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What is a Megawatt?
utilipoint.com/issuealert/article.asp?id=1728 What is a Megawatt? (reprint), Jun 25, 2003,
groups.yahoo.com/group/energyresources/message/37867 Energy Future Coalition :: Headquarters
1225 Connecticut Ave., 4th Floor, NW,
Washington, DC 20036 :: (202) 463-1947
E-Mail us at info@energyfuturecoalition.org
energyfuturecoalition.org/ RENEWABLES ENVIRONMENTAL ACCOUNTING: Emergy and
Environmental Decision Making by Howard T. Odum; Wiley, 1996 ;
amazon.com/exec/obidos/ASIN/0471114421/brainfood.a
From page 314, we find that in 1993 total US
fuel use was 4.78 x 10e24 sej (increasing about 2% per year ever since). From
page 187, we find that total net solar radiation absorption for Alaska and the
lower 48 was 4.48 x 10e22 sej. In other words, the US is presently using fossil
fuel energy more than 100 times greater than the total absorption of solar
radiation across the entire US! Much more in Jay's synopsis:
dieoff.com/synopsis.htm
Calculations show that solar cells consume
twice as much sej as they produce. dieoff.com/pv.htm So even if all the energy
produced were put back into production, then one can only build half as many
cells each generation -- they are not sustainable. Even if the sej efficiency
of solar cells doubled, ALL of the energy produced would have to be used to
manufacture new cells, which still leaves a zero net benefit to society!
eMergy calculations of solar energy.
dieoff.com/pv.htm Sliver CellTM
This new technology may change the Emergy calcs considerably.
A joint venture between the Australian National University and Origin Energy
has developed a new type of solar cell with the potential to revolutionise the
global solar power industry.
Director of the ANU Centre for Sustainable Energy Systems, Professor Andrew
Blakers today unveiled the Sliver CellTM, which uses just one tenth of the
costly silicon used in conventional solar panels while matching power,
performance and efficiency.
Professor Blakers said, "A solar panel using Sliver CellTM technology needs the
equivalent of two silicon wafers to convert sunlight to 140 watts of power. By
comparison, a conventional solar panel needs about 60 silicon wafers to achieve
this performance.
"By dramatically reducing the amount of expensive pure silicon, the largest
cost in solar panels today, this new technology represents a major advance in
solar power technology."
ANU Vice-Chancellor, Professor Ian Chubb welcomed the research breakthrough.
"Origin Energy is to be congratulated for its foresight and persistence in
supporting the ANU team in this project. The company has made a substantial
contribution since establishing the research partnership with ANU," Professor
Chubb said.
The most expensive part of traditional solar power panels is the silicon from
which the individual cells are made. The Sliver CellTM is a radically different
concept in photovoltaics. Sliver CellsTM are produced using special
micro-machining techniques, then assembled into solar panels using similar
methods to those used to make conventional solar panels.
The new technology reduces costs in two main ways – by using much less
expensive silicon for similar efficiency and power output, and needing less
capital to build a solar panel plant of similar capacity.
The unique attributes of Sliver CellTM technology could open many new Sliver
CellTM applications, in addition to conventional rooftop and off-grid uses,
including:
*Transparent Sliver CellTM panes to replace building windows and cladding
*Flexible, roll-up solar panels
*High-voltage solar panels, and
*Solar powered aircraft, satellite and surveillance systems
About the ANU Centre for Sustainable Energy Systems: ANU is the premier
research University in Australia. The ANU Centre for Sustainable Energy Systems
(CSES) involves a group of 45 staff & PhD students working on renewable energy
technologies. About 80% of its turnover comes from external sources; primarily
from companies and from government funds provided on a matching basis with
industry. CSES has substantial activities in the areas of photovoltaics, solar
thermal power and solar energy systems. Further information and pictures of
systems can be obtained at
solar.anu.edu.au
Origin Energy
Phone +61 8 8217 5817
Mobile 0417 876 470
originenergy.com.au
Concentrator PV technology, Roger Arnold, June 21, 2003.
groups.yahoo.com/group/energyresources/message/37638
"
Found an interesting paper on
concentrator PV technology at:"
sunpowercorp.com/html/Technical%20Papers/ProgPV.pdf
Discussion:
"There's been a lot of debate here
on the energy payback times for
photovoltaics. Payback times are
very dependent on whose results
one
chooses to believe, and the
assumptions on which particular
results
are based. Estimates range from
three years to "never". But even
the low end of that range
represents an energy payback time
that is
quite long, compared to most competing systems. The reason for it is
well understood: the high energy cost of producing silicon wafers.
Approaches based on use of solar concentrators cut through that issue
by delivering from 100 - 1000x the intensity of solar irradiance to
the cells. Electrical output per square cm of cell is increased, and
energy payback time is reduced, by a corresponding factor. In fact,
the output is increased by an even larger factor, relative to flat
plate PV modules, because the huge reduction in silicon cost per watt
of output makes it feasible to use much fancier and more efficient
cell designs that are not economically feasible for one-sun modules.
So why haven't solar concentrators caught on? The paper recaps work
done and looks at that question. The answer is not really too
surprising. Although the silicon cost and energy payback times are
slashed to (relative) insignificance, other costs are still high
enough to prevent concentrator PV plants from being economically
competetive, at current coal, oil and gas prices, with conventional
power plants. At the same time, the requirement for tracking the sun
makes concentrator PV unsuitable for the niche where flat-panel
modules have caught on: small scale, ultra-reliable, near zero-
maintenance power for off-grid sites. I.e., "no current market".
But the technology is viable. Given a 3-4x increase in the cost of
fossil fuel, concentrator PV modules would be able to break through,
and then, over a decade, ride the scaling and learning curves back
down to electrical power costs that are comparable to what we see
today."
EnergyResources Moderator Comment
"Of course when you run those increased energy prices back through the
production system, what do you have then.
Also, for what it's worth, the concept of "payback time" injects unnecessary
confusions into the more simple idea of Energy Returned on Energy Invested
or
ERoEI.
This list has been demonstrating for some time now how important it is to
keep
it simple."
EnergyResources Moderator, Tom Robertson
See how easy it is to understand photovoltaic
energy?
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