[CrashList] Re: Why 'alternatives' are no alternative
shmage at pipeline.com
Sun Sep 17 22:41:55 MDT 2000
The following, from the 16/9 Science News, is only one of many refutations
of the manic doomsday pessimism of Mr. Jones:
" Device ups hydrogen energy from sunlight
Here's a recipe for a cleaner, healthier planet:
Take some water, add solar energy, extract
hydrogen, and use it to power fuel cells for running
cars and other machines. Then, collect their
water emissions and start the procedure again.
One look at the list of ingredients in today's fuel
cells, however, shows that this ideal isn't yet
being followed. Because processes that use sunlight
to extract hydrogen remain costly and
inefficient, fossil fuels still supply the hydrogen
in most fuel cells.
Hoping to break the fossil fuel habit, a team of
Israeli, German, and Japanese scientists has
created a device that boosts the efficiency of
solar-powered hydrogen extraction by 50 percent.
The group placed a photovoltaic cell on top of two
flat, finger-long electrodes. The combination
"is very efficient in converting solar energy [into
an electric current] but also provides nearly the
ideal voltage for splitting water" into hydrogen and
oxygen, says team leader Stuart Licht of the
Technion in Haifa, Israel. A water molecule splits,
or undergoes electrolysis, at only 1.23 volts.
Licht and his colleagues describe their device in
the Sept. 14 Journal of Physical Chemistry B.
The gadget converts sunlight to an electrolysis
current with 18.3 percent efficiency. In turn, the
current creates hydrogen gas as it passes through
The device is "showing the pathway towards higher
efficiencies for direct solar-to-hydrogen
production," comments John A. Turner of the National
Renewable Energy Laboratory (NREL) in
Golden, Colo. The newly achieved efficiency may
already be high enough for commercial
hydrogen generators to be feasible. "That still
needs to be figured out," Turner says.
In 1998, he and Oscar Khaselev, then also of NREL,
demonstrated a novel apparatus for
solar-to-hydrogen conversion (SN: 4/18/98, p. 246).
To achieve unprecedented efficiency, the
device used multiple layers of semiconductor
materials. The researchers arranged the layers to
form two active regions, or junctions, that would
absorb solar photons that dislodge electrons.
Some of the less energetic photons weren't captured
in the first junction but passed to the
second, where they generated more current.
The design gained an energy advantage by combining
solar electricity and water splitting into one
unit. Their cell's 12.4 percent efficiency-nearly
twice that of any previous solar-to-hydrogen
device-has held as the record until now.
Licht and his colleagues have improved upon that
pioneering effort in several crucial ways. In one
sense, the NREL device was all wet: It had to be
completely immersed in water to operate. That
feature forced the researchers to select
semiconductors that wouldn't break down in solution.
By keeping their stack of semiconductor layers high
and dry, Licht and his group were free to
optimize them for both converting sunlight to
electricity and water splitting. Their design permits a
low electrolysis current, which also reduces energy
Licht and his coworkers say that besides besting the
solar-to-hydrogen conversion record, their
work opens the way to efficiencies not considered
possible before. Using measured
photoelectric efficiencies of seven semiconductor
combinations not yet tested in hydrogen
generation, they predict maximum solar-to-hydrogen
conversion efficiencies of up to 31 percent.
Thermodynamics theory says the maximum could range
above 40 percent for a two-junction
converter, but no one has previously predicted
better than 24 percent performance for practical
devices, Turner says. Experimentally achieving the
new prediction "would be an accomplishment
indeed!" he adds."
Something is happening, but you don't know what it is, do you.....?
>It is said frequently and often nowadays that the future economy will be
>'hydrogen-driven'. Most of what is written on the subject shows signs of
>being untouched by the human mind. For one thing, hydrogen is an
>energy-carrier, not an energy-source. You have to *manufacture* hydrogen,
>and it is an energy-intensive process, requiring huge amounts of
>electricity. Where will the electricity come from? One answer is natural
>gas, which in itself is hardly a real answer if you're talking about moving
>beyond fossil fuels that pour greenhouse gas into the air. And where will
>the natural gas come from? According to some petrogeologists, there is no
>shortage of natural gas, particularly in the USA. Eminent member of the
>American Association of Petroleum Geologists, "Skip" Hobbs recently assured
>the US Senate that the US has plenty of natural gas (his testimony is in the
>Crashlist message archive). But the reality is that existing gas reserves
>are depleting at an alarming, and unexpected rate; meanwhile the US
>Department of Energy assumes that a supply of 35 quads of natural gas p.a.
