Global wind capacity reaches 100,000 megawatts

March 31, 2008

Global wind capacity

Earth Policy Institute: At its current growth rate, global installed wind power capacity will top 100,000 megawatts in March 2008. In 2007, wind power capacity increased by a record-breaking 20,000 megawatts, bringing the world total to 94,100 megawatts—enough to satisfy the residential electricity needs of 150 million people. Driven by concerns regarding climate change and energy security, one in every three countries now generates a portion of its electricity from wind, with 13 countries each exceeding 1,000 megawatts of installed wind electricity-generating capacity…..

The chart is from GWEC; Worldwatch. 

Advertisements

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 


Superconductivity at room temperature, with graphene

March 24, 2008

Graphene crystalsScientificBlogging.com: Graphene, a single-atom-thick sheet of graphite, is a new material which combines aspects of semiconductors and metals. University of Maryland physicists have shown that in graphene the intrinsic limit to the mobility, a measure of how well a material conducts electricity, is higher than any other known material at room temperature – and 100 times faster than in silicon. A team of researchers led by physics professor Michael S. Fuhrer of the university’s Center for Nanophysics and Advanced Materials, and the Maryland NanoCenter said the findings are the first measurement of the effect of thermal vibrations on the conduction of electrons in graphene, and show that thermal vibrations have an extraordinarily small effect on the electrons in graphene.In any material, the energy associated with the temperature of the material causes the atoms of the material to vibrate in place. As electrons travel through the material, they can bounce off these vibrating atoms, giving rise to electrical resistance. This electrical resistance is “intrinsic” to the material: it cannot be eliminated unless the material is cooled to absolute zero temperature, and hence sets the upper limit to how well a material can conduct electricity.

In graphene, the vibrating atoms at room temperature produce a resistivity of about 1.0 microOhm-cm (resistivity is a specific measure of resistance; the resistance of a piece material is its resistivity times its length and divided by its cross-sectional area). This is about 35 percent less than the resistivity of copper, the lowest resistivity material known at room temperature. “Other extrinsic sources in today’s fairly dirty graphene samples add some extra resistivity to graphene,” explained Fuhrer, “so the overall resistivity isn’t quite as low as copper’s at room temperature yet. However, graphene has far fewer electrons than copper, so in graphene the electrical current is carried by only a few electrons moving much faster than the electrons in copper.”

In semiconductors, a different measure, mobility, is used to quantify how fast electrons move. The limit to mobility of electrons in graphene is set by thermal vibration of the atoms and is about 200,000 cm2/Vs at room temperature, compared to about 1,400 cm2/Vs in silicon, and 77,000 cm2/Vs in indium antimonide, the highest mobility conventional semiconductor known.

“Interestingly, in semiconducting carbon nanotubes, which may be thought of as graphene rolled into a cylinder, we’ve shown that the mobility at room temperature is over 100,000 cm2/Vs” said Fuhrer (T. Dürkop, S. A. Getty, Enrique Cobas, and M. S. Fuhrer, Nano Letters 4, 35 (2004)).

Mobility determines the speed at which an electronic device (for instance, a field-effect transistor, which forms the basis of modern computer chips) can turn on and off. The very high mobility makes graphene promising for applications in which transistors much switch extremely fast, such as in processing extremely high frequency signals.

Mobility can also be expressed as the conductivity of a material per electronic charge carrier, and so high mobility is also advantageous for chemical or bio-chemical sensing applications in which a charge signal from, for instance, a molecule adsorbed on the device, is translated into an electrical signal by changing the conductivity of the device.

Graphene is therefore a very promising material for chemical and bio-chemical sensing applications. The low resitivity and extremely thin nature of graphene also promises applications in thin, mechanically tough, electrically conducting, transparent films. Such films are sorely needed in a variety of electronics applications from touch screens to photovoltaic cells.

