MIT physicists make breakthrough in understanding superconductivity
MIT physicists have taken a step toward understanding the puzzling nature of high-temperature superconductors, materials that conduct electricity with no resistance at temperatures well above absolute zero. If superconductors could be made to work at temperatures as high as room temperature, they could have potentially limitless applications and help solve part of the energy and climate crisis. But first, scientists need to learn much more about how such materials work.
Using a new method, the MIT team made a surprising discovery that may overturn theories about the state of matter in which superconducting materials exist just before they start to superconduct. The findings are reported in the February issue of Nature Physics.
Understanding high-temperature superconductors is one of the biggest challenges in physics today, according to Eric Hudson, MIT assistant professor of physics and senior author of the paper. Most superconductors only superconduct at temperatures near absolute zero, but about 20 years ago, it was discovered that some ceramics can superconduct at higher temperatures (but usually still below 100 Kelvin, or -173 Celsius).
Such high-temperature superconductors are now beginning to be used for many applications, including cell-phone base stations and a demo magnetic-levitation train. But their potential applications could be much broader. If you could make superconductors work at room temperature, then the applications are endless, said Hudson.
Superconductors are superior to ordinary metal conductors such as copper because current doesn't lose energy as wasteful heat as it flows through them, thus allowing larger current densities. Once a current is set in motion in a closed loop of superconducting material, it will flow forever.
In the study, the MIT researchers looked at a state of matter that superconductors inhabit just above the temperature at which they start to superconduct.
When a material is in a superconducting state, all electrons are at the same energy level. The range of surrounding, unavailable electron energy levels is called the superconducting gap. It is a critical component of superconduction, because it prevents electrons from scattering, thus eliminating resistance and allowing the unimpeded flow of current.
Just above the transition temperature when a material starts to superconduct, it exists in a state called the pseudogap. This state of matter is not at all well understood:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: bio-electricity :: superconductivity :: efficiency :: physics ::
The researchers decided to investigate the nature of the pseudogap state by studying the properties of electron states that were believed to be defined by the characteristics of superconductors: the states surrounding impurities in the material.
It had already been shown that natural impurities in a superconducting material, such as a missing or replaced atom, allow electrons to reach energy levels that are normally within the superconducting gap, so they can scatter. This can be observed using scanning tunneling microscopy (STM).
The new MIT study shows that scattering by impurities occurs when a material is in the pseudogap state as well as the superconducting state. That finding challenges the theory that the pseudogap is only a precursor state to the superconductive state, and offers evidence that the two states may coexist.
This method of comparing the pseudogap and superconducting state using STM could help physicists understand why certain materials are able to superconduct at such relatively high temperatures, said Hudson. Trying to understand what the pseudogap state is is a major outstanding question, he added.
Lead author of the paper is Kamalesh Chatterjee, a graduate student in physics. MIT physics graduate students Michael Boyer and William Wise are also authors of the paper, along with Takeshi Kondo of the Ames Laboratory at Iowa State University and T. Takeuchi and H. Ikuta of Nagoya University, Japan. The research was funded by the National Science Foundation and the Research Corporation.
Image: Electrons, when scattered by static random disorder, form standing waves that can be imaged using scanning tunneling microscopy. Such interference patterns, observable by the recently developed technique of Fourier transform scanning tunneling spectroscopy (FT-STS), carry unique fingerprints characteristic of the electronic order present in a material.
References:
Kamalesh Chatterjee, M. C. Boyer, W. D. Wise, Takeshi Kondo, T. Takeuchi, H. Ikuta, E. W. Hudson, "Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances", Nature Physics, 4, 108 - 111 (01 Feb 2008) Letters
Eurekalert: MIT reveals superconducting surprise: A better understanding of material could bring 'endless applications' - February 12, 2008.
Article continues
Using a new method, the MIT team made a surprising discovery that may overturn theories about the state of matter in which superconducting materials exist just before they start to superconduct. The findings are reported in the February issue of Nature Physics.
