below the surface of the world's oceans, lies a vast and inexhaustible
energy source, completely untouched by humans. Capable of providing
enough power to make 20 GW+ generating stations a realistic expectation,
its exploitation has only been awaiting the moment that a practical
means of utilizing it could be developed.
the Earth, our longest continuous mountain range extends over 65,000km
(80,000 km if you include non-contiguous mountains), and yet it
doesn’t even have one official name. This system interconnects
every ocean of the world like a seam around a baseball.
lines show the boundaries of tectonic plates around the earth. The
points where plates
diverge, as noted by the red arrows, are prime locations for hydrothermal
called Mid-Ocean ridges, they are a product of plate tectonics,
the points at which the continental plates are pulling away from
each other at a divergent boundary. Islands sometimes form where
the ridges extend above sea level. Iceland, Bermuda, the Azores,
and Tristan da Cuhna are products of the Mid-Ocean Ridge system.
the plates separate from each other, magma rises from within the
earth to fill the gap.
plates are moving away from each other at about the same rate that
human fingernails grow, about 2 cm a year. As they stretch and weaken,
a complex convection process fills the gap between the plates with
new volcanic crust drawn from the earth's magma.
crust is formed at an oceanic ridge, while the lithosphere is subducted
back into the asthenosphere at trenches.
is this intense volcanic activity along these ridges that results
in a phenomenon known as hydrothermal vents. Deep ocean pressures
force seawater through cracks in the crust of the earth, where it
ultimately makes contact with the magma. That water is eventually
vented back into the ocean in a continuous geyser of superheated
water (hereafter referred to as "fluid" because of the
chemical changes it undergoes while in contact with the magma),
exiting at velocities of 1-5 m/sec and at temperatures of 200-400°
C (400-750° F), hot enough to melt lead.
"black smoker". The "black smoke" consists of
an abundance of dark,
fine-grained suspended particles of various metals and minerals
precipitate when mixed with the cold seawater and rain down onto
sea floor below.
the temperatures are extremely hot, the high (225 bar or 3,200 psi)
ambient pressure keeps the fluid from boiling, and the liquid fluid’s
contact with 2° C or colder surrounding seawater causes a fantastic,
uninterrupted and uninterruptible cocktail of metals and minerals
to precipitate out of the fluid and rain down upon the seabed below.
The precipitate includes iron, gold, silver, copper, zinc, cadmium,
manganese, and sulfur, along with significant amounts of methane
gas mixed into the fluid. Halides, sulphates, chromates, molybdates
and tungstates are also abundant. For this reason, the best surface
mines are located over hydrothermal veins of the geologic past.
energy available is simply immense, far beyond anything ever before
harnessed by mankind. National Geographic estimates the energy escaping
from just the known vents to be 17,000,000 MW, an amount that approximates
all human consumption on the planet, and there are tens of thousands
of kilometers of ridge system that have never even been explored.
red dots are known hydrothermal and geothermal locations worldwide.
This is only a partial map, since there
are tens of thousands of kilometers of the Mid-Ocean Ridge system
that have never even been explored. Note
their proximity to energy-hungry areas such as China, Japan, Korea,
the U.S., South America, and Europe.
There are also some vent fields fairly close to India and the Middle
since the long-postulated hydrothermal vents were first confirmed
in 1977, every observer has understood the vast energy content of
the fluid, but no one has had the slightest idea of how to utilize
this amazing natural phenomenon. What kind of equipment could be
used 2,300 m below the surface? How could it be serviced?
problems of hostile environment, inaccessible locations, and the
impossible demands placed on equipment by any imagined utilization
scheme seemed to be insurmountable, leaving this magnificent resource
untouchable at the bottom of a cold, dark sea.
California inventor Bruce C. Marshall has patented the first practical
system for commercializing the energy flowing from these vents.
