The big missing piece to the wind-solar puzzle is….

April 15, 2008

SolveClimateThis file is from the Open Clip Art Library, which released it explicitly into the public domain, using the Creative Commons Public Domain Dedication: A massive energy storage system that can guarantee uninterrupted power delivery. Meaning: clean electricity all the time, even when the winds aren’t blowing and the sun isn’t shining. And now there’s a battery unit being produced in Japan that claims it can provide just that. They’re called sodium-sulfur systems. And they offer a way to store power from the sun and wind, and then dispatch it to the grid when demand is greatest.

It’s welcome news if they can pull it off. Because without that missing piece, solar and wind will continue to play second fiddle to fossil fuels. Bloomberg has the full story on the sodium-sulfur batteries — and their Japanese maker too, NGK Insulators Ltd.

In Japan, the NAS storage units — as NGK calls them — have been a hit. They’re used at over 30 sites already, totaling 28 megawatts. But in the US they’re still an anomaly with just two customers. American Electric Company is one of them. The coal giant has been testing a 1.2 megawatt NAS system since mid-2006 but not in connection with renewables at all. And Xcel Energy is the other. It will be the first American utility to use NAS for wind energy storage beginning in October, when it starts testing a one-megawatt system in Minnesota….

First global solar index, from Melvin and Company

April 11, 2008

Solar corona photo by NASASolar Daily: MAC Indexing has announced the introduction of the MAC Global Solar Energy Index, the first index to independently track the rapidly growing solar energy sector. Dow Jones will publish the Index, which was developed and is maintained by MAC Indexes, an affiliate of Melvin and Company that specializes in clean energy equity research and index development. The MAC Global Solar Energy Index has been licensed to Claymore Advisors, LLC, which anticipates launching the first solar power exchange-traded fund (ETF) on the NYSE-Arca under the symbol “TAN” in April (

“The creation of the MAC Global Solar Energy Index recognizes the growth of the solar sector and its maturing in terms of investment depth,” said Christopher C. Melvin, Jr. Chairman and Chief Executive Officer of Melvin and Co. “Solar continues to be one of the fastest growing sectors within the clean-tech industry with a recent 47% annual growth rate and an expected 40% continued growth in the next few years.” A global portfolio of 25 leading solar companies with a combined market capitalization of nearly $100 billion comprise the index. The average market capitalization of the stocks in the Index is approximately $3.8 billion and the median is approximately $1.2 billion….

The Index is designed to track companies within the following business segments of the solar power industry: solar power equipment producers; suppliers of materials or services to solar equipment producers; companies that derive a significant portion of their business, measured by the methodology set forth below, from solar power system installation, integration or finance; and companies that specialize in selling electricity derived from solar power …

Crystalline solar cell market grew 39 percent in 2007, says Gartner

April 7, 2008

PVTech : The crystalline silicon solar cell market had another robust year, according to figures from Gartner, Inc. The sector saw revenues increase 39 percent in 2007 compared with 2006, resulting in a 42 percent CAGR from 2004 through 2007. Ongoing demand in 2008 is expected with solar silicon consumption expected to exceed that of electronic semiconductor consumption for the first time, Gartner sai.

Crystalline silicon solar cell leaders were able to secure silicon material sufficiently for strong growth in 2007, though short supply actually hampered growth rates. Gartner noted that Q-Cells took the number one slot for the first time as Sharp and other Japanese manufacturers struggled to secure polysilicon supplies. Q-Cells now holds 17.2 percent of the market with revenues climbing 70 percent in 2007 compared to 2006…

Silicon chips for optical quantum technologies

March 28, 2008

Generating and detecting single photons, by Carmel King, from the University of Bristol websiteDoes this have implications for solar physics? Some fascinating research from the University of Bristol: A team of physicists and engineers has demonstrated exquisite control of single particles of light – photons – on a silicon chip to make a major advance towards the long sought after goal of a super-powerful quantum computer.

