Hehe, thanks for the cue, Audie. For those who haven't realized it, I run the commercial side of an ocean-wave energy company. So I'm very bullish on using moving water to produce power.
To help the discussion, there are five categories of water-based generation:
- Traditional hydro: dam-across-a-river a la Hoover Dam. This is a mature technology and represents nearly all of the hydro-power production.
- Pumped storage: a variant of traditional hydro, where the generator turbines can be reversed to pump water back up into the reservoir.
- Tidal: uses the fact that tides create a "head" between the high- and low-tide mark
- Current: uses the flow of water to generate power. Note that many installations in tidal zones are actually using the current, not the head; such generators have to be able to flip around or use bi-directional input.
- Wave: uses the action of ocean swells to generate power. See, e.g. Ocean Power Technology or Pelamis.
The invention you provided the link to is in #4. I'd like to see the calculations of how they get to 5 cents/kWh; in particular, have they included in that number all the maintenance, licensing, installation, interconnection, and taxes? Regardless, even if that's low by a factor of two, it's a good number.
I am not an engineer, but I don't see anything about their technology that strikes me as fishy (pun intended). I like several elements of the design, including the general robustness of the structures, the use of flexible mooring cables (instead of fixed mounts), and simplicity of design. Presumably they have data regarding interaction with riverine fauna, and they've figured out how to deploy these in navigable rivers. If would want to know how they deal with currents above the rated speed (if that's a potential issue during, say, spring flooding), and how survivable the device is after impact with large objects e.g. tree trunks, boats that have slipped mooring.
On the whole, though, I think this is a promising technology that could tap an under-used resource.