Called the Marshall Hydrothermal Recovery System, it literally has
the potential of revolutionizing electric power generation worldwide.
starts with a deceptively simple system of insulated pipes and a
funnel. Rather than attempting to deal with the superheated hydrothermal
fluid at the bottom of the ocean, the heart of the Marshall System
lies in ducting that fluid to the surface to be processed on platforms
similar to those used for oil exploration and drilling.
logic is inescapable. If the fluid is trapped when it is hot and
is maintained within an insulated structure, it can do nothing but
stay hot and rise. It would move through the pipe by a combination
of vent flow velocity, convection, conduction, and flash steam pressure
generated as the superheated fluid rises and the ambient pressure
diminishes. A funnel mouth at the input end would act as a venturi
to increase flow velocity within the pipe.
fluid would be utilized at the surface by providing the heat for
traditional steam turbine generation. The superheated fluid would
either be used directly or it could heat a clean working fluid within
a heat exchanger to ultimately drive the turbines. It could also
be used with more exotic technologies such as thermoelectric generation
or even magneto-hydrodynamics, or several or all of the technologies
could be combined to drain every last watt that the heat energy
contains. The Marshall System provides the vehicle to deliver a
continuous, high-volume stream of superheated fluid to the surface,
and once there, it's up to the discretion of system operators to
decide how best to utilize it.
appreciate the astonishing scale of the Marshall System's potential,
one needs to first appreciate the astonishing scale of the vents
the Juan de Fuca Ridge for example, which lies about 200 miles off
the coast of Seattle, the main active vent field is about 180 m
wide and 350 m long. Within that field are more than 15 large [up
to 30 m in diameter and >20 m in height], actively venting structures
and numerous smaller, less active or inactive structures.
order to find out what the energy potential of various sites would
be, Marshall wrote a computer program to do the calculations. Simply
entering the parameters of pipe size, flow rate, and temperature
provides the predicted outputs.
inputs used are based on numbers provided by such reputable sources
as the USGS, NOAA, NASA, and Woods Hole Oceanographic Institution.
They show the temperature of vents on the Juan de Fuca Ridge at
380°C (716°F). They also show flow rates ranging from 3-5
are the numbers chosen to use to visualize the amount of energy
available for recovery from the vent system. Choosing a 3m diameter,
and a 3m/second flow rate, along with a 360°C fluid temperature
at the surface were all reasonable assumptions based on actual measurements.
When considered against a 20°C ambient temperature, an incredible
30 GW of heat energy is being brought to the surface.
Screenshot of Marshall's energy calculator
showing the potential of a
3m diameter pipe with a 3 m/second flow rate, along with a 360°C
output temperature at the surface and a 20°C ambient temperature.
only a portion of that will be convertible to electrical energy,
the raw power can easily be put into perspective. The largest power
plant of any kind in the U.S. is the nuclear plant at Palo Verde,
Arizona, and its output is slightly less than 4 GW, while Hoover
Dam’s output is about 2 GW. A hydrothermal plant based on
these figures potentially has an output that is an order of magnitude
greater than hydroelectric, and at least five times greater than
nuclear. The generating capacity of the whole state of Florida is
about 48 GW, and the raw energy available from one three-meter pipe
is equal to 62% of that.
source of the fantastic numbers becomes evident when it's noted
that 76,000,000 liters of superheated fluid is brought to the surface
every hour. When one considers the energy content of nearly a superheated
swimming pool brought up every second, it's easy to see why the
numbers are as high as they are. 20 GW or even larger renewable
energy power plants are truly on the immediate horizon. That's enough
to power 20 million homes.
mathematics used for the energy calculations are straightforward.
At a flow rate of 300 cm (3 m) per second, a pipe with an area of
1 cm2 would deliver 300 cc, or .3 liters of water per
second. A 3 m diameter pipe has an area of 70,685 cm2,
so that would translate to 21,205 liters per second of volume.
one considers the amount of heat it took to raise the water to a
given temperature, we can also know how much energy it contains.
