An idea struck me about tidal power....

...how about a series of floats,tethered to the ocean floor at low tide and then released at high tide and their rise used through reduction gearing to power large flywheels and then slip belted to generators....six hours later the tethers could be drawn back in or re-shackled...think gyro toys and minutes of power multiplied by the limits of flywheel size and bearing efficiency-and I know from personal experience that air pressure bearings should allow massive inertial loads and high rotational speeds...any thoughts???

There's enough power in a bolt of lightening to do a lot of things, but we cannot harness it because it comes too fast and too hard.

While your proposal would allow the power to be distributed in time, in order to generate a signifigant amount of power, it would also involve a very large amount of force to be supported by the system -- the float would have to be extremely large, the forces involved in holding the float down while power is trickled through the mechanics very large as well.

In general, you'll find the most effective power systems harness low-level forces that are easy to build around -- a constant flow power that will not overwhelm the structure of a small device. So tidal tends to use horizontal flows where the water flow is effectively deflecting that energy into higher-speed, lower force form.

Tidal is a promising avenue I would say. My personal favorite is wave power, but I think we need to attack this on all fronts with every form of generation we can muster.

(EDIT: Oh and by the way, off topic, but you might like this little beast here: http://en.wikipedia.org/wiki/Underwater_gliders)

...and believe that capturing drifting waters (currents,tides,river flow,etc...) is both good and soon necessary,though fish breeding makes impoundments dams problematic,meaning that seasonal flow streams will take longer to be brought on line.But being from New England and having traveled the Bay of Fundy, I pictured a tethered float (think concrete in the ocean bed as anchors) pulling a large cogged belt through a drive like a child's gyro toy,but on a massive scale...the downside is just what you describe-just 2 massive inputs in a day-but the upside is also interesting in terms of ecological disruption-instead of a large fixed installation of gates there would be just the floats that would block passage till submerged but then be of no effect until released on the next high tide-after their release they would float,again with no ecological impact till tethered at the next low tide....If staggered then even a series of floats would merely impede,not block,marine species even at low tide...so that was the thought,and as always the big problem with any "free energy" is storage and it's efficiency....But I did love your low impact Floaters reference just as much as I love solar soarers...

the sea tends to destroy everything, whether slowly or quickly. It would be a large energy investment in device infrastructure which may not be "paid off" before the inevitable downtimes, replacement parts, rebuilding, rendered it impractical. (sorry to be a pessimist).

Say your float was 100m x 100m x 4m, and could rise 5m. It displaces a maximum of 40000 cubic metres of water (a bit less in reality, allowing for the weight of the float and associated machinery), with a mass of 4 * 10^7 kg - 40,000 tonnes (as skids says, there's a lot of force involved). The potential energy of that rising is 'mgh' - 4 * 10^7kg * 10m/s/s * 5m = 2 * 10^9 joules - about 500 kWh. So in a day, you get 1000 kWh (if your machinery was 100% efficient - it won't be, of course), and an average American household currently uses 8900 kWh per year - about 25 kWh per day, so that's 40 houses powered from a behemoth the size of 2 football pitches, if it is perfectly efficient. In practice, I don't think you'd be able to even approach that kind of efficiency = you've got to convert the weight of 40,000 tonnes into a torque.

Very few ocean power systems produce enough electricity to justify the maintenance costs. The more complicated an ocean system is, the less likely it is to be economical.