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Printing on Aluminum Boosts Solar Efficiencies May 13, 2010

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Nanosolar, a San Jose (CA) energy company, has opened an automated facility for manufacturing an innovative new process for cheaper solar panels.  The solar panels are made by printing a semiconductor material called CIGS on aluminum foil.

Nanosolar located the factory in Luckenwalde near Berlin, Germany, in part because German government incentives for the purchase of solar cells has created a large market for solar panels.  The panel factory is automated to sustain a production rate of one panel every ten seconds, or an annual capacity of 640MW when operated 24×7.

It’s not that the cells are that much more efficient than others.  On average, the company’s solar panels convert just 11 percent of that energy into electricity, about the same as most good quality cells, and a little less than high-end cells, which have demonstrated up to 16% efficiency.

What makes Nanosolar’s technology unique is the producability improvements of the panels, and the transmission increases in the panels.  By using large aluminum-foil sheets to collect electrons from each panel, Nanosolar decreases the amount of wiring per panel and has increases the current its panels can generate, up to 160 watts each, compared to 70 watts for standard panels.

But what matters most to consumers is that making panels this way eases installation and lowers production and operations cost.  Based on DoE’s life cycle amortized cost methods,  using these in sunny locations could produce electricity at less than six cents per kilowatt hour (compared to 12 cents for conventional panels), almost as low as coal-fired generation plants.

Nanosolar started in a small laboratory in 2002.  It strives to be a “green” company both in its products and its practices.  It also strives to maintain a  small company feel.  For example, “almost everyone eats lunch in the office café, sitting at whatever table has an opening and enjoying conversations with Nanosolar people from all different departments, executives and operators alike.”

sources: Technology Review, NanoSolar website

Concentrated Solar Shines Bright May 7, 2010

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Concentrating the sun’s rays on a smaller spot is a great approach to boosting efficiency of solar power.  It’s a half-step toward making solar economically viable.

Traditional solar thermal systems use highly concentrated sunlight to create steam that drives electric turbines.  Trouble is, that way takes massive amounts of water to create steam, but abundant clean water is coming to be one of the scarcest commodities in the world.  And taking water from fish and wildlife habitats puts you sideways from environmental regulators.

What Amonix (a California-based startup) has done is to combine Fresnel lenses, a tracking system, and solar cells for large, highly efficient solar-power installations.

Step one is the lens. I know about Fresnel lenses from theater. It takes a small light source (a bulb) and spreads it out to provide wide coverage of an area on stage. Amonix turned it around, to take a wide coverage of sunlight and concentrate it on a small solar collector. These thin, plastic Fresnel lenses, measuring about 350 square centimeters, focus sunlight down to a 0.7 square centimeters spot. That concentrates the sunlight to 500 times its normal intensity.

That concentrated sunlight hits an ultra-efficient multi-junction solar cell made by Spectrolab, the most efficient in the world. They’ve shown 41% efficiency in the lab, and Amonix is able to get 39% in field tests.

These cells are set in an array that’s 23.5 meters by 15 meters, 165 co-joined panels worth. Then Amonix uses a tracking system that keeps the lenses pointed to within .8 degrees of the angle of the sun all day long.

That’s a lot of miracles happening all at once. And we’re worried about the long-term viability of plastic lenses exposed to that much UV radiation. But at least it holds promise for the future.

source: http://www.technologyreview.com/business/25209/?a=f

July 8, 2009

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Bill Gross is CEO of eSolar, and thinks he’s finally found a way to use the power of the sun to generate massive amounts of energy.  He calls it a “disruptive revolution” in carbon-free energy.

Rather than using direct solar to electric conversion, which remains a technical challenge to do efficiently, Gross wants to use a “field of tabletop-sized glass panels” to reflect solar rays on liquid-filled towers.  The heat creates steam to drive a traditional turbine.

The system incorporates video cameras, a bank of Dell servers and complex software to monitor and move the mirrors to track the sun’s position.

Gross claims his power will cost around 10 cents per kilowatt-hour. That would make it less than wind power.    But then, Gross has been called a”serial entrepreneur” –  he’s launched more than 30 tech companies.  He’s also founder of startup incubator Idealab, based in Pasadena, CA.

I hope it works.

Sources:  Technology Review/Solar Thermal Heats Up, by Evan I. Schwartz and eSolar website.

Dollar-a-Watt Solar March 1, 2009

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This week, First Solar, Inc announced tests for thin-film photovoltaic panels that dropped the cost per watt generated below $1 per watt.  When First Solar began operation in 2004, they were manufacturing panels at $3 per watt.

