Having identified the requirement for a viable vertical axis turbine, FreeFlow 69 designed the Osprey. A model rotor was constructed and successfully tested and a half size model of the prototype was fabricated to assess stresses and specifications of components required. The full size prototype was designed and manufactured based on the findings of the model turbine.

To test and validate the prototype, in a range of simulated flows, a 30’ aluminium catamaran test rig with surveying capabilities was designed and built by our associate company Able Engineering.

The test rig includes a purpose made hydraulic scissor lift for lowering and retracting the turbine into the flow and is fitted with the following instrumentation... 

  1. Calibrated hydraulic braking system to measure torque.

  2. Rev counter.

  3. Log - boat/water speed.

  4. Depth sounder.

The test rig is fitted with two engines for low to medium speed trials to prove the concept and validate the predicted output.

Having proved the concept and confirmed the output, the research project is ready to move to Stage 3, as soon as funds are secured.


The objective of Stage 3 is to fully optimise the performance and output of the Osprey prototype turbine, at low, medium and full speed trials.

Accurate data from these trials will be available and will be used to calculate the cost of the installation and maintenance, of the Osprey, relative to output of electricity produced.  The components of the turbine will be tested for reliability prior to commercial use.

Following the trials a feasibility study of the first commercial river system to be connected to the National Grid, incorporating an array of Osprey turbines, will be produced.

To be covered in Stage 3:-

  1. Purchase of fluid dynamics computer software.

  2. Analysis of fluid flow using new software.

  3. Optimise prototype blade size and shape.

  4. Matching of performance of port rotor against starboard rotor with different blade configurations.

  5. Duplication of instrumentation for confirmation of data.

  6. Modifications to test rig including the fitting of more powerful engines to conduct full-speed trials.

  7. Design and incorporate venturi deflectors for boosting power.

  8. Update computerised power output model for future applications and financial budgets.

It is planned for Stage 3 of the project to now be completed before the end of summer 2009.