# I want to find the energy capture from a submerged "waterwheel" type turbine with converging plating of 21 degree to form a ducted funnel

The inlet end would be 1.545 m wide x 1.170. The outlet to the flat turbine blades would be 0.806 m wide x 0.67 m and length would be 1.043.5 m. There are 8 x turbine plates of 0.415 m long x 0.67 wide rotating around a shaft at a mean distance of 0.342 m from plate centre to shaft centre. The flow rate at intake is 2 m/s. of sea-water at s.g. of 1.027

• Draw a diagram and max output is based on the energy of the water moving but won't be 100% efficient. Mar 19 at 12:02

Need a diagram and more info for an accurate calculation. It's impossible to know turbine efficiency from your description. Even with images and complete description you would probably need some software to accurately calculate its efficiency. Not a job to be done by hand.
Assuming efficiency of turbine is high (about 30%) and input area to turbine is about 6sf at 4.5mph from this websiteyou can calculate about 750w.

Their formula for power from a turbine is:
Power = (1/2)(Turbine Efficiency) (Water Density) (Turbine Flow Area) (Water Velocity)^3

If you take the input as the beginning of the funnel, and the water retained its energy through the tunnel you might get three times that, or about 2kW if the efficiency of the turbine is 30%.

• Thank you Rich, for such an informative answer. You do agree then, that the funneling will add more energy capture at the blades? Mar 20 at 13:45
• @RayHinks this article about ducted water current turbines gives some details: tethys-engineering.pnnl.gov/sites/default/files/publications/… They say "Put another way, large flow area containing a large amount of energy is concentrated into a smaller area so that a smaller, lower cost turbine can be used for a given power output."
– Rich
Mar 20 at 15:00

In open flow, the power and efficiency are the same as a free propeller with the same diameter as the duct's maximum diameter - less friction effects, of course. Ducts can sometimes help with mechanicals and multimodal operation, but they can't improve power extraction from a given disc area.

• Hi Phil - thanks for your comment but I am conued Mar 20 at 13:31