Fuhrer and co-workers showed that although the room temperature limit of mobility in graphene is as high as 200,000 cm2/Vs, in present-day samples the actual mobility is lower, around 10,000 cm2/Vs, leaving significant room for improvement. Because graphene is only one atom thick, current samples must sit on a substrate, in this case silicon dioxide.

Trapped electrical charges in the silicon dioxide (a sort of atomic-scale dirt) can affect the electrons in graphene and reduce the mobility. Also, vibrations of the silicon dioxide atoms themselves can also have an effect on the graphene which is stronger than the effect of graphene’s own atomic vibrations. This so-called “remote interfacial phonon scattering” effect is only a small correction to the mobility in a silicon transistor, but because the phonons in graphene itself are so ineffective at scattering electrons, this effect becomes very important in graphene.

“We believe that this work points out the importance of these extrinsic effects, and creates a roadmap for finding better substrates for future graphene devices in order to reduce the effects of charged impurity scattering and remote interfacial phonon scattering.” Fuhrer said.

Article: J. H. Chen, C. Jang, S. Xiao, M. Ishigami, M. S. Fuhrer, ‘Intrinsic and Extrinsic Performance Limits of Graphene Devices on SiO2, Nature Nanotechnology published online: 23 March 2008 | doi:10.1038/nnano.2008.58

Graphene crystals, “Vinograd19,” from Wikimedia Commons


Scientists fabricate non-cryogenic superconducting material

March 21, 2008

The chemical structure of silaneThis could be huge. Imagine the ability to transmit power from remote solar and wind sites without huge powerlines. From Next Energy News: A new breakthrough superconducting material fabricated by a Canadian-German team has been made out of a silicon-hydrogen compound and does not require cooling. The implications of the discovery are enormous and could transform the way people live by cutting power usage from everything from refrigeration to cell phones.

Instead of super-cooling the material, as is necessary for conventional superconductors, the new material is instead super-compressed. The researchers claim that the new material could sidestep the cooling requirement, thereby enabling superconducting wires that work at room temperature.

“If you put hydrogen compounds under enough pressure, you can get superconductivity,” said professor John Tse of the University of Saskatchewan. “These new superconductors can be operated at higher temperatures, perhaps without a refrigerant.”

He performed the theoretical work with doctoral candidate Yansun Yao. The experimental confirmation was performed by researcher Mikhail Eremets at the Max Plank Institute in Germany.

The new family of superconductors are based on a hydrogen compound called “silane,” which is the silicon analog of methane–combining a single silicon atom with four hydrogen atoms to form a molecular hydride. (Methane is a single carbon atom with four hydrogens).

Researchers have speculated for years that hydrogen under enough pressure would superconduct at room temperature, but have been unable to achieve the necessary conditions (hydrogen is the most difficult element to compress). The Canadian and German researchers attributed their success to adding hydrogen to a compound with silicon that reduced the amount of compression needed to achieve superconductivity.

Tse’s team is currently using the Canadian Light Source synchrotron to characterize the high pressure structures of silane and other hydrides as potential superconducting materials for industrial applications as well as a storage mechanism for hydrogen fuel cells….

The chemical structure of silane,  SiH4, “Jrockley,” from Wikimedia Commons


Transmission issues — the key to alternative energy?

March 20, 2008

PowerlinesThis Yakima Herald Republic story highlights a major obstacle to the acceptance of renewable energy – transmission lines: … Renewa bles — wind, solar and biomass — make up about 2 percent of the state’s current energy sources. Customer interest also is adding to the push for wind. “On the customer side, we have heard that they want their utility to be moving into the area of clean power,” said Andy Wappler, senior public relations manager for Puget Sound Energy, which has 1 million utility customers in Western Washington and Kittitas County and has the most wind capacity developed. Puget Sound is in the hunt for another 1,000 megawatts of wind energy to meet the 2020 target.

But the biggest reason for the growth of wind lies just out of sight from Wild Horse: the Columbia River with its huge hydroelectric generating capacity and the transmission lines that crisscross the state and region. Because of its intermittent nature, wind energy needs a solid base of other sources to sustain delivery of power to homes and businesses. Hydro dams are that base.