Dr Jeremy O’Brien, his PhD student Alberto Politi, and their colleagues at Bristol University have demonstrated the world’s smallest optical controlled-NOT gate – the building block of a quantum computer. The team were able to fabricate their controlled-NOT gate from silica wave-guides on a silicon chip, resulting in a miniaturised device and high-performance operation. “This is a crucial step towards a future optical quantum computer, as well as other quantum technologies based on photons,” said Dr O’Brien. The team reports its results in the March 27 2008 Science Express – the advanced online publication of the journal Science.

Quantum technologies aim to exploit the unique properties of quantum mechanics, the physics theory that explains how the world works at very small scales. For example a quantum computer relies on the fact that quantum particles, such as photons, can exist in a “superposition” of two states at the same time – in stark contrast to the transistors in a PC which can only be in the state “0” or “1”.

Photons are an excellent choice for quantum technologies because they are relatively noise free; information can be moved around quickly – at the speed of light; and manipulating single photons is easy. Making two photons “talk” to each other to realise the all-important controlled-NOT gate is much harder, but Dr O’Brien and his colleagues at the University of Queensland demonstrated this back in 2003 [Nature 426, 264]. Photons must also “talk” to each other to realise the ultra-precise measurements that harness the laws of quantum mechanics – quantum metrology…

Generating and detecting single photons, by Carmel King, from the University of Bristol website

Thin-film solar cell now competitive with silicon

March 26, 2008

IndiumSolar Daily: Researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory have moved closer to creating a thin-film solar cell that can compete with the efficiency of the more common silicon-based solar cell. The copper indium gallium diselenide (CIGS) thin-film solar cell recently reached 19.9 percent efficiency, setting a new world record for this type of cell.

Multicrystalline silicon-based solar cells have shown efficiencies as high as 20.3 percent. The energy conversion efficiency of a solar cell is the percentage of sunlight converted by the cell into electricity. “This is an important milestone,” said NREL Senior Scientist Miguel Contreras. “The thin film people have always looked for matching silicon in performance, and we are reaching that goal.”

CIGS cells use extremely thin layers of semiconductor material applied to a low-cost backing such as glass, flexible metallic foils, high-temperature polymers or stainless steel sheets. Thin-film cells require less energy to make and can be fabricated by a variety of processes. Because of this, they provide a promising path for providing more affordable solar cells for residential and other uses.

The CIGS cells are of interest for space applications and the portable electronics market because of their light weight. They are also suitable in special architectural uses, such as photovoltaic roof shingles, windows, siding and others. Researchers were able to set the world record because of improvements in the quality of the material applied during the manufacturing process, boosting the power output from the cell, Contreras said.

Members of the record-setting team at the National Center for Photovoltaics include Contreras, Ingrid Repins, Brian Egaas, John Scharf, Clay DeHart and Raghu Bhattacharya.

Electron shell diagram for indium, “Pumbaa” and Greg Robson, Wikimedia Commons 

Toward cheaper, robust solar cells, using organic dye

March 14, 2008

Polycrystalline silicon wafer, from Q-Cells. Photo by George Slickers, Wikimedia CommonsTechnology Review: Cheap and easy-to-make dye-sensitized solar cells are still in the early stages of commercial production. Meanwhile, their inventor, Michael Gratzel, is working on more advanced versions of them. In a paper published in the online edition of Angewandte Chemie, Gratzel, a chemistry professor at the École Polytechnique Fédérale de Lausanne in Switzerland, presents a version of dye-sensitized cells that could be more robust and even cheaper to make than current versions.Dye-sensitized solar cells consist of titanium oxide nanocrystals that are coated with light-absorbing dye molecules and immersed in an electrolyte solution, which is sandwiched between two glass plates or embedded in plastic. Light striking the dye frees electrons and creates “holes”–the areas of positive charge that result when electrons are lost. The semiconducting titanium dioxide particles collect the electrons and transfer them to an external circuit, producing an electric current.

These solar cells are cheaper to make than conventional silicon photovoltaic panels. In principle, they could be used to make power-generating windows and building facades, and they could even be incorporated into clothing. (See “Window Power” and “Solar Cells for Cheap.”) A Lowell, MA-based company called Konarka is manufacturing dye-sensitized solar cells in a limited quantity. But the technology still has room for improvement.