If one calorie is the amount of energy it takes to raise 1 gram
of water by 1o C, then it would take 21,205,000 calories/second
to raise the one-second flow volume by the required 1o
C. To create a 330o differential between water and ambient
temperature would therefore need 7 Gcal/second of heat energy in,
and it also graphically demonstrates just how much energy is available
for recovery. That same amount of energy, expressed in terms of
a nuclear explosion, would total about 605 kilotons over the course
of one day.
deceptively simple innovation of the system is what Marshall refers
to as a Thermal Enhancement Pipe, a device that requires almost
no maintenance. There is a layer in any deep body of water called
the thermocline, above which the water is relatively warm, and below
which the water is always very cold. This occurs because sunlight,
and its warming effect, will only penetrate a relatively short distance
into the sea. Currents, wind, and other activity mix that water
and the upper layer is created. However, below that point, the water
is so cold and dense that it simply has no energy to rise, so it
stays there, unable to break through the thermocline to the warmer
Thermal Enhancement Pipe is nothing more than an insulated pipe
open at both ends like a huge drinking straw, with the surface end
extending several feet out of the water to prevent the contents
mixing with the surrounding seawater, and the bottom end extending
down below the thermocline. Water is pumped from the surface within
the open pipe, and as it is withdrawn, it is refilled by atmospheric
pressure at the only point open to the sea, with frigid water from
water is withdrawn from within the pipe, it can only be replaced
by extremely cold water from below the thermocline, and within a
very short time the pipe will contain nothing but water just a degree
or two above freezing. Since thermal energy availability is determined
by the temperature difference between two points, by using the water
withdrawn from it for the cold side of any thermal extraction process,
this very simple device adds at least 1.5 GW to the expected output
of the system, and yet it consumes no more energy than would be
required to pump water from the sea surface to the platform height
where energy extraction would take place.
minor addition increased the plant's potential output by 1.5 GW,
a virtually free add-on that is more powerful in itself than the
output the great majority of plants currently operating in the U.S.
the 3 meter pipe diameter was chosen for discussion only because
it seemed a reasonable size to work with, there is nothing to stop
even larger sizes from being used as long as they can be dealt with
practically. The only physical limitation on the system is what
the real world of manufacturing and pipe handling will allow. If
a vent system could support the necessary volume of flow, and one
allows for a 4-meter pipe, the numbers appear to come straight out
of a science fiction novel about nuclear fusion.
Screenshot of Marshall’s energy calculator
showing the potential of a 4m diameter pipe
with a 3 m/second flow rate, along with a 360°C output temperature
at the surface,
utilizing the thermal enhancement pipe and a 5°C ambient temperature.
single 4-meter pipe would deliver an astronomical 53 GW of raw energy
to the surface. And that number comes from using a 20°C ambient
temperature. If the Thermal Enhancement Pipe is used, the available
energy increases to a mind-boggling 56 GW, or 75 million horsepower.
with a concept like that of the Marshall System, how does one stand
a pipe up in the middle of a 30 m wide hole in the ocean floor?
Marshall System includes a conical base structure that is large
enough to surround the vent, which would allow the recovery pipe
to pass down through the center of it as deep into the vent as practical
to recover fluid at the hottest possible temperatures. Then pipe
sections are added one at a time, with the weight of the column
of pipe supported by the cone structure itself.
Marshall System's base is constructed of highly stable circles and
triangles. The horizontal support arms only take the
weight of the one section of pipe to which it is attached. The first
section of pipe at the top of the cone is the one that takes
the weight of the column of pipe to be built above. It would be
constructed on land or aboard a ship and then lowered into
place as a complete unit. The intake pipe is placed as deep down
into the vent as possible, to recover the highest temperature
fluid. Anchors can be drilled through the bottom ring and into the
seabed below for additional stability.
funnel at the intake end is designed to act like a venturi to increase
the velocity of the fluid within the pipe.
