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 FUTURE ENERGY eNEWS
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         September 2010

Dear Subscriber,
 
 We are happy to announce that Dr. Eric Wachsman, the Director of the Energy Research Center at the University of Maryland, will be a plenary speaker at the upcoming 2011 joint SPESIF conference (click on "COFE4" from our homepage). He will also be leading the Maryland Clean Energy Summit 2010 at the Hilton Inner Harbor, October 4, 2010 with a wide range of speakers and panelists.
 
This month we are featuring stories that convert or store electricity. It is fascinating to see the improvement in conversion of solar light and heat as Stanford University has achieved for up to 40% efficiency. In 2007, Rensellaer Polytech reported a similar invention with moving lenses for up to 80% efficiency (ScienceDaily.com, "Bringing Sunlight Inside").
 
The "artificial leaf" article is the most recent one and certainly an energy breakthrough. The flexible, rechargeable battery and organic battery articles are also cutting edge technology. However, that's what you have come to expect from Future Energy eNews!
 
Mark your calendars if you are in the DC area for the "USA Science & Engineering Festival and Expo" on the National Mall, October 23-24, 2010, 10AM - 5:30 PM, which should be very educational and scientific! See www.usasciencefestival.org for more details.
 
Onward and upward,
 
    
Thomas Valone, PhD, PE
Editor
www.IntegrityResearchInstitute.org 
 
IN THIS ISSUE
1) A New Way to Use the Sun's Energy
2) Electron Switch Points New Way to Power Batteries
3) Flexible Battery Power
4) Artificial Leaf Produces Electricity
5) GE Challenge Deadline Approaching
 
 
 
 
 
 
QUICK LINKS
 
1) A New Way to Use the Sun's Energy

 by Katherine Bourzac.  Technology Review, August 2010.
Researchers have demonstrated a new mechanism for converting both sunlight and heat into electricity

A new type of device that uses both heat and light from the sun should be more efficient than conventional solar cells, which convert only the light into electricity.

The device relies on a physical principle discovered and demonstrated by researchers at Stanford University. In their prototype, the energy in sunlight excites electrons in an electrode, and heat from the sun coaxes the excited electrons to jump across a vacuum into another electrode, generating an electrical current. The device could be designed to send waste heat to a steam engine and convert 50 percent of the energy in sunlight into electricity--a huge improvement over conventional solar cells.

NIcholas Melosh .
Sun
The most common silicon solar cells convert about 15 percent of the energy in sunlight into electricity. More than half of the incoming solar energy is lost as heat. That's because the active materials in solar cells can interact with only a particular band of the solar spectrum; photons below a certain energy level simply heat up the cell.

One way to overcome this is to stack active materials on top of one another in a multijunction cell that can use a broader spectrum of light, turning more of it into electrical current instead of heat, for efficiencies up to about 40 percent. But such cells are complex and expensive to make.

 Looking for a better way to take advantage of the sun's heat, Stanford's Nicholas Melosh was inspired by highly efficient cogeneration systems that use the expansion of burning gas to drive a turbine and the heat from the combustion to power a steam engine. But thermal energy converters don't pair well with conventional solar devices. The hotter it is, the more efficient thermal energy conversion becomes. Solar cells, by contrast, get less efficient as they heat up. At about 100 C, a silicon cell won't work well; above 200 C, it won't work at all.

The breakthrough came when the Stanford researchers realized that the light in solar radiation could enhance energy conversion in a different type of device, called a thermionic energy converter, that's conventionally driven solely by heat. Thermionic converters consist of two electrodes separated by a small space. When the positive electrode, or cathode, is heated, electrons in the cathode get excited and jump across to the negative electrode, or anode, driving a current through an external circuit. These devices have been used to power Russian satellites but haven't found any applications on the ground because they must get very hot, about 1,500 C, to operate efficiently. The cathode in these devices is typically made of metals such as cesium.

Melosh's group replaced the cesium cathode with a wafer of semiconducting material that can make use of not only heat but also light. When light strikes the cathode, it transmits its energy to electrons in the material in a way that's similar to what happens in a solar cell. This type of energy transfer doesn't happen in the metals used to make these cathodes in the past, but it's typical of semiconductor materials. It doesn't take quite as much heat for these "prexcited" electrons to jump to the anode, so this new device can operate at lower temperatures than conventional thermionic converters, but at higher temperatures than a solar cell.

The Stanford researchers call this new mechanism PETE, for photon-enhanced thermionic emission. "The light helps lift the energy level of the electrons so that they will flow," says Gang Chen, professor of power engineering at MIT. "It's a long way to a practical device, but this work shows that it's possible," he says.

The Stanford group's prototype, described this month in the journal Nature Materials, uses gallium nitride as the semiconductor. It converts just about 25 percent of the energy in light into electricity at 200 C, and the efficiency rises with the temperature. Stuart Licht, professor of chemistry at George Washington University, says the process would have an "advantage over solar cells" because it makes use of heat in addition to light. But he cautions: "Additional work will be needed to translate this into a practical, more efficient device."

