ScienceDaily (Feb. 19, 2009) — Diamond-like carbon films created at Sandia National Laboratories are helping probe the far boundaries of the solar system as part of a NASA mission to study how the sun’s solar wind interacts with the interstellar medium – the matter that exists between the stars within a galaxy.
The films are in the low-energy sensor (IBEX-Lo) on board NASA’s Interstellar Boundary Explorer (IBEX), which lifted off in October on a mission to study the farthest fringes of the solar system. IBEX’s two bucket-sized sensors, covering high and low energy ranges, are designed to capture particles bouncing back toward Earth from the distant boundary between the hot wind from the sun and the cold wall of interstellar space.
The active conversion surface of the low-energy neutral atom detector is coated with Sandia’s diamond-like films created by Tom Friedmann.
“The primary purpose of the diamond-like carbon films is to provide a surface that will ‘efficiently’ ionize energetic neutral atoms,” Friedmann says, “so they can then be detected. Smooth surfaces are required so that the scattered particles can be efficiently collected. If the surface is rough, scattered particles are lost, decreasing efficiency. The diamond-like carbon films have an average surface roughness that is about one angstrom. This is less than the diameter of a carbon atom.”
To create the 30 films aboard the system, Friedmann used pulsed-laser deposition to deposit the films on the conversion surfaces. Carbon was used because it has relatively high conversion efficiency, low sputter yield, and is very smooth, he says. Single crystal diamond has the highest efficiency but is too expensive to grow over large areas and difficult to polish to the extremely low surface roughness needed. The diamond-like carbon films naturally grow smooth and require no polishing.
Friedmann says the project took about one and a half months to complete and he says he was pleased with the outcome. Now the IBEX team is awaiting the results from the mission.
Eric Hertzberg, from LockheedMartinAdvancedTechnologyCenter, approached Friedmann to create the films. Hertzberg is the lead engineer for the IBEX-Lo Sensor. Bob Nemanich, ArizonaStateUniversity, also played a key role in passivating the films. Friedmann says Sandia uses similar films in studies of electron field emission and in microelectromechanical Systems (MEMS) devices.
Voyager 1, launched in 1977, made the first direct measurements of this boundary (the heliopause) as it was the first spacecraft to leave the inner solar system and head toward interstellar space. Voyager 2, launched the same year, will also relay observations of the boundary, but these measurements are of only one place and time.
IBEX is designed to provide a three-dimensional map of the boundary. IBEX is the latest in NASA’s series of low-cost, rapidly developed Small Explorers spacecraft. The IBEX mission was developed by Southwest Research Institute, led by Principal Investigator David McComas, with a national and international team of partners.
Super Solar Cells? Certain Nanocrystals Shown To Generate More Than One Electron
ScienceDaily (Feb. 18, 2009) — A team of Los Alamos researchers led by Victor Klimov has shown that carrier multiplication—when a photon creates multiple electrons—is a real phenomenon in tiny semiconductor crystals and not a false observation born of extraneous effects that mimic carrier multiplication. The research, explained in a recent issue of Accounts of Chemical Research, shows the possibility of solar cells that create more than one unit of energy per photon.
Questions about the ability to increase the energy output of solar cells have prompted Los Alamos National Laboratory researchers to reassess carrier multiplication in extremely small semiconductor particles.
When a conventional solar cell absorbs a photon of light, it frees an electron to generate an electrical current. Energy in excess of the amount needed to promote an electron into a conducting state is lost as heat to atomic vibrations (phonons) in the material lattice. Through carrier multiplication, excess energy can be transferred to another electron instead of the material lattice, freeing it to generate electrical current—thereby yielding a more efficient solar cell.
Klimov and colleagues have shown that nanocrystals of certain semiconductor materials can generate more than one electron after absorbing a photon. This is partly due to strengthened interactions between electrons squeezed together within the confines of the nanoscale particles.
In 2004, Los Alamos researchers Richard Schaller and Klimov reported the first observations of strong carrier multiplication in nanosized crystals of lead selenide resulting in up to two electron-hole pairs per absorbed photon. A year later, Arthur Nozik and coworkers at the National Renewable Energy Laboratory reproduced these results. Eventually, spectroscopic signatures of carrier multiplication were observed in nanocrystals of various compositions, including silicon.
Recently, the claims in carrier multiplication research have become contentious. Specifically, some recent studies described low or negligible carrier multiplication efficiencies, which seemed to run contrary to earlier findings. To sort out these discrepancies, Los Alamos researchers analyzed factors that could have led to a spread in the reported carrier multiplication results. These factors included variations between samples, differences in detection techniques, and effects mimicking the signatures of carrier multiplication in spectroscopic measurements.
