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From: (no name) (no email)
Date: Sat Mar 22 2008 - 22:53:14 EDT
Oh no! Not another polemic.
It looks like diesel fuel will cost well above $4 a gallon this season. Fuel
prices at some marinas along the Hudson are at that stratospheric level
already and it's just the second day of spring. The high price of petroleum fuels
has reawakened interest in alternative fuel technologies for transportation. I
say "reawakened" because the first surge of interest was during the oil crisis
of 1974. Our university did a lot of research on the topic for both the Dept.
of Energy and for New York State but support and funding dropped off after the
decline in oil prices.
The '74 crisis was not due to a shortage in oil but rather to a political
decision by OPEC to flex its collective muscle. The present crisis is due to
increased demand for fuel by the surging economies of China and India coupled with
controlled output and reduced supply. Iraq production is a fraction of pre
1990 levels and new oil fields are slower in coming on line. It is not likely
that oil prices will decline significantly in the near future. But enough gloom
and doom. What can we use to power our fuel hungry boats?
I pulled our 1974 era research file recently to refresh my failing gray cells
on its conclusions. To put it simply, the prime value of petroleum fuels is
in their energy density. Other fuels are cheaper for their energy content, but
not as convenient. A case in point. My Willard has a range of 1000 miles using
diesel. Filling my 120 gallon tank at current prices costs me about $460. The
fuel weighs 864 lb. If I were to convert to stored electric power, using lead
acid batteries, I would require 128,000 pounds of battery (64 tons) to
achieve the same range.
A 50 pound golf cart battery stores about the same amount of energy as that
contained in 6 oz of diesel. Lithium ion batteries will save about 2/3 the
weight but will be 10 times more costly. On the other hand, I could buy the
approximately 1200 kWh of electricity necessary to fill the batteries for $190, even
at Con Edison's high prices. If I could somehow manage to run my boat on
coal, the equivalent energy content could be bought for about $50.
Several alternative energy sources have been proposed and even have come into
occasional use. Coal can be converted to a liquid diesel like fuel by a
process that the Germans used during WW2. The process uses so much water and
releases so much carbon dioxide that it drives environmentalists into a fury.
Biofuels, biodiesel, ethanol, and the like, are reasonable substitutes for
petroleum. Rudolph Diesel used peanut oil in his first engines and we seem to have come
full circle. Biodiesel has almost the same energy density as regular diesel
fuel, ethanol about 20% less than gasoline. The downside is that, if not for
government subsidies, they are as expensive as petroleum fuels and compete for
agricultural resources with food crops. Food prices rise as more and more land
is used for biofuels. We may well run our boats and cars on biodiesel, but we
will be paying $10 for a loaf of bread.
What about solar and wind power? There is potentially enough solar and wind
energy available to supply US energy needs. The problems are cost, location,
and storability. The desert areas of the Southwest are prime areas for the
generation of solar electricity. Unfortunately long range transmission of energy
requires an expensive infrastructure. Storage of energy in the amounts needed
for periods when the sun doesn't shine is beyond the scope of present
technology. Wind power has similar problems. Atomic power is one answer but cost and
public fear have stymied atomic power plant construction for decades. Further,
electric power, even if available in adequate quantities, is not suitable for
boats because of the onboard battery weight problem.
Electricity, whether from solar, wind, atomic, or coal plants can be stored
in a denser form. Power can be extracted as needed. Water can be electrolyzed
to release hydrogen and oxygen, transmitted as gas or liquid to distant
locations, then recombined in a fuel cell to provide electricity. This is the likely
scenario for US energy independence a generation or two from now. Commercial
electrolysis is about 80% efficient, 20% of the electrical energy being lost in
the process as heat. This is roughly equivalent to the energy losses of a
conventional 200 mile long high voltage power line. The hydrogen and oxygen can
be stored in compressed or liquid form until needed. This approach is best
adapted to electrical generating technology where the output varies or is
intermittent (solar, wind, tidal) but the fuel cost is essentially free. But, of
course, using compressed gasses to run a fuel cell, is unlikely to find much
application aboard powerboats. The energy density is too low and it would be like
sitting on a bomb.
