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kitarey

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Buoyant Lift Creates Useful Energy?

I work at a manufacturing plant. One by product of this plant is the issuance of 2000 cfm (cubic feet per minute) of clean air. It is determined that this air could be released from as small as a 3 inch pipe with no adverse harm to the manufacturing process. It would be exhausted at 100 psi. So it got me thinking, how can this be put to use?

Please look at the attached diagram-

My general idea is to build a 100 ft tall (x18x8) tank and fill it with water. You see three shafts; top, middle, and bottom. I have received some information from Winergy, a subsidiary of Siemens regarding gearbox/generators. They manufacture a gearbox that requires 16 kiloNewton meters (11,800 ft lb) of force to operate. This, in conjunction with a matched generator, will produce 100 kilowatts of power, so that a total of 300 kw can be realized in this system.

The input of 2000 cfm at a water depth of 100 ft would mean that each cubic foot would be compressed to approx. one-fourth its surface volume. This means that the 2000 cfm will be entering the bottom of the tank at 500 cfm, then expand to 2000 cfm as it rises to the top of the tank.

A roller chain with “air lift containers” could be attached to the shafts as shown. These containers could be made of carbon fiber, plastic or maybe aluminum. If each were a hollow sphere of 6.5 feet diameter, then the volume would be 143 cubic feet. One factor I have not considered yet (infant stage of idea) is the volume loss of the sphere once the “top” is cut off to resemble a deep bowl. For discussions sake, ignore that at this time. One cubic foot of air will lift 62 pounds to the surface. You see numbers next to each of the rising containers. I roughly calculated what the lifting capability would be for each ascending container at points along the roller chain (snapshot of system). As the air enters the base of the tank it will only fill one-fourth of the container and expand, filling the container as it rises, becoming nearly full at the top of the system, and gaining lift capability as it rises.

Each of the 3 shafts would need to rotate at 60 rpm to generate the 100 kw each. I do not know if this can be achieved. If the cog on the shafts were 2 ft circumference then the containers would need to rise at 2 ft per second. This seems feasible to me to accomplish. I have not located answers regarding natural rising speed of air in water, or filled containers for things such as salvage diving, etc.

With these figures, I calculate that the total, constant lifting capability would be approx. 42,000 lb. If the three shaft require 11,800 ft lbs each, totaling 35,400, then am I close in believing that this can work? I understand that system weight, drag, and water drag need to be considered. Regarding such issues as water drag, it can be minimized once the system is up and running and the water is moving in the same direction as the system. Also, right in the middle of the tank, between the ascending and descending chain, I have drawn a vertical line that represents a separator that would lessen the commingling of water.

One other issue I do not understand how to calculate is the cog size and how it changes things. I had someone tell me the following –

With the chain on a sprocket radius equal to 0.32, there is only 13,370 ft-lbs of torque generated by the buoyant force of 42,000. This is confusing to me. Remember that I had calculated a circumference of 24 inches, which could be adjusted of course. I just decided on that to make calculating the 2 ft per second rise simple. Am I to assume that the larger the cog the less torque?

Anyways, I would welcome any thoughts on this idea.

Thanks so much for reading this. Go easy on me though. I believe that I have a decent amount of common sense, but no great intellect, especially in the area of physics and mechanical engineering.

Kit

I work at a manufacturing plant. One by product of this plant is the issuance of 2000 cfm (cubic feet per minute) of clean air. It is determined that this air could be released from as small as a 3 inch pipe with no adverse harm to the manufacturing process. It would be exhausted at 100 psi. So it got me thinking, how can this be put to use?

Please look at the attached diagram-

My general idea is to build a 100 ft tall (x18x8) tank and fill it with water. You see three shafts; top, middle, and bottom. I have received some information from Winergy, a subsidiary of Siemens regarding gearbox/generators. They manufacture a gearbox that requires 16 kiloNewton meters (11,800 ft lb) of force to operate. This, in conjunction with a matched generator, will produce 100 kilowatts of power, so that a total of 300 kw can be realized in this system.

The input of 2000 cfm at a water depth of 100 ft would mean that each cubic foot would be compressed to approx. one-fourth its surface volume. This means that the 2000 cfm will be entering the bottom of the tank at 500 cfm, then expand to 2000 cfm as it rises to the top of the tank.

A roller chain with “air lift containers” could be attached to the shafts as shown. These containers could be made of carbon fiber, plastic or maybe aluminum. If each were a hollow sphere of 6.5 feet diameter, then the volume would be 143 cubic feet. One factor I have not considered yet (infant stage of idea) is the volume loss of the sphere once the “top” is cut off to resemble a deep bowl. For discussions sake, ignore that at this time. One cubic foot of air will lift 62 pounds to the surface. You see numbers next to each of the rising containers. I roughly calculated what the lifting capability would be for each ascending container at points along the roller chain (snapshot of system). As the air enters the base of the tank it will only fill one-fourth of the container and expand, filling the container as it rises, becoming nearly full at the top of the system, and gaining lift capability as it rises.

Each of the 3 shafts would need to rotate at 60 rpm to generate the 100 kw each. I do not know if this can be achieved. If the cog on the shafts were 2 ft circumference then the containers would need to rise at 2 ft per second. This seems feasible to me to accomplish. I have not located answers regarding natural rising speed of air in water, or filled containers for things such as salvage diving, etc.

With these figures, I calculate that the total, constant lifting capability would be approx. 42,000 lb. If the three shaft require 11,800 ft lbs each, totaling 35,400, then am I close in believing that this can work? I understand that system weight, drag, and water drag need to be considered. Regarding such issues as water drag, it can be minimized once the system is up and running and the water is moving in the same direction as the system. Also, right in the middle of the tank, between the ascending and descending chain, I have drawn a vertical line that represents a separator that would lessen the commingling of water.

One other issue I do not understand how to calculate is the cog size and how it changes things. I had someone tell me the following –

With the chain on a sprocket radius equal to 0.32, there is only 13,370 ft-lbs of torque generated by the buoyant force of 42,000. This is confusing to me. Remember that I had calculated a circumference of 24 inches, which could be adjusted of course. I just decided on that to make calculating the 2 ft per second rise simple. Am I to assume that the larger the cog the less torque?

Anyways, I would welcome any thoughts on this idea.

Thanks so much for reading this. Go easy on me though. I believe that I have a decent amount of common sense, but no great intellect, especially in the area of physics and mechanical engineering.

Kit

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