To analyze how a particular detection technique might affect an outcome, John McGuire, a postdoctoral researcher on Klimov's team, investigated carrier multiplication using two different spectroscopic techniques—transient absorption and time-resolved photoluminescence. The results obtained by these two methods were in remarkable agreement, indicating that the use of different detection techniques is unlikely to explain discrepancies highlighted by other researchers. Further, although these measurements revealed some sample-to-sample variation in carrier multiplication yields, these variations were much smaller than the spread in reported data.
After ruling out these two potential causes of discrepancies, the researchers focused on effects that could mimic carrier multiplication. One such effect is photoionization of nanocrystals.
"When a nanocrystal absorbs a high-energy photon, an electron can acquire enough energy to escape the material," Klimov explained. "This leaves behind a charged nanocrystal, which contains a positive 'hole.' Photogeneration of another electron by a second photon results in a two-hole, one-electron state, reminiscent of one produced by carrier multiplication, which can lead to false positives," he said.
To evaluate the influence of photoionization, the Los Alamos researchers conducted back-to-back studies of static and stirred solutions of nanocrystals. Stirring removes charged nanocrystals from the measured region of the sample. Therefore, when crystals are subjected to light, the stirring eliminates the possibility that charged nanocrystals will absorb a second photon. While stirring of some samples did not affect the results of the measurements, other samples showed a significant difference in the apparent carrier multiplication yields measured under static and stirred conditions. Since most previous studies were performed on static samples, these results suggest that discrepancies noted by other researchers arise at least in part from uncontrolled photoionization, which stirring seeks to eliminate.
The Los Alamos researchers re-evaluated carrier multiplication efficiencies when photoionization was suppressed. The results are encouraging.
While the newly measured electron yields are lower than previously reported, the efficiency of carrier multiplication is still greater than in bulk solids. Specifically, both the energetic onset and the energy required to generate an extra electron in nanocrystals are about half of those in bulk solids.
These results indicate significant promise for nanosized crystals as efficient harvesters of solar radiation.
"Researchers still have a lot of work to do," Klimov cautioned. "One important challenge is to figure out how to design a material in which the energetic cost to create an extra electron can approach the limit defined by a semiconductor band gap. Such a material could raise the fundamental power conversion limit of a solar cell from 31 percent to above 40 percent."
The Los Alamos nanocrystal team's research is funded by the U.S. Department of Energy Office of Basic Energy Sciences and Los Alamos' Laboratory-Directed Research and Development (LDRD) program.
lugging In Molecular Wires To Capture Light Energy
ScienceDaily (Feb. 17, 2009) — Plants, algae, and cyanobacteria (blue-green algae) are masters of everything to do with solar energy because they are able to almost completely transform captured sunlight into chemical energy. This is in part because the electrons set free by the photons are transported out of the “light receptor” 1:1 to be used as the driving force for chemical reactions.
Japanese researchers have now developed a new process to capture light energy with nearly equal efficiency. As they report in the journal Angewandte Chemie, they “plug” a molecular “wire” directly into a biological photosynthetic system to efficiently conduct the free electrons to a gold electrode.
The efficiency of photovoltaic energy conversion is of critical significance for the practical application of solar installations. Theoretically, every photon absorbed should release one electron. Whereas modern solar cells are far from achieving high efficiency, natural photosynthetic systems achieve nearly 100 % quantum yield. To improve the efficiency of synthetic systems, experiments were attempted in which biological light-capturing units were deposited onto electrodes as thin films. However, the transfer of electrons from the light-capturing layer into the circuit in this type of system is so inefficient that most of the electrons don’t even make it to the target electrode.
The secret to the success of natural photosystems is the perfect fit of the individual components. The molecules fit precisely together like plugs and sockets and can pass electrons on directly and nearly without loss. The new approach taken by the Japanese researchers cleverly connects photosystem I (PSI) from the blue-green algae Thermosynechococcus elongatus with a synthetic apparatus. An important component of the electron transmission sequence of PSI is vitamin K1. The researchers removed the vitamin K1 from the PSI protein complex and replaced it with a synthetic analogue.
This consists of three parts:
The same molecular “plug” with which vitamin K1 is bound to the protein complex (napthoquinone group) is used to “plug in” the synthetic binding component to PSI;
a molecular “wire” (hydrocarbon chain) with the same length as in vitamin K1 ensures that the binding component protrudes from the protein complex; and
at the other end of the wire is an additional “plug” (viologen group) that anchors the ensemble to a specially coated gold electrode.
Electrons released by irradiation of PSI and transmitted along the wire are very efficiently transmitted to the gold electrode by the viologen group.
It may be possible to use this new strategy to integrate other biocomponents into synthetic systems.
The new Celebrity Cruises 122,000 ton Luxury cruise ship "Celebrity Solstice" has many of the latest energy efficient features that mostly go unnoticed by the average passenger but make a huge contribution towards energy efficiency on the high seas.
The "Celebrity Solstice" is fitted with 216 solar panels, which power 7000 LED lights in all of the ship's guest elevators.
