Solar panels quit the moment the sun goes down, and wind turbines slow to a crawl whenever the air goes still. That intermittency is the oldest knock against
Sounds cool. Naive question: you need many of them. Thousands or more. Is that not going to further slow down the river’s current, which in consequence will provide less for the turbines further down the stream? And so on… There is no comment about that in the article.
The mass of earth provides arbitrary acceleration potential per unit of vertical drop, the roughness of the stream determines how much of that is converted into nonsense like hydropower or cool rapids that throw water in every direction.
What limits the density of turbines is a potential energy calculation frameable in terms of the minimum vertical drop between each turbine that still allows enough kinetic energy to be harnessed to make the practical engineering worth it.
Also turbulence in the immediate vicinty to the turbine is always going to increase entropy downstream making any energy extraction process less efficient past a certain density.
Finally remember that rivers are fundamentally histories of the path of least resistance as it changed over time, anything you stick into that context will have to have a preceding artificial structure to draw the whole of the river together or at least a critical mass of it in order to harness the energy otherwise if whatever you construct is too “inefficient” for the water vs. another path than the bulk of the water will take the lower energy path and make your construction irrelevant. This is a basic point but it is easy to miss if you only think with an engineer hat on and only consider the raw stats of the turbine and the raw physical energy in the river.
The rivers flow rate is the product of its cross section times the flow speed.
The flow rate is also the sum of all the runoff and streams that end in the river above any given point.
So, if what you assume were true, the flow speed would sink. The ingress flow rate would not reduce though, why should it, so the only way to keep the ratio between flow speed and cross section, aka the flow rate constant would be to increase the cross section area. So, the water level would have to rise, no other way to achive that. So the question is: “Will the river in its entire length raise its level when we put these turbines in at any point?” - that would be a great way to get hundres kilometers of deeper shipping lanes for free, but no, of course it won’t.
Sounds cool. Naive question: you need many of them. Thousands or more. Is that not going to further slow down the river’s current, which in consequence will provide less for the turbines further down the stream? And so on… There is no comment about that in the article.
The mass of earth provides arbitrary acceleration potential per unit of vertical drop, the roughness of the stream determines how much of that is converted into nonsense like hydropower or cool rapids that throw water in every direction.
What limits the density of turbines is a potential energy calculation frameable in terms of the minimum vertical drop between each turbine that still allows enough kinetic energy to be harnessed to make the practical engineering worth it.
Also turbulence in the immediate vicinty to the turbine is always going to increase entropy downstream making any energy extraction process less efficient past a certain density.
Finally remember that rivers are fundamentally histories of the path of least resistance as it changed over time, anything you stick into that context will have to have a preceding artificial structure to draw the whole of the river together or at least a critical mass of it in order to harness the energy otherwise if whatever you construct is too “inefficient” for the water vs. another path than the bulk of the water will take the lower energy path and make your construction irrelevant. This is a basic point but it is easy to miss if you only think with an engineer hat on and only consider the raw stats of the turbine and the raw physical energy in the river.
Lets think about that.
So, if what you assume were true, the flow speed would sink. The ingress flow rate would not reduce though, why should it, so the only way to keep the ratio between flow speed and cross section, aka the flow rate constant would be to increase the cross section area. So, the water level would have to rise, no other way to achive that. So the question is: “Will the river in its entire length raise its level when we put these turbines in at any point?” - that would be a great way to get hundres kilometers of deeper shipping lanes for free, but no, of course it won’t.