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First, a bit of background:
MHD is an abbreviation for magneto-hydro-dynamic.
An MHD generator works by first taking a high pressure
fluid, making it conductive if it isn't already so, then
passing the fluid between a pair of magnets.
Due to the shape of the piping and the shape of the
field, some of the fluid's kinetic energy is
converted to electrical energy.
People have built pumps that use the MHD principle for
all sorts of liquids, including hot molten metals and cold
seawater... there's even been an MHD propelled boat.
People have also build MHD generators using all sorts of
fluids, including flames from fossil fuel combustion,
molten salts, and molten metals.
No one has physically constructed an MHD generator
using moving seawater, but simulations have been done.
This idea takes an MHD generator, and feeds it with the
hot water from an undersea hydrothermal vent.
The liquid from these vents is acidic, approximately the
PH of vinegar, which undoubtedly sours the vast
majority of other half-baked ideas for making use of
deep sea hydrothermal vent energy.
But since MHD doesn't require that there be any moving
parts in contact with the fluid, it should still work in
spite of the caustic hot water.
As with any hydro-power generator, the greater the
pressure differential between the inlet and the outlet,
the greater the power produced.
To maximize power, the exhaust stream of the
generator would leave through a pressure resistant,
thermally insulated, manmade chimney, a few hundred
feet tall. This chimney would prevent the hot
wastewater from mixing with ambient seawater until it
exited at the top.
Since the density of the wastewater would be less than
that of the surrounding water (due to it's temperature),
this would result in relatively low pressure in the MHD
generator's exhaust, compared to it's input.
MHD for the high seas
MHD for converting salty water into elctricity. [travbm, Oct 30 2015]
||One of us took a crack at this one a while back using some
crackpot variation on geothermal generation. I like the
MHD angle much better, and will enjoy watching it torn
apart by the engineering section. Here's a bun to munch on
while we wait.
||If the water's acidic then it can't be caustic. I think you
||While "caustic" is most commonly used in "caustic soda" or "caustic lye", it is not necessarily indicative of an aggressive base; it can, indeed, be acidic. Root is from "burning", as in "holocaust", "hypocaust"... [goldbb]'s usage, while unusual, is correct.
||I shall refrain from snide and insulting remarks.
||(it's a campaign promise, shortly to be forgotten)
||The water flow from the vent travels along the path of least resistance; when you add the generator, that will be quite a bit of resistance to the flow, and the water will want to go elsewhere. Since the "chimneys" built by the venting water's precipitates are not extremely structurally sound, preparing the base to get the water into the generator will be a quite a major part of the project. I think it will be a pretty tough construction environment.
||Because they would be caustic remarks.
||I hate to burst your bubble but someone already developed this idea. SARA has developed a cost-effective solution to energy extraction from ocean waves that is based on the companys patented magnetohydrodynamics (MHD) generator (US Patents 7,166,927 & 5,136,173). The application of this technology promises to cut the costs of wave energy conversion (WEC) systems by a factor of three. With low capital and operating costs the SARA MWEC system has the potential to finally capitalize on this abundant and renewable energy resource.
||SARA has designed, built and tested a 100 kW MHD generator that is a laboratory demonstration of a MWEC design and is also developing a deep-ocean-moored concept that is based on the MHD generator. This combination will lead to the development of cost-effective, rapidly deployable systems not only for coastal communities, but also for deep ocean applications for the Navy and the offshore oil industry. Although putting this over an under water volcano or hydrothermal vents may be new to the idea.
||Well, based on [goldbb]'s own post the idea was already preheated.
||" No one has physically constructed an MHD generator using moving seawater, but simulations have been done."
||Welcome to the Halfbakery, [travbm]. Careful you don't sprain something posting so hard on the first day here - it's a good idea to work into it gradually.
||Your post about SARA reads as though you are a stockholder.
||what normone said, adding to point out that the link this time
is to the point.