That was my knee jerk reaction, but really the way you would do this wouldn't actually HAVE big water flow/ecological considerations. You aren't just going to pump it back up from downriver, you're going to build a reservoir at the bottom sized on the capacity of energy storage you're adding. Your fixed water cost is the amount it takes to fill that reservoir, (which you could in theory refund in case of a drought by pumping it back into the river) Your marginal water cost is the additional evaporation that takes place in a reservoir. So in theory from a water management standpoint, you're almost just adding additional water reservoir capacity.

Exactly what everyone wants to see, a mathematical proof. Of course if you look at his free body diagram and his second equation. You'll see that he has his force vector Fp going the wrong way. He shows the apparent wind on the propeller causing it to propel itself in the opposite direction. Also includes the drag force on the turbine but not on the propeller. Ironically not that it matters at this point, but later he also assumes that a wheel functions identically to a water turbine, which is actually not the case in this scenario. So yeah, like 90% of sensationalist science, does not hold up to more than casual scrutiny.

1) i'm not sure why you point out that a sailboat cannot go faster than windspeed. It can, just not in the same direction as the wind. Look up how sailboats/airfoils/tacking actually works. 2)I hate it when people use treadmill arguments its virtually never the same thing as the "actual" setup. one thing people forget is that wheels are 0 velocity at their contact with the ground REGARDLESS of actual speed provided there is no slip (the highest point is 2 times speed at the highest point on the wheel) If there is no wind there is no way to beat the treadmill (no way to keep up if you don't ignore losses) The question is how is this energy supposedly being extracted. The treadmill has only 1 way to impart energy into the system and that is through the traction/friction of the wheels. Take a wheel on a perfectly efficient/0 friction bearing and no friction from the air. (not possible obviously) that is supported off he treadmill and allow the wheel to get up to speed. The wheel would maintain speed, there would be no force imparted to the bearing from the wheel because there would be no relative motion between the point of contact of the wheel and the treadmill. No energy is being imparted into this system at all. It's all well and good to talk about extracting energy, but this setup doesn't do it.

Intresting concept. One huge logical flaw. speed at a point on the wheel that is in contact with the ground is 0. Speed at a point on the wheel that is at the top of the wheel is 2 times the velocity of the wheel. If you're trying to go DIRECTLY downwind the apparent wind of the sail will never be greater than ground speed.

No fan of bush here.
But, for those who think this is just a move by the government to jack up oil prices.

-The government is not instituting a ban on solar plants. This directive is about whether or not the government supports solar plants by using government land to build on.
-Key point: There is a difference between solar panel (light to electricity) and solar thermal (light to thermal to electricity) solar panel. I'm not an expert on this so I'd suggest if your interested to read up on them seperately.
Key Features of Solar Panel
-buildable in small scale to large scale (personal use or plant wide)
-EXTEREMLY ABSORPTIVE OF LIGHT, captures virtually all of it, but...
-EXTREMELY inefficient. Not just because of slow technology but because of theoretical limits of silicon.
-Less effective in hotter climates. Heat is a limiting factor on these, and since they're absorbing it all too... This is bad for power plants because of all the heat from collecting and transmitting power.
-This means that if you put a solar panel on your roof, you will get some electricity, however you will also heat up your house to a larger degree then if you had a reflective rooftop.
Solar Thermal
-collects solar energy on a tank of some sort and uses that to generate energy.
-inefficient on small scale much more efficient on large scale Many of the new plants such as the 300MW plant developed in Arizona are based on this technology.
-The hotter the better! Some can generate electricity hours after the sun goes down.
Long story short, I THINK that someone realized that there is potential here, but it should be researched properly before we go forward with this. I just wish someone had done the same thing for ethanol...