Subject: Hydrogen Faq

From: Larry London <london@calypso-2>
Date: Mon, 7 Mar 1994 13:22:48 -0500

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Article: 450 of sci.energy.hydrogen
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Comments: Gated by [email-masked]
Newsgroups: sci.energy.hydrogen
Date: Wed, 15 Dec 1993 15:11:58 MST
Sender: Hydrogen as an alternative fuel <[email-masked]>
From: Rod Gallagher <[email-masked]>
Subject: Hydrogen Faq
Lines: 318

Here is an advanced copy of the Hydrogen FAQ as it now stands.  It could
use some midification and some additions, so everyone is encouraged
to comment back to me ([email-masked]) so that the FAQ will be greater
and more complete next round.

With great fanfare <yeah> we humbly submit ....

            HYDROGEN FAQ

I.      General Description
II.     Production Methods
                A. Electro-chemical
                B. Chemical
                C. Biological
                D. Photoconversion
III.    Storage
                A. Gas
                B. Liquid
                C. Slush
                D. Metal Hydrides
                E. Other
IIIA.   Purification
                A. Iron/Water cycle
                B. Etc.
IV.     Transportation
                A. Pipeline
                        1. Hythane
                B. Other
V.      Use
                A. Fuel Cells
                B. Internal Combustion Engines
                        1. Rotary-Type Engines
                C. Other
VI.     Sources For Further Information
                A. Professional Associations
                B. Periodicals and Newsletters
                C. Calendar of Events
                D. Publications Bibliography
                E. Vendors List
                F. Government Organizations
                G. Related Electronic Lists/Newsgroups

Questions can be directed to Rod Gallagher ([email-masked]) or Robert
Cinq-Mars ([email-masked]).  See also the newsgroup
Sci.Energy.Hydrogen or the listserv at [email-masked].

Special thanks go to Roy McAlister, President of the American Hydrogen
Association, and Daniel Morgan, Ph.D. for their help in putting
together this FAQ.

I.      General Descriptions

        Hydrogen is the universes most abundant element, but most of
it is bound up in chemical compounds.  It must be extracted from these
compounds rather than simply collected before use.  Some methods
of this extraction process are outlined later in this FAQ.  The following
chart is a summary of some of the chemical properties of hydrogen:

--------------------------------------------------------------------
TABLE 1.  PHYSICAL AND CHEMICAL PROPERTIES OF HYDROGEN

1.  Electron Structure                  S1
2.  Covalent Radius                     0.37 A (He = 0.93 A)
3.  Electronegativity (Pauling)         2.1
4.  Specific Heat                       (Cp)     3.44 Cal/Gram
                                        (Cv)     2.46 Cal/Gram
                                        (Cp/Cv)  1.40 Cal/Gram
5.  Gas Density                 (Deg. C, 1ATM)   0.0899 Gram/Liter
6.  Gas Specific Gravity        (Air - 1.0)      0.0695 Gram/Liter
7.  Gas Self Diffusion Const.   (Deg. C, 1ATM)   0.61 Cm2/Sec
8.  Boiling Point                       -252.7 C
9.  Melting Point                       -259.2 C
--------------------------------------------------------------------

        Hydrogen is extensively used in the chemical process, food,
and fuels industries.  Many electricity power plant generators are
cooled by gaseous hydrogen because it provides the highest specific
heat and best combination of dielectric strength and low viscosity.
Hydrogen is used in hydride heat pumps, in Joule-Thompson cooling,
and as a heat transfer medium.

II.     Production Methods

        Since hydrogen must be extracted from other sources, it can be
considered an energy carrier rather than an energy source.  The energy
that is produced when it is used is simply the amount of energy that
was stored, minus any losses.  There are several different methods of
extracting hydrogen from sources.  They are outlined as follows:

                A. Electro-chemical

        Electrolysis is the process whereby electricity is passed
through a meduim, in the case of hydrogen is usually water, and the
basic elements are released.  In the case of water, one mole of water
yields two moles of hydrogen and one-half mole of oxygen.
        Common energy efficiencies for electrolysis are 65 percent, with
80-85 percent currently possible.  Cost of production is high, so
electrolysis is expected to be limited to niche markets in the near
and mid term.
        The primary idea in lowering the cost of electrolysis is in lowering
the cost of the electricity to run through the water.  In the solar
hydrogen scenario, solar collectors would be utilized to run electricity
from the sun through water and create hydrogen.  The hydrogen could then
be captured and stored or used immediately.  The cost of producing
hydrogen in such a manner would probably drop quite a bit.

