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Author Topic: Energy losses, Thermodynamics and Efficiency  (Read 12925 times)

Offline SimpleEngineer

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Energy losses, Thermodynamics and Efficiency
« on: 30/09/2013 15:12:02 »
My colleagues and I constantly discuss ways to do things that seem ever so simple in our heads and on paper, that when these silly things called "The Laws of Thermodynamics" tell us to stop being silly and shows us the error of our ways.. (this never stops us trying to break them)

However we discussed the hydrolysis of water, how the energy you have to give (fair enough it can be free) would be more than the energy you would get back (sources tell us 85%-95% in comparison).. and this gives us wonder on what happens to that energy.. realizing that our typical foes of the three commandments tell us this is not possible!

We considered the forms of energy, and how realistically heat is usually the sources of loss.. BUT if we captured that heat (not hard in a water system) and used that energy to split the next lot of water.. Our thoughts began making all manner of perpetual motion designs involving hydrolysis cells, gas turbines and steam turbines..

BUT this cannot be the only source of loss, our wandering thoughts stressed over the balance of energy's through the hydrolysis cell,  the gains the losses and how to capture any slight implication of energy gain and we kept coming up with hard questions such as..

"If energy cant be created, then how does buoyancy work?" Free kinetic & potential energy?

"If energy cant be destroyed, then why are things not 100% efficient?" Where is the rest of the energy going?

Our perpetual motion machine was as such..

Sunlight turns water to oxygen and hydrogen, these are then burned across a gas turbine to give HP steam, through turbines and condensed within the reservoir of water that is then fed to the hydrolysis cell. Power from turbines used to pressurise the gasses and a self contained heat engine to take heat from the water to the gasses.

Considered within a single 'box' with only a section exposed to sunlight.

Mechanical losses, we call.. BUT.. if its all self contained.. Where does that energy go? if through heat it would be contained within the system. and anything this puts out could be turned to energy in one way or another.. (such as any extraneous kinetics from the turbines)

Can anyone help end our tussling with the LoT.. and set us back into the legal thought process.


 

Offline SimpleEngineer

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #1 on: 30/09/2013 15:22:06 »
Sorry my mistake.. not perpetual motion.. but a means to generate rotational energy (for electricity generation say) from sunlight.. and why wouldn't it be the same output from the same input

The perpetual motion was an idea dropped very early.
 

Offline alancalverd

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #2 on: 30/09/2013 22:43:05 »
Entropy.

As energy moves around a system, it becomes less potentially useful and entropy increases.

Imagine you have a million dollars. You can offer this to a group of people in exchange for their labour to make something you want. Say you employ a thousand people to build a posh yacht. Now each of them has a thousand dollars and you have a yacht. The amount of money hasn't changed but now nobody can afford a yacht.
 

Offline Supercryptid

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #3 on: 01/10/2013 04:57:06 »
"If energy cant be created, then how does buoyancy work?" Free kinetic & potential energy?

I'm not exactly sure what you are asking here, as an object floating on the surface of the water is neither expending nor absorbing energy.

Quote
"If energy cant be destroyed, then why are things not 100% efficient?" Where is the rest of the energy going?

You're right, it isn't being destroyed. It's being transformed into more than one form of energy. If you have an internal combustion engine that is 55% efficient (just a hypothetical number), then 55% of the chemical energy contained in the fuel can be converted into mechanical energy for pushing the car forward. The other 45% of the energy is either lost as unburned fuel in the exhaust, waste heat or vibrational/sound energy. Waste heat is one of the biggest problems when it comes to efficiency, as you cannot collect it all and change it into useful work. Some of it is conducted away by the air and some of it is lost as infrared radiation.

Quote
Sunlight turns water to oxygen and hydrogen, these are then burned across a gas turbine to give HP steam, through turbines and condensed within the reservoir of water that is then fed to the hydrolysis cell. Power from turbines used to pressurise the gasses and a self contained heat engine to take heat from the water to the gasses.

Considered within a single 'box' with only a section exposed to sunlight.

Mechanical losses, we call.. BUT.. if its all self contained.. Where does that energy go? if through heat it would be contained within the system. and anything this puts out could be turned to energy in one way or another.. (such as any extraneous kinetics from the turbines)

It can't be completely contained, not even in a vacuum. If the transformation of energy heats or vibrates the box itself by even a tiny amount, then at least some part of the energy will be radiated away as infrared/microwave/other radiation.
 

