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Nanowires Produce More Efficient Thin-Film, Polymer-based Photovoltaics

Last month I submitted a blog entry that suggested if there were a third generation of photovoltaics (first-generation solar cells (single-crystal silicon wafers) and second-generation solar cells (thin-film semiconductors)) using quantum dots that could reach or exceed the 32% Shockley-Queisser Limit than the economics of photovoltaics could improve and their adoption accelerated.

To add to this mix has been recent research at the University of California San Diego in which electrical engineers have added nanowires to polymer-based thin-film photovoltaics to create solar cells that increased the forward bias current by six to seven orders of magnitude as compared to their polymer-only control device.

The work was published in American Chemical Societyâ''s NanoLetters.

When one considers how much cheaper thin-film polymer photovoltaics are compared to single-crystal silicon wafers, and then factor in the possibility of thin-film polymer solar cells becoming orders of magnitude more efficient, things start to look pretty rosy.

But hold on, there remains some pretty fundamental problems, most notably that the polymers begin to degrade quite rapidly when exposed to air. However, the researchers point to work going on around the world to improve the properties of organic polymers that could overcome this problem.

In light of the recent series of entries here and here on this site regarding a potential â''Photovoltaics Mooreâ''s Lawâ'' based on ever decreasing price points as opposed to the ever increasing number of transistors per unit of a chip, and the strong reaction to them, it may be worth adding that we may not have to remain bound to the paradigm of silicon wafers and its incremental improvements.

Is Photovoltaic Moore Law Really on Track?

Last week, based on an IEEE photovoltaics conference that had just taken place in San Diego, I reported on some positive developments: a kind of Mooreâ''s law allegedly at work, a better outlook for first-generation silicon cells, and a growing expectation that solar electricity may be commercially competitive in some parts of the world by 2015. It appears that I misstated and overstated the case for a photovoltaic Mooreâ''s law, havingâ''Iâ''m most embarrassed to sayâ''misread one of my own previous blog entries.

I said last week that PV costs per watt had dropped from about $7 in 2004 to $4-5 in 2007, but â''Halâ'' pointed out in a comment posted May 22 that my previous blog in fact cited 2007 PV costs of $7.6 or $6.2 (depending on whose numbers you believe). That would be tantamount to a cost reduction of 15 percent at most, and perhaps none at allâ''not the 40 percent reduction I thought I had discerned, consistent with the â''photovoltaic Mooreâ''s lawâ'' that postulates a 20 percent reduction with every doubling of cumulative production capacity.

In recent years, total capacity has been doubling about every 18 months, but longer term the rate has been more like 30 months, according to John Benner of the National Renewable Energy Laboratory, who takes some credit for originating the PV Mooreâ''s law postulate. Benner says the three years from 2004 to 2007 were anomalous because of a run-up in silicon prices and, perhaps too, the deteriorating value of the dollar.

Even so, relative to wind, photovoltaic costs do indeed appear to have improved rather dramatically between 2004 and 2007, from 7:1 to 4:1 or 5:1, close to 40 percent. Thatâ''s significant, as distributed PV only needs to be about half as costly as central wind to be competitive. But PVâ''s better standing owes as much to an escalation in windâ''s costsâ''connected with booming global demand for turbines and the general run-up in power plant costs, most likelyâ''as to any cost reductions of its own.

The solar-wind comparison is a reminder that the photovoltaic Mooreâ''s law is subject to market forces in a way that the real Mooreâ''s law is not, as comments on my May 17 blog emphasized. Even the semiconductor Mooreâ''s law is of course not a law in the normal sense; itâ''s a prediction that happens to have been born out, so far, by reality. But it at least is stated strictly in terms of physical parameters (how many transistors per unit area of chip). The PV Moore law is stated in terms of costs, making it subject to extraneous market forces.

â''It used to be an axiom that solar power grew steadily cheaper as time passed,â'' The Economist magazine noted last April. â''After all, it had done so reliably for the previous 40 years.â'' But in the last years, Germanyâ''s extravagant solar subsidies have driven up global prices for silicon, from $25 per kilogram in 2003 to around $400/kg now. â''We didnâ''t have a silicon shortage, we had an over-stimulated market,â'' comments Benner.

Even if the consternation the higher silicon prices have aroused among solar boosters is somewhat misplacedâ''after all, just about every other energy cost is sky-rocketing tooâ''the situation has prompted arguments that solar subsidies should be eliminated in favor of R&D support.

Is there an optimal rate of PV growth? If we try to give the industry too much of a kick can that backfire, disrupting the learning curve thatâ''s supposed to yield â''grid parityâ'' by middle of the next decade? Should research and production incentives be targeted or technology-neutral, and what is the right mix? Who provides the better model, Germany or Japan? Those were just the questions under discussion at the San Diego PV Accelerator Forum, and which will continue to be discussed by all who have the future of solar electricity and renewable energy at heart.

