From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Gasoline Fuel Cell on "the market"
Date: Mon, 24 Mar 1997 10:07:28 LOCAL
In article <email@example.com>
firstname.lastname@example.org (Bill Ward) writes:
>Could someone post a mini-FAQ or tutorial on the reforming process which
>converts hydrocarbons, etc to H2? If there are no insurmountable
>theoretical obstacles, it might provide a clean transition from IC
>engines to practical EVs. (Practical meaning actually competitive w/o
>subsidies, "incentives", and other market meddling.)
Here's a post of mine from last year to get you started.
Date: Nov 29 1996
email@example.com (Tim Jebb) wrote:
>In article <329b1084.414006235@Newshost.grace.cri.nz>,
>>This is more of a brief pointer to some of the historical data on EVs.
>At the risk of asking you a question which you may well have been asked n
>times before where n is a number between 0 and infinity minus one, and
>possibly even by me, What do you think about electric cars powered by
>fuel cells? I'm interested in the detail of your opinion rather than a
Well, let's start with what I put in the Gasoline FAQ ( available via FTP
from the Usenet FAQ archives at rtfm.mit.edu in the
pub/usenet-by-hierarchy/rec/autos/tech directory ).
9.6 What are "fuelcells" ?
Fuel cells are electrochemical cells that directly oxidise the fuel at
electrodes producing electrical and thermal energy. The oxidant is usually
oxygen from the air and the fuel is usually gaseous, with hydrogen
preferred. There has, so far, been little success using low temperature fuel
cells ( <200C ) to perform the direct oxidation of hydrocarbon-based liquids
or gases. Methanol can be used as a source for the hydrogen by adding an
on-board reformer. The main advantage of fuel cells is their high fuel-to-
electricity efficiency of about 40-60% of the nett calorific value of the
fuel. As fuel cells also produce heat that can be used for vehicle climate
control, fuel cells are the most likely candidate to replace the IC engine
as a primary energy source. Fuel cells are quiet and produce virtually no
toxic emissions, but they do require a clean fuel ( no halogens, CO, S, or
ammonia ) to avoid poisoning. They currently are expensive to produce, and
have a short operational lifetime, when compared to an IC engine [125-127].
125. Kirk-Othmer Encyclopedia of Chemical Technology - 4th edition.
Wiley. ISBN 0-471-52681-9 (1993-)
- Volume 11. Fuel Cells.
This is an extensive and up-to-date monograph on modern fuel cells and
is highly recommended. It discusses the various types, and provides
details of various prototypes, and the problems that have yet to
solved - many of which are economic rather than technical.
126. The Clean Machine.
Technology Review, April 1994. p.21-30.
This is a fairly detailed review of the relative costs of both the
fuel cell technology and the fuel itself, and contains plenty of
data and claims.
127. Fuel Cells: Energy Conversion for the Next Century.
Physics Today, November 1994. p.54-61.
This briefly describes the fuel cell powered Ballard Bus trialled
in Vancouver, Canada, and then goes into the theory of various
fuel cell systems. So now we move from the general to the specific.
What are the options if we go to fuel cells?. Well, available types
of fuel cells include:-
Type Temperature Pressure Anode Cathode Electrolyte
degrees C MPa % mass
PEFC 80 0.1 - 0.5 Pt Black Pt Black Nafion
or Pt-C or Pt-C
AFC(1) 80 - 90 0.4 80%Pt-20%Pd 90%Au-10%Pt 35-45% KOH
(2) 260 ~0.4 Ni Li-doped NiO 85% KOH
PAFC 200 0.1 - 1 Pt-C Pt-C 100% H3PO4
MCFC 650 0.1 - 1 90%Ni-10%Cr Li-doped NiO 62% Li2CO3
+ 38% K2CO3
(mol% not mass%)
SOFC 1000 0.1 Ni-ZrO2 Sr-doped Yttria-stabilised
Cermet LaMnO3 ZrO2
PEFC = Polymer Electrolyte Fuel Cell
Although Nafion has been widely used, new ion exchange polymers
from Dow Chemical and Chlorine Engineering overcome some of the
major problems of water transport that Nafion has. PEFCs are
the fuel cell type being considered for vehicles, but the
problems with electroosmotic water transport through the membrane,
CO intolerance,and expensive catalysts still have to be solved.
AFC = Alkaline Fuel Cell
(1) was used in the space shuttle "Orbiter"
(2) was used in the Apollo programme.
PAFC = Phosphoric Acid Fuel Cell
Typically 40% efficient, climbing to 70-80% with cogeneration.
These are % of the gross calorific value of the fuel ( which is
usually a gaseous hydrocarbon stream ). Gives about 1.1g/GJ NOx
and 450kg/MWh CO2 when using natural gas fuel.
