perpetual hydroelectricity?

[Grant-53]

For those who might want to see a similar system in action visit the Robert Moses power plant in Niagara Falls, NY. The turbines use water from the Niagara River in addition to a reservoir into which water also can be pumped at off peak hours. No free lunch but better control to maintain stable output.

[gone-ot]

SOLAR energy evaporating WATER into VAPOR, which upon rising & cooling, then falls back to earth as RAIN, usually at higher geographic locations (gravity)...is truly efficient and 100% solar powered...no electricity required.

[JRMichler]

He claims to be able to compress 200 cubic meters of air per minute (7060 CFM) to 20 bar (290 PSI) with 750 Kw (1000 hp). Only in the Unicorn World is this possible.

In our world, a water cooled two stage reciprocating air compressor needs 200 hp (150 Kw) to compress 1100 CFM to 100 PSI (6.9 bar). Most air compressors are less efficient than that. But if we use the most efficient air compressor, we would need 200 hp X 7060 / 1100 = 1280 hp to compress 7060 CFM to 100 PSI. Compressing to 290 PSI takes a lot more power than compressing to 100 PSI.

If somebody could build an air compressor capable of that performance, they could get stinking rich selling air compressors.

[t vago]

Originally Posted by xist

this reminds me of manuel garcia o'kelly davis, the main character of "the moon is a harsh mistress" by robert a. Heinlein: "he's a typical loonie: Independent, apolitical, and willing to bet on anything if the odds are at least one-in-ten."

tanstaafl

[freebeard]

If I understand the proposal, it's aims to achieve over-unity without the usually required Magic Pixie Dust™.

Here's how to make it work:
The facility needs to be built in tidal waters, with a chamber that has a large area compared to the depth (bore vs stroke). There's an air inlet above low tide and the top of the chamber is below high tide. The swept volume of air is exhausted through Tesla turbines, and the chamber empties as the tide falls.

Moon power. It's the future.

[Xist]

Originally Posted by Grant-53

For those who might want to see a similar system in action visit the Robert Moses power plant in Niagara Falls, NY. The turbines use water from the Niagara River in addition to a reservoir into which water also can be pumped at off peak hours. No free lunch but better control to maintain stable output.

There was also something about this on the study guide for my Energy in the Global Arena final. The professor reviewed the last day of class, mostly just answering questions, but since the TA posted a different study guide than he had wanted her to, he said that we would review for the first hour of the final, which would leave us plenty of time. Unfortunately, it did not seem like either review really helped. He discussed nuclear power, but asked about the order of incidents, which he did not cover.

Fortunately, that question was not on the final. I wanted to ask how much energy would be lost. Couldn't they divert water into the reservoir in the first place?

Originally Posted by Old Tele man

SOLAR energy evaporating WATER into VAPOR, which upon rising & coolings, then falls back to earth as RAIN, usually at higher geographic locations (gravity)...is truly efficient and 100% solar powered...no electricity required.

Okay okay okay, go build your own hydroelectric power plant already!

Originally Posted by JRMichler

Compressing to 290 PSI takes a lot more power than compressing to 100 PSI.

If somebody could build an air compressor capable of that performance, they could get stinking rich selling air compressors.

Is there an equation for the power required to reach a certain amount of pressure? I would not expect it to be linear.

[user removed]

EnergyBC: Tidal Power

regards
Mech

[IamIan]

Originally Posted by Xist

Is there an equation for the power required to reach a certain amount of pressure? I would not expect it to be linear.

If you define enough of the context yes.

Pressure is a type of force... PV=nRT (ideal gas law)
Energy is the force acting over a distance.
Power is the rate of energy flow per unit time.

While not 100% linear in the real world ... under most conditions materials that work similar to the ideal gas law , are fairly linear.

Either way , the point remains the same = their calculations are incorrect.

Each step is less than 100% efficient ... compressing , storing , de-compressing, etc... the best one can hope for it as has been posted about the source of the energy you are consuming (solar, etc.) ... free to me isn't free , but I don't have to pay for it.

[gone-ot]

IamIan -- Agreed, just three 90% efficient serial processes drops the TOTAL efficiency to less than 73%.

[JRMichler]

Originally Posted by Xist

Is there an equation for the power required to reach a certain amount of pressure? I would not expect it to be linear.

Yes, but I'm too lazy to dig out my thermo book and find it. There are actually three equations. One for compressing air at constant temperature (isothermal), one for compressing air without taking any heat out (adiabatic), and the third for real world situations where only some of the heat of compression is taken out during compression (I forget the name).

And a real world rule of thumb: In industrial compressed air systems, it takes four hp of air compressor to run one hp of air motor.