Meanwhile, I apologize to my readers for having overly accentuated the positive. I hope I read your writing more meticulously than I sometimes reread my own.

The Long and Short of Carbon Nanotubesâ¿¿ Similarity to Asbestos

A recently published paper in Nature Nanotechnology submitted by researchers at Edinburgh University led by Ken Donaldson has provided evidence that some carbon nanotubesâ''specifically multi-walled carbon nanotubes (MWNT) that are longer than 20 µmâ''have the same pathogenic effects as asbestos.

Like asbestos, the MWNTâ''s toxicity is not due to their chemical composition but their physical characteristics, namely their length.

The pathogenic quality of both MWNTs of a certain length and asbestos occurs when the bodyâ''s phagocytes attempt to engulf the fiber, and when unable to get around the entire length of the fiber, the phagocytes try to kill the fiber with toxic products. The attempt fails to kill the fiber but succeeds in damaging the surrounding tissue.

If you donâ''t have a subscription to Nature, I suggest reading Richard Jones blog entry at Soft Machines, which gives a pretty thorough review of the findings and what it all means.

As Jones notes, â''not all carbon nanotubes are equal when it comes to their toxicity. Long nanotubes produce an asbestos-like response, while short nanotubes, and particulate graphene-like materials donâ''t produce this response.â''

Jones further emphasizes, â''the experiments do not say anything about issues of dose and exposure.â''

While Jones did not initially know what percentage of the carbon nanotubes on the market fit the description of those that were used in the tests, the International Council on Nanotechnology (ICON) provided a backgrounder that provides some information in this area.

The MWNTs that might fit this description, Jones notes, are integrated into a material matrix, which leaves the threats of exposure in two areas: workers who are working with the MWNTs before they are integrated into a material matrix and what happens in the life cycle of the products, especially after disposal.

Phoenix Landing on Mars Makes History

This time it all went perfectly. After a voyage of 422 million miles lasting 10 months, NASA's Phoenix Mars Lander came to a rest on a spot on the Martian Arctic yesterday at 7:38 pm EDST. The long-awaited journey's end had its handlers shouting in triumph, savoring the success of one of the most complicated interplanetary missions in history. The last time the U.S. space agency attempted to send a big exploration platform to an ice cap on the Red Planet, with the 1999 flight of the Mars Polar Lander, it ended in failure during the critical landing sequence, which astronautic engineers call the "seven minutes of terror" (see video below).

Those seven minutes, this time, rolled by with every item on the technical checklist kicking in nearly as programmed by scientists many months ago. A minor glitch caused the Phoenix's parachute to open seven seconds later than scheduled, sending the research craft several miles downrange of its target on a stretch of northern plains dubbed Green Valley by mission planners. Nonetheless, yesterday's operation resulted in a historic milestone in space exploration, the first successful mission to a Martian polar region, where subsurface ice is believed to exist.

Due to the great distance its radio signals had to travel, confirmation of touchdown did not reach Earth, at NASA's Goldstone Space Communications Station in California's Mojave Desert, for about 15 minutes, where the result was instantly relayed to the Jet Propulsion Laboratory, in Pasadena, Calif. The JPL team, in charge of the flight portion of the mission, immediately broke out in boisterous applause at the confirmation (see video below): "Touchdown signal detected."

Led by JPL Project Manager Barry Goldstein, the flight team shouted, "It's down, baby, it's down!"

The Phoenix's perilous descent saw it decelerating from some 12 000 miles per hour at the edge of the Martian atmosphere to about 5 mph as it approached the surface using eight pulsed retro-rockets to gently coast it to a landing. The US $420 million spacecraft then released its remaining helium fuel and, after waiting for dust to settle, began deploying its twin solar-power arrays.

"It was better than we could have imagined. Everything just worked like a charm," said Goldstein. "The hardest part is over," he added.

Photo: NASA

FLOATING TO MARS: A spectacular image captured by the Mars Reconnaissance Orbiter's HiRISE camera showed the Phoenix with its parachute deployed high above the polar plains.

About two hours after touchdown, according to an update from NASA last night, the Phoenix's cameras began to transmit the first images of the northern polar landing zone, including this colorized photo of the ground around the settled vehicle.

"We see the lack of rocks that we expected, we see the polygons that we saw from space, we don't see ice on the surface, but we think we will see it beneath the surface," said Peter Smith of the University of Arizona at Tucson, principal investigator for the Phoenix mission. "It looks great to me."

"Seeing these images after a successful landing reaffirmed the thorough work over the past five years by a great team," Goldstein commented yesterday (the 47th anniversary of Pres. John Kennedy's call to to send a man to the moon).

Now, the real work of interplanetary science begins for Phoenix: scooping the Martian "permafrost" soil for evidence of frozen water.