                B. Chemical

        Every elemental metal that is less noble than hydrogen will
displace hydrogen from water.  A well know reaction is between an
active metal such as sodium or potassium and water:

        2Na + 2H2O ----> H2 + 2NaOH + HEAT

        The "producer" reaction has been practiced since its discovery
in about 1800 for producing hydrogen from a carbon donor and water:

        HEAT + C + H2O ----> H2 + CO

        Since the discovery of petrocarbons such as oil and natural
gas, hydrogen has been produced in large quantities by reacting steam
with petroleum hydrocarbons:

        HEAT + CxHy + xH2O ----> (x + 0.5y) H2 + xCO

                C. Biological

        Bacteria and other microorganisms (particularly those that live
in anaerobic conditions) may release hydrogen in the process of
creating heavier hydrocarbons or oxygen for assimilation.  All methane
that has been produced from biomass probably involved the precursor
steps of hydrogen production by an anaerobic microorganism
and fixing of the hydrogen with carbon from carbon dioxide as the
microorganism derived the oxygen for its own use.

                D. Photoconversion

        Numerous bacteria and all green plants dissociate water into
hydrogen and oxygen as the first step of photosyntheses.  Hydrogen
is retained to build plant tissues by reactions that combine carbon
from atmospheric carbon dioxide with hydrogen.  Oxygen is released
to the atmosphere in the process.

        LIGHT + H2O  -------> 2H2 + 0.5O2

        LIGHT + H2 + CO2 --------> Plant Tissues

III.    Storage
                A. Gas

        Compressed gas storage and transportation has been widely
used for more than 100 years.  Common materials for storage canisters
are mild steel, aluminum, and composites.  Storage pressures of
3,000 to 10,000 PSI are common.

                B. Liquid

        Cooling hydrogen to below the boiling point of -252.7 C allows
storage as a cryogenic liquid without the need for pressurization.
Cryogenic storage of hydrogen allows regular commercial shipment
by truck and rail.  Many commercial processes such as glass manufacturing,
brazing, heat treating, food hydrogenation, and semiconductor
manufacturing are served by deliveries of liquid hydrogen.  Liquid
hydrogen has facilitated the U.S. space exploration program.

                C. Slush

        If liquid hydrogen is suddenly subjected to a vacuum it will
evaporate with a subsequent cooling of the liquid mass to cause the
temperature to fall below the freezing point of -259.2 C and solid
hydrogen will be produced.  This mixture of liquid and solid
hydrogen is called "slush" and provides more dense storage of
hydrogen than liquid hydrogen.

                D. Metal Hydrides

        Metal hydride systems store hydrogen in the interatom spaces
of a granular metal.  Various metals can be used.  The hydrogen is
released by heating.  These systems are reliable and compact, but they
can be heavy and expensive.

                E. Other

IIIA. Purification

                A. Iron/Water cycle

                B. Etc.

IV.     Transportation

                A. Pipeline

        Hydrogen can be transported via pipelines much the same way natural
gas and oil are currently transported.

                        A1. Hythane

                B. Other

V.      Use
                A. Fuel Cells

        A fuel cell works so that the hydrogen is sent through a PEM
(proton exchange membrane).  The hydrogen molecule is broken up so that
a proton is stripped off and sent through a loop while the rest of
the molecule goes through the membrane.  The proton migrates around the loop
and rejoins the molecule, having been harnassed for energy along the way.
In this manner, we are able to get energy out of a fuel cell without
polluting at all.

                B. Internal Combustion Engines

        Engines can be converted from gasoline to hydrogen fairly simply.
The biggest cost involvement is in purchasing the tank, although in many
cities these tanks can be leased or rented.  Engines can also be made to
run on hydrogen initially.  These would be more effective since they would
have the little things needed to make the engine more practical for running
hydrogen.  Many of the automobile companies have already designed cars
and trucks that use hydrogen, most notibly BMW, Mazda, and many others
have made prototype cars.  Contact the professional associations listed
below for more information as this is a rapidly changing field.

                        1. Rotary-Type Engines

        Mazda is currently pioneering this effort and have built several
cars running this type of engine on hydrogen.  There are numerous articles
on this type of engine, see SAE technical paper #920302 for more information.
This type of engine also has been reviewed in many popular magazines.

                C. Other

        There are many other kinds of uses for hydrogen.  It is being used
in stationary turbines and aircraft engines.  Most notably, there were jets
that were powered by hydrogen, and in 1980 a propellor plane was fitted to
run on hydrogen.

VI.     Sources for Further Information
                A. Professional Associations

American Hydrogen Association
216 S. Clark, #103
Tempe, AZ 85281
(602) 921-0433

National Hydrogen Association
Suite 910
1101 Connecticut Avenue, S.W.
Washington, DC 20036
(202) 223-5547

International Association for Hydrogen Energy
PO Box 248266
Coral Gables, FL 33124

                B. Periodicals and Newsletters

Hydrogen Today
American Hydrogen Association
216 S. Clark, #103
Tempe, AZ 85281
(602) 921-0433

                C. Calendar of Events
                D. Publications Bibliography
                E. Vendors List
                F. Government Organizations
                G. Related Electronic Lists/Newsgroups

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