# Hydro-electric generation from river beds

## Recommended Posts

i ment building and matenecice cost but i see the piont given the world we live in if some bright spark has a good idea then everyone has to have or do what they do

##### Share on other sites

i ment building and matenecice cost but i see the piont given the world we live in if some bright spark has a good idea then everyone has to have or do what they do

It has nothing to do with "having to do the same as everyone else".

Well... at least not directly. Everybody follows an idea that is the most profitable.

At least two people here suggested that hydro power is cheaper than the other options. I claimed that hydro power is even cheaper than fossil fuels. That price includes the building and maintenance.

Source (look under "costs")

So, to continue the discussion, perhaps you can respond to our points. Talk about the economics of the river-bed-turbines. Talk about efficiency. We need to compare it. This is a science forum, we need data!

Edited by CaptainPanic
##### Share on other sites

hiw big do you think these turbine are they are only small so that they dont desturb anything for ages

also i was talking about the turbines in the water being cheaper then dams not fossil feuls

only an idiot would think they are cheap with the comsupmtion rate they will most definatly run or sooner rather then later

this teard was onrianly called globel warming in the genetics area so i was thinking about the enviroment when i posted this

whats better to save the ecomimy that can sort it self out or the enviroment that has to have lots of help being sorted out because unless a imagenery fairy pixie thing will save who will. we the adluts have to be resonceible for making sure children inherit a clean safe beautiful world not some stink hole full of pollution

plus i am responding your your points i just might have said the wrong words to exspress my self

##### Share on other sites

hiw big do you think these turbine are they are only small so that they dont desturb anything for ages

also i was talking about the turbines in the water being cheaper then dams not fossil feuls

only an idiot would think they are cheap with the comsupmtion rate they will most definatly run or sooner rather then later

this teard was onrianly called globel warming in the genetics area so i was thinking about the enviroment when i posted this

whats better to save the ecomimy that can sort it self out or the enviroment that has to have lots of help being sorted out because unless a imagenery fairy pixie thing will save who will. we the adluts have to be resonceible for making sure children inherit a clean safe beautiful world not some stink hole full of pollution

plus i am responding your your points i just might have said the wrong words to exspress my self

First of all, a minor complaint. I am having trouble reading and understanding your post because of all the misspellings. Please try to do better (I know we aren't all perfect) so I can understand.

Now, about what I think you said. Certainly the river ecology is an important consideration. A turbine does screw the the river ecology; its effect is not zero. To generate energy from the kinetic energy of the flow must slow the waterflow down. When all is said and done, there is always a tradeoff. Which is more harmful to the river ecology; one middle sized dam at only one point in the river or turbines throught the entire river plus a coal fired plant for when the river is dry/flood stage?

##### Share on other sites

but i have a point about the econimy or environment plus the trubines a small about the size of a car tire so they would not cause upsets to the local ecosystem

##### Share on other sites

but i have a point about the econimy or environment plus the trubines a small about the size of a car tire so they would not cause upsets to the local ecosystem

Well... you are right about one thing: a turbine the size of a car tire has a small impact on the ecology. Let's assume that the car-tire-sized turbine generates 1 kW (kilowatt). That's probably overestimating it, but who cares.

A 1 kilowatt turbine has a much smaller ecological impact than a 1 Gigawatt dam. That's true.

The point is that we still need electricity... and using less electricity seems to be no option (I personally disagree with that, but the majority of the people on earth just use more and more).

So: You are right that one small turbine has a small impact on the ecology...

But we need 1 million (*puts pinky finger at corner of mouth*) of such turbines to replace one big dam! One million of them will have a massive impact.

##### Share on other sites

I'm guessing it would be more than a million. Not sure what the design you have in mind is, but 1 kilowatt seems like a lot for something the size of a car tire, harnessing just the horizontal flow of a river. I could be wrong about that, though.

I just looked up the soon to be completed Three Gorges Dam in China. It will be the largest dam in the world, and is very controversial because of the flooding it caused, destroying habitats (though creating others), forcing the mass relocation of over a million people, and drowning archeological sites. However, it will have a mind-boggling capacity of 22.5 gigawatts (about 11 times the Hoover Dam), supplying tens of millions of people with electricity and reducing the amount of coal they need to burn by about 40 million tonnes per year, including the more efficient ship transport it allows via ship elevator and smoothing out droughts and floods. It will also pay for itself in ten years.

##### Share on other sites

I'm guessing it would be more than a million. Not sure what the design you have in mind is, but 1 kilowatt seems like a lot for something the size of a car tire, harnessing just the horizontal flow of a river. I could be wrong about that, though.

$Power = flow * head * g$

The flow is equal to: $flow= area(frontal) * velocity$

So, indeed, there are plenty of cases where a frontal area the size of a car tire will generate less than 1 kW. But there might also be cases where it will generate even more.

But the actual point I wanted to make is that we're comparing the ecological impact of one single 1 kW turbine with a 1 gigawatt dam... which isn't really a fair comparison.

We must compare one million, or more, or less (but certainly a lot!) with one dam. Then we have a decent comparison.

