# Converting Pressure to Energy

## Is a system for converting high pressures to energy possible?

• ### Unlikely for 75-250

• Total voters
13

#### caumaan

I'm not completely sure that this is the propor Engineering message board for this topic, but I am not an engineer so I have an excuse!

While I was watching something about sub-oceanic and sub-terranian colonies, I got an idea about a structure's exterior to use the force applied to it by the high pressure for two purposes;

1.To divert pressure from the structure.
2.To use this diverted pressure as an energy source for the colony.

I know that this is a radical idea, but I still don't know if it is possible in the near future (50 years or more). Tell me what you think.

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#### one_raven

Do you have some idea of how the mechanism that would convert the pressure might work?

#### Artman

There is a direct relationship between steam pressure and temperature. You can actually tell what temperature the steam is if you know the pressure. There are tables to indicate how much sensible heat and how much latent heat (heat of vaporization) energy there is in each lb of steam at many different pressures.

Diverting the pressure is another story. Good idea, but how do you accomplish it?

#### Integral

Staff Emeritus
Gold Member
Humm... Suppose you have a sizable underwater structure. The distance from top to bottom would represent a significant pressure differential. If you were to run a duct from the bottom to the top there could/should be a current flowing through it. Insert a turbine and you could conceivably generate power. The amount of power would depend on the size of your structure.

Edit:
The more I think about this the more conviniced I become that it CANNOT work. It seems to imply that if you were to submerse a open ended pipe into water. Water would come gushing out the top end. This does not happen, so there is something missing.

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#### caumaan

No, I don't have a single idea as to how the strucutre itself would work, and the idea isn't to have some sort of pipe coming from the strucutre, but to have the exterior of a structure itself have this purpose.

Once again, I am not an engineer, but I beleive that if one were to deterine how water would act on the structure, that would help the system along significantly.

Hmm, I never really thought of vertical pipes for this concept.

There are some things in this world that will never change.

#### russ_watters

Mentor
Pressure doesn't work the way you think it does, caumaan. You seem to be saying it is downward forces only. It is not. When you are underwater, you have the same pressure pushing at you from all directions - even from underneath you.

#### wimms

The only way to consume energy stored in pressure and let it do some work is to stop resisting its crushing force? Not very practical it seems.

#### NateTG

Homework Helper
It might be feasible to use water pressure to pressurize gasses as an energy storage medium though.

With a valve arrangement, you could concievably just lower a tank into deep water and use it to pressureise the gas in the tank. Unfortunately the pressure gradient of water and neccessary tank size would probably make this approach less than ideal.

A much more interesting technology is to use the temperature difference in the water at different depths to generate electricity. This is currently being done in Hawaii, and would be quite feasible for deep-water colonies.

#### NateTG

Homework Helper

The principle is proven, and could plausibly be developed for sufficient power within the next 50 years.

Your colony could also use tidal or geothermal power.

#### young e.

No, it is not possible to convert even very high pressures into energy. In the sense that pressure is an amount of force per unit area while energy is the amount of doing work expressed in joules or calorie or btu .Take the following formula:

Energy= (force X distance)

Pressure= Force/ area

We can eliminate and create pressure but we can't eliminate and create energy. As the law of conservation of energy states that

"ENERGY CAN'T BE CREATED NOR DESTROYED IT JUST TRANSFORM FROM ONE FORM TO ANOTHER"

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#### NateTG

Homework Helper
Originally posted by young e.
No, it is not possible to convert even very high pressures into energy. In the sense that pressure is an amount of force per unit area while energy is the amount of doing work per unit time.
For physicists, the amount of work per unit time is referred to as power.

Regarding your claim that energy cannot be converted to pressure - pressure is a form of potential energy, and there are many machines that use pressure differences to do work. These include all combustion motors and all pumps.

#### young e.

Originally posted by NateTG
For physicists, the amount of work per unit time is referred to as power.

Regarding your claim that energy cannot be converted to pressure - pressure is a form of potential energy, and there are many machines that use pressure differences to do work. These include all combustion motors and all pumps.
I think the right thing to say that statement is pressure is one of the media to create potential energy. Regarding your claim that pressure is one form of potential energy, all i can say is that the fact there is a presence of pressure, energy is there but not pressure is converted into energy. In fact the unit of pressure such as Pascal and Psi has no equivalent to Joules, Calorie or British Thermal Unit.

#### NateTG

Homework Helper
Ah, I think there is a miscommunication here -- we're thinking of different meanings of convert.

#### russ_watters

Mentor
Originally posted by young e.
In fact the unit of pressure such as Pascal and Psi has no equivalent to Joules, Calorie or British Thermal Unit.
Pressure itself isn't energy, but the relationship is real. In a device like a compressor, using the pressure difference and volume you can easily find the energy. I think that was his point.

In any case, there are plenty of devices that convert pressure to energy and vice versa. There are even some newer ones such as piezzoelectric plastics that convert linear mechanical energy directly into electrical energy: when you stretch it, a voltage is induced. Very useful thing.

The way the question was originally posted (a dome at the bottom of the ocean) you have static pressure in an equilibrium situation. So there is no energy change to harness. The conversions we are talking about involve a CHANGE in pressure.

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#### pallidin

I agree with russ.
Pressure can easily be converted into useful energy. This has not been a problem for some time now.
To make it work, however, one must remember that the source of a pressure MUST propagate from a higher to a lower pressure environment in order to extract energy.(Think of hydroelectric dams, for instance)
In an underwater colony, one could easily designed a portion of the shell to perform a "controlled collapse" from water pressure, and thereby convert to useful energy. However, it is short-lived, and to return the system to a further potential state would require as much energy as was extracted. So, it would be a "one-shot" affair.

#### young e.

okay i understand now what you all mean, i have just misinterpreted the statement " conversion of pressure to energy". My point is rely purely on the law on conservation of energy that is energy is energy and can only be converted into another form of energy also. So guys I've got ur points. NateG was right that I hve misinterpreted him.

#### kishtik

We can use pressure differences of air to do work and generate electric. This bleeding-edge technology is called "windmill" among ordinary people.

#### russ_watters

Mentor
Originally posted by young e.
okay i understand now what you all mean, i have just misinterpreted the statement " conversion of pressure to energy". My point is rely purely on the law on conservation of energy that is energy is energy and can only be converted into another form of energy also. So guys I've got ur points. NateG was right that I hve misinterpreted him.
Your interpretation aside, your point is still quite valid and far too often ignored.

#### Averagesupernova

Gold Member
Originally posted by kishtik
We can use pressure differences of air to do work and generate electric. This bleeding-edge technology is called "windmill" among ordinary people.
This very real technology is technically solar since the winds involved originate from the heating of the sun. It works, it is used, and has been used for centuries. And if you wanna get REALLY technical, it is nuclear energy. The sun is a nuclear furnace. We should exploit it as much as possible. No matter what we do here on earth, the sun will continue to shine. It's there for collecting.

#### ///mon3y

pallidin said:
I agree with russ.
Pressure can easily be converted into useful energy. This has not been a problem for some time now.
To make it work, however, one must remember that the source of a pressure MUST propagate from a higher to a lower pressure environment in order to extract energy.(Think of hydroelectric dams, for instance)
In an underwater colony, one could easily designed a portion of the shell to perform a "controlled collapse" from water pressure, and thereby convert to useful energy. However, it is short-lived, and to return the system to a further potential state would require as much energy as was extracted. So, it would be a "one-shot" affair.
well put ^^

"Converting Pressure to Energy"

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