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Disposable Solar Cells and other Solar Developments

by Chris Kulczycki Fri Dec 9th, 2005 at 07:26:57 AM EST

Solar is certainly the most attractive of alternative energy technology. It's clean, long lasting, has no moving parts, and it's starting to come down in cost. If only we could figure out a way to store power for a cloudy day.

I've noticed a lot of small advances in solar power in the last couple of months and I thought you might be interested. There are solar panels for the roofs of cars, solar trains (sort of), , and lots more below the fold.

How cheap will solar cells get? Disposable printed paper solar cells may soon be a available. From Mongabay.com :

Scientists at the University of Cape Town are exploiting the nano-scale properties of silicon to develop a super-thin disposable solar panel poster which they hope could offer rural dwellers a cheap, alternative source of power. Many people living in remote areas are not linked to the national electricity grid, and use batteries or run their own generators to supply their power needs. The scientists have developed technology for printing specialised inks containing tiny nanoparticles of silicon and other semiconductors onto paper. The solar panels are printed in much the same way as conventional colour images, using three or four separate print runs with black, blue, yellow and magenta ink. They print the metal contacts, then the semiconductor structure, then more contacts. The voltage and power output of the solar cell is determined by the size of the poster. An A2-sized poster will deliver up to 100W of power, enough to charge a cellphone, power a radio or provide five hours of lighting, said Prof David Britton, a physicist specialising in nanotechnology. Many families cannot afford R1000 for a solar panel designed to last 30 years, but they can afford R10 every three to six months for a 'disposable' panel, he said.

Shops could stock rolls of solar panel posters, and cut it to meet a customer's needs. The poster could be mounted behind a window or attached to a cabinet. Britton's team has built a successful prototype and is seeking to commercialise the project.

Solar curtains developed by Sweden's InteractiveIinstitute  are another innovative use of solar technology. They capture light during the day and glow at night. From Inhabitat :

Though guilt is a common and effective remedy for changing wasteful behavior, it's certainly nobody's favorite. In order for sustainable ideas to catch on, they need to be pleasurable and desireable. Not many products consist of equal parts ecological responsibility and innovative design, but Re:Form has struck the balance. Their Energy Curtain is a window shade woven with solar-collecting and light-emitting materials that store sunlight during the day and emit it at night. By choosing how much sunlight to collect and how much to use, the curtain "acts to stimulate reflection on the trade-offs of a local, sustainable system and [help the user] evolve a relationship with their own energy behaviors over time."


A solar train? Well yes and no. This is from Green Car Congress :

ANSA. Italy has unveiled Europe's first solar-power-assisted train. The solar panels on the train's roof do not drive it but provide energy for its air conditioning, illumination and safety systems.

The PVTRAIN project, partly funded by the EU, has been under development since 2003, and involves 10 prototype units: 5 carriages, 3 cargo wagons and 2 locomotives. -snip-

The panels on a rail car can deliver approximately 1.36 kW of peak power. In the development and testing from July 2003 to May 2005, the solar panel system generated a total of 1,017.41 kWh.

Solatec LLC has introduced flexible, rooftop-mounted solar panels for hybrid vehicles, starting with a kit for the 2004-2006 Toyota Prius. The downside is the cost, $2,195 They've also patented an unmanned solar powered spy plane. From Yahoo Finance :

A prototype (pictured) has been operating in the Northeast for several months under mixed driving conditions. With Solatec panels installed on the roof, the prototype SolaPrius® averages 55 MPG city and 62 MPG highway - an overall 10 percent improvement over the pre-installation numbers. All-season testing is in progress.

Solatec's photovoltaic kit (patents applied for) adds two flexible, conformal panels that charge the hybrid automobile's auxiliary battery through a proprietary charger/current-limiter system concealed behind interior trim panels. The self-adhesive, rooftop-mounted panels are only 0.6mm thick and cause no change in aerodynamic drag.


The cost of super-pure silicon crystals is one of the major factors in the price of solar cells. An article in September Nature Materials outlined a way to use far less expensive "dirty silicon" for solar cells. This would be a major breakthrough in affordable solar technology. Here is a summary from Science News Online :

Silicon is the second most abundant element in Earth's crust, but nature's primary sources of silicon--sand and quartz--are tainted with metals. Converting silicon from these sources into superpure crystals is an expensive and time-consuming process.

While there had been enough pure stock for the electronics industry, the needs of the growing photovoltaic industry--which uses silicon for more than 90 percent of its solar cells--caused overall demand to exceed supply in 2004, notes Eicke R. Weber, a materials scientist at the University of California, Berkeley and the Lawrence Berkeley (Calif.) National Laboratory. This triggered a drastic price increase in pure silicon, dealing a blow to the solar cell makers.

Silicon stock that is less pure and therefore less expensive is available, says Weber. But the increased amounts of iron, copper, and other metal contaminants in these stocks reduce solar cell efficiency. Clusters of these metal atoms attract the solar cell's charge-carrying electrons, reducing the amount of current that the cell can generate.