>will be found to meet expected demand by the year 2020; that is almost
>double existing US natural gas consumption. Most analysts think the target
>is unreachable. In short, natural gas will be (a) scarce and (b) much more
>expensive than it is today. Natural gas supplies 20 per cent of world energy
>(25% in the US). But to replace petroleum as the prime transportation fuel
>will mean finding *double* that amount: in the US it would mean finding
>perhaps 70 quads a year, and even Skip Hobbs isn't suggesting that is
>feasible. But if all the yhpe and public optimism about fuel-cells is on
>track, that is exactly what WOULD have to be found. So someone is lying
>Maybe the hydrogen can be found using *alternatives* to produce the
>necessary electricity? The alternatives comprise: nuclear, photovoltaics,
>wind and biomass. Together these alternatives today provide less than 5% of
>total US energy. Can they be ramped up?
>If alternatives CAN fill the gap left by declining oil, then both capitalism
>and the biosphere might be saved.
>In this scenario, hydrogen-driven fuel cells will be the motive-power source
>of the future; you'll even plug them into your home and power domestic
>electricity with them, so goes the hype which is repeated even by
>responsible and well respected people, for example people like legendary
>James Hansen, the Nasa scientist who practically invented the term 'global
>warming'. His most recent paper, "Global warming in the twenty-first
>century: An alternative scenario" (James Hansen, Makiko Sato, Reto Ruedy,
>Andrew Lacis, and Valdar Oinas) (available from www.pnas.org for $5 or for
>free by writing offlist to me). This paper, published in August 2000, is
>already notorious because in it Hansen seems to backtrack on earlier
>global-warming doom-mongering. He is optimistic about reducing atmospheric
>CO2, mostly because of a new-found enthusiasm for technology. Hansen now
>beliecves that fuel cells and similar innovations will save the day:
>"Investments in technology to improve energy efficiency and develop
>nonfossil energy sources are also needed to slow the growth of CO2 emissions
>and expand future policy options," Hansen writes.
>Hansen is employed by NASA, which practically invented the things, but it is
>clear that when it comes to fuel-cells he doesn't know what he is talking
>about, and his new-found techno-optimism is misplaced: natural-gas (or
>methanol) powered fuel-cells cannot replace gasoline engines, and unluss
>there is some other way out, the 'hydrogen economy' is likely to be
>still-born, even assuming fuel-cells can *ever* be manufactured cheaply and
>in volume, which remains unproven.
>Enthusiasm for alternatives, borne largely of desperation, is widespread
>these days. Even James Lovelock, father of the Gaia theory, believes that
>nuclear power is a possible, and necessary, alternative to fossil fuel, to
>judge from recent remarks of his (archived in the Crashlist).
>To replace the world's existing petroleum-based transportation fleets with
>hydrogen-powered systems (assuming this was technically or financially
>possible) will require the construction of around 25,000 new nuclear
>reactors. Oil demand today is about 75 million barrels per day, a power
>equivalent of 5 trillion watts. Supposing the nuclear plants were 40 percent
>efficient in transferring nuclear energy to gaseous hydrogen, that requires
>12.5 terawatts of electrciity-genertaing capacity. But hydrogen must be
>condensed somehow, and this raises the input power by, in the representative
>case of cooling hydrogen until it liquefies at ambient pressure, a factor
>close enough to 2. This entails an extra global capacity of 25 terawatts, ie
>about 25k conventional pressurised water reactors of 1 Gw output.
>Unfortunately, there is already a world shortage of exploitable uranium.
>Absent viable fusion technologies, such a massive increase in nuclear power
>generation is not feasible in resource terms (let alone safety terms).
>Whether such a massive construction of new nuclear power stations would be
>socially acceptable and/or politically feasible is a separate and
>Others argue for photovoltaics. Actually we can take photovoltaics and
>biomass together, because both entail using available land (and possibly
>ocean) surface areas to capture solar energy fluxes. So far no technology
>exists (either by plant-based photosynthesis or silicon-based or other
>photovoltaic technology) which is capable of capturing enough solar energy
>to substitute for more than about 10 percent of today's use of fossil fuels.
>This leaves wind-power and some other mnore exotic methods (subsea turbines,
>geothermal). In all cases even the massive application of known technologies
>will provide orders of magnitude less energy than we get today from fossil
>fuels. In short, there is no way to make the transition to a non-fossil
>economy without massive social and economic upheaval and dislocation, even
>in the *best* case.
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