First Solar, of Tempe, Arizona, is using cadmium telluride (CdTe) technology and needs to get the costs below 65 cents if the installed costs make it beneficial to be installed commercially. Solar panels generally cost $4.81 per watt in commercial quantities.  (The lowest thin film module price commercially available is $3.57 per watt in a 60 watt module.)

Unfortunately, a Popular Mechanics review suggests this technology can’t scale up fast enough or easily enough to make much of an impact on national energy needs.  CdTe raw materials are difficult to extract and require a great amount of energy to convert into a usable crystalline form.

Cyrus Wadia, a researcher with Univerity of California – Lawrence Berkeley National Laboratory, warns that

“Even if the solar cell market were to grow at 56 percent a year for the next 10 years—slightly higher than the rapid growth of the past year — photovoltaics would still only account for about 2.5 percent of global electricity”

Wadia admits First Solar is capable of producing small quantities of solar cells,  “But as soon as they have to start rolling out terawatts, that’s where I believe they will reach some limitations.”

And “even if the solar cell market were to grow at 56 percent a year for the next 10 years—slightly higher than the rapid growth of the past year—photovoltaics would still only account for about 2.5 percent of global electricity.”

sources:

popular mechanics
First Solar Press Release
Solarbuzz Module Prices, Feb 09

Solar Updraft for Energy Production September 13, 2008

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There’s an interesting but still untried approach that combines solar power and wind power.

The principle of Solar Updraft is that a solar collector is laid down across an open field, such as a desert wasteland.  In the center is a tall hollow tower.  The result is an updraft inside the tower.  If one or more wind turbines is placed inside the tower, the constant wind can generate a steady stream of electrical energy, with virtually no carbon footprint once the tower is finished construction.  (Carbon payback on construction is generally 2-3 years.)

Some have suggested the collector field can be fitted with solar storage mechanisms, such as tubes of liquid, which heat during the day and generate a secondary heat source after the sun has gone down.

Unfortunately, most of the concepts involve very tall towers.  A prototype plant with a 200 meter-tall  tower built in Manzanares, Spain in the early eighties, and was operated successfully for several years.  However, a production plant was never constructed, in part because the finished tower will be almost a mile high (1.5km) and 280 meters wide.  And it will take a large amount of land, as currently designed.  The prototype plant included a 44,000-m² collector; the production unit uses a 37 square km collector field.

Of course, you don’t need to leave the collector field empty.  The solar tower proposed for Nambia includes a design to use that collector field as a greenhouse.

It’s an interesting concept.  I’m a little concerned about how they would construct a tower that is nearly 5 times taller than the Eiffel Tower (325 m).  It would be twice as tall as the world’s tallest building, the Burj Dubai in downtown Dubai (still under construction), which will be 688m (160 floors) when finished.

The expected power output – 400MW of energy – is impressive, but I wonder whether it might be better to stick with more, smaller towers, even if they generate less  energy each.

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sources:

http://www.inhabitat.com/2008/09/10/solar-updraft-towers-in-namibia/

http://www.sbp.de/en/html/solar/aufwindkraftwerk.html

http://en.wikipedia.org/wiki/Solar_updraft_tower

Solar Power Prospects Dim September 7, 2008

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According to an article in Scientific American, harvesting the sun’s rays for electricity production holds the promise of producing 2/3 our current and projected energy needs by 2050.  “Converting only 2.5 percent of that radiation (that falls on the USA) into electricity would match the nation’s total energy consumption in 2006.

The energy in sunlight striking the earth for 40 minutes is equivalent to global energy consumption for a year. The U.S. is lucky to be endowed with a vast resource; at least 250,000 square miles of land in the Southwest alone are suitable for constructing solar power plants, and that land receives more than 4,500 quadrillion British thermal units (Btu) of solar radiation a year. Converting only 2.5 percent of that radiation into electricity would match the nation’s total energy consumption in 2006.”

Unfortunately, that doesn’t include the costs to improve the technology.  For this magic to work means a 50% increase in efficiencies:  the article assumes 14 percent efficiency, but current state of the art is barely 10%, and efficiencies have been improving only slowly.

It also doesn’t account for the economic incentive to install that systems.  The current break-even point means that the solar generators would have to cost no more than $1.20 per watt, and the current cost is $4 per watt.  That means that when the article says it will cost $400B, the real cost is more than a trillion.

And you’d have to cover vast tracts of land, around 30,000 square miles of photovoltaic arrays. I know there’s a lot of open land in the southwest USA (the area around the Grand Canyon is pretty empty).  But you’d also have to solve transmission problems.

In short, despite the opportunities for solar power, the prospects aren’t near as bright as they’d have you believe.

Advent Solar Shuts Manfacturing Plant August 1, 2008

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Solar is hot, right?  Then why aren’t solar companies selling products hand over fist?  That brings us to the story of Advent Solar.

