Creating electricity utilzing water particles in a vacuum

[ChrisMackintosh]

Hi. I'm a first year Engineering student at QUT here in Brisbane. My problem is I come up with all these great ideas but lack the confidence and skills to carry them through to realization. I am currently taking 6 months deferment from my degree due to the difficulty of the maths. I have this idea, but am limited by my inability to code, yet, which means I couldn't design the computerized temperature/pressure control mechanism needed and I wanted to know if the idea was feasible before I went ahead with it.

I guess this idea has already been thought of and isn't feasible or somebody else would have thought of it by now.

My question is. Can I utilize the movement of water boiling in a vacuum to create electricity?

My thinking is I could place an electric motor within a volume of water in a sealed compartment and place that within a vacuum, that has had all air removed from the water so it is just water, and the water particles would begin to boil, turning the electric motor and generating electricity. Now I know that the water would eventually cool and freeze. So what I would do is have a computer controlled system that adjusted the pressure and temperature of the vacuum chamber to keep the water at a point where it boils indefinitely. This computer system would be powered by a rechargeable battery that could charge using the electricity created by the electric motor, enabling it to stay charged during any intermittent changes in electricity output caused by part of the water freezing.

I guess I would have to also connect a heating element up to this computer and place it on one end of the water compartment, and continually have the water defrosted as it froze to keep the particles moving.

I envision a system that using water, a vacuum chamber, an electric motor, a heating element, a rechargeable battery and a bit of temperature/pressure control via a computer I could create an indefinite source of electricity that did not rely on any outside force and was self contained and safe and easy.

These YouTube videos got me thinking about this. I just want to know from expert physicists on here, is this a viable project to consider working on or a waste of my time? Feel free to let me know what the Achilles heel of this idea is, as I am sure there is one.

http://sleet.aos.wisc.edu/~gpetty/wp/?p=930

 

[DrClaude]

Closed pending moderation.

 

[russ_watters]

This thread was temporarily locked because it smells like an attempt at perpetual motion and we wanted to discuss/evaluate it. I don't have time to go through it in detail to figure out for sure, but I have a soft-spot for lost souls, so I'm going to attempt to give you some help and we'll see where it goes. Please note that perpetual motion is against the laws of physics and therefore also this forum, so if it becomes evident that this is an attempt at perpetual motion (even an honest, misguided one), this will be permanently locked and/or deleted.

First things first, I think you already know this and probably don't want to hear it, but you need to:

Your interest in this idea shows that mechanical engineering is the right course of study/career path for you, but there are no shortcuts. The things you are investigating are pretty much all covered in a Thermodynamics 1 course, generally taken in your second year. So if you're having trouble with first year math, the thing to do is set aside your pet project, focus harder on the math and get back on track academically. Then you can pick this pet project back up later - and viola - figure it out much faster because you've learned the tools needed to analyze it!

That said, a little hint, which may be all that's needed to dispense with this:

A steam engine is a steam engine. They are all basically the same. They all have four processes (and all other thermodynamic systems are variations on the same themes):
1. Heat addition/boiling the water.
2. Running the steam through a turbine to generate rotational power (which lowers the pressure of the steam).
3. Heat rejection/condensing the steam back to water.
4. Compressing the water to get it back to the initial pressure.

https://en.wikipedia.org/wiki/Rankine_cycle

So, my first pass at your post tells me you want to run the cycle below ambient pressure to enable the water to boil at ambient temperature. That's fine. A passive heat exchanger can provide the heat addition in step 1 to boil the water. But after you've run the steam through a turbine it's now at even lower pressure. So how are you going to get it back to water? You need heat rejection to condense it: You need something to cool it below ambient temperature. Do you have it?

See, all heat engines do the same thing: they harness a pre-existing temperature difference to generate energy by moving heat in the direction it wants to go anyway...and then getting in the way. So you need that temperature difference to harness. Do you have it?

I could envision this working to harness small temperature differences, such as warm summer air versus a cool stream. Or a sun-heated surface versus the cooler air in the shade below it. But there's something else you'll need to learn in the first few weeks of that first thermodynamics class: power and efficiency are a function of temperature difference. So if your temperature difference is small, your power output and efficiency will be very low.

 

[DrClaude]

This computer system would be powered by a rechargeable battery that could charge using the electricity created by the electric motor, enabling it to stay charged during any intermittent changes in electricity output caused by part of the water freezing.

