| The original video at the start of this thread just demonstrates the gullibility of the press in this country. As many have stated the basic laws of thermodynamics prevent getting more energy out of a chemical system than you put in.
That said, I would like to make a statement on the use of hydrogen as an energy source at least with respect to chemical energy. Hydrogen is not an energy SOURCE. There is no natural source of hydrogen on this planet that we can exploit. All hydrogen must be made by dissociating it from other chemicals to which it has bonded. This takes energy which can be generated in any number of ways, which means at best, hydrogen can be thought of as an energy storage or transportation medium. Like a battery you will never get more energy out of it than you put in, and in actuality it will always be less. In addition hydrogen is a difficult product to store and transport. Hydrogen is volumetrically inefficient due to its low density. To be stored efficiently on a volumetric basis it must be liquefied or compressed or stored as a metal hydride. The first two require a tremendous amount of energy. The second requires heavy metal storage tanks capable of holding thousands of PSI in pressure, and the last a heavy tank of spongy metal. In addition, most inexpensive metals react with hydrogen and become brittle over time (not that long of time by industrial standards). If we changed current natural gas pipelines to hydrogen we'd have to dig them up and replace them every couple of years. Despite all of the hype a chemical hydrogen based future makes little sense (IMNSHO).
On the question of water as an energy source, I think people are a bit confused by the difference between extracting energy from moving water and water as a chemical energy source. The earlier statement about magnetohydrodynamic drives could probably have been better stated as magnetorhydrodynamic generation. Saltwater is a conductor and as those of us who took physics in high school know, if you move a conductor in a magnetic field you generate an electric current. It is the basis by which all of the alternators and generators, we all know and love, work. In magnetohydrodynamics the saltwater is simply the conductor and moving that through a magnetic field generates electricity. The energy is extracted from the motion of the water, not the chemicals of the water. The water was placed in motion by some other energy source such as solar (non-tidal currents, evaporation) or gravity (tidal currents). Again water is not the source of the energy, but just a storage medium. The issue with Magnetohydrodynamics is that the conductor must be very good and moving very fast (hot) for maximum efficiency. Saltwater is neither of these. This is why magnetohydrodynamic generation works best with plasmas rather than saltwater. I'm not sure that magnetohydrodynamics in seawater can ever overcome the system losses to generate usefull amounts of electricity. If it could I suspect someone would have built a little donut shaped magnet with a couple of wires hooked to it that we could drag behind our sailboats to recharge our batteries.
There are no magical answers to the energy problems we face as a society. The ugly truth is that hydrocarbons (petroleum) are very efficient form of transportation fuel. It has a very high energy content by weight and volume and and can be stored in light weight containers at normal temperatures and pressures. It will be very hard to displace hydrocarbons as transportation fuels. The best bet might be to concentrate on biofuels. Note that biofuels (biodiesel and alcohols) are hydrocarbons, but their carbon source is atmospheric carbon instead of fossil carbon so they are by enlarge carbon neutral. I am aware of the arguments and actually agree with arguments that current biofuel technologies, especially those based on grain actually take more fossil fuel input than they replace. I do believe that developing technologies in these areas based on cellulose have the potential to fix that issue.
Now I'll get off my soap box.
Bill
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