The naval architects optimized the center of buoyancy of the ship to reduce hull resistance and designed an aft-duck tail to reduce the ship's drag through the water, minimize the ship's wake and use less fuel.
A silicone hull coating reduces the friction of the ship through the water further improving the fuel efficiency of the vessel.
"Celebrity Solstice" transitions from higher wattage incandescent and halogen bulbs to longer lasting fluorescent and LED lights which generate 50% less heat. This results in improved energy efficiency for the ship's lighting and less air-conditioning is required.
Highly glazed windows produced by the 3M company allow natural light in but filter out 99.9% of UV light, which reduces heat transfer and minimizes the need for air-conditioning.
Chilled river rocks are used instead of ice beds in buffet areas, which reduce both water and energy consumption, and result in less need for ice in the restaurants.
An advanced waste water purification system produces near-drinkable quality water before discharge into the ocean thus minimizing any potential negative environmental impact.
This exciting 2,850 passenger cruise ship represents a quantum leap in applying energy efficient measures at sea and generates some good ideas that can easily be replicated in buildings and facilities on dry land.
With EPA Ruling on Ethanol Looming New Research Highlights Environmental Costs
Contact: Regina Weiss – 212-991-1069; 917-288-5251; regina@gracelinks.org
Study indicates corn ethanol more polluting than regular gasoline
July 29, 2008 - With the EPA about to announce whether it will waive a federal requirement that would increase the amount of biofuel drivers get at the pump, some analysts are pointing to the environmental costs of ethanol.
Recent debate over corn ethanol has focused on its role in higher food prices, with environmental costs taking a back seat. However, research published in the journal Science indicates that producing corn ethanol creates twice the global warming emissions of regular gasoline due to the conversion of forest and grassland to cropland. At the same time, a report by the Network for New Energy Choices details current environmental costs of corn ethanol production, including soil erosion, depletion of fresh water supplies and destruction of ocean habitat endangering fish and other marine life.
Last year alone 12 million new acres of corn were brought into production in the U.S., contributing to the depletion of fresh water supplies and adding to agro-chemical runoff from the nation’s corn belt that has already created an enormous "dead zone" – the size of New Jersey and growing – in the Gulf of Mexico.
"The environmental damage caused by the rapid conversion of land for corn production, including recent analysis showing that ethanol will increase, rather than decrease greenhouse gas emissions, strongly argues against new federal mandates for additional ethanol production," said Dulce Fernandes, associate director of the Network for New Energy Choices. "Meanwhile, there are immediate steps we believe our nation should take to balance energy demands with the need to address climate change and preserve the nation’s farmland and water supply."
The Network’s report, "The Rush to Ethanol: Not All Biofuels Are Created Equal," is available here. In a letter sent to members of Congress last week accompanied by the report, Network analysts advised that the EPA should be allowed to waive the corn-based component of the federal biofuels mandate and initiate research authorized by the 2007 federal energy bill to study the impacts of expanding corn ethanol production. In addition, they proposed that sustainability criteria be established for the production of ethanol and the feed stocks grown to make it.
"Biofuels will undeniably play a part in our energy future," Fernandes said. "Now is the time to study the effects, so that we adopt them in ways that are beneficial, rather than destructive."
Tips from the Office of Energy Efficiency of Natural Resources Canada
10 more Energy Saving Tips for Everybody
1.Use sinks full of water rather than running water for washing pots and cleaning vegetables.
2.Defrost freezers frequently since frost build ups reduce efficiency
3.Most foods can be placed in ovens during pre-heating. Only bakery goods must wait until ovens reach the correct temperature.
4.Dimming controls are useful for providing supplemental illumination in areas where natural light is available during the day.
5.Daylighting refers to the use of natural light in interior and perimeter areas. Windows, skylights and translucent daylighting can reduce your daytime lighting requirements by over 50 percent.
6.Pick the right hot water system for your facility or home. A unit that is too small may leave you and your guests without hot water, and too large a unit will consume more energy than necessary.
7.Use photocells to ensure outside lights operate only at night.
8.Do not over-dry dishes. Adjust power dryers to deliver heated air just long enough to dry dishes.
9.Switch energy-intensive lights off as soon as you leave an unoccupied area of the premises and add a Last Person Out switch.
10.Break the habit of turning everything on first thing in the morning. Leave equipment off until it is needed and turn it off when it is no longer needed.
Solar and Heat Tips Newsletter January 2009 Part 5
Offshore Wind Turbines Planned in UK
According to a report from Reuters, Clipper Windpower Plc plans to build the world's biggest offshore wind turbines in Britain, which hopes to catch up in green energy after lagging behind others in Europe despite its rich wind resources. Jim Dehlsen, chairman of the London-listed, U.S.-based company, told Reuters it will set up a factory in northern England, which would have an annual capacity to manufacture about 200 turbines by 2014-2015.