Offline evan_au

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #4 on: 01/10/2013 10:46:29 »
Quote
"If energy cant be created, then how does buoyancy work?" Free kinetic & potential energy?
  • It takes energy to push a buoyant object under the waves (some of which goes into friction and heating the water), so it's not free.
  • You can retrieve some of this energy by letting the buoyant object rise through the water (minus some of which goes into friction and heating the water), so you can't break even. 

To expand on Supercryptid's response:
Quote
Waste heat is one of the biggest problems when it comes to efficiency
Back in the days of steam engines, Carnot worked out the maximum possible efficiency of an engine running on heat - it was one of the first applications of thermodynamics. The energy you can extract from a source of heat depends on the temperature difference between a hot body and a cold body. After you run the engine for a while, the hot body tends to cools down, and the cool body tends to warm up; when the temperature is equal, the efficiency drops to zero.

Practical heat engines can attain efficiencies of up to 50% by operating at very high temperatures, but petrol-driven automobile engines are much lower.

Trying to extract useful energy from "low-grade" heat sources such as the friction of lubricated bearings retrieves a very small fraction of the already-small amount of heat energy present.

See: http://en.wikipedia.org/wiki/Carnot%27s_theorem_%28thermodynamics%29

Cosmologists imagine the "heat death of the universe", where all matter and radiation converges to a common temperature. Although the amount of energy present is the same as today, it is evenly spread out through the universe, and heat engines cannot work.
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #5 on: 01/10/2013 13:24:00 »
Hi,
Interesting topic free energy versus perpetual energy, it has been on my mind a lot of late. I am not sure quoting Carnot is as relevant today as it was even 25 years ago, things have changed a lot, become more sophisticated, questions and answers are no longer as simple as they once were. I was in fact thinking about sailing ships. I was reading somewhere (and in fact a simple calculation based on the weight of a laden ship, number of days, distance etc., will probably bear me out) that the clipper ships could generate about 3000 hp (2.5 MW) continuously over a period of 3 months or so.  This in itself is fantastic considering that about 4 acres of solar PV panels would be needed to generate  a similar amount of power, during hours of peak sunlight or who knows how many tons of coal.  Even more peculiar is the fact that these ships were able to sail into  the wind almost as fast as they could sail with the wind behind them.  My question is how does this happen ? Take that same ship out of the water put it on castors that can turn 360 degrees in any direction, and create an artificial wind in front of it, what will happen, it will move backwards sideways, but never, ever under any circumstances forwards. What good is all the free energy in the world if you can only move when the wind is blowing from behind. The answer of course is that it is no good at all.  OK, now look at the question from another point of view. Take a 100 Kg weight up a height of 10m and when you drop it you get about 9.8KJ of energy. The point is, does the same question apply ? What good is this (.9.8 KJ if you only have it when the weight is falling), or does it fall into the category of ‘it is impossible and it is like trying to get perpetual motion or free energy', and so on.

« Last Edit: 01/10/2013 13:36:49 by McQueen »
 

Offline SimpleEngineer

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #6 on: 01/10/2013 14:26:59 »
Carnot Efficiency does not seem to apply to a closed system in which the hot and cold body are in fact the same process media in different states. The hot and cold body are in relative terms which we can manipulate with small applications of technology. All we can come up with is that the energy required to achieve the manipulations MUST increase.. however since there are no losses why is this so? the water might get too hot, in this case we could remove energy through power generation.. (free energy - impossible) the water might get too cold, but where does that energy go?

Buoyancy was questioned through the generation of bubbles underwater, and how the different pressures, density and even temperature seem to give rise to free energy as you can gain significant potential and kinetic energies just by having a lower density.

