Submersible load measuring pins for tidal power

Ocean and tidal currents are a sustainable and reliable energy system. Minesto’s Deep Green converts tidal and ocean currents into electricity with minimal visual and environmental impact.  Minesto’s Deep Green power plant is the only marine power plant that operates cost efficiently in areas with low-velocity currents.

Minesto needed to measure the strut force in Deep Green’s kite assembly. The measuring device needed to withstand permanent underwater submersion. The load measuring pin’s stainless steel construction and ability to be customised to IP68 submersion rating made this a suitable choice for use in Deep Green’s control system. Its 17-4 PH stainless steel construction makes them perfect for marine and seawater applications. The DBEP load measuring pin was modified to have an IP68 protection rating to a depth of 30 metres and was fitted with a polyurethane (PUR) submersible cable and cable gland, ensuring the entire measuring system was suitable for this underwater marine application.

The load measuring pin needed to fit within Deep Green’s control measuring system. The load measuring pin’s dimensions can be customised to suit a specific design. As Deep Green needed to retain its small and lightweight construction, the DBEP load measuring pin was manufactured to their exact dimensions, ensuring that it fitted within the control assembly without adding unnecessary additional weight to the structure, thus maintaining the efficiency of the Deep Green kite.

Deep Green is an underwater kite assembly with a wing and a turbine, attached by a tether to a fixed point on the ocean bed. As the water flows over the kite’s wing, the lift force from the water current pushes the kite forward. The rudder steers the kite in a figure of 8 trajectory enabling Deep Green to reach a velocity 10 times faster than the water current, generating 1000 times more power. As the water flows through the turbine, electricity is produced in the gearless generator. The electricity is transmitted through the cable in the tether and along subsea cables on the seabed to the shore. Customised versions of our DBEP load measuring pins and DSCC pancake load cells are used within the control system of the kite.

Minesto also needed to monitor the varying tension load of the tether created by the wing.  Using our high accuracy DSCC pancake load cells we were again able to make a custom design to fit into their existing assembly. Our pancake load cells are also manufactured from stainless steel and can be modified with alternative threads, custom dimensions, mounting holes, higher capacities and higher protection ratings. The DSCC pancake load cell used in Minesto’s marine power plant was IP68 rated for permanent submersion in seawater to 50 metres depth. The pancake load cells design delivers excellent resistance to bending, side and torsional forces and its low profile makes it ideal where a low physical height is required.

Within the pancake load cell we fitted a high performance ICA2H miniature load cell amplifier.  The ICA2H miniature amplifier is only Ø19.5mm and 7.6mm high and is designed to fit inside a broad range of strain gauge load cells where a larger amplifier cannot. It has a low current consumption and delivers a 0.1 to 5Vdc high stability output.  Using an integrated miniature amplifier kept Deep Green’s control assembly small and lightweight. The ICA2H miniature amplifier was chosen because of its high stability and fast response which is essential for the safe and efficient operation of Deep Green.