MCFC = Molten Carbonate Fuel Cell
These are emerging as the current favorite for commercial power
production, mainly for economic reasons, with early demonstration
250KW plants around $1,600/KW. The minimum electrical conversion
efficiency is around 54%, and when steam cogeneration is added
the efficiency climbs to 66%, and if lower quality heat is also
recovered as hot water, the efficiency can climb to 85%. Gives
about 4.1g/GJ NOx, and 335-385 kg/MWh CO2 with natual gas.
SOFC = Solid Oxide Fuel Cell
Typically 40-45% efficient, climbing to 70% with cogeneration.
Gives 2.6g/GJ NOx and 440 kg/MWh CO2 with natural gas.
Nafion = perfluorocarbon sulfonate sulfonic acid ion-exchange membrane.
For those that understand sensible pressure units like psi, just
multiply the MPa value by 145. Much more detail of the differing types
can be found in the above references.
It should also be pointed out ( and I'm sure I'll be corrected by
one of the experts in the sci.environment Entropy thread :-)), that
the thermodynamic parameters for some of the fuel cell reactions can
result in fuel cell theoretical efficiencies over 100%. This is
allegedly because the entropy of the products is greater the entropy
of the reactants, thus, as the reaction reversibly proceeds, the system
could absorb heat from the environment and convert it into electrical
power. A reaction with more gaseous products than gaseous reactants
will tend to have a positive change in entropy.
Fuel Reaction dNo dH dG TV TE
(eV) (eV) (V) (%)
Hydrogen H2 + 0.5O2 -> H2O -1.5 2.97 2.46 1.23 83.0
Methane CH4 + 2O2 -> CO2 + 2H2O -2 9.25 8.50 1.06 91.9
Methanol CH3OH + 1.5O2 -> CO2 + 2H2O -0.5 7.55 7.29 1.21 96.7
Carbon C + O2 -> CO2 0 4.09 4.10 1.02 100.2
Formic Acid CHOOH + 0.5O2 -> CO2 + H2O 0.5 2.81 2.96 1.48 105.6
Carbon C + 0.5O2 -> CO 0.5 1.15 1.43 0.71 124.0
CO CO + 0.5O2 -> CO2 -0.5 2.94 2.67 1.34 90.9
dNo = Change in number of gaseous constituents
dH = Change in enthalpy
dG = Change in Gibbs free energy
TV = Theoretical Voltage
TE = Theoretical Efficiency.
Virtually all proposed vehicle systems use PEFCs because they offer
the ideal temperature range for a gaseous ( hydrogen, as used on the
Ballard bus) or a volatile liquid fuel like methanol that can be
distributed through existing gasoline systems with some modifications.
Using hydrogen, efficiencies of around 60% are obtained, but with
methanol that drops to around 40% ( because of the front end 275C
reformer where methanol and steam are converted to H2,CO2, and trace CO
usually over CuO/ZnO catalyst, and residual methanol is converted
using a water gas shift reaction over Pt/Alumina that also reduces
the CO level to <0.5% ). After the reformer a preferential oxidiser
is used to reduce the CO concentration to the few ppm that the fuel
cell can tolerate.
There is a large amount of work going on the DMFC ( Direct Methanol
Fuel Cell ) but there remain major problems with catalysts, however
if the recent advances continue it may appear not long after the
reformed methanol fuel cell. The development of a viable catalyst
for the direct electrochemical oxidation of methanol would remove
the need for the reformer and preferential oxidiser, and even
a more CO-tolerant anode electrocatalyst would eliminate the
oxidiser. ( "Electrocatalysis and the Direct Methanol Fuel Cell"
A.Hamnett, G.L.Troughton. Chemistry & Industry 6 July 1992 p.480-483 ).
Energy Partners have built a 50KW PEFC car when the cells cost $1
million using bottled 3,000psi hydrogen gas ( like the Ballard bus )
as the fuel. The car's fuel cells were 36x36x61cm stacks weighing 81kg
producing 60VDC@170A on air and 60VDC@950A on oxygen. The top speed
was 160km/h, 0-60mph in 14.9secs. It got 350km from 14,000litres of
hydrogen that cost $45, and the membranes were expected to last for
650,000km. The car initially had 180kg of Pb/H+ batteries for provision
of peak power, but they were being eliminated by retuning the fuel cell
to produce peak loads, and the loss of 180 kg from the overall weight
of 910kg should make that possible.