The Stanford group is now working to do just that. The researchers are testing devices made from materials that are better suited to solar energy conversion, including silicon and gallium arsenide. They're also developing ways of treating these materials so that the device will work more efficiently in a temperature range of 400 C to 600 C; solar concentrators would be used to generate such high temperatures from sunlight.

Even at high temperatures, the photon-enhanced thermionic converter will generate more heat than it can use; Melosh says this heat could be coupled to a steam engine for a solar-energy-to-electricity conversion efficiency exceeding 50 percent. These systems are likely to be too complex and expensive for small-scale rooftop installations. But they could be economical for large solar-farm installations, says Melosh, a professor of materials science and engineering. He hopes to have a device ready for commercial development in three years.

 
 
 
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2) Electron Switch Between Molecules Points Way to New High-Powered Organic Batteries
ScienceDaily (Sep. 16, 2010)
 
- The development of new organic batteries -- lightweight energy storage devices that work without the need for toxic heavy metals -- has a brighter future now that chemists have discovered a new way to pass electrons back and forth between two molecules.
  

molecules
The research is also a necessary step toward creating artificial photosynthesis, where fuel could be generated directly from the sun, much as plants do.

University of Texas at Austin chemists Christopher Bielawski and Jonathan Sessler led the research, which was published in Science.

 
This is an illustration of an assembled set of different molecules. These molecules meet, exchange electrons and then disassemble because chloride ions, which are represented as green spheres, are present. If these chloride ions are removed, the entire process can be reversed

When molecules meet, they often form new compounds by exchanging electrons. In some cases, the electron transfer process creates one molecule with a positive charge and one molecule with a negative charge. Molecules with opposite charges are attracted to each other and can combine to form something new.

In their research, the chemists created two molecules that could meet and exchange electrons but not unite to form a new compound.

"These molecules were effectively spring-loaded to push apart after interacting with each other," says Bielawski, professor of chemistry. "After electron transfer occurs, two positively charged molecules are formed which are repelled by each other, much like magnets held in a certain way will repel each other. We also installed a chemical switch that allowed the electron transfer process to proceed in the opposite direction."

Sessler adds, "This is the first time that the forward and backward switching of electron flow has been accomplished via a switching process at the molecular scale." Sessler is the Roland K. Pettit Centennial Chair in Chemistry at The University of Texas at Austin and a visiting professor at Yonsei University.

Bielawski says this system gives important clues for making an efficient organic battery. He says understanding the electron transfer processes in these molecules provides a way to design organic materials for storing electrical energy that could then be retrieved for later use.

"I would love it if my iPhone was thinner and lighter, and the battery lasted a month or even a week instead of a day," says Bielawski. "With an organic battery, it may be possible. We are now starting to get a handle on the fundamental chemistry needed to make this dream a commercial reality."

The next step, he says, is to demonstrate these processes can occur in a condensed phase, like in a film, rather than in solution.

Organic batteries are made of organic materials instead of heavy metals. They could be lightweight, could be molded into any shape, have the potential to store more energy than conventional batteries and could be safer and cheaper to produce.

The molecular switch could also be a step toward developing a technology that mimics plants' ability to harvest light and convert it to energy. With such a technology, fuel could be produced directly from the sun, rather than through a plant mediator, such as corn.

"I am excited about the prospect of coupling this kind of electron transfer 'molecular switch' with light harvesting to go after what might be an improved artificial photosynthetic device," says Sessler. "Realizing this dream would represent a big step forward for science."

Bielawski and Sessler credit graduate student Jung Su Park for his detailed work growing crystals of the two molecules. Other collaborators include graduate student Elizabeth Karnas from The University of Texas at Austin, Professor Shunichi Fukuzumi at Osaka University and Professor Karl Kadish at the University of Houston.

3) Flexible Battery Power
ScienceDaily http://www.sciencedaily.com/releases/2007/03/070323141052.htm
 
 A paper-like, polymer based rechargeable battery has been made by Japanese scientists.
 
Paper Like Polymer Based rechargeable Battery
With recent advances in the technology of portable electronic devices, there is a demand for flexible batteries to power them.

Drs Hiroyuki Nishide, Hiroaki Konishi and Takeo Suga at Waseda University have designed the battery - which consists of a redox-active organic polymer film around 200 nanometres thick. Nitroxide radical groups are attached, which act as charge carriers.

The battery has a high charge/discharge capacity because of its high radical density.

Dr Nishide said: "This is just one of many advantages the 'organic radical' battery has over other organic based materials which are limited by the amount of doping.

"The power rate performance is strikingly high - it only takes one minute to fully charge the battery. And it has a long cycle life, often exceeding 1,000 cycles."

The team made the thin polymer film by a solution-processable method - a soluble polymer with the radical groups attached is "spin-coated" onto a surface. After UV irradiation, the polymer then becomes crosslinked with the help of a bisazide crosslinking agent.