I personally dont understand entropy, I can do the calcs and pass an exam on it, but the practical applications do not make sense to me (I am not that bright ;) ) I dont have a tangible grip on how it behaves.. 
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #7 on: 01/10/2013 15:03:03 »
My interest arises from the fact that after so many years of trying to switch to renewables, we are in no sense closer to a solution than when we first started with the result that things like fracking are being let loose on the public and YET there seemingly were free energy solutions, like sailing ships that worked very well, while generating  appreciable amounts of what must be considered free energy by any criteria.  Yes, we do have modern wind turbines, but they are  intermittent, sailing ships were so successful because they enjoyed more or less continuous uninterrupted power, since the oceans contained no significant obstructions to the wind. Surely, especially considering the circumstances we are in, with fossil fuels running out and the pollution caused by them reaching unacceptable levels,  we have to leave ourselves open to the possibility that   a  free energy solution similar to the free energy solution enjoyed by sailing ships does exist and can be found.  Or is that too daring a prospect to undertake?
 

Offline SimpleEngineer

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #8 on: 01/10/2013 15:34:35 »
When the answer to how to extract this free energy is by strapping a dirty great gearbox and dynamo to a fan on top of a very large pole.. no I doubt we will get much further.. they are horrendously inefficient.. I KNOW how much energy it takes to build one.. and if you think you will be getting that back anytime soon...

The tidal and wave generators are seemingly much more efficient although not as practicable, and please let us not follow the chain of thought that led to someone suggesting we put wind turbines on moving platforms again..

My fear is that energy is not limitless..and the more we leech out of the earth's systems the less there will be? Is there any data about climate change and windmills? They MUST have some impact on the weather, however minor.
 

Offline Supercryptid

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #9 on: 01/10/2013 16:24:44 »

Carnot Efficiency does not seem to apply to a closed system in which the hot and cold body are in fact the same process media in different states. The hot and cold body are in relative terms which we can manipulate with small applications of technology. All we can come up with is that the energy required to achieve the manipulations MUST increase.. however since there are no losses why is this so? the water might get too hot, in this case we could remove energy through power generation.. (free energy - impossible) the water might get too cold, but where does that energy go?

No physical device is a truly closed system, even if all of its components are in the same container. Waste heat (and therefore energy) can always escape in the form of radiation, even in a vacuum. Sure, you could put your device inside of a box that attempts to capture the waste heat and convert it into useful energy, but this new box itself will emit some degree of waste heat itself. You could put that box inside of a second box that does the same thing, but you'd need to have an infinite series of boxes-within-boxes to keep all of the waste heat from escaping.

Quote
My fear is that energy is not limitless..and the more we leech out of the earth's systems the less there will be? Is there any data about climate change and windmills? They MUST have some impact on the weather, however minor.

You're right, it isn't limitless. All potential energy on Earth can be theoretically exhausted, but it will take a very long time (especially as a large amount of the energy available on Earth comes from the Sun). At the very least, we'd have to wait for the Sun to die before we run out of usable energy here (and the Earth itself may be consumed by the Sun before that happens).
 

Offline alancalverd

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #10 on: 01/10/2013 20:28:10 »
Quote
sailing ships were so successful because they enjoyed more or less continuous uninterrupted power, since the oceans contained no significant obstructions to the wind.


Apart from the Doldrums, and the fact that the prevailing wind is westerly everywhere, and often just stops completely for weeks at a time.... And however much power you can generate from a moving sail at sea, it isn't a lot of use to the rest of the population standing on land a thousand miles away.

Sailing ships were "successful" because there was buggerall else around until the advent of steam, whereupon they all disappeared in a few years.
« Last Edit: 01/10/2013 20:29:45 by alancalverd »
 

Offline syhprum

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #11 on: 01/10/2013 21:31:50 »
I think we must distinguish between perpetual motion which we see around us all the time (the rotation of the earth for instance) and machines that produce power from nowhere which of course cannot exist.

PS supercriptid

55% thermal efficiency for an IC engine is not hypothetical, the largest ships Diesels can just about reach this figure
« Last Edit: 01/10/2013 21:40:59 by syhprum »
 

Offline Supercryptid

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #12 on: 01/10/2013 21:59:09 »
In regards to perpetual motion machines, I'd like to point out that there are three types. Two are forbidden by the laws of physics and one is not.

Perpetual Motion of the First Kind: A device or phenomenon that can increase the total energy content of a closed system. This violates the first law of thermodynamics (energy cannot be created nor destroyed). This kind is currently thought to be impossible.