detailed topographical mapping of the area surrounding the vent
would be done, and a reverse matching contour would be built into
the underside of the bottom ring. That would allow a stable, level
surface upon which to build regardless of the irregularity of the
sea floor below it.
was an issue that received serious consideration. One section of
insulated 3m pipe, 3m long would clearly weigh more than a ton,
and with 700 or more sections added together to reach the surface,
the support stucture would have a hefty load to bear.
further source of concern was vertical stability. With a height
more than 800 times the diameter of the base, the pipe column was
an extremely unstable shape that would topple over long before it
ever reached the surface. Both problems were minimized with one
Buoyancy collars were added to the design, each sized to provide
lift between 95-99% of the weight of each segment. In doing so,
the cumulative weight on the support structure at the bottom would
be reduced to only 1-5% of the actual weight. Also, because things
that float want to go upwards and not sideways, the vertical stability
would be greatly enhanced. Adding in swiveling connections between
the pipe segments to allow flexibility and using intermittent mooring
lines to stabilize the column were the finishing touches.
One possible configuration of flexible pipe
vents also come in many different shapes and sizes. The giant vents
of the Juan de Fuca Ridge are the exceptions, but many are quite
small, 20 cm (8 inches) across or so. They are often found in close
proximity to each other within a confined geographical field. Another
problem that had to be addressed was making the system work under
these conditions as well.
hydrothermal vent field showing several active vents in close proximity
to each other.
the end, an almost identical solution was settled upon, utilizing
the same type of conical structure, but instead of a single pipe
it would employ multiple recovery pipes and a manifold to combine
the outputs of the different vents into one single pipe for transit
to the surface. With the bottom ring approximately the same size
as for the large vents, 30m or more in diameter, an area of over
700 m2 (7,800 ft2) would be under the framework.
That is room enough to capture and combine the fluid from a lot
of small vents in a dense field.
configuration for capturing the output of many small vents and combining
it into a single pipe through a manifold.
was apparent from the beginning that along with the superheated
fluid would come the incredible mineral cocktail mentioned earlier,
and Marshall has patented not only the first hydrothermal energy
system, but also the first practical deep sea mining system. It
is envisioned that the slurry that remains after the heat has been
extracted would be either processed on-site or loaded aboard ships
for processing elsewhere. Removal of valuable metals and minerals
from the slurry will be far easier than trying to mine them from
the ground because of their extremely high concentrations, and because
they are being delivered to the mine operators along with the hydrothermal
fluid rather than being forcibly pulled from the earth.
complete Marshall Hydrothermal Recovery System, showing electric
generation, water desalination, and mining
facilities operating together.
shapes on the pipe segments are buoyancy collars to reduce weight
total and increase vertical stability.
Waste Return Pipe has also been included because there is certain
to be an unneeded byproduct of the mining and energy production
system that will require removal. It’s simply a pipe extending
deep down from the platform through which leftovers from the mining
operation can be disposed.
should not be considered as a source of pollution, since what is
being returned through the Waste Return Pipe came from the sea in
the first place. Strict safeguards need to be implemented to assure
that real pollutants are not disposed of through the return system,
but the logic of sending extraneous natural materials back where
they came from is inescapable.
energy and mining are of themselves ample reason to build the Marshall
Hydrothermal Recovery System, there is one more benefit that became
obvious as it was being developed.
immense volume of superheated fluid that would be brought to the
surface would spontaneously flash to steam as pressure is released,
and it was a small leap to realize that the steam can be distilled
back into fresh water. It became quite obvious that this is also
a water desalination system unlike any previously conceived. While
some measure of further processing is likely to be required after
distillation, incredible volumes of water could be made to be quite
pure with little additional effort and energy input.
key is in the figures for a 3m pipe that show 76 Ml of water being
brought to the surface every hour. Even when using a very conservative
figure of only 50% of it recovered as fresh water, the total figure
is still just short of a billion liters of water a day.
