Did you ever realise that a mountain is a power dam?

As long as you feed the water originally higher then the input at the top of a mountain; you could furthermore dig down lower into this mountain and as long again that you come out lower than your bottom; you may end up with quite a high pressure. As also for instance; if the existing dams were encasing the incoming water within a pipeline; and of course having turbines at the source instead; or for that matter if those dams were to pipeline their exausting water on a downslope for miles; they would then have that suction force added to that of that other force which would create incredible difference that you would not comprehend.

theres a variation on this idea at chatsworth house in derbyshire, search chatsworth house emperor fountain in google

reply to post by MichelJCardin


and this is how not to do it.
Northfield mountain in Massachusetts.
it takes more power to pump the water up than it creates coming down.


Engineering studies began in October 1964, with early site preparation starting three years later. In 1972 its 1,080-megawatt hydroelectric plant became operational as the largest such facility in the world.

The plant was built entirely underground, and located about 5.5 miles (8.9 km) up the Connecticut River from Turners Falls Dam. A stretch of the Connecticut River, extending some 20 miles (32 km) north from this dam to the Vernon Dam, Vermont, serves as the station's lower reservoir. During periods of lower electrical power demand, the plant pumps water from this lower reservoir to a man-made upper reservoir. At times of high demand, water is released to flow downhill from this upper reservoir through a turbine generator, where it then collects in the lower reservoir to be stored until again pumped to the upper reservoir.

Northfield Mountain's upper reservoir covers 300 acres (1.2 km2) at 800 feet (240 m) above the river, with total storage of 5.6 billion US gallons (21,000,000 m3) of water. Its underground powerhouse lies at 700 feet (210 m) below the surface and is accessible through a 2,500-foot (760 m)-long tunnel; it includes four large reversible turbines, each of which can pump about 20,000 US gallons (76,000 L) of water per second and generate 270,000 kilowatts of electricity.

Originally posted by MichelJCardin
As long as you feed the water originally higher then the input at the top of a mountain; you could furthermore dig down lower into this mountain and as long again that you come out lower than your bottom; you may end up with quite a high pressure. As also for instance; if the existing dams were encasing the incoming water within a pipeline; and of course having turbines at the source instead; or for that matter if those dams were to pipeline their exausting water on a downslope for miles; they would then have that suction force added to that of that other force which would create incredible difference that you would not comprehend.

This idea is in fact, well comprehended by engineers, and is the basis for all power generating dams around the world. If a reservoir of water is connected to another reservoir of lower height, the gage pressure at the lower end is proportional to the density of water*gravitational constant*height difference. Therefore the higher the height differential, the higher the pressure.

However, if you added turbines to the top of the pipeline as well as the bottom, you will not be able to generate more power as the water would lose mechanical energy going through the first turbine. And due to the inevitable inefficiencies in turbines and generators, you will simply reduce the overall efficiency by adding further turbines.

Originally posted by citizen6511
and this is how not to do it.
Northfield mountain in Massachusetts.
it takes more power to pump the water up than it creates coming down.

Of course it takes more power, it always will when you have no natural water sources doing the work for you, but it's not about that, it's about money.

The idea is to pump the water up during the night hours, when the electricity is the cheapest, basically storing the cheap energy in the dam, and then have it come back down during peak hours, generating more expensive electricity, and thus, monetary profit.

reply to post by MichelJCardin


Yes it works and is widely used in hydro schemes but you might want to look into what happens when you exceed a 32 foot or so of suction head (with water). You'll draw a vacuum at the top end.

Also, placing a turbine at the top end of a long drop is wasting energy because the available energy (for driving a turbine) is determined by the simple formula P=Q.G.H where P is the power in KW, Q is the flow rate in m^3/second, G is gravity 9.82m/sec^2 and H is the applied head in metres. Considering that vacuum limitation, the limitation on H with the turbine at the top will be 32' or 9.8 metres. The head above the turbine is virtually unlimited though so you'll always find the generator at the bottom with perhaps a small bonus suction head in the draft tube below the runner. You don't even need to get very close to that 9.8m limit to be suffering disastrous cavitation damage at high flow rates so roughly half that is the typical limit in these designs and I've witnessed sufficient cavitation to cause sonoluminescence even in high head installations with very modest suction heads.

Multi-stage schemes will require a tail-pond below each turbine to control the amount of suction head and act as the head on the next turbine in the sequence (head being the vertical height of the pond surface above the centreline of the turbine runner). Very common in schemes that employ multiple turbines located along lengthy river valleys where a single dam and turbine location is impractical and known as a 'cascaded scheme'.

Originally posted by Naphariel

Originally posted by citizen6511
and this is how not to do it.
Northfield mountain in Massachusetts.
it takes more power to pump the water up than it creates coming down.

Of course it takes more power, it always will when you have no natural water sources doing the work for you, but it's not about that, it's about money.

The idea is to pump the water up during the night hours, when the electricity is the cheapest, basically storing the cheap energy in the dam, and then have it come back down during peak hours, generating more expensive electricity, and thus, monetary profit.

since Massachusetts produces half of it's electricity from oil and natural gas, the accounting to produce a profit must be very creative.
but i understand that Hawaii pays more than we do, at least were not number one.

reply to post by citizen6511


Pumped storage schemes are based on the idea of pumping the water up in off-peak times when energy is cheap and releasing it in peak times when energy prices are high enough to recoup the losses incurred in pumping and derive a profit. Energy is cheap in off-peak because thermal schemes don't want to shut down their boilers so they bid the minimum output they can safely maintain into the energy market at very low prices just to stay online overnight and not have to suffer the costs of a 'cold' startup every morning (significant costs in terms of fuel and lack of readiness to capitalise on any transient high prices caused by equipment failures elsewhere). They also provide a degree of system security in readiness to cover for any contingency events causing a loss of overall generation capacity IE they can go to maximum generation output in a matter of minutes.