Other states, principally Montana and North Dakota, have better wind than Washington. But the lack of transmission is stunting development . The nonprofit Renewable Northwest Project, a primary proponent of the initiative, estimates Washington, Oregon and Idaho have potential for 20,000 megawatts of wind energy. Montana has as much as six times the potential as the three other Northwest states combined.

“The Northwest, I think, proves to be more attractive than you would think based on the wind potential because wind is very compatible with the hydro system,” said Tim Stearns, a senior energy policy analyst for the state Department of Community, Trade and Economic Development. While wind development has taken off in the last couple of years, developers have long been looking at the region, said Doug Carter, senior vice president for Chicago-based Invenergy Wind North America LLC.

…Energy planners agree the region has the existing facilities to handle up to 6,000 megawatts of wind energy with minor improvements to the system. But near the 6,000-megawatt barrier, major investments will be needed to keep the energy coming for a growing region.

The federal power-marketing agency, the Bonneville Power Administration, estimates the cost of new transmission lines range from $300,000 to $2 million a mile depending on costs due to terrain, capacity and land acquisition. Bonneville is preparing to take those costs into account when it proposes new rates for 2009.

“What it gets down to is we owe it to our customers to make sure the proper parties are being charged for the cost of running the system,” said Scott Simms, Bonneville spokesman in Portland. “As we look at some of these wind farms, where they are located and where they are going, a large part of the wind is serving customers beyond BPA borders.” The search for new wind sites has brought developers to Yakima County. The county hearing examiner is mulling a request by Northwest Wind Partners, a joint venture between Goldendale’s Ross Management and EnXco, a French company, to place meteorological stations on four parcels, three north of Sunnyside and the other south of Moxee….

Power lines, Tony Boon, Wikimedia Commons 


A smart grid plan for the city of Boulder, Colorado

March 18, 2008

Boulder, ColoradoClean Edge: Xcel Energy announced recently it will put in motion its vision to make Boulder, Colo. the nation’s first fully integrated Smart Grid City.

The advanced, smart grid system – when fully implemented over the next few years – will provide customers with a portfolio of smart grid technologies designed to provide environmental, financial and operational benefits. Xcel Energy anticipates funding only a portion of the project, and plans to leverage other sources including government grants for the remainder of what could be up to a $100 million effort.

“Smart Grid City is the first step toward building the grid of the future,” said Dick Kelly, Xcel Energy chairman, president and CEO. “In Boulder, we’ll collaborate with others to integrate all aspects of our smart grid vision and evaluate the benefits. The work we’re doing will benefit not only Boulder, but also customers throughout our eight-state service territory. We’re pleased to partner with the city and our Boulder customers as we begin this journey.”

…In addition to its geographic concentration, ideal size and access to all grid components, Boulder was selected as the Smart Grid City because it is home to the University of Colorado and several federal institutions, including the National Institute of Standards and Technology, which already is involved in smart grid efforts for the federal government.

Smart Grid City could feature a number of infrastructure upgrades and customer offerings – for the first time fully integrated through the partnership’s efforts in Boulder – including:

  • Transformation of existing metering infrastructure to a robust, dynamic electric system communications network, providing real-time, high-speed, two-way communication throughout the distribution grid;
  • Conversion of substations to “smart” substations capable of remote monitoring, near real-time data and optimized performance;
  • At the customer’s invitation, installation of programmable in- home control devices and the necessary systems to fully automate home energy use; and
  • Integration of infrastructure to support easily dispatched distributed generation technologies (such as plug-in hybrid electric vehicles with vehicle-to-grid technology; battery systems; wind turbines; and solar panels).

The potential benefits of the Smart Grid City include operational savings, customer-choice energy management, better grid reliability, greater energy efficiency and conservation options, increased use of renewable energy sources, and support for plug-in hybrid electric vehicles and intelligent-home appliances.