Yea, I question this a bit. States, "The smallest unit would be likely to produce about 5kW at 15 knots." A quick reference check using a CP of 0.40 and rounding 15 knots down to 17mph suggests a "swept area" of 500 square feet, roughly 22 feet high and wide. That is a very large superstructure to go hanging up in the air for 5kW. A traditional 25 foot radius turbine would have a difficult time producing 5kWh in a 17mph wind, and I suspect this turbine would as well.
I went and did some reading up on the "Tesla turbine" as I was unfamiliar with it. Very interesting indeed. I am not sure it is applicable to modification for wind use, but it would seem to be an interesting choice for low pressure steam. It also appears to have a very high TSR (in this case Edge Speed Ratio may be more accurate). There are a bunch of youtube videos, and in one of them a tach showed 17k RPM with ~40 PSI of compressed air! I am not exactly sure how that works out in mph or TSR, but it was pretty impressive hearing it "spool up".