First allow me to direct you to this link on TG Daily telling you about the potential development of a 'water powered engine.'
Let me summarize how this engine might work: streaming water across an Aluminium/Gallium surface induces the catalytic breakdown of H2O into its component molecules H2 and O2. H2 bubbles away while O2 sticks to the Aluminium surface. H2 can now be burned in a conventional heat engine.
My objection: The bond energy for water is 458.9 kJ/mol which means that this is the energy required to dissociate a molecule of water into its component atoms is roughly twice this. That is quite a lot. Spontaneous dissociation may occur in the presence of the catalyst, but typically, the catalyst will be used up in the reaction. In this context, that would mean that the surface of the catalyst would be 'coated' with a layer of O2 which would prevent further catalysis. To regenerate the catalyst, one would have to 'scrub' the surface; and this will probably need more energy than we can recoup by burning the bubbled off H2. This is because of the Second Law of Thermodynamics, which tells us that one cannot gain any energy by making a spontaneous process run in reverse. An example: water flows downhill, and this is used to rotate turbines and generate electricity. If we had to pump the water uphill in the first place, we would be spending energy in that, and much more than we would recover it flowed downhill. Lesson: there are no free lunches.
Let me summarize how this engine might work: streaming water across an Aluminium/Gallium surface induces the catalytic breakdown of H2O into its component molecules H2 and O2. H2 bubbles away while O2 sticks to the Aluminium surface. H2 can now be burned in a conventional heat engine.
My objection: The bond energy for water is 458.9 kJ/mol which means that this is the energy required to dissociate a molecule of water into its component atoms is roughly twice this. That is quite a lot. Spontaneous dissociation may occur in the presence of the catalyst, but typically, the catalyst will be used up in the reaction. In this context, that would mean that the surface of the catalyst would be 'coated' with a layer of O2 which would prevent further catalysis. To regenerate the catalyst, one would have to 'scrub' the surface; and this will probably need more energy than we can recoup by burning the bubbled off H2. This is because of the Second Law of Thermodynamics, which tells us that one cannot gain any energy by making a spontaneous process run in reverse. An example: water flows downhill, and this is used to rotate turbines and generate electricity. If we had to pump the water uphill in the first place, we would be spending energy in that, and much more than we would recover it flowed downhill. Lesson: there are no free lunches.
No comments:
Post a Comment