Understanding high-temperature superconductors is one of the biggest challenges in physics today, according to Eric Hudson, MIT assistant professor of physics and senior author of the paper. Most superconductors only superconduct at temperatures near absolute zero, but about 20 years ago, it was discovered that some ceramics can superconduct at higher temperatures (but usually still below 100 Kelvin, or -173 Celsius).
Such high-temperature superconductors are now beginning to be used for many applications, including cell-phone base stations and a demo magnetic-levitation train. But their potential applications could be much broader. If you could make superconductors work at room temperature, then the applications are endless, said Hudson.
Superconductors are superior to ordinary metal conductors such as copper because current doesn't lose energy as wasteful heat as it flows through them, thus allowing larger current densities. Once a current is set in motion in a closed loop of superconducting material, it will flow forever.
In the study, the MIT researchers looked at a state of matter that superconductors inhabit just above the temperature at which they start to superconduct.
When a material is in a superconducting state, all electrons are at the same energy level. The range of surrounding, unavailable electron energy levels is called the superconducting gap. It is a critical component of superconduction, because it prevents electrons from scattering, thus eliminating resistance and allowing the unimpeded flow of current.
Just above the transition temperature when a material starts to superconduct, it exists in a state called the pseudogap. This state of matter is not at all well understood:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: bio-electricity :: superconductivity :: efficiency :: physics ::
The researchers decided to investigate the nature of the pseudogap state by studying the properties of electron states that were believed to be defined by the characteristics of superconductors: the states surrounding impurities in the material.
It had already been shown that natural impurities in a superconducting material, such as a missing or replaced atom, allow electrons to reach energy levels that are normally within the superconducting gap, so they can scatter. This can be observed using scanning tunneling microscopy (STM).
The new MIT study shows that scattering by impurities occurs when a material is in the pseudogap state as well as the superconducting state. That finding challenges the theory that the pseudogap is only a precursor state to the superconductive state, and offers evidence that the two states may coexist.
This method of comparing the pseudogap and superconducting state using STM could help physicists understand why certain materials are able to superconduct at such relatively high temperatures, said Hudson. Trying to understand what the pseudogap state is is a major outstanding question, he added.
Lead author of the paper is Kamalesh Chatterjee, a graduate student in physics. MIT physics graduate students Michael Boyer and William Wise are also authors of the paper, along with Takeshi Kondo of the Ames Laboratory at Iowa State University and T. Takeuchi and H. Ikuta of Nagoya University, Japan. The research was funded by the National Science Foundation and the Research Corporation.
Image: Electrons, when scattered by static random disorder, form standing waves that can be imaged using scanning tunneling microscopy. Such interference patterns, observable by the recently developed technique of Fourier transform scanning tunneling spectroscopy (FT-STS), carry unique fingerprints characteristic of the electronic order present in a material.
References:
Kamalesh Chatterjee, M. C. Boyer, W. D. Wise, Takeshi Kondo, T. Takeuchi, H. Ikuta, E. W. Hudson, "Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances", Nature Physics, 4, 108 - 111 (01 Feb 2008) Letters
Eurekalert: MIT reveals superconducting surprise: A better understanding of material could bring 'endless applications' - February 12, 2008.
Article continues
Wednesday, February 13, 2008
Norbord opens biomass power plant at Scottish fibreboard factory - bioenergy meets almost 70 percent of company's total energy needs
The bioenergy plant will utilize abundant residues from the Cowie factory: bark and wood residue from the manufacturing process. The total amount of biomass now used in green power plants at Nordborg's factories is 1 million tons, equivalent to two million barrels of oil per year.
The company said it had invested £2.5 million (€3.4/US$4.9 million) in new environmental protection measures, including this new biomass power and heat generating unit. By using biomass, emissions were greatly reduced over the last five years: from more than 420,000 tons of CO2 per year in 2002 to 261,000 tons in 2006. The new green energy facility will push these reductions further.
Norbord has been able to slash its reliance on fossil fuels by relying on waste biomass instead. The use of fossil fuels dropped by 40 per cent over the last five years, and now makes up only a fifth of all energy used at the company's mills and factories. Biomass contributes 67 per cent (graph, click to enlarge).
