I know a small self made Kaplan turbine,
which is in use with a friend of mine.
It is about 1 kW and with high technologies
such as automatically adjusted vanes.
The flow head is there low, a few meters.
I think that the good performance with
that machine is because of the really
high level workmanship of the machine.
In general as far as I know it is easier
to make a crossflow turbine than a well
working Kaplan turbine.
I will ask my friend to check this discussion
and about further details of his Kaplan.
- Hannu