Perpetual Motion of the Second Kind: A device or phenomenon that increases the available energy to do work in a closed system by decreasing the total entropy of that system. This violates the second law of thermodynamics (the total entropy in a closed system cannot decrease with time). This is actually only prevented by probability. In a technical sense, entropy can decrease in a closed system spontaneously. However, the chances of that occurring are so amazingly small that it is highly practical to consider it impossible (at least on a human time scale).

Perpetual Motion of the Third Kind: A device or phenomenon that can remain in motion indefinitely so long as it doesn't do any work. In practice, one could consider the motion of subatomic particles to be an example of this. A cloud of subatomic particles or atoms should always retain some motion forever due to both Heisenberg's Uncertainty Principle and the impossibility of reaching absolute zero. However, you can't extract useful work from a particle cloud which is already in its lowest energy state.

Quote
55% thermal efficiency for an IC engine is not hypothetical, the largest ships Diesels can just about reach this figure.

I have to admit, the reason I said "hypothetical" is because I had no idea what a reasonable efficiency figure for internal combustion engines would be.
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #13 on: 02/10/2013 06:04:10 »
Quote
In regards to perpetual motion machines, I'd like to point out that there are three types. Two are forbidden by the laws of physics and one is not.
What category would a sailing ship fall into, it certainly doesn't fit into any of the categories describing perpetual motion of the first, second or third kind? Would it be regarded as free energy, in a sense, although it does take a lot of work raising and lowering sails etc.,
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #14 on: 02/10/2013 06:13:07 »
Quote
Sailing ships were "successful" because there was buggerall else around until the advent of steam, whereupon they all disappeared in a few years.

The point, surely, is that even that 'buggerall' wouldn't have been available if not for certain circumstances. As I had pointed out a sailing ship that sails only before the wind is no good to anyone at all.
 

Offline evan_au

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #15 on: 02/10/2013 13:21:35 »
Question from McQueen:
Quote
These ships were able to sail into  the wind almost as fast as they could sail with the wind behind them.  My question is how does this happen ? Take that same ship out of the water put it on castors that can turn 360 degrees in any direction, and create an artificial wind in front of it, what will happen, it will move backwards sideways, but never, ever under any circumstances forwards.

A sailing ship is not on castors; in a steady breeze, a vehicle on castors will be pushed roughly downwind, once the initial inertia is overcome.
A racing boat can sail within 30 degrees of directly upwind. When sailing into the wind, the sail acts like an aeroplane wing, and provides a sideways force. This sideways force is resisted by the force of the water on the hull, causing a small sideways motion to be accompanied by a larger motion into the wind.

If you saw the recent America's Cup races, most of the time these catamarans were up on hydrofoils; in this case the hydrofoils provide the sideways resistance.

Quote
What category would a sailing ship fall into... Would it be regarded as free energy?
Energy is delivered from the Sun for "free", in that we did not pay to build & operate the Sun, or for transmission lines that cross millions of kilometers of vacuum.

The Sun delivers energy in various ways, including the direct photons, heating the atmosphere (producing winds), heating the sea (producing thermal gradients and currents plus rainfall for hydropower), photosynthesis (producing chemical energy, including fossil fuels); the rotation of the Earth interacting with the gravity of the Sun also produces tides. These could be considered "free", if it didn't cost anything to harness them.

However, photovoltaics, wind turbines & sails, ocean thermal power systems, planting/harvesting/processing crops, prospecting/mining/refining fossil fuels and tidal barrages cost considerable amounts of money to construct and maintain. So it comes down to cost-effectiveness.

Some modern cargo ships with engines also have sails that can be deployed to add some extra thrust (and save fossil fuels) when the wind is in a suitable direction. Some of the sail concepts are somewhat novel, such as rigid sails, or kites.
« Last Edit: 02/10/2013 13:28:03 by evan_au »
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #16 on: 02/10/2013 14:58:53 »
Hi evan_au,

Nicely put, it figures, water is about a thousand times more dense than air, so it doesn’t really matter how hard the wind blows, water acts almost like a solid. Then, depending on the boats design, her sails etc., it will take the easiest way out which if correctly positioned will be forward on a tack. 

