Re: GAS-L: Re: Hydrogen Economy greatly overrated, biomass underrated...

[Luiz Alberto Magri <luizmagri@yahoo.com>]

I stick to Tom's remarks as follows

--- wskletzker@aep.com wrote:
> Tom,
> Some feedback from one of my work group on your
> interesting note below.
> --------------------
> 
> In what sense are today's vehicles "non-polluting"
> compared to the 2H2 + O2 -> 2H2O equation?

Is there a non-polluting way to producing H2? If not
the vehicle will be polluting as well, and it is.

> Why is it insignificant that hydrogen has an energy
> content of 60,000 
> BTU/lb compared to gasoline's 21,000 BTU/lb?

Hydrogen cannot be carried in low pressure small
tanks. Much more care is needed regarding the handling
of H2. Most of the time the hydrogen will be at
gaseous satate (very low density). Equipment
(instrumentation, electrical installation) should be
explosion proof. At vehicles so far there is not a
commercial way to carry hydrogen. Hydrates have been
used - probably very slow to fill in and low capacity
as well. Given the above is almost pointless the
specific calorific value (mass based) is bigger.


> Combined cycle gas generation is running 58-60%, not
> 30% as stated.

Combined cycle generation in real life is struggling
to go above 50%. The standard thermal power plant is
between 20% (old Rankine cycle installations and old
gas turbines) and 40% (new ones of the same stuff).
Combined cycle is not so common and almost unknown to
small producers. Then 30% is not far from reality.

> Why is it significant that hydrogen contracts from 3
> moles to 2 moles on 
> combustion?

Volumetric displacement after combustion. This will
make difference in flow engines. Maybe not a concern
at Rankine cycles - but I never been told about using
hydrogen in boilers.

> While I recall the Free Electricity claims from the
> nuclear side, I don't 
> ever remember a Free Hydrogen claim from the
> hydrogen economy side. I 
> guess I missed the Playboy Club meeting.

No comments. I missed the meeting as well.