In existing versions of the solar cells, the electrolyte solution uses organic solvents. When the solar cells reach high temperatures, the solvent can evaporate and start to leak out. Researchers are now looking at a type of material that may make a better electrolyte: ionic liquids, which are currently used as industrial solvents. These liquids do not evaporate at solar-cell operating temperatures. “Ionic liquids are less volatile and more robust,” says Bruce Parkinson, a chemistry professor at Colorado State University.

New dyes are also being investigated. In commercial cells, the dyes are made of the precious metal ruthenium. But researchers have recently started to consider organic molecules as an alternative. “Organic dyes will become important because they can be cheaply made,” Gratzel says. In the long run, they might also be more abundant than ruthenium.

In the recent paper, Gratzel and his colleagues describe making a dye-sensitized solar cell that combines these two material advances. In their prototype cell, they use an ionic liquid as the electrolyte and a dye based on the organic compound indoline. The solar cells convert light to electricity with an efficiency of 7.2 percent. Ruthenium-based dyes get efficiencies of about 11 percent, says Gerald Meyer, a chemistry professor at Johns Hopkins University. But, he says, “to my knowledge, these are the highest efficiencies with organic [dyes].”

. In a dye-sensitized solar cell, electrons go to the titanium dioxide layer, while the holes go to the electrolyte. This separates the charges so that they do not recombine and reduce the current generated by the cell. Keeping the charges separated is the challenge with organic dyes. Gratzel and his colleagues attach long hydrocarbon chains to one end of the indoline-based dye molecule. These hydrocarbon chains, which do not conduct electrons, act as barriers between the titanium dioxide layer and the electrolyte. “It is like a molecular insulator that stops electrons from coming out and recombining with the positive charges in the ionic liquid,” Gratzel says.With this charge barrier in place, the researchers can make the titanium dioxide layer thinner. That shortens the distance that the electrons have to travel to get to the external circuit, increasing the cell’s efficiency.

Parkinson cautions, though, that work on organic-dye solar cells is still at a very early stage. Going from a laboratory prototype to a commercial module typically reduces efficiencies significantly. To capture a larger share of the solar-power market, dye-sensitized solar cells will require some more improvements. “We really need a breakthrough to get up to 15 percent efficiency in the lab,” Parkinson says.

Konarka announces first-ever demonstration of ink-jet printed solar cells

March 4, 2008, via Business Wire: Konarka Technologies, Inc., an innovator in development and commercialization of Power Plastic®, a material that converts light to energy, today announced the company successfully conducted the first-ever demonstration of manufacturing solar cells by highly efficient inkjet printing. The company discusses and analyzes the performance of highly efficient inkjet printed organic bulk heterojunction solar cells in a paper recently published in Advanced Materials, entitled, “High Photovoltaic Performance of Inkjet Printed Polymer:Fullerene Blends” by Dr. Stelios A. Choulis, Claudia N. Hoth, Dr. Pavel Schilinsky and Dr. Christoph J. Brabec, all of Konarka.

“Demonstrating the use of inkjet printing technology as a fabrication tool for highly efficient solar cells and sensors with small area requirements is a major milestone,” commented Rick Hess, president and CEO at Konarka. “This essential breakthrough in the field of printed solar cells positions Konarka as an emerging leader in printed photovoltaics.”

Inkjet printing is a commonly used technique for controlled deposition of solutions of functional materials in specific locations on a substrate and can provide easy and fast deposition of polymer films over a large area. The demonstration confirms that organic solar cells can be processed with printing technologies with little or no loss compared to “clean room” semiconductor technologies such as spin coating. The most popular printing tool for organic electronics, inkjet printing could become a smart tool to manufacturer solar cells with multiple colors and patterns for lower power requirement products, like indoor or sensor applications. Inkjet printing is considered very promising because the polymer devices can be fabricated very easily because of the compatibility with various substrates and it does not require additional patterning.