One more issue:

I just realized one more problem challenge with the turbines: since they use no difference in height at all, the energy comes from a difference in velocity of the water. Therefore, water behind the turbine flows slower than in front of it. Therefore, the river must get wider.

I'm not saying that this is equal to a lake behind a dam... but lots and lots of turbines will severely disrupt the flow of the water.

##### Share on other sites

But the actual point I wanted to make is that we're comparing the ecological impact of one single 1 kW turbine with a 1 gigawatt dam... which isn't really a fair comparison.

We must compare one million, or more, or less (but certainly a lot!) with one dam. Then we have a decent comparison.

I agree.

One more issue:

I just realized one more problem challenge with the turbines: since they use no difference in height at all, the energy comes from a difference in velocity of the water. Therefore, water behind the turbine flows slower than in front of it. Therefore, the river must get wider.

I'm not saying that this is equal to a lake behind a dam... but lots and lots of turbines will severely disrupt the flow of the water.

That is a good point. It can't not disrupt the flow, in fact, since that is where its getting its energy from. One million 1kw turbines have to extract the same kinetic energy as a 1 gigawatt dam. I don't know for sure, but it seems at least plausible that the overall effect would actually be a lot greater if you spread them out over a long stretch of river. (Or it might be the other way around.) [/speculation]

##### Share on other sites

thanks for the tips

the dam would have a larger impact because of the siz of the damp and the flooding of the area

also would small pencil size turbine in pipes and sewers be a good idea

##### Share on other sites

thanks for the tips

the dam would have a larger impact because of the siz of the damp and the flooding of the area

also would small pencil size turbine in pipes and sewers be a good idea

I first want to see some sign that you actually read what we posted. then I'll reply. Respond to one of the previous comments here please (something more than just "thanks"). I don't get the feeling you read them, or understood them.

##### Share on other sites

i allready know that there would not be much power be i had put 10000 leters of water into drains in a year with 4 other people i live with that has to turn the trubins a little bit and even slitly cut down on the gas prices

##### Share on other sites

i allready know that there would not be much power be i had put 10000 leters of water into drains in a year with 4 other people i live with that has to turn the trubins a little bit and even slitly cut down on the gas prices

You can't be serious here.

I think using the natural fall of the sewer lines to generate a miniscule amount of energy is a "good" idea. [/sarcasm] Until these turbines plug up the works (how good are you at plumbing? With this you will probably get a lot of practice). Or until these turbines cause a leak (keep in mind raw sewage is a health hazard).

There are better ways to generate energy; why do something hard for so little return. For much less work (and less raw sewage you have to clean up) you could simply install a small windmill or solar panel on your roof. I'll wager either of these will generate many, many times the energy that a sewage turbine would. The maintenance costs for these would be very considerably less (plumbers are expensive you know) as well.

But maybe I am mistaken on the energy potential from this idea. You should prove me wrong. The equations for calculating the energy that can be generated are in this thread (post # 33). Do the math and show us please.

##### Share on other sites

i allready know that there would not be much power be i had put 10000 leters of water into drains in a year with 4 other people i live with that has to turn the trubins a little bit and even slitly cut down on the gas prices

Let's assume the average water consumption of a household is about 100 m3/yr, so 100000 liters, 10x more than you said, or 100000 kg/yr.

Let's assume that it falls 10 meters down.

Let's assume we have a 100% efficient turbine.

$Energy = m*g*h$

$Energy = 100000*9.81*10=9810000 J$ in 1 year.

$Power = energy/time$

$Power = 9810000/(3600*24*365)=0.31 W$

0.31 W isn't even enough for your phone charger.

##### Share on other sites

was a good idea but too costly

still my piont still stands about the turines in the beds they ae eco friendly effincant and safe for the enviroment please dont openly disrespect me or my ideas as i am only trying to helpthe cause to susseed and make the world a better place

##### Share on other sites

was a good idea but too costly

still my piont still stands about the turines in the beds they ae eco friendly effincant and safe for the enviroment please dont openly disrespect me or my ideas as i am only trying to helpthe cause to susseed and make the world a better place

Openly disrespect? Where did that come from? I hope you understand that all the arguments given here are objective. This means that you can read them, check them, counter them (with equally objective arguments).

The point is:

If you want to make the world a better place ("help the cause"), then you must do the most environmentally friendly and ecologic thing.

Did it occur to you that 1 million turbines in the river bed might actually be a really bad idea? You have to place 1 million machines, with moving parts in a river. They will break and litter the river with broken parts.

In addition, I have reason to assume that the construction will require more material than a single dam (because those turbines will need a serious foundation, if they are not to be washed away):

this means that your 1 million turbines can use a maximum of 6 ton of concrete per turbine. That's 3 m3 / turbine. I believe that that would actually be realistic... because you'll need to drill poles into the soil. Therefore 1 million turbines might use the same amount of concrete as 1 dam.

I am helping "the cause" here... and you're "openly ignoring" all arguments given here.

Edited by CaptainPanic
##### Share on other sites

sorry about the comment but i was not thinkking about 1million trubines just about ten in diffrent river and diffrent pionts puls there would not be moving parts(other then the turbines) in the atuall river

## Create an account

Register a new account