closed loop system was also developed that would heat a clean working
fluid in a heat exchanger positioned over the vent. It would then
be sent to the surface for energy extraction, and would be returned
back to be reheated and start the cycle again. Because the hydrothermal
fluid itself is not brought to the surface, mining is not possible
in this configuration, but there are some strong advantages to it
system that directly uses hydrothermal fluid will have to deal with
the technical issues that would surround the utilization of a potentially
corrosive, high-velocity, superheated fluid containing particulate
matter. The closed-loop system completely obviates any of those
concerns. The only product dealt with is superheated clean working
this closed loop configuration, the Marshall System does not actually
bring the hydrothermal fluid to the surface. Instead,
hydrothermal vents heat a clean working fluid through a heat exchanger,
which is then returned for reheating after its energy
has been extracted on a platform similar to an oil platform.
have expressed a valid concern about environmental issues, since
hydrothermal vents are home to an amazing variety of life forms
that are unknown anywhere else on earth. Rather than using photosynthesis,
they use chemosynthesis to produce energy in the depths where no
light is available.
blood-red tubeworms are one form of life that flourishes in the
chemical-rich environment surrounding
hydrothermal vents. The color comes from hemoglobin, the same substance
that makes our own blood red.
best method of dealing with the life encountered is to simply transplant
a sample of each unique form to another nearby vent where it can
continue to thrive, but it can also be considered reasonable to
ignore the life forms completely and allow them to perish.
that may seem to be a barbaric approach to anyone with an environmental
conscience, it must be realized that vents open and close by nature
all the time, and the natural cycle will have all the life forms
around any given vent system die at some point even if there is
no human intervention of any kind. This process has been going on
uninterrupted since the earliest evolutionary days of our planet.
It seems that life regenerates spontaneously as new vents are formed.
was noted in a Rutgers
University study that showed a remarkable regeneration only
nine years after an undersea volcanic eruption sealed some known
vents and killed all the surrounding life. It is also important
to recognize that the number of untouched natural vents that will
remain with their ecosystems intact would dwarf the tiny overall
percentage of vents that might ever ultimately be tapped for human
use. Only by keeping the incredible scale of the Earth's tectonic
plate system in mind can that fact be adequately appreciated.
Marshall System seems to have a Jules Verne quality about it, but
the fanciful ideas are based on science fact, not science fiction.
There is no technology used that has to be developed from the ground
up, even if some may have to be modified for this application. It
marries the existing technologies of deep-water oil platforms, electric
generation, undersea cables, water desalination, and pipe laying
and manufacture. The Marshall System is really no farther into the
future than the time involved in decision making, securing of financing,
engineering, production lead-time, and construction. It is almost
inevitable that it will be producing energy, minerals, and fresh
water somewhere in the world within five years if a concerted effort
to do so is made.
domestic and international patents are pending on the Marshall System,
and the goal is to license the technology to any government, company,
or consortium that wants to build it. The first systems will most
likely be a shared venture between energy, water, and mining companies.
Since this article was originally published, a major oil company
has run two computer simulations on the Marshall Hydrothermal Recovery
System. The company verbally shared the results of its simulations
but declined to be identified. These are their findings.
2,500 m depth
3740 psi (258 bar) ambient pressure
350o C vent temp
Surface vent temp 340o C
12.13" (31 cm) ID pipe diameter
50% efficiency of steam turbine
Ocean temp at bottom 2o C
Surface ambient 15o C
Platform 30m above water line
83 MW energy
Energy density (83 MW/area of 31 cm pipe) roughly 1 MW/10 cm2
pipe area, or about 3.3x106 more intense than solar radiation
>100m/sec (218 mph or 360 kph) steam velocity at surface
30 KT/day steam (25,000m3)
Useful surface temp 340o C
Useful surface pressure 70 bar (1015 psi)
25,000 tons/day delivered to surface
25-35 kg solid/ton
25,000 tons x 25-35kg solids/ton = 625,000 kg- 875,000 kg solids