Tapping Energy from Buoyancy ```Name: Blake Status: Educator Grade: Other Location: FL Country: United States Date: August 2008 ``` Question: If I were to place an on demand HHO producing fuel cell at the bottom of the ocean - creating a situation where all of the gas production has a mile journey to the surface - Could I utilize the buoyancy force X distance to create more energy than needed to produce the original gas. Obviously it would be done with proper water/electrolyte solution in a partitioned cylinder, not of particularly large diameter but VERY deep, along with a mechanism to harness to buoyancy and convert it into mechanical energy, finally into electricity. Replies: We do not get any net energy from the buoyancy of the gas. It is easier for me to visualize the mechanical part of the problem by imagining a mile-long pipe full of water sticking straight up in the air. To make a bubble of gas at the bottom of the pipe, we have to raise the water in the pipe. When we allow the bubble to travel up to the top of the pipe, the water will get lowered by the same amount it previously was raised. It does not matter whether the bubble is produced mechanically, or by electrolysis; we still have to supply the energy to raise the water to accommodate it. OK, I have glossed over a detail: the water actually gets lowered slightly more than it got raised, because some water was converted to gas, after all, and is no longer in the pipe. But this cannot help, because we would get the same final state whether water at the top or the bottom of the pipe were electrolyzed. I would say this idea works better as an energy-storage method, than as an energy-production method. Tim Mooney If something seems "too good to be true" -- it probably is. I think you run into trouble with the laws of thermodynamics. There is a major link that your cycle does not take into account, that is the work that has to be done by the gas at the bottom of the ocean to form the initial bubble. This is: W = Pexternal x dV. where "Pexternal" is the hydrostatic pressure at the bottom of the ocean. Even if the cycle is reversible, that is, there are no frictional or thermal losses, that work term is the same as the buoyant force but with an opposite sign. Think of the reverse cycle of taking a large bubble of gas at the surface being compressed to the size of the bubble at the bottom of the ocean. The first law of thermodynamics wins again. Vince Calder If I understand your question, you are suggesting that water be electrolyzed in the deep ocean to create hydrogen and oxygen gas, the buoyancy of which can be harnessed to create energy. Unfortunately, it takes more energy to electrolyze water at high pressure at the bottom of the ocean than at low pressure, nullifying any energy you can recover due to buoyancy. If you take a class in thermodynamics, you will encounter equations that take account the pressure at which a reaction takes place. It can be any reaction: a chemical reaction can be sped up or slowed down with pressure; freezing points of materials are altered by pressure; solubility is affected by pressure, and yes, even electrolysis is helped or hindered by pressure (temperature too). Robert Erck Hi Blake, A significant amount of energy is required to split the water to form hydrogen and oxygen gases -- it is not clear from your description from where that energy is coming. A fuel cell does not make HHO from water -- in fact, the opposite, the fuel cell converts the energy of converting HHO to water into electricity. By HHO, I assume you mean a mixture of hydrogen and oxygen gases. I have seen in various on-line sources other non-scientific explanations of "special" hydrogen-oxygen mixtures, but these "special" formulations do not stand scientific scrutiny. So you have to input energy -- you do not get any extra out of the process. However, if you happened to have compressed gas (and it does not have to be at the bottom of the ocean), yes you can do work with that compressed gas. It requires work to compress the gas, and the potential energy of the compressed gas can then be converted into other forms of energy or work. The thing to keep in mind is that there is no such thing as an 'energy creation' device, only energy conversion. Anything that claims to create more energy than it started with is simply not possible. These are generally classified as 'perpetual motion machines', and unfortunately, real, working perpetual motion machines simply do not exist. Even worse, in any energy conversion, some energy is wasted (converted to a non-useful form) -- so not only can you not win (no energy can be created), you cannot even tie! Hope this helps, Burr Zimmerman Click here to return to the Engineering Archives

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