I guess I would have to also connect a heating element up to this computer and place it on one end of the water compartment, and continually have the water defrosted as it froze to keep the particles moving.

I don't see how you'll be able to achieve this, including creating the vacuum, without using more energy than your device will provide.

 

[mfb]

Creating the vacuum will need much more energy than you get out of some boiling water.

 

[CWatters]

I envision a system that using water, a vacuum chamber, an electric motor, a heating element, a rechargeable battery and a bit of temperature/pressure control via a computer I could create an indefinite source of electricity that did not rely on any outside force and was self contained and safe and easy.

If all the component parts could somehow be made to work 100% efficiently then at best you would break even. eg There would be no surplus electricity that you could extract to do anything useful with. In effect any electricity generated would all be used to run the component parts.

The Achilles heel is you said it would "not rely on any outside force" which I take to mean no outside energy source. The law of conservation of energy means that you can only take out what you put in, and in this case you say there is no outside energy source putting any energy into the system so there will be no surplus you can extract.

 

[russ_watters]

While the OP seems to say perpetual motion is desired, it is so thin on details as to be very difficult to tell if that's really what this is about or if he just misunderstands how such a cycle would work. However, the basic idea of a below-ambient pressure steam cycle is not inherrently flawed. Heat pipes utilize the concept:

An interesting property of heat pipes is the temperature range over which they are effective. Initially, it might be suspected that a water-charged heat pipe only works when the hot end reaches the boiling point (100 °C, 212 °F) and steam is transferred to the cold end. However, the boiling point of water depends on the absolute pressure inside the pipe. In an evacuated pipe, water vaporizes from its melting point (0 °C, 32 °F) to its critical point (374 °C; 705 °F), as long as the heat pipe contains both liquid and vapor. Thus a heat pipe can operate at hot-end temperatures as low as just slightly warmer than the melting point of the working fluid, although the maximum power is low at temperatures below 25 °C (77 °F).

https://en.wikipedia.org/wiki/Heat_pipe
I'm not sure that's worded great, but for example a system charged to 0.1 atm has a vaporization temperature of 115F/46C. As it cools, the mixture becomes more water at a lower temperature. This works great for cooling a computer CPU.

All that is required to circulate the water/steam in a heat pipe at near ambient temperatures is a temperature difference and there are a lot of ways one can be generated for free.

Creating the vacuum will need much more energy than you get out of some boiling water.

No: the vacuum creation doesn't have to be a continuous process. Once you charge a thermodynamic system to whatever pressure it is going to operate at, you're done. A heat pipe can be charged in seconds and operate for decades. The charging cost is arbitrarily close to zero.

 

[SciencePerson]

What I'm seeing here is that it absorbs energy from the water, then he would let the natural air heat it back up maybe even by a tunnel in the vacuum (like a cube with a hole going down) and then back to vacuum it burst apart again by photons flying the molecules off with themselves as I like to say and moves the motor by photons going into it moving the motor~ I'm going analyze this idea yet.

 

[mfb]

No: the vacuum creation doesn't have to be a continuous process. Once you charge a thermodynamic system to whatever pressure it is going to operate at, you're done. A heat pipe can be charged in seconds and operate for decades. The charging cost is arbitrarily close to zero.

I don't see any mention of a system where the vapour is condensed again.

What I'm seeing here is that it absorbs energy from the water, then he would let the natural air heat it back up maybe even by a tunnel in the vacuum (like a cube with a hole going down) and then back to vacuum it burst apart again by photons flying the molecules off with themselves as I like to say and moves the motor by photons going into it moving the motor~ I'm going analyze this idea yet.

That does not make sense at all.

 

[russ_watters]

I don't see any mention of a system where the vapour is condensed again.

Agreed. There's no mention of much of anything. I'd sure hope he's not thinking of using a turbine and and a vacuum pump (fan) in series, because there's no need to boil any water if that's all you're doing (and of course, no thermodynamic cycle and no energy output)! But yeah, we've seen exactly that before too (a Venturi tube as a pmm).

At this point, with the OP coming back it may be that we've covered the relevant problems with whatever he was thinking and may be better to close the thread.

Chris: PM me if there's more you can/want to add to this and I'll re-open if appropriate.