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Report KD 598 about a floating water turbine availabe

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Adriaan Kragten:
Public report KD 598: "Ideas about the 3-bladed VIRYA-0.65 water turbine with 20 degrees inclined shaft coupled to the generator of the VIRYA-2.68 windmill for 12 V battery charging", from November 2015, can be copied for free from my website: www.kdwindturbines.nl at the menu KD-reports.

This report describes a floating water turbine which is coupled direct drive to the PM-generator of a windmill for which a measuring report (KD 78) is available. The 0.65 m diameter rotor of the water turbine is designed using the same theory as also used for wind turbines and the characteristics therefore can be estimated accurately. The construction is rather simple but has not yet been tested.

keithturtle:
The attached report addresses some of the complexities of extracting power from a moving stream.  Probably makes sense to get the most velocity you can to drive the impeller.

Somewhere I saw a spiral VAWT-looking impeller that claims to get more energy than a propeller type, but can't find it just now

Turtle

Adriaan Kragten:
I have looked at the article about ducted water turbines. It is true that the water speed can be increased by a well designed venturi and ducting the rotor also has as advantage that the rotor can't touch the bottom of the river. However, manufacture of such a venturi is a lot of work, rather costly and it requires special skills. So I think that one should do this only for rather large designs.

In report KD 598 I have described an option for which I think that it can be made by almost every small workshop. It is meant for 12 V battery charging and in figure 6 of KD 598 it can be seen that even for low water speeds, an acceptabel power is supplied for a single house hold.

Adriaan Kragten:
Report KD 598 has been reviewed. Some small mistakes have been corrected and a new part is added to chapter 6. This new part gives the characteristics for star rectification and 24 V battery charging.

Adriaan Kragten:
A new chapter 7 has been added to report KD 598 about the VIRYA-0.65 floating water turbine. In this chapter it is investigated if the matching in between rotor and generator can be improved by taking a simple 2-bladed rotor with a slightly smaller rotor diameter of 0.625 m in stead of 0.65 m and a design tip speed ratio of 3.5 in stead of 3. The matching of this VIRYA-0.625 for 26 V battery charging and star rectification of the original 230/400 V winding is better than for the VIRYA-0.65. The better matching results in reduction of the cut-in water speed from 0.7 m/s up to 0.6 m/s. The starting water speed is increased from 0.37 m/s up to 0.5 m/s but, as it is still lower than the cut-in water speed of 0.6 m/s, this is no problem. The maximum power at V = 2 m/s is 160 W, so the same as for the VIRYA-0.65. The negative effect of the slightly smaller rotor diameter is compensated by the better matching.

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