There are quite a few sources of energy that are termed renewable, some of these could be considered as sources of free energy. Here is a list that might be commonly found:-
1)   Solar, including PV and thermal and CSP and CPV.
2)   Wind
3)   Tidal
4)   Wave
5)   Biomass
6)   Bio-fuels ( including algae)
7)   Geothermal
8)   Hydroelectric
9)   Osmotic
10)   Ocean thermal
The amazing thing about this list is that it does not include either atmospheric pressure or gravity as a source of energy. Having said that look at this video:

It is quite astonishing the way in which the elevator cage with passenger is lifted using just a partial vacuum and atmospheric pressure, don’t you agree! When descending it is just gravity. If this had been described in words one in ten would have said it is impossible but since it isn’t ……!

 

Offline alancalverd

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #17 on: 02/10/2013 17:46:25 »
Big difference between square riggers, which really couldn't sail much into the wind, and aerofoil sails as on yachts and clippers. A modern sail is like a single-surface wing and generates "lift" by streamlined (nonturbulent) deflection of the wind. If you rotate the sail so that its chord (the line from the luff to the leech) points into the wind it produces a lift vector roughly perpendicular to the chord. If you now point the boat in that direction it will move forward, but in doing so it alters the apparent direction of the wind, which now seems to be coming from slightly ahead of the true wind. As the boat accelerates so the apparent wind moves further ahead until you reach the stall angle, with the apparent wind roughly 16 degrees either side of the true wind - interestingly, the same angle of attack at which a glider stalls. So by tacking +/- 16 degrees, you can progress upwind in a zigzag.

Windmills works in exactly the same way but in a rotating frame of reference, where the tips are travelling faster than the roots, so the wing is warped to maintain a constant angle of attack at each point. 

You can't use atmospheric pressure as a source of energy except by allowing air to flow in and out of a box, rather like the tide, as the weather changes - not terribly useful, though some clocks can be driven by their associated barometer. Atmospheric railways and lifts use a conventional engine to suck or blow: the air is a storage and transfer medium for the power of the engine   

     
« Last Edit: 02/10/2013 19:13:57 by alancalverd »
 

Offline evan_au

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #18 on: 02/10/2013 18:54:31 »
Quote
generation of bubbles underwater...seem to give rise to free energy
It is true that bubbles rising through a water column could turn a water-wheel and generate power, such as is done in the common fish-tank ornament.

However, pumping the air down under the water consumes all of the energy you could capture as the bubbles rise to the surface.

Actually most of the energy from the bubbles rising to the surface is lost in friction and turbulence.

Quote
gravity as a source of energy

It is true that by rolling rocks down a hill, you can use their initial gravitational energy as a source of energy. But once all of the mountain rocks have filled all of the valley holes, there is no more energy to be gained*. This is a non-renewable form of energy on human timescales, and it is certainly not "free".

Rather than say "gravity is a source of energy", I would rather say that "gravity can temporarily store energy", such as is done in pumped-storage hydroelectricity.

I liked the phrase in the YouTube video: "the cabin falls gently under gravity". If the cabin fell more than 2 floors under gravity, it would do some severe damage to the occupants. What is happening here is that air is slowly released back into the top of the cylinder through a valve, allowing the cabin to fall gently despite gravity.

Air leaking through the valve causes turbulent flow - this is a series of vortices which spawn smaller vortices, which in turn small even smaller ones. At sufficiently small scales (the Kolmogorov length scale), this turns the initial source of potential energy (a pressure difference) into heat. As mentioned in the post on Carnot, heat is one of the least reusable forms of energy (even though much of our energy needs are met via this route).

Avoiding turbulence is why most proposals for efficient machines assume they are working in a vacuum, as turbulence of air or water irretrievably wastes energy.

If you are looking for efficiency, try electromagnetism, as electric motors can often achieve efficiencies of around 90%, twice that of very good heat engines. Better yet, if you want high efficiency, avoid motion of any kind, as that wastes energy through friction and turbulence.