We'll continue to keep you posted on the progress of Phoenix. In the meantime, for more on the mission's background and implications, please review this account, "Martian Cliffhanger Resolved at Last", at MSNBC by our Spectrum Online contributor (and mentor) Jim Oberg.

It's the stuff history is made of.

Out of Africa: Ultralow power PCs

Africa's electricity shortages are getting the attention of some very clever desktop computer designers in San Francisco -- at an innnovative technology and development organization called Inveneo.

I first encountered Inveneo's marvelous low-power PC in a dusty, poor village in Rwanda, the country made infamous by the 1994 ethnic genocide and then famous by the Hollywood blockbuster film, "Hotel Rwanda.". Late one afternoon, I visited an Internet cafe -- a small shop where people pay about a dollar an hour to send emails and search the Web. Instead of a normal bulky, power-hungry computer, I found a small, simple and energy-efficient one.

Indeed, the electricity footprint of this PC was unbelievable small: a mere six to eight watts, many times less than a normal computer.

The power requirement is so low that a simple solar device, costing less than $500, can drive this computer for eight hours -- day after day.

More than a year passed before I met the talented people who devised this computer. The other day, I went to the offices of Inveneo, whose staff hang out in a scruffy building in the trendy but still-funky "South of Market" neighborhood. There I met Robert Marsh, Inveneo's engineering guru, and the group's charismatic chairwoman, Kristin Peterson.

In the 1970s, Marsh was a founding member of the legendary Homebrew Computing Club, a font of creativity for what became the PC industry in Silicon Valley. Marsh designed the Inveneo PC using off-the-shelf parts. they are cheaper of course. He chose an ultra-low-power AMD chip-set and a low-power flat-panel monitor. "I tested a ton of them," Marsh recalls, "until I got it right."

Inveneo sells the PC for $469. First released about a year ago, the computer is usually purchased by foreign donors, supporting one of the dozens of African partners that Inveneo works with to expand technology expertise in the region. To date, about one thousand of these PCs are being used in Africa.

"The benefits are various," says Peterson, who travels often to the region. "These computers work in areas where electricity is undependable, or maybe there is no electricity."

Even in African cities, "there is heat, dust and humidity," she adds. "These are punishing environments for computers."

By going against the grain of the computer industry -- where ample electricity is taken for granted -- Marsh was able to conceive of a novelty -- that makes perfect sense in the sub-Saharan.

Today, Inveneo's PCs are assembled in the U.S., so the obvious next challenge is to bring assembly closer to Africans. That will require more training and resources in the places using these computers. And that reminds Peterson of a central insight that animates her work in human development: "Technology alone isn't enough."

[For more about Inveneo, watch this clip from CNN]

Japan Experiences a Flight from Science

According to a recent article in The New York Times, Japan is running out of engineers and scientists.

After decades of eminence in the fields that made it a world leader in technology, Japan now finds itself worrying over its future, as its young people flock to professions in other areas. Japanese educators have even given the trend a name: rikei banare (or "flight from science").

By one estimate from the nation's ministry of internal affairs, there is a shortfall of almost half a million engineers available to Japan's industrial infrastructure.

Much like American youngsters, Japanese students increasingly are choosing career paths in more lucrative or glamorous sectors such as finance or the arts. The drop-off in those studying math, science, and engineering has become so severe, the Times reports, that Japanese industrial firms have begun advertising campaigns designed to make these pursuits "look sexy and cool."

More pragmatically perhaps, Japanese business planners have initiated programs to invite young engineers and scientists to their shores to fill in the looming gaps--as well as to send high-tech assignments overseas to where the talent pool is potentially deeper, such as India and Malaysia.

So far, these efforts have failed to turn the tide in terms of meeting the country's enormous future needs for brain power, according to the Times.

"Japan is sitting on a demographic time bomb," Kazuhiro Asakawa, a professor of business at Keio University, told the U.S. newspaper. "An explosion is going to take place. They see it coming, but no one is doing enough about it."

If it sounds like a familiar refrain to many in Western industrial nations, it's because Japan is hardly alone. The more prosperous a nation becomes, the more it tends to squander the very source of its own prosperity.

Swiss Snowfall the Lowest Ever Recorded

Because snowpack in the worldâ''s major mountain chainsâ''the Himalayas, Rockies, Alps and Andesâ''are so immensely important to river flows and water supplies across huge regions, hardly anything is more important than their fate in a warming world. Switzerlandâ''s Neue Zuercher Zeiting, one of the globeâ''s top business newspapers, reports today, May 22, that during the last two decades, there have been fewer snowy days in the Alps than any time since measurements began.

The news report is based on findings by Christoph Marty of the Swiss Federal Institute for Snow and Avalanche Research. He found that at lower elevations (200-800 meters), the number of snow days has declined 50 percent in the last twenty years. At middle elevations, there are three weeksâ'' fewer snow days, a drop of 40 percent.