In February, Advent Solar won a marketing award.  Advent is a leading manufacturer of innovative solar cells and modules. Its unique, exclusive EWT cell technology was originally developed at Sandia National Laboratories and is in a class of solar cells referred to as back-contact cells. This technology is the basis for Advent’s high performance products with the potential for dramatically lower cost than conventional solar photovoltaic technology.

So, fresh off such prestigious press, with notice to the world that this company produces some of the best solar cells available, Advent Solar decided it wasn’t enough.  Less than 3 weeks after the award was announced, Advent has closed up manufacturing.   Rather than produce solar cells for sale, they laid off all 68 manufacturing staff (but not the marketing staff).

They say they want to retool for new technology.  The CEO, on the job less than a single fiscal quarter, announced he wanted to retool the whole plant for a new kind of solar cell.  Rather than continue manufacturing, providing collaboration between R&D and those who actually produce the results, he sent his workforce packing.

“Once the technology solution is perfected and put into place, this company has excellent long-term prospects,” said CEO Peter Green. “We will be looking to hire back any of our employees who are interested in returning. There’s not a one I wouldn’t hire back.”

They freely admit that “The industry is growing at 30% to 40% per year, and with the cost of oil going through the roof, demand will remain strong.”

All I have to say is, it better be a huge improvement, at an appropriate price point, or Green will have just closed the company.  And unless he can offer significant incentives to the employees who trust he has just destroyed, it’s gonna take more than a year to get them back.

Look for solar to take off in the market place.  Just be careful putting too many bets on Advent.

Windows as Solar Electricity Collectors April 10, 2008

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One of the most energy inefficient parts of commercial buildings- those massive walls of glass – could soon become the means of powering that same building.

Researchers at the Institute of Sustainable Resources (ISR)  at Queensland (Australia) University of Technology (QUT) have been working with Dyesol (an Australian company) to develop transparent solar cells that act as both windows and energy generators in houses or commercial buildings.

Officials at Dyesol explain that “the solar the panels are constructed in a laminated structure, with the tiles connected and sandwiched between two panes of glass and fully encapsulated in the UV resistant transparent laminating polymer (Solar Wall Panels). … Electrical interface can be typically via a short DC bus to a local area network for distribution or inversion to AC.”

Professor John Bell explained that the solar cells contain titanium dioxide coated in a dye that increases light absorption.

“The transparent solar cells have a faint reddish hue but are completely see-through,” Professor Bell said.  “The glass captures solar energy which can be used to power the house but can also reduce overheating of the house, reducing the need for cooling.”

“As long as a house is designed throughout for energy efficiency, with low-energy appliances it is conceivable it could be self-sustaining in its power requirements using the solar-cell glass,” he said.

sources:  expertguide.com.au and Dyesol web site

The Future of Solar is Bright March 26, 2008

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Instead of stiff and heavy traditional solar cells, recent advances are creating light-weight and flexible structures that can be used in more situations.  Although not quite at the 8% minimum power efficiency, new methods are getting close.

The first approach is using “organic plastic” solar cells that have “nano-filaments”  embedded in light absorbing plastic, similar to the veins in tree leaves.  This process  is able to capture more of the sun’s light, although state of the art is still only 6% efficiency, only half of traditional, rigid solar cells.

David Carroll, director of the Wake Forest nanotechnology center, where this technology is being developed, expects to reach 10 percent in the next year.

Meanwhile, at New Jersey Institute of Technology (NJIT) have developed an inexpensive solar cell that can be painted or printed on flexible plastic sheets.  Dr Somenath Mitra is looking for the day when sheets of solar cells could be printed on home printers, similar to today’s inkjet printers.  “Consumers can then slap the finished product on a wall, roof or billboard to create their own power stations.”

Or you could paint the solar cells on buildings or other exposed surfaces.  Imagine painting the top of an electric or hybrid car.  The car could recharge itself while sitting in the parking lot while you’re at work, providing enough power for a normal commute home. (My commute is 7 miles.)

NJIT’s approach uses carbon nanotubes, which are better conductors than copper, and tiny carbon Buckyballs (known as fullerenes) to grab solar electrons and pass it along the nanotubes.

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Information for this report came from Science Daily,  here and here.

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note:  A large part of Dr Carroll’s research at Wake Forest is funded by the United States Air Force, which is interested in the potential uses of more efficient, light-weight solar cells for satellites and spacecraft.  Other members of Carroll’s research team include Jiwen Liu and Manoj Namboothiry, postdoctoral associates at Wake Forest’s nanotechnology center, and Kyungkon Kim, a postdoctoral researcher at the center, who has moved to the Materials Science & Technology Division at the Korea Institute of Science and Technology in Seoul.