*Dumping stars into a black hole is just rolling bigger rocks into a a bigger valley; it is still a non-renewable source of energy, and it is still not "free".
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #19 on: 02/10/2013 22:40:20 »
Reading such beautifully written posts brings on nostalgia ! Still you are wrong when you say that atmospheric pressure cannot be considered a source of energy:
Quote
You can't use atmospheric pressure as a source of energy except by allowing air to flow in and out of a box, rather like the tide, as the weather changes - not terribly useful, though some clocks can be driven by their associated barometer. Atmospheric railways and lifts use a conventional engine to suck or blow: the air is a storage and transfer medium for the power of the engine
Look at this link to the Grand Junction 90 inch, that was used to pump water out of the Thames, up to 7.5 million gallons a day! Considered one of the finest examples of the Newcomen atmospheric engine. The counterweight weighed 32.5 tons and was operated using only atmospheric pressure.
http://www.kbsm.org/engines/90-inch-engine
Quote
If you are looking for efficiency, try electromagnetism, as electric motors can often achieve efficiencies of around 90%, twice that of very good heat engines. Better yet, if you want high efficiency, avoid motion of any kind, as that wastes energy through friction and turbulence
I read  somewhere that most coal fired power plants in Britain  operate nowhere near 90% but closer to 40%, I am not sure if this is true. In any case the idea is not to discuss efficiency but to see if it is possible to get something better than windmills or other present day renewable sources that work only intermittently and are therefore almost useless in practical terms. 
« Last Edit: 02/10/2013 22:57:15 by McQueen »
 

Offline alancalverd

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #20 on: 03/10/2013 08:08:22 »
Quote
Still you are wrong when you say that atmospheric pressure cannot be considered a source of energy:.....the Newcomen atmospheric engine.


Sadly, I have to say I was right. Newcomen engines use the condensation of steam to evacuate a chamber to produce a pressure differential with the ambient atmosphere. A brilliant idea because you can generate the steam with a low pressure boiler - nothing more than a big kettle - which simpllifies the engineering, as long as you don't need anything to move quickly. Perfect for pumping water out of tin mines, which is what he originally designed it for: you can use the recovered water to chill the vacuum cylinder and top up the boiler.  But read the last line of the Kew Museum website
Quote
Returned to steam 1976
As I said above, air is the working fluid but the prime energy source is burning wood or coal. Hence the expression "nineteen to the dozen" - a good pump would shift 19 tons of water per dozen bushels of Welsh steam coal.

The conversion of mechanical to electrical energy in a big power station is well over 90% efficient - hence the reason why "micropower" is not a good idea for sustainability as small dynamos (less than 100 kW) rarely exceed 80%. But the Carnot efficiency of the prime mover (converting coal energy to mechanical energy in high temperature steam) just approaches 60% (35% is good for a small boiler) hence 54% overall thermal efficiency is considered extremely successful and only achievable in the largest and most modern stations - the ones the EU insists that we shut down. .
« Last Edit: 03/10/2013 08:15:18 by alancalverd »
 

Offline SimpleEngineer

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #21 on: 03/10/2013 09:12:05 »
Quote
generation of bubbles underwater...seem to give rise to free energy
It is true that bubbles rising through a water column could turn a water-wheel and generate power, such as is done in the common fish-tank ornament.

However, pumping the air down under the water consumes all of the energy you could capture as the bubbles rise to the surface.

Actually most of the energy from the bubbles rising to the surface is lost in friction and turbulence.


What if the bubble forms underwater.. as in a submerged PV cell.. the cell splits the water by hydrolysis causing bubbles to form on the surface, when the bubble gets to a certain size it will float to the surface.. does it get to the surface at a lower temperature than the water? does it cool the water by gaining energy? I cant see how the PV cell gives it any energy rather than that which was needed to split the molecule. So where does this energy come from?



 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #22 on: 03/10/2013 09:44:03 »
Agreed, Newcomen engines were horribly inefficient as James Watt proved with his improved steam engine. The thing to remember is that the working principle was different and that soon after Watt improved it the design was abandoned in favour of steam pressure, as far as can be seen no-one ever looked at the technology again. Until, that is the vacuum elevator came along, using roughly the same principle with an electric motor instead of steam as the prime mover. It was low pressure steam that was used in the Newcomen engine, the piston was lifted because the rocker beam was unevenly balanced and as soon as equilibrium was reached in the air pressure above and below the piston, gravity pulled the beam down and the piston up.
Here are a few more facts and figures about the vacuum elevator, that you might ( or might not) be interested in.  The lift cage is 32 ins (81cms approx) across, it can work up to a height of 10m. and no more. It uses 3 KW of energy to turn three turbines. It can lift a weight of 204.5 Kg, but taking into account safety regulations can probably lift about 30% to 40% more than that.  The turbines seem to take a few milliseconds (judging by the video) to evacuate air from the cylinder above the lift cage. This raises an interesting question look at the diagram below:-