Luiz Magri
Rio de Janeiro

> ---------------------------
> 
> 
> 
> 
> 
> 
> "Tom Reed" <tombreed@attbi.com>
> 09/21/2002 04:18 PM
> Please respond to "Tom Reed"
> 
>  
>         To:     "Harry W. Parker"
> <Harry.Parker@coe.ttu.edu>, "bioenergy" 
> <bioenergy@crest.org>, "Stoves" <Stoves@crest.org>,
> "gasification" 
> <gasification@crest.org>, "Milne, Thomas"
> <thomas_milne@nrel.gov>
>         cc:     "John Reardon" <jreardon@gocpc.com>,
> "Al Balch" <ahbalch@attbi.com>
>         Subject:        Hydrogen Economy greatly
> overrated, biomass underrated...
> 
> 
> Dear All Biomassers:
>  
> The message below from my good friend Tom Milne, Bob
> Evans and all 
> anouncing a new report on hydrogen needs to be put
> in context.  Speaking 
> as a fuel scientist, I hope I may be permitted a
> personal diatribe in this 
> forum.  If you are emotionally convinced that
> hydrogen is the world's best 
> fuel, and wish to stay convinced, delete this
> message. . 
>                                                     
>            ~~~~~~~~~
> HYDROGEN has been known and used since the early
> part of the 19th century. 
>  It is easy to make in the laboratory from iron and
> HCL or by 
> electrolysis. 
>  
> Hydrogen is unique amongst the elements with
> outstandingly good and bad 
> properties.
>  
> As a fuel it has the highest Mass Energy Density of
> any fuel by a large margin, so liquid hydrogen 
> isn't too bad a fuel if you can afford the cost and
> keep it well 
> insulated.  As a gas it also has a very low Volume
> energy density (same as CO, 1/3 that of methane). 
> It is an 
> important component of synthesis gas (CO + H2) and
> producer gas (CO + H2 + 
> N2). 
>  
> Hydrogen also has a flame velocity (2.83 m/s in air
> compared to .5 m/s for 
> methane, propane etc.).  For this reason it is a
> difficult automotive 
> fuel, since stoichiometric combustion produces
> "hydrogen knock".  However, 
> it has the widest flamability limits so can be
> burned very lean for better 
> efficiency. 
>  
> Another hydrogen problem I haven't heard discussed
> is that it contracts 
> chemically 1/3 on burning according to
>  
> H2 + 1/2 O2 [1.5 moles or voumes] ===> H2O [1 mole]
>  
> by contrast, methane gets full value, since     CH4
> + 2 O2 [3 moles] ===> 
> CO2 + 2 H2O [3moles]
>  ~~~~~~~
> Hydrogen is an important chemical for converting
> vegetable oils to 
> margarine etc. and is widely used in large chemical
> plants.  Electrolysis 
> of water to make hydrogen is only 72% efficient (due
> to high overvoltage), 
> and conversion of heat to electricity is typically
> 30% efficient, so 
> electrolysis is 18% base efficiency. Hydrogen can be
> made from methane and 
> hydrocarbons using steam reforming and the water gas
> shift reaction - 
> probably 80% efficient. 
>  
> So for 150 years pure hydrogen was only used by
> quartz workers.  However, 
> many gases, including our producer gas, can contain
> large fractions of 
> hydrogen - 18% in our current producer gas at CPC. 
>  ~~~~~~~~
> So how has hydrogen risen so high in research
> circles as a target fuel?
>  
> It all started with "The Hydrogen Economy" about
> 1970.  At that time we 
> were naively told that nuclear electric power would
> be too cheap to meter 
> in a short time (Ha!).  But you can't run a car on
> electricity so we would 
> still need a "fuel tank".  Since power had no cost,
> hydrogen from water 
> would have no cost!  Voila.  I remember hearing
> these arguments at the 
> first "Hydrogen Economy" conference held
> appropriately at the Playboy Club 
> in Miami about 1974. 
>  
> We have since become disenchanted with the nuclear
> energy side of this 
> argument, but dreamers still talk of hydrogen
> combustion being "non 
> polluting" and therefore the ultimate fuel. 
>  
> Today's cars are amazingly clean compared to those
> of the smoggy ''70s, so 
> they are relatively "non polluting" in the
> atmospheric sense. However our 
> current fossil fuels do increase atmospheric CO2
> levels so can be 
> considered "polluting" from a global warming
> perspective. Don't worry, the 
> oil will be gone soon at the present rate of
> usage/wastage. 
>  
> For a REALISTIC view on hydrogen, check out..  
>
http://www.nrel.gov/ncpv/hotline/pdf/hydrogen_economy.pdf
> 
>  
> Your Skeptical Fuel Scientist,                TOM
> REED    BEF GASWORKS
>  
> ----- Original Message ----- 
> From: "Milne, Thomas" <thomas_milne@nrel.gov>
> To: "Milne, Thomas" <thomas_milne@nrel.gov>;
> <gasification@crest.org>; <stoves@crest.org>;
> <bioenergy@crest.org>
> Sent: Friday, May 24, 2002 12:36 PM
> Subject: GAS-L: RE: Biomass to Hydrogen Report Web
> Address
> 
> > 
> > 
> > >  -----Original Message-----
> > > From: Milne, Thomas 
> > > Sent: Friday, May 24, 2002 11:27 AM
> > > To: 'gasification@crest.org';
> 'stoves@crest.org'; 'bioenergy@crest.org';
> > > 'hydrogen@pete.URI.edu'
> > > Subject: FW: Biomass to Hydrogen Report Web
> Address
> > > 
> > > Interested parties may access our recent IEA
> report, "Hydrogen from
> > > Biomass--State of the Art and Research
> Challenges", at the WEB address
> > > listed below.   The authors would welcome
> corrections or additions to
> > > references, as a supplement for Year 2002 is
> planned.
> > > 
> > > Tom Milne, Carolyn Elam and 
> > > Robert Evans.
> > > 
> > > 
> > >  -----Original Message-----
> > > From: Elam, Carolyn 
> > > Sent: Thursday, February 28, 2002 11:10 AM
> > > To: Milne, Thomas
> > > Subject: Biomass to Hydrogen Report Web Address
> > > 
> > >
>
http://www.eren.doe.gov/hydrogen/iea/pdfs/hydrogen_biomass.pdf
> 
=== message truncated ===


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