The 68hp brushless motor weighs 31kg and is only about 30x30cm with
fully adjustable regenerative braking. Energy Partners projected the
fuel cells would cost $20,000 in 1998, and $8,000 in 2003, and the car
would cost $85,000 in 1998. The extra long life and reduced maintenance
would offset some of the price premium, but they recognise that further
technology breakthroughs are needed to make it cost competitive with
IC powerplants. They didn't use oxygen in place of air to eliminate the
batteries because of safety issues. They appear far more realistic in
their projections ( the vehicle's fuel cell new price dropped from $1
million to $0.2 million in the first 9 months after installation ),
than some of the EV manufacturers and proponents.
For example, Mark DeLuchi projected a hydrogen powered Fuel Cell car
similar to the Ford Taurus with a 250 mile range would have a retail
cost of $24,000 (in 1992 $), a methanol powered fuel cell car would
cost $22,500, the gasoline ICV version would be $17,300, and the
battery EV version would cost $27,000. There is no doubt that mass
production would dramatically reduce the cost of fuel cells, with
some estimates around $4,000 per vehicle system, but some of the
solutions to the the above PEFC problems will probably be costly for
the first few years at least.
So, what are the environmental advantages - well let's assume they
can match the fuel cell response time to driving requirements, thus
removing the need to carry a large battery pack ( but we should
remember that should battery technology improve for EVs it also
helps fuel cell vehicles, which probably will want to reclaim some
energy through regenerative braking ). The major emission is water,
with CO2, CO and NOx from the reformer if methanol is used as the
source of hydrogen. If hydrogen is used as the fuel, there are
minimal unwanted emissions, but if methanol is used, some emissions
will occur,and both will have some fuel escape.
The source of the hydrogen or methanol will affect the amount of
greenhouse gas emissions, but in all cases they will be much lower
than from fossil fuels in ICVs, and lower than US EVs emissions
using the projected electrical energy sources. Assuming gasoline
equals 100%, the EV will produce 55%, methanol from natural gas
will produce 40%, hydrogen from natural gas will produce 34%,
hydrogen from biomass 10%, and methanol from biomass 7%, with
hydrogen from electrolysis approaching zero. Overall, a fuel cell
vehicle seems to be good for the environment because the fuel can
be obtained from different sources as technology advances.
In my opinion, a fuel cell vehicle, with minimal electrical energy
storage ( using ultracapacitor, flywheel, or battery ) may well
start to replace the ICV, at minor additional cost to the consumer,
in the next decade. If the technical advances that have occured in
the last decade continue unabated, then fuel cells will replace
ICEs as the preferred powerplant for automobiles.
Well, you said you wanted more than one line :-)
Subject: Re: Gasoline Fuel Cell on "the market"
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Date: Mon, 24 Mar 1997 18:45:32 GMT
firstname.lastname@example.org (Ian Gay) wrote:
>In article ,B.Hamilton@irl.cri.nz (Bruce Hamilton) wrote:
>>In article email@example.com (Ian Gay) writes:
>>>Indeed, I expect electrolysis is an overall loser. The electrochemical
>>>efficiency of electrolysis is similar to fuel cells - since the
>>>problems are the same.
>i.e. poor kinetics at the oxygen electrode, leading to large overvoltage.
>(Although I would expect that at a large fixed electrolysis plant you could
>make tradeoffs that would not be appropriate for a vehicle fuel cell, and
>hence do a little better)
According to the " Hydrogen Energy " monograph in the Kirk Othmer
Encyclopedia of Chemical Technology, solid polymer electrolyte
electrolysis using proton-selective, water saturated, membranes
( making the circulating pure water encounter an acidic environment
equivalent to 10% sulfuric acid ) is already 60 - 80% efficient,
and is still being actively researched. They point to the compact,
lightweight system as being especially suitable for smaller
renewable sources of energy such as solar. A New Scientist article
last year ( 23 November 1996 ) noted that two major German utilities
were spending DM60 million investigating hydrogen using energy from
solar cells or concentrated solar heat. Then, the process cost was
60X that of H2 from methane, but continually decreasing.
The reason that fuel cell look so attractive for smaller commute
type vehicles is because they have highest efficiencies at low
outputs. For example a 30kW ICE and Proton Exchange Membrane with
Fuel Cell and methanol reformer gave the following efficiences in
a 1991 paper.
kW ICE PEMFC
0 0.01 0.6
5 0.2 0.53
10 0.28 0.5
15 0.31 0.46
20 0.34 0.42
25 0.32 0.36
30 0.31 0.32
Whilst some Japanese ICV producers have improved the efficiencies
of their ICEs, the need to develop EVs to comply with mandates
has moved the focus from improving the ICV, which is a real pity
because major short term gains in emissions reductions could
have been achieved. There are some interesting developments since
the Ultralite that would help improve ICE efficiency in the low
power region of the engine map.