As can be seen the counterweights are connected to an open ended shuttle, so that when the counterweights are released there is practically no resistance to their descent except for the friction at the generator spool and the friction where the open ended shuttle is touching the tube. Suppose the height at which the counterweight is situated is 10m and that the generators which they are turning by means of the cable (just as in a car alternator) are capable of generating 5 KW.  http://www.aurasystems.com/pages/prod_exploded.html
Lastly the vacuum motor seen (attached by ducting to the tubes containing the shuttles) at the bottom right of the picture needs 3 KW.  Then the sequence is as follows the counterweight weighing 150 Kg  is released, generating 14.7 KJ of energy and taking about 1.4 seconds. This means that 7.25 KW approx. are available to turn the generator which needs only 5KW ! The generator which is generating 5 KW of electricity supplies the vacuum motor which needs only 3KW of power.  All this time the counterweight has been descending and the open ended shuttle has been rising. When the shuttle is almost at the top of its tube it is sealed by means of an actuator or similar converting the open ended shuttle into a closed piston.

Atmospheric pressure is now introduced above the piston with the result that there exists a partial vacuum below the piston and atmospheric pressure above. If a vacuum of 1 torr is achieved. The piston (30 cms dia) would have 706.5 Kgf acting on it while it needs to lift only 150 Kg ( i.e., the weight of the counterweight) . As the shuttle travels downwards under the force of atmospheric pressure the counterweight travels upwards till it reaches its original position. The piston is once more unsealed turning it into an open ended shuttle and the whole cycle keeps repeating.  Looking at the diagram above one of the tubes and counterweights is used exclusively to create a vacuum in the system while the other tubes and counterweights, use this vacuum in a parasitical manner to produce usable electricity by spinning their generators, the generators are geared to produce electricity both while the counterweights are descending and ascending.
Another even better design but slightly more complicated, is if the energy of the descending counterweight was stored in ultracapacitors or flywheels, when the counterweight has reached the bottom the energy in the ultracapacitors is used to activate the vacuum machine so that a partial vacuum exists all during the descent of the sealed shuttle (piston).

The great thing about this design is that in excess of 10 KW can be generated continuously, in a manner similar to the way wind turbine motors generate energy.

« Last Edit: 04/10/2013 01:48:39 by McQueen »
 

Offline alancalverd

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #23 on: 03/10/2013 10:56:47 »
Vacuum systems are still in widespread use, the only difference being that the prime mover nowadays tends to be a mechanical or electrical pump rather than steam. You will find three vacuum-driven gyros in the cockpit of most small aircraft, and atmospheric office document transport systems are still on sale.

But the "continuous 10 kW" in your example still comes from the prime mover, and it isn't continuous.   
 

Offline McQueen

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #24 on: 03/10/2013 11:32:38 »
Quote
But the "continuous 10 kW" in your example still comes from the prime mover, and it isn't continuous.   

Surely the significant fact here is that the 'prime mover' is being powered by the kinetic energy of the descending and ascending counterweight and not from an electrical outlet, if the generators are continuously putting out power both while the counterweights are ascending and descending, why is the output not continuous ?

What I really want to know is , is our technology up to it ? I think it is, things like valves, vacuum pumps ( turbines, blowers etc,.) friction reducing materials, pulleys etc., have changed beyond comprehension, in fact it would even be possible to monitor the whole process, through strategic placing of pressure sensors.  If that is indeed the case and it can be done, the system has a small footprint, needs little maintenance and what maintenance there is will be basic. Put one in every house (or garden) it would generate enough electricity, to cook, bathe, wash clothes, run all of the household appliances, heat the house AND still have enough left over to (a) either charge your cars lithium ion battery OR make and compress enough hydrogen through electrolysis to use in a hydrogen fuel cell. So what's all the fuss about ?
« Last Edit: 03/10/2013 12:12:34 by McQueen »
 

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Re: Energy losses, Thermodynamics and Efficiency
« Reply #24 on: 03/10/2013 11:32:38 »

 

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