According to NZZ, Martyâ''s findings appeared in the AGUâ''s Geophysical Research Letters on Wednesday. Watch the site; so far a search turns up no 2008 publications for Marty, and the most recent issue posted was from April.

Italy Opts for New Nuclear Construction Program

Franceâ''s Le Figaro reports today, May 22, that the Italian government has opted to build a new group of nuclear power plants. Following Chernobyl, Italians voted in a national referendum to close their existing reactors, and so if the country follows through on the governmentâ''s new commitment, it will be not merely a matter of adding reactors but of initiating an all-new nuclear program.

Italy is highly dependent on natural gas, which it obtains in large quantities from Russia and states in the Russian sphere of influence. Its development minister said it had no choice now but to re-embrace the atom, given nuclearâ''s economic and environmental advantages.

Global Governance for Nanotechâ¿¿Perhaps. But What Kind of Nanotech?

I was drawn to the headline for a recent opinion piece over at Nanotech-Now that reads: â''Nanotechnology and the Potential for Global Governanceâ''. This was intriguing to me based on my most recent musings on the current way we are addressing toxicological issues surrounding nanoparticles.

While I see a current vacuum in leadership and global governance on the toxicology and safety of nanoparticles, this article concerns itself with global governance for mechanosynthesis and desktop factories. According to the author, Mike Treder for the Center for Responsible Nanotechnology, we need to start thinking about how the world is going to regulate this technology because it could be so significant even though it doesnâ''t exist yet.

The article was enlightening for me because I hadnâ''t realized that â''the formerly active debate over the feasibility of mechanosynthesis and exponential general-purpose molecular manufacturing seems to be largely over.â''

I suppose that "feasible" is broad enough a term that it may be true that debate is largely over. But there still remain some important science issues to be addressed before mechanosynthesis is capable of being realized, which I think is more or less what "feasible" is supposed to mean.

What is odd about the article is that it uses testimony by David Rejeski, director of the Project on Emerging Nanotechnologies, before a Senate subcommittee to support the contention that we need global governance of mechanosynthesis now, even though Rejeski was arguing that we need to be proactive in addressing toxicology issues of nanoparticles or face a potential backlash against the technology.

I imagine that Rejeski provided his testimony because environmental, health and safety concerns over nanoparticles are here today. I am not sure that he had desktop factories on his mind when he made his comments.

I donâ''t want to postpone the setting up of a global governance body to oversee desktop factories too long because it could become a reality in 20 years or so. But maybe we can see how it goes with safety regulations for nanoparticles firstâ'¿since theyâ''re already here.

Out of Africa: Alternative lighting

The World Bank keeps raising the curtain on an unusual campaign to stimulate alternative and non-traditional sources of â''off-gridâ'' electricity for Africans. The World Bankâ''s â''Lighting Africaâ'' initiative held its first business development conference last week, in Accra Ghana. The conference is the latest move by the initiative to link private businesses with African partners in the area of â''off-gridâ'' electricity â'' solar, small hydro, wind, geothermal and other self-contained systems.

The campaign is a big departure for the World Bank, which for decades has loaned money â'' or helped back loans â'' to national governments who built large generating capacity for national grid networks. These networks, by their nature, are large, centralized and relatively expensive. Even worse, in most African countries these networks have failed to reach large parts of the population.

Off-grid networks are potentially a boon for rural Africans, most of whom live so far from national electric grids that they have no hope of receiving a connection, ever. By building and managing their own small grids â'' to create enough power for villages or even single schools or hospitals â'' rural Africans can get a more secure supply of electricity â'' and less expensively and more under their own control. The barrier is both financial, managerial and technical. Rural Africans and small communities often lack the money and expertise to run these systems (though many are simple enough to be easily maintained by locals.

Trying to mediate between rural Africans and their small community institutions, on the one, and the international market for alternative energy services, on the other, is new ground for the World Bank. Why far-flung alternative energy companies, interested in small projects in remote Africa, would do business with the World Bank is an open question. But the experiment is well conceived, responds to a huge need and has great potential as a learning experience, if nothing else. In short, this experiment is worth watching. If it succeeds â'' or it other institutions can do the same thing more effectively â'' the potential for rural Africa is staggering. No single technological input is more important in rural Africa than electricity; and because these communities are decentralized, the electricity solution can be too.

Worth noting also is the potential PR windfall for the World Bank. Usually to finance large-scale national grid systems, the bank must cozy up to authoritarian rulers in Africa. The â''Lighting Africaâ'' initiative helps burnish the World Bankâ''s â''greenâ'' image and also presents this large bureaucratic institution as looking out for Africaâ''s little guys. So even the PR value alone of the initiative is substantial.

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