Producing electricity with kinetic energy

[jsiems]

have an idea or theory to produce clean electricity. My idea starts with a weight with a rope connected to a generator. If the weight is thrown off a cliff it would turn the generator and produce electricity until the weight stopped. This is an example of kinetic energy to create electricity. What if the weight was a submarine like object and instead of a cliff you place it in deep water? The weight would turn the generator as it submerged, then rise to the top and do it again. What if you could connect the weight to a generator as it’s rising? This would generate power as it is going down and as it is rising. Has something similar been done? Can this be done? Can it be done efficiently?

[the tree]

This would generate power as it is going down and as it is rising.

Where would the energy for that come from?

 

Most power stations use kinetic energy in one way or another.

[gcol]

Where would the energy for that come from?

 

Most power stations use kinetic energy in one way or another.

 

The sub could generate power on the way down, but consume it in the mechanism that made it rise. Always a net consumption, always a loss in a closed system?

 

Do not only hydroelectric systems produce power from a true kinetic source, the kinetic energy of the falling water?

[JustStuit]

Potential energy is turned to Kinetic energy and back at the same rate. It would take the same amount of energy to go up than it made going down. And that is in a perfect frictionless enviroment. When friction is present,

PE[math]_1[/math]+KE[math]_1[/math]=KE[math]_2[/math]+PE[math]_2[/math]+Energy(Work done by Friction)

Which Reduces to

PE[math]_1[/math]=KE[math]_2[/math]+Energy[math]_o[/math][math]_u[/math][math]_t[/math]

 

Therefore, it takes more energy than it produces.

Hydroeletric systems rely on the potential energy the water has but it also relys on the sun to evaporate the water to rivers and resupply the water up high.

[the tree]

Do not only hydroelectric systems produce power from a true kinetic source, the kinetic energy of the falling water?

The vast majority of power stations involve something being hot (either because it's widly radioactive or because it's burning), boiling some water and then the kinetic energy of the steam pusing some huge turbines.

The sub could generate power on the way down' date=' but consume it in the mechanism that made it rise. Always a net consumption, always a loss in a closed system?[/quote']It wouldn't be a closed system but yes there would always be a loss. Friction on the sub, weight of the water above the sub, vacum below the sub, heat from the generator, heat/noise from the motor.

[YT2095]

ever seen the tide come several miles inland through an estuary?

Billions of litres of water pass through daily!

now if it had to do work in order to Pass (as dictatated by Gravity), THEN you`de be on your way towards "free" energy

[swansont]

Do not only hydroelectric systems produce power from a true kinetic source, the kinetic energy of the falling water?

 

Ultimately it's solar energy, since you rely on rain, from evaporation due to the sun, to provide you with the water in the right location.

[BhavinB]

I saw something like this on Discovery. Someone was researching a really big buoy that rises and falls with the waves that pass by it. Its connected to a stationary generator which takes it vertical motion and converts that to electricity. Didn't catch anything on how much electricity it'd make.

[Klaynos]

I saw something like this on Discovery. Someone was researching a really big buoy that rises and falls with the waves that pass by it. Its connected to a stationary generator which takes it vertical motion and converts that to electricity. Didn't catch anything on how much electricity it'd make.

 

 

There are several systems like this under development. There are also ones that instead of working on waves (up and down) work using tides (in and out). For those living in the UK, working lunch has been covering them alot recently...

 

A link from: http://www.bbc.co.uk/bbctwo/programmes/?id=working_lunch

 

http://www.ourplanet.com/imgversn/123/ross.html

 

Also probably worth viewing for links:

 

http://news.bbc.co.uk/1/programmes/working_lunch/default.stm

 

Don't expect these to be scientific discussions, it's a finance/business orientated programe.

[chilehed]

The efficiency of tidal generators is limited because the working fluid moves at a low velocity. The same would hold for a system using the motion of a bouy riding on ocean waves. They're both expensive on a cost per kWh basis, but in some locations it may be worth it to have a system that doesn't require a high temperature source.

[YT2095]

low velocity sure, but high volumes, so it`s really only a simple matter of gearing ratios

Augmetation of Thames barrier would easily supply enough energy to run itself for "free".

[Apeofman]

low velocity sure' date=' but high volumes, so it`s really only a simple matter of gearing ratios

Augmetation of Thames barrier would easily supply enough energy to run itself for "free".[/quote']

How about using the kinetic energy to directly drive a heat pump. That would provide a lot more energy than an electric generator. The heat source would be the River Thames. Hot water could be distributed to the local area in much the same way as Battersea Power Station used to do with it's waste hot water.

 

Vacuum insulation technology could be used in the piping to reduce thermal losses.