Energy Minister Wicks congratulated Norbord on its impressive green efforts.
Steve Roebuck, director of health, safety and environmental affairs at Norbord, said it was time biomass material was diverted from landfill sites. At present there is a huge amount of available biomass currently going to landfill that is being ignored. This waste degrades and generates harmful greenhouse gas emissions, while it can be used for the production of green electricity and heat:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: wood :: waste :: renewable :: emissions :: cogeneration :: Scotland ::
Waste should only go to landfill after all recyclable parts have been recovered and then the rest burned to produce energy, Roebuck said. He added that this source should be used in preference to virgin biomass material, which should be used and then recycled, only being combusted for energy generation when it has reached the end of the recycling chain.
The biomass to be used in its factory will come from bark and wood residue in the manufacturing process with none being purchased from outside sources.
Rapid growth
Biomass is a rapidly growing energy sector in the UK, mainly because it is the most competitive of the renewables and relies largely on existing infrastructures. The world's largest biomass plant is under construction in the country: a 350MW power facility that will provide energy to not less than half of all homes in Wales.
The £400 million plant to be located in Port Talbot will meet the electricity needs of around 1.5 million people in a sustainable, renewable and carbon-neutral way. When completed, the 350MW biomass plant will produce about 70% of the Welsh Assembly Government's entire 2010 renewable energy target. This makes it the region's single strongest weapon in the fight against climate change.
Energy giant E.ON runs several biomass co-firing operations, is building a 44MW plant in Lockerbie, capable of providing energy to 70,000 homes in Scotland, while another one, rated at 25MW is in the pipeline and to be build near Sheffield. It will power 40,000 homes. The renewable energy plants burn a combination of recycled wood and specially grown energy crops such as willow or tropical elephant grass (Pennisetum purpureum). E.ON operates three coal fired power stations in the UK (Ratcliffe, Kingsnorth and Ironbridge), and in al three of them biomass is co-fired. The type of fuels that are being burnt include waste cereal pellets, olive cakes and wood.
Scottish and Southern Energy plc, the UK's second largest power company, recently completed the acquisition of Slough Heat and Power Ltd from SEGRO plc for a total cash consideration of £49.25m. The 101MW CHP plant is the UK’s largest dedicated biomass cogeneration energy facility fueled by wood chips, biomass and waste paper.
Sembcorp Industries (Sembcorp) brought a 30MW biomass power plant online in November last year. The £64 million (€90.7/$132.5 million) plant utilizes no fossil fuels at all and generates green energy for industries located at the manufacturing site in Teesside, in the Northeast of England. Feedstocks range from waste wood to biomass obtained from dedicated energy crops.
Many other, smaller biomass power initiatives are underway, with companies using the resource to lower their emissions footprint. A recent example would be British Sugar's multimegawatt biomass cogeneration plant, used to power its sugar processing operations.
According to the recently published UK Biomass Strategy, the total amount of virgin wood available to England, Scotland and Wales for use as fuel is set to increase by 55% over the next decade, from 1.1 million oven dry tonnes to 1.7 million oven dry tonnes per year. Waste wood and biomass resources are larger still.
Norbord Inc. is an international producer of wood-based panels with assets of $1.5 billion. The company has 15 plant locations in the United States, Europe and Canada and is one of the world’s largest producers of oriented strand board (OSB). In addition to OSB, Nordbord manufacture particleboard, medium density fibreboard (MDF), hardwood plywood and related value-added products.
References:
Norbord: environmental policy and data.
BBC Scotland: Company opens new biomass plant - February 13, 2008.
Biopact: UK approves world's biggest (350MW) biomass plant: will power half of all homes in Wales - November 21, 2007
Biopact: UK's largest biomass plant approved, biomass task force created - June 16, 2007
Biopact: E.ON UK submits application for 25MW biomass plant - July 20, 2007
Biopact: UK outlines Biomass Strategy: large potential for bioenergy, bioproducts - May 28, 2007
Biopact: UK opens first large scale 30MW biomass power station - November 13, 2007
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