Indian scientist developed Software to save PC energy

Bangalore: A new software called SleepServer has been developed by a team led by an Indian American scientist that will be able to save energy in the PCs in offices.

Accessible via remote connections, the sleep-working enterprise PCs maintain their presence on voice over IP, instant messaging and peer-to-peer networks.

The software reduces energy consumption by about 60 percent , according to a new peer-reviewed study presented by University of California, San Diego, computer scientists on June 24 at the 2010 USENIX Annual Technical Conference in Boston.

Yuvraj Agarwal, the UC San Diego Research Scientist in the Department of Computer Science and Engineering who developed SleepServer, said: "One of the big benefits of SleepServer is configurable on-demand wakeup. SleepServer enables enterprise PCs to remain asleep for long periods of time while still maintaining the illusion of network connectivity and seamless availability."

Attuned with existing networking infrastructure, SleepServer works with Windows and different versions of Linux and a Mac OSx version is being developed.

It makes lightweight virtual images of sleeping PCs, which maintain connectivity and respond to applications on behalf of the sleeping PCs.

"According to our measurements, SleepServer provides $60 dollars of cost savings per PC on average over an entire year. By deploying SleepServer across the CSE Department, we expect to save approximately $60,000 dollars annually in direct energy costs alone," said Rajesh Gupta, Professor and Chair of the Department of Computer Science and Engineering at the UC San Diego Jacobs School of Engineering. 

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Highly Efficient Solar Cells Could Result from Quantum Dot Research

ScienceDaily — Conventional solar cell efficiency could be increased from the current limit of 30 percent to more than 60 percent, suggests new research on semiconductor nanocrystals, or quantum dots, led by chemist Xiaoyang Zhu at The University of Texas at Austin.
Zhu and his colleagues report their results in this week's Science.

The scientists have discovered a method to capture the higher energy sunlight that is lost as heat in conventional solar cells.

The maximum efficiency of the silicon solar cell in use today is about 31 percent. That's because much of the energy from sunlight hitting a solar cell is too high to be turned into usable electricity. That energy, in the form of so-called "hot electrons," is lost as heat.

If the higher energy sunlight, or more specifically the hot electrons, could be captured, solar-to-electric power conversion efficiency could be increased theoretically to as high as 66 percent.

"There are a few steps needed to create what I call this 'ultimate solar cell,'" says Zhu, professor of chemistry and director of the Center for Materials Chemistry. "First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy."
Zhu says that semiconductor nanocrystals, or quantum dots, are promising for these purposes.

As for the first problem, a number of research groups have suggested that cooling of hot electrons can be slowed down in semiconductor nanocrystals. In a 2008 paper in Science, a research group from the University of Chicago showed this to be true unambiguously for colloidal semiconductor nanocrystals.

Zhu's team has now figured out the next critical step: how to take those electrons out.
They discovered that hot electrons can be transferred from photo-excited lead selenide nanocrystals to an electron conductor made of widely used titanium dioxide.

"If we take the hot electrons out, we can do work with them," says Zhu. "The demonstration of this hot electron transfer establishes that a highly efficient hot carrier solar cell is not just a theoretical concept, but an experimental possibility."
The researchers used quantum dots made of lead selenide, but Zhu says that their methods will work for quantum dots made of other materials, too.

He cautions that this is just one scientific step, and that more science and a lot of engineering need to be done before the world sees a 66 percent efficient solar cell.

In particular, there's a third piece of the science puzzle that Zhu is working on: connecting to an electrical conducting wire.

"If we take out electrons from the solar cell that are this fast, or hot, we also lose energy in the wire as heat," says Zhu. "Our next goal is to adjust the chemistry at the interface to the conducting wire so that we can minimize this additional energy loss. We want to capture most of the energy of sunlight. That's the ultimate solar cell.
"Fossil fuels come at a great environmental cost," says Zhu. "There is no reason that we cannot be using solar energy 100 percent within 50 years."

Funding for this research was provided by the U.S. Department of Energy. Coauthors include William Tisdale, Brooke Timp, David Norris and Eray Aydil from the University of Minnesota, and Kenrick Williams from The University of Texas at Austin.

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Towards Nanowire Solar Cells With a 65-Percent Efficiency

ScienceDaily — Eindhoven University of Technology (TU/) researchers want to develop solar cells with an efficiency of over 65 percent by means of nanotechnology. In Southern Europe and North Africa these new solar cells can generate a substantial portion of the European demand for electricity. The Dutch government reserves EUR 1.2 million for the research.

The current thin-film solar cells (type III/V) have an efficiency that lies around 40 percent, but they are very expensive and can only be applied as solar panels on satellites. By using mirror systems that focus one thousand times they can now also be deployed on earth in a cost-effective manner. The TU/ researchers expect that in ten years their nano-structured solar cells can attain an efficiency of more than 65 percent. Jos Haverkort: "If the Netherlands wants to timely participate in a commercial exploitation of nanowire solar cells, there is a great urgency to get on board now." The research is conducted together with Philips MiPlaza.

 
They think that nanotechnology, in combination with the use of concentrated sunlight through mirror systems, has the potential to lead to the world's most efficient solar cell system with a cost price lower than 50 cent per Watt peak. In comparison: for the present generation of solar cells that cost price is 1.50 euro per Watt peak.

Stacking Nanowires make it possible to stack a number of subcells (junctions). In this process each subcell converts one color of sunlight optimally to electricity. The highest yield reported until now in a nanowire solar cell is 8.4 percent. Haverkort: "We expect that a protective shell around the nanowires is the critical step towards attaining the same efficiency with nanowire solar cells as with thin-film cells." Haverkort thinks that at 5 to 10 junctions he will arrive at an efficiency of 65 percent.

Scarcity of raw materials In addition, the researchers expect considerable savings can be made on production costs, because nanowires grow on a cheap silicon substrate and also grow faster, which results in a lower cost of ownership of the growth equipment. What is more, the combination of the mirror systems with nanotechnology will imply an acceptable use of the scarce and hence expensive metals gallium and indium.

An agency of the Ministry of Economic Affairs, will grant the EUR 1.2 million to researchers dr. Jos Haverkort, dr. Erik Bakkers en dr. ir. Geert Verbong for their research into nanowire solar cells. It is their expectation that, when combined with mirror systems, these solar cells can generate a sizeable portion of the European electricity demand in Southern Europe and North Africa.

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