General > General Technical Chat
Unusual design of a free-flow hydropower station
Andy Chee:
--- Quote ---Закон сохранения энергии в гидродинамике vs понятие альтернативной энергии. Критические заметки по поводу статьи «Альтернативная энергетика vs лженаука»
и цитированных и нецитированных в ней работ.
The law of conservation of energy in hydrodynamics vs the concept of alternative energy. Critical notes on the article “Alternative energy vs pseudoscience”
and works cited and uncited therein.
--- End quote ---
ebastler:
I don't think this proposal conflicts with the conservation of energy. I just think it is not very practical.
You can, of course, design a device which extracts energy from water by using the difference in the water's potential energy (i.e. a height difference) rather than its kinetic energy. And you can arrange things such that the water flow speed is higher after the device than in front of it. This device is called a dam. 8)
And you can, of course, create a "dynamic dam" by putting some obstruction into flowing water. This will also create a height difference behind vs. before the obstruction, and a speed difference (because you slow down the flow in front of the obstruction). By letting some water flow through a little turbine or whatever other mechanism you fancy, I'm sure you can extract some power.
I have no idea whether and how the guys in the initial video are connected with the guy who wrote that paper. Their contraption with the "blades on a belt" seems like a very inefficient way to create an obstruction in flowing water and extract some power from it.
tggzzz:
--- Quote from: Hydro on January 03, 2024, 12:13:45 pm ---
--- Quote from: eutectique on January 03, 2024, 12:06:13 pm ---Thank you.
Perhaps, this explanation brought you to some conclusions, practical or otherwise.
Would you please share them in 3-6 sentences?
--- End quote ---
It can be done in one sentence.
"A principle has been developed on which free-flow hydraulic turbines of various designs can be designed with increased energy efficiency"
--- End quote ---
So what? Principles mean absolutely nothing until they have been demonstrated to be correct and independently duplicated.
Science 101:
* observe something
* develop a principle/hypothesis that explains the observation
* based on the principle/hypothesis, make a prediction that can be proved and disproved
* develop a test that for that prediction, ensuring it proves or disproves the prediction
* do the test
* publish the principle, the prediction, the test, and the test results in sufficient detail that someone else can duplicate them
* if necessary, return to (2)
So far you have only mentioned step two. Where are steps 3,4,5,6,7 documented?
IanB:
--- Quote from: ebastler on January 03, 2024, 03:13:37 pm ---You can, of course, design a device which extracts energy from water by using the difference in the water's potential energy (i.e. a height difference) rather than its kinetic energy.
--- End quote ---
Practical hydro-power units make use of elevation difference (head, potential energy), since this is much more useful energetically than velocity (kinetic energy).
For example, to change the elevation of 1 kg of water by 1 m corresponds to a potential energy change of 9.8 J. To change the kinetic energy of that 1 kg of water by the same 9.8 J you would have to accelerate it to 4.4 m/s or 16 km/h, which is much faster than the typical flow velocity of a river, which would typically be only a fraction of that.
Therefore practical small scale hydro-systems (like water wheels) divert the water down a side channel while the river falls, and then let the water descend back to the river over the wheel, using gravity to do the work.
Well engineered hydraulic turbines can have a mechanical efficiency around 90%, so there are only marginal gains to be made by improving on this. Claims of a 3x improvement in efficiency would only hold water if the original efficiency was less than 30%, which is terrible by most standards.
In any hydro-power system, if the water leaves the apparatus at high velocity it is taking kinetic energy with it and therefore reducing the efficiency.
Hydro:
--- Quote from: ebastler on January 03, 2024, 03:13:37 pm ---I don't think this proposal conflicts with the conservation of energy.
--- End quote ---
I think so too. Or rather, I'm sure of it
--- Quote ---This device is called a dam. 8)
--- End quote ---
The fact of the matter is that it is without a dam
--- Quote ---I have no idea whether and how the guys in the initial video are connected with the guy who wrote that paper. Their contraption with the "blades on a belt" seems like a very ineffective way to create an obstruction in flowing water and extract some power from it.
--- End quote ---
The guy who wrote the article, in my opinion, did not show any design at all, only a diagram.
Does the guy’s contraption from this video also seem ineffective to you?
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