Submersible Load Cells Lower the Cost of Large Tidal Turbine Designs

AIM – Assess the Performance of Alternative Large Scale Tidal Turbine Designs

close up of tidal turbine test rig
Tidal turbine test rig using DDEN submersible load cells to measure torque and thrust in a state-of-the-art test tank.

Industries:

  • Marine
  • Hydropower
  • Renewable Energy

Products Used:

One of the costlier items in current large >15m diameter tidal turbine designs is the rotor blades.

The EPICTidal Team consisting of Lab-Sea-Systems Dr Florent Trarieux, Cranfield University’s Dr Joao Amaral-Teixeira and Nick Barlow, Managing Director of Designcraft Ltd (UK-based blade design and manufacturer) wanted to know the performance implications of employing lower cost methods for the manufacture of large scale tidal turbine rotors.  Lowering the cost of rotor blade manufacture would make this renewable energy more economical to use and widely accessible, benefiting not only the UK tidal energy markets but developing tidal energy countries too.

Solution – DDEN Submersible Load Cells

To assess the rotor blade performance they developed a submersible tidal turbine test rig incorporating 2 x DDEN load cells.  The rotor blade design to be tested was coupled to the tidal turbine test rig and placed in a state-of-the-art test tank, where the team were able to increase the size, flow rate and turbulence levels within the tank.  The first DDEN load cell measured the torque and the other measured the thrust of the tidal rotor design.

“The DDEN were ideal to use in this application as they are fully submersible up to 10 metres” explains Bob Davies, Applied Measurements’ Production Director.

DDEN In-line submersible load cell with 10m PUR cable
The DDEN submersible load cells were fitted with 10m of PUR cable to guarantee complete submersible protection.

The DDEN in-line submersible load cells are low profile and very compact and designed to measure both tension and compression underwater.  They come with an IP68 rating and are sealed using ‘O’ rings to guarantee integrity during long term submersion.  Their IP68 rating and ‘O’ ring sealing makes them ideal to use underwater or in areas at risk of flooding.  The DDEN submersible load cell comes in capacities from 0-250N up to 50kN with customised capacities, threads and dimensions on request, as well as versions rated to greater submersion depths in seawater, oil and other more aggressive media.

For this submersible application the DDEN load cells were fitted with 10 metres of submersible 4-core screened polyurethane cable for complete submersible protection underwater.  They have a guaranteed accuracy to <±0.15% of the rated capacity (0.05% typical) enabling precise thrust and torque blade measurements which was crucial to this renewable energy application.

DDEN Submersible Load Cell Outputs

DDEN submersible load cell with ica miniature amplifier
The ICA amplifier shown in the above image fits inside the DDEN load cell to deliver a high performance analogue output.

A small ICA6H amplifier was fitted within the bodies of both the DDEN submersible load cells.  At only 19mm diameter this amplifier is ideal for fitting inside the body of a load cell.  An ICA6H amplifier was used in this application so it could easily fit within the load cell, maintaining the submersible protection needed for underwater testing.   The ICA6H load cell amplifier delivered a high-level ±10Vdc analogue output, for use with their data acquisition and control systems.

Other outputs are available for the DDEN including 0-5Vdc, 0-10Vdc or 4-20mA, which can be used with many data acquisition and control systems.  For a digital output, a DCell load cell digitiser can be used instead of an ICA to deliver a RS485 digital output.

If you have an underwater application you would like to discuss, then please contact our technical sales team using the quick enquiry form on the right or email us on [email protected].

For more information about this exciting renewable energy project read the article Rotor Tests With DesignCraft Ltd – Haslar Series on Lab-Sea-Systems Website.