A drawback of some organic radical polymers is the fact they are soluble in the electrolyte solution which results in self-discharging of the battery - but the polymer must be soluble so it can be spin-coated.

However, the photocrosslinking method used by the Japanese team overcomes the problem and makes the polymer mechanically tough.

Dr Nishide said: "This has been a challenging step, since most crosslinking reactions are sensitive to the nitroxide radical."

Professor Peter Skabara, an expert in electroactive materials at the University of Strathclyde , praised the high stability and fabrication strategy of the polymer-based battery.

He said: "The plastic battery plays a part in ensuring that organic device technologies can function in thin film and flexible form as a complete package."

Dr Nishide envisages that the organic radical battery could be used in pocket-sized integrated circuit cards, used for memory storage and microprocessing, within the next three years.

He said: "In the future, these batteries may be used in applications that require high-power capability rather than high-energy density, such as a battery in electronic devices and motor drive assistance in electric vehicles."

The news is reported in the latest edition of the Royal Society of Chemistry journal Chemical Communications.

 
4) Mimicking Nature, Water-Based 'Artificial Leaf' Produces Electricity
 ScienceDaily (Sep. 24, 2010)    http://www.sciencedaily.com/releases/2010/09/100924121218.htm
 
- A team led by a North Carolina State University researcher has shown that water-gel-based solar devices -- "artificial leaves" -- can act like solar cells to produce electricity. The findings prove the concept for making solar cells that more closely mimic nature. They also have the potential to be less expensive and more environmentally friendly than the current standard-bearer: silicon-based solar cells.

leacesThe bendable devices are composed of water-based gel infused with light-sensitive molecules -- the researchers used plant chlorophyll in one of the experiments -- coupled with electrodes coated by carbon materials, such as carbon nanotubes or graphite. The light-sensitive molecules get "excited" by the sun's rays to produce electricity, similar to plant molecules that get excited to synthesize sugars in order to grow, says NC State's Dr. Orlin Velev, Invista Professor of Chemical and Biomolecular Engineering and the lead author of a paper published online in the Journal of Materials Chemistry describing this new generation of solar cells.

Velev says that the research team hopes to "learn how to mimic the materials by which nature harnesses solar energy." Although synthetic light-sensitive molecules can be used, Velev says naturally derived products -- like chlorophyll -- are also easily integrated in these devices because of their water-gel matrix.

Now that they've proven the concept, Velev says the researchers will work to fine-tune the water-based photovoltaic devices, making them even more like real leaves.

"The next step is to mimic the self-regenerating mechanisms found in plants," Velev says. "The other challenge is to change the water-based gel and light-sensitive molecules to improve the efficiency of the solar cells."

Velev even imagines a future where roofs could be covered with soft sheets of similar electricity-generating artificial-leaf solar cells.

"We do not want to overpromise at this stage, as the devices are still of relatively low efficiency and there is a long way to go before this can become a practical technology," Velev says. "However, we believe that the concept of biologically inspired 'soft' devices for generating electricity may in the future provide an alternative for the present-day solid-state technologies."

Researchers from the Air Force Research Laboratory and Chung-Ang University in Korea co-authored the study. The study was funded by the Air Force Research Laboratory and the U.S. Department of Energy. The work is part of NC State's universitywide nanotechnology program, Nano@NC State.

NC State's Department of Chemical and Biomolecular Engineering is part of the university's College of Engineering.

 
5) GE  Ecomagination Challenge Deadline Approaching
General Electric Press Release  http://challenge.ecomagination.com/ct/a.bix?c=ideas
 

Challenge 2: Connect - Grid Efficiency
The U.S. should have the most efficient grid in the world. But we don't. Our grid wastes energy at every point during every day. The solution is to connect advanced power generation to a more intelligent and more efficient grid -- that then connects with consumers.

GE is looking at different grid technologies that help lower delivery losses and those that anticipate and monitor demand. Reducing losses frees up grid capacity, reduces the need for infrastructure capital expenditure, and protects consumers from steep rate increases. Reducing voltage eliminates the over-delivery of energy, so customers are not paying for unused energy.

In terms of technology, processes and policy, what do you think are the best means to help us realize greater gains in grid efficiency and outage management?
Challenge 3: Use - EcoHomes/EcoBuildings
Energy consumption is growing so quickly that it's creating an imbalance between demand and supply. This mismatch short-circuits power production and distribution, leading to higher energy costs for consumers and businesses. We need to change how, and when, we use energy.

We're looking at many promising technologies to help power companies and their customers share information and manage their energy use better.

At GE, we are already working on a wide range of promising technologies, including smart meters and appliances that let consumers' appliances "talk" to their power utility; wireless AMI; home area networks; renewable integration tools; demand response systems; home energy use monitoring; time-of-use pricing; plug-in hybrid electric vehicle integration; and neighborhood micro grids.

What new technologies, processes or business models can help consumers use energy more wisely and improve our energy balance?


 
 
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