[Norman Albers]

There are many ideas to "capture" mechanical energy As these gents say the question is where is it from? TRICK QUESTIONS: Some smart fellow observes that bridges move a good bit as loads transit them; they are indeed pinned on large pins (!), at least the river bridges around here. So we could make power by letting that squeeze something, yes? Now think carefully, where is that energy going to come from? I've not figured this exactly yet, but without the generator, consider the bridge as an elastic element.

[Klaynos]

The energy comes from the engines of the cars...

[Norman Albers]

Clearly somehow, yes! I'd approach this like the generator was a viscous (friction) term and design it first a critical damping for the average load at an average speed to the bridge center. I can also note that a component of give downward is of no gain to the truck if it is purely plumb vertically. yah?

[gcol]

Questions:

 

(a) The bridge flexes/moves. The movement is used to generate useful energy. The movement of the bridge is reduced, ultimately to an extent where the bridge becomes a rigid structure. So 1, where then is the movement that generates useful power? 2, How much of the movement can be used before the bridge becomes effectively rigid?

 

(b) Generating power from river or tidal flow restricts the flow, so 1, the more power you take out, the less flow remains to generate power. 2, Who compensates the upstream flood victims inundated because the river does not now drain? Crackpots who want to restrict the flow of, say, the Missisippi and Thames should beware threatened citizen lynch mobs!

[Norman Albers]

One could look at vector components, and/or make relevant energy arguments like I did about dropping in the middle. To the extent that this happens 'more than it did', the truck loses energy, like walking in sand. I suspect that vectors will show it experienced less of an angle coming to the center and so accelerated less. You can choose different impedances for your mechanical transducer, and always you work against the static deformation curve. I figure there is a time lag with the generator load making this analysis so. . . . . . . .HOW MUCH SHOULD WE TAKE??? Take more and kill more fish. Blades don't lacerate them; they are large and slow, and efficient at producing a large pressure drop suddenly across them!

[Apeofman]

Questions:

(b) Generating power from river or tidal flow restricts the flow' date=' so 1, the more power you take out, the less flow remains to generate power. 2, Who compensates the upstream flood victims inundated because the river does not now drain? Crackpots who want to restrict the flow of, say, the Missisippi and Thames should beware threatened citizen lynch mobs![/quote']

 

I share the same general concerns about restricting water flow. However i do'nt think i'll lose much sleep over the Thames Barrier, as it is a done deal,and i haven't heard of any victims. There are now plans to build affordable housing on the flood plane. That doesn't seem like a good idea to me, but that's an uniformed opinion.

 

The Thames Barrier exists to protect London and upstream from Tidal Flooding. The last time that central London flooded was in 1928 when 14 people drowned. In 1953 there was disastrous flooding on the East Coast and the Thames Estuary with a toll of over 300 lives. If this flood had reached central London's highly populated low lying areas the result could have been horrifying beyond measure.

 

Given that it exists, any other use to which it might be put is surely a bonus.

[Norman Albers]

I'm only starting to psyche out what you are speaking of but it's somewhat clear. Any throttling back should be controllable by spill. They dam a small river here to hold some floodwaters for summer. Major floodgates must be part of it, sized for maximum rate and height events. Release is always controlled from both top and bottom of the fairly deep pool, here.

[Apeofman]

The ...

 

I take this to mean that if the movement of cars over the bridge is the energy source causing movement, their miles/gallon kilometers/litre reduce below normal. Seem's right to me.

 

Questions:

 

(a) The bridge flexes/moves. The movement is used to generate useful energy. The movement of the bridge is reduced' date=' ultimately to an extent where the bridge becomes a rigid structure. So 1, where then is the movement that generates useful power? 2, How much of the movement can be used before the bridge becomes effectively rigid?

 

[/quote']

 

From what little i know about the subject.

 

I reckon that if the bridge is made rigid, the car drivers would find, their fuel consumption miles/gallon kilometers/litre are normal.

 

Useful energy cannot be extracted from the system without reducing the m.p.g l/km of the car.

[Norman Albers]

The bridges do give and spring back. This is called elasticity. A bit of energy is lost in bearing points and internal stress of steel and asphalt, etc. We should expect, however, that as much as the bridge continues to bow down more as a truck approaches its center, so much will it spring back as the truck transits. Taking power out by a 'big piston' under the center will give the physics I described.

[Norman Albers]

Lo and behold, a major article on levees and controllable dykes in this issue of Sci.Am..

[gcol]

The bridges do give and spring back. This is called elasticity. A bit of energy is lost in bearing points and internal stress of steel and asphalt, etc. We should expect, however, that as much as the bridge continues to bow down more as a truck approaches its center, so much will it spring back as the truck transits. Taking power out by a 'big piston' under the center will give the physics I described.

 

This only works for one truck passage. When the trafic flow is steady, the deflection will be static. Bad luck, unless you allow only one vehicle on the bridge at a time. The truckers union would be at your door.