."

To me it appeared that the buoy might have more than one power take off unit housed within the buoy.

The quote from below leads me to believe that was the message they were trying to convey.

The article below is dated March 2016, suggesting it is probably the only information we have on power take off linked to Ceto 6.  The wavePOD PTO has been undergoing testing in Aachen University for about two years, so you would expect substantial progress to have been made.

Given that the development of wavePOD was done using grant money, it seems to me that this power take off system is the favourite to go into Ceto 6.

http://reneweconomy.com.au/carnegie-wave-wins-2m-grant-towards-development-of-uk-ceto-project-29638/

The schematic diagram shows what appears to be three hydraulic units and another three unidentifiable units, (possibly generators???).

"A tenth-scale, 80-kW prototype is currently on test at the Institute for Fluid Power Drives and Controls (IFAS) at RTWH Aachen University, Germany. The test rig simulates WEC motion to generate hydraulic flow to the WavePOD. According to a paper published in the International Journal of Fluid Power, a basic system has two hydraulic cylinders connected to high and low-pressure lines, and check valves control flow from the cylinders to the WavePOD. An accumulator smooths flow of high-pressure fluid to a variable-displacement hydraulic motor, which then turns a generator. Other hydraulic components include a reservoir, feed pumps, pressure relief valves and filters. Mineral oil serves as the hydraulic fluid.

But various WECs interact with waves differently, so a standard PTO must be designed to operate efficiently over a range of inputs. While the basic concept uses a single accumulator in the high-pressure line, the actual set-up uses two sets of accumulators with different pre-charge pressures to better reduce pressure fluctuations. Additional accumulators pre-charge the low-pressure lines to the cylinders to ensure adequate flow and avoid cavitation during fast movements.

Also, instead of a single hydraulic motor and electrical generator, the prototype has three same-size motors connected to generators. This set-up increases performance at low-power wave conditions by only running a single motor at higher efficiency, rather than two or all three at low efficiency. Fixed-speed, asynchronous generators simplify grid connections."

http://www.fluidpowerworld.com/offshore-hydraulics-is-key-to-electricity-from-the-sea/