If we need high energy density fuels, given free or very cheap power, other
intermediate chemical means can be used for energy storage. One potential
candidate is the Cornish hydrogen generating system patented in 1982. The patent
has now expired so the technology is in the public domain. Prof. Cornish
proposed using a process essentially the reverse of aluminum refining to release
hydrogen from water to power an engine. In conventional aluminum refining with the
Hall process, it takes about 15 kwh of electricity to produce one kilogram of
metal from bauxite. Aluminum is a very reactive metal and when immersed in a
sodium hydroxide solution (lye) will release hydrogen, the metal combining
with the water's oxygen to form aluminum oxide. Cornish developed a mechanism by
which aluminum wire was continuously fed against a rotating metal drum in a
sodium hydroxide electrolyte. A small oscillating electric current assisted the
process, releasing hydrogen which was collected at low pressure.
BMW tested the Cornish system and reported that a 900 kg car ran 600 km using
the hydrogen generated from 1 kg of aluminum wire and 20 liters of water. The
main problem, as reported by BMW was accumulation of the spent aluminum oxide
on the bottom of the generator. The collected hydrogen was burnt in a
conventional engine. For more information, search Google for "Cornish hydrogen." It
is all reminiscent of the last film in the "Back to the Future" trilogy when
empty aluminum soda cans were used as the fuel source for the time traveling
DeLorean car.
All in all, the process is not energy efficient. Cradle to grave, the energy
efficiency is only about 9 or 10%, about that of a steam engine. Much of the
energy loss comes from burning the hydrogen in a conventional engine. A fuel
cell would do much better, perhaps raising the overall energy efficiency to 25%.
The attraction of the process is the very high energy density of processed
aluminum, higher even than petroleum fuels. If BMWs results can be replicated, a
10 lb spool of aluminum wire could power my Willard the same 1000 miles as
800 lb. of diesel fuel. Currently aluminum wire costs $3 to $4 a pound in
commercial quantities. That is until the tax people get to it.
Science magazine had a recent article suggesting that researchers have
managed to convert carbon dioxide, a greenhouse gas, back into hydrocarbon fuel
using prodigious amounts of electrical energy. This would have the side effect of
being a carbon free process, the carbon dioxide removed from the air balancing
the carbon added by burning the recovered hydrocarbon fuel. Again a
possibility only if very low cost electricity can be provided. A related technology
uses massive amounts of electricity to convert nitrogen from the air into ammonia
which can then be transported to distant locations and used to power fuel
cells. With cheap electricity, many things are possible.
What about the direct use of solar energy for boat propulsion? If the entire
deck area of a light, easily propelled boat, say a catamaran, were covered
with solar cells, it could move the boat at hull speed in bright sunlight. For
night sailing or cloudy days additional solar capacity and battery storage would
be required. It's possible but very expensive. Efficient solar cells run
about $5 a watt and at least a thousand watts would be needed for each horsepower
required. But both the Atlantic and the Pacific have been crossed by such
boats so it is possible. To be practical, however, cheaper and/or more efficient
solar cells and better batteries would be needed. No fast trawlers are in sight
with this technology. Of course sails use indirect solar energy in the form
of wind but discussion of sails is frowned on in this forum. Might as well wait
for :"cold fusion."
But for boaters today, the best way of coping with high fuel prices is simply
to use less fuel. This was the main finding of our 1974 study. It is far
cheaper to conserve fuel than to find and develop new resources. Naturally this
was not popular with our petrocentric administrations over the last few decades.
Even so, you can stretch your dollars at the fuel pump by a few simple means.
First check to see that your engine is running properly. No black smoke. Have
the prop shop check your propeller for pitch and balance. If necessary have
it repitched for better efficiency. An increase in propeller efficiency from
35% to 45% will cut your fuel cost by 1/3. Keep the hull clean. Marine growth
and fouling can waste 10% or more of engine power. Dive or have someone dive a
couple of times a season to clean the bottom, paying particular attention to
getting barnacles off the prop.
Finally, and probably least popular, go slower. Power required to move a
trawler rises as the cube of the speed. If it takes 3 gallons per hour to drive
your boat to its hull speed of 8 knots, it will only take 1.3 gallons per hour
at 6 knots. Dropping your speed by 25% saves more than 50% in fuel. If you want
to go faster, what are you doing on a trawler?
Larry Z
**************
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AOL Home.
(http://home.aol.com/diy/home-improvement-eric-stromer?video=15?ncid=aolhom00030000000001)
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