Dams are often built to generate electricity.
The way this works is that the dam impedes the flow of water, and thus increases the potential energy of the water behind the dam – creating a large potential energy difference between the two sides of the dam.
This large difference in potential energy allows for a high energy flux through the turbines which drive the generators.
Hope this doesn’t come off wrong, but maybe you should try going back to your usual style. Just dismiss the idiots. Explaining this stuff is basically making the argument for the other side wrt to lack of science from your readers and by association yourself (however wrongly).
I am a teacher at heart. My mission is to educate. Truth will always win out in the end.
But vapour isn’t a gas. /sarc I don’t know where you find the patience. Good on you though.
Dams are built to offset Sea Level Rise…. Similar to Al Gore’s Carbon Credit Scheme …. Carbon offsets..
<<<>>>
Prepare yourself for the Frigid Heat in all but 6 States this week… Climate Disruption!!
https://stevengoddard.wordpress.com/2014/11/08/shaping-the-data-to-match-the-theory/
Sorry…may fingers are so cold from the heat I pasted the wrong link…
Snow predicted in all but 6 States!!
http://www.drroyspencer.com/2014/11/only-6-states-not-expecting-snow-in-the-coming-week/
And Obama is getting ready to release executive actions to fight global warming. The economy needs some more damage….rules on ozone, on ghg and coal plants, states can’t pollute states downwind, billions in aid for global warming. They are going to lie their arses off to do as much damage as possible. Absolute fanatics using agw as a springboard for their heinous agenda. China is playing him for a fool.
http://www.politico.com/story/2014/11/climate-rules-obama-112792.html
Hi
Don’t forget water storage as the boneheads here in California have. The sierra Club and people in San Francisco wanted to tear down Hetch Hetchy until the recent drought started and now they have approved a voter initiative to build guess what? More dams!! More water supply could mean more growth which they are historically opposed to.
Wait! Don’t they build dams because “they” (whoever they are) want to obstruct the endangered fish from swimming up stream and so they can scar up the land in order to just be…. evil? If not, then my Kindergarten teacher may not have been completely honest with us.
I have often thought that we could use the weight of cars and trucks going in and out of cities day and night to create power, some sort of road that would turn a turbine and create power , just a thought ?
The old perpetual motion machine.
I wasn’t thinking perpetual energy that’s not possible just that we could harvest some of the energy to use on other things like street lighting or such . It just seems such a waste all that energy going to waste . PS I not a scientist i was just thinking aloud .take
Interestingly, the ore trains from Butte Montana used to run down to Anaconda by gravity and the electricity thus generated powered the empty cars back up to the mines.
Would this so called dam have safety valves that allow the water to release at a set height rather than building up, wouldn’t it be great if the earths atmosphere had a similar ability.
They build dams because they are little boys at heart, Hydro Pwr is just the rationalization.
Why do “they” build dams?
If “they” are beavers, they build a dam to create an artificial pond where the beavers can safely live.
The first human dams were water management tools–to save water from the spring run-off for the hot, dry summer days. That way the crop fields could be irrigated, livestock watered, and there’d be plenty of water for humans all year long.
Steve is right about hydroelectric plants–the energy of the flowing stream was “stored up” by blocking the flow of water and the restricted water flow was channeled from the bottom of that large water mass (the stuff on top being pulled down by gravity) to impact against turbine blades and turn generators.
Liberal politicians build dams for the same reason that every other politician does–public support, fame. Ask LBJ the next time about the TVA dams and rural electrification (tipping hat to Steve again).
Then there are dams built for land developers as recreational sites.
I wouldn’t be surprised if dams were built to rid an area of people. Lake Mead and Hoover Dam were named after politicians–and St. Thomas (among other towns) vanished beneath the water. Yes, the residents were moved out. Eminent domain and all that. http://en.wikipedia.org/wiki/Lake_Mead
Dams are now disliked by the Green Mob–but at one time hydroelectric power was a big thing, lessoning dependence upon dirty fossil fuels and dangerous nuclear energy. There ain’t no such thing as a free lunch–dams are expensive in many ways. Especially when cities spring up downstream and then the dam bursts…
When a dam is built to hold back the sea, it is called a dike or a levee. http://en.wikipedia.org/wiki/Levee
Why do “they” build dams? It depends upon who “they” are.
I commissioned a dam in Pergau Malaysia, they are incredibly useful for stabilizing an electric grid, as they can run up to full load in minutes, and shut down just as fast, wonderful for peak lopping, or emergency situations, the one at Pergau eventually did not even have operators as it was controlled remotely from KL grid control center.
Dams are built to shore-up the energy deficit in Trenberth’s energy budget cartoon.
🙂
Let’s say the streams at the headwater of a river are at 1000ft above sea level (arbitrary number). How much potential energy difference is possible between the two sides of that dam?
Let’s suppose the average flow of that river is 10000 cubic feet per second (also arbitrary number). What will be the average flow through the dam?
For added points, how much power is available in the river, and how much power can the dam extract?
It’s almost like there’s some sort of conservation of energy in the universe or something. Even when you convert energy into some other sort of energy, that thermodynamic thingy just keeps coming back at ya. Weird.
With a thousand feet of head and ten thousand cu ft/sec flow rate you get 846.7 megawatts (MW) (~1.135 million HP) – that’s a lot of energy!
http://en.wikipedia.org/wiki/Roselend_Dam
A 546MW dam in France – 4,101 foot head.
That’s all the power available in the river. The dam will necessarily extract a fraction of that.
Suppose you have a good site in a valley, so you dam on end of the valley, now the valley fills up with water. Total power in the river is exactly the same, total head is exactly the same, but now you might have perhaps 500 ft of head across you dam wall.
There no increase in average power, but now you have additional stored energy behind the dam and you have reduced the impediment to flow further upstream (i.e. the valley is now flooded and the surface of that lake is flat). This allows you to put the largest head across the turbines. When the valley is full, that’s the absolute most head you are going to get out of it.
The head has merely been moved around to a more convenient place. Nothing has been created that wasn’t there before. Also, the lake starts to silt up, because the power that previously went to smashing rocks and scouring the valley floor, now goes into the turbine.
Flux sounds neat, but it really is simply flow. For flux you need to see Backaroo about flux capacitors.
If water is continuously flowing into the reservoir and through the turbines and I close one of the valves the water in the reservoir will rise increasing the available, i.e. potential, energy. If the energy absorbed or not by CO2 fluctuates the incoming solar energy at the global atmospheric system boundary does nothing.
Is it necessary to explain in 2014 why do we build dams? This is a 19th century technology !! Are you going also to explain a steam locomotive? Or how to make a baby ? I am astonished how little educated is the populace you educate or feel necessary to educate ! By the wat is this population able to understand a micro-bit of supposed global warming?
Cheers