The researchers found that silicon hosting larger but fewer numbers of clusters performed better than did samples with smaller but many more clusters. They tested this result by heating samples and then cooling them at different rates, which enabled the researchers to control the distribution of the metal. Weber's team found that silicon with micrometer-size clusters, spaced hundreds of micrometers apart, was four times as efficient as silicon with more-finely-distributed, nanosize clusters.

"Without changing the total metal content--only changing the way it is distributed--we get a drastic change in the electrical property," says Weber. "If it is possible to concentrate the metals in a few big clusters, in principle, one can make good solar cells out of dirty starting material."

Pyron Solar has developed a solar array that they say can generate power at competitive costs. The unit is 37.3% efficient.  From their web site:

PYRON SOLAR INC., an R&D company in La Jolla, California, developed in cooperation with Boeing-Spectrolab a novel system to convert sunlight into electricity.

This revolutionary design is a low-profile floating system with short-focal-length lenses concentrating direct sunlight by 400X onto photovoltaic cells. These advanced multi-junction cells produce 800 times more electricity than conventional non-concentrating cells the same size.

The National Renewable Energy Laboratory of the U.S. Department of Energy confirmed 37.3% efficiency. -snip-

The first PYRON-SOLAR solar power plant with BOEING-SPECTROLAB photovoltaic cells has been built in El Cajon CA, near San Diego. The platform, 23 feet in diameter and just 12 inches high, generates 6.6 kW peak. The picture shows that except for the cutout areas along the perimeter, the whole surface of the platform collects sunlight. In full-sized power plants, such cutout areas amount to less than 2% of the circle.

·    BOEING-Spectrolab holds the world record in efficiency of solar cells.

·    PYRON-SOLAR, INC. holds the world record in lens-surface per unit ground-surface.

·    The world record in the lowest solar-electricity production costs can be achieved by combining these innovations.

Yield: At 2,850 kWh/m2yr direct-sunlight as in sunny deserts, the annual electricity yield will be 450 kWh/m2year or 450 GWh per km2year.

Performance-comparison: Per unit of total land area Pyron power plants produce:

·    14.5 times more electricity than the world's largest plant SOLAR II in Dagget, CA.

·    8.6 times more electricity than the huge LUZ power plants in California.

·    189 times more electricity than the Manzanares (Spain) Solar Chimney power plant.

System Price: The extremely high efficiency and the low material requirements make the new system competitive with conventional power plants. For large Pyron power plants a calculation shows that the price for the high-tech parts including the cell and the material for the low-tech parts will be $1.87 per watt. Depending on where the units are constructed, the labor costs will vary. With manufacture in the U.S. the total cost is estimated to be around $3 per watt.

These are some startling developments that show both how solar energy may soon be affordable and how it can be used in new and innovative ways.

Cross posted on dKOS, should you care to recommend. link


Do not feel safe. The poet remembers.
Czeslaw Milosz

by Chris Kulczycki on Fri Dec 9th, 2005 at 07:31:31 AM EST
Not to nit-pick, but when you say solar is clean, are you including the impact of manufacturing and disposing of solar panels?

As far as solar technology goes, we have a long way to go before we match what nature has done with chlorophyl.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman

by Migeru (migeru at eurotrib dot com) on Fri Dec 9th, 2005 at 07:36:01 AM EST
Oh no, chlorophyll efficiency is dreadful, 11% peak, 3 to 6% in practice, and [I don't have a reference handy] overall biomass efficiency is in the order of 1%.

The upside is that you don't have to build it...
by Francois in Paris on Sat Dec 10th, 2005 at 08:36:46 PM EST
[ Parent ]
Interesting news.

Two small bits from me: one, multi-junction cells are feverishly developed in Germany too. Two, this years' expectation of new German photovoltaic (PV) installations has been raised by the industry association from 360 to 450 MW (previous years' world record was 363 MW), as the supply problems seem to be topping out. (Germany may overtake Japan in total installations too in two years, and all-European production may catch up with Japan in a little longer.)

Finally, for 2004 data, you can view truckloads of statistics at the IEA-PVPS site.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Dec 9th, 2005 at 01:50:13 PM EST
It's worth to check the monthly module price survey at Solarbuzz - they track it separately for Europe and the USA. (Note: figures not inflation-corrected.) Here is the effect of the German boom on the world market (prices start climb from June 2004):

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Dec 9th, 2005 at 02:01:54 PM EST
[ Parent ]
the prototype SolaPrius® averages 55 MPG city and 62 MPG highway - an overall 10 percent improvement over the pre-installation numbers.

That 10% sounds very impressive, tough I'm somewhat sceptical regarding how practice-close the tests were.

On the other hand, I always forget that California has much more Sun than Central Europe...

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Dec 9th, 2005 at 01:52:50 PM EST

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