A 177 km underground power line that started commercial operation in early October 2002 is supplying about 220 MW of power to as many as 120,000 Southern Australian households. The MurrayLink Interconnector consists of two DC cables buried 1.2m deep, extending from Redcliff in Victoria to Berri in South Australia. At each end is a converter station that converts the AC into DC and vice versa. The longest of its kind in the world to date, the transmission is carried out using HDVC Light technology from ABB, Norwalk, CT. Tougher environmental concerns are placing heavy restrictions on right-of-ways for building new overhead transmission lines and for the construction of new generating plants. Conventional HVDC technology transmits electricity over long distances via overhead transmission lines or submarine cables, also interconnecting separate power systems where traditional AC connections cannot be used. Capitalizing on these benefits, HVDC Light interconnects two power grids, with power exchange between the networks very easily controlled and measured, while improving the feasibility to connect small-scale, renewable power generation plants such as wind, solar, hydro and tidal, to the main AC network. As a voltage source converter, HDVC Light uses pulse width modification to generate the fundamental voltage. If there is a surplus of generating capacity in one of the grids, it can be shared with the other. With the HVDC Light converter, the polarity does not change when the power flow changes, according to ABB. Instead, the current direction changes, making it easy to use a converter as a building block in a multi-terminal system. The HVDC Light cable, an extruded polymer cable for HVDC transmissions, can work in deepwater or with dynamic floating platforms. In a platform-to-platform design, platforms of different frequencies (e.g., 50 and 60 Hz) can be combined, optimizing operations.
Sugars can be converted to electricity with efficiency much higher than previously known, according to researchers at the University of Massachusetts Amherst, in the October issue of
Nature Biotechnology. Professor Derek Lovley and postdoctoral researcher Swades Chaudhuri have discovered a microorganism,
Rhodoferax ferrireducens, is capable of stable, long-term electricity production by oxidizing carbohydrates. The organism transfers electrons directly onto an electrode as it metabolizes sugar into electricity, producing carbon dioxide as a byproduct. Because sugars are a substantial component of many types of waste and carbohydrate-rich crops, such as corn (a renewable energy source), carbohydrates could become economical alternatives to fossil fuels in the production of electricity, according to Lovley. “There’s been a lot of interest in microbial fuel cells trying to covert sugar into electricity,” Lovley observes. “But in the past, they’ve converted 10 percent or less of the available electrons, and we’re up over 80 percent. And previous attempts to convert carbohydrates to electricity have required an electron shuttle, or mediator, which is typically toxic to humans.”
Rhodoferax does not require a mediator because it attaches directly to the surface of the electrode. “That’s one of the big advances,” said Lovley. “People have done it without a mediator before, but their recovery of energy was less than 1 percent. Moreover, not having to use toxic elements is an obvious advantage in creating electricity. In the end, the electrons in the fuel cell are transferred to oxygen, so what we are really doing is putting a wire in between the microbe and the oxygen and harvesting this electron flow that otherwise would just go directly to oxygen.” The downside, however, is that it is a slow process. That cup of sugar could take weeks to digest. Still, a slow but steady trickle of electricity can be used to charge up a battery, which can then discharge large amounts of power when needed. The organism isolated in Lovley’s UMass Amherst lab came from aquifer sediments in Virginia during a U.S. Department of Energy study. “We found it had the unique ability to oxidize sugars with the reduction of iron oxides,” Lovley said. “This was of interest to us because last year we reported in Science that another group of iron reducers, known as Geobacter, could transfer electrons to electrodes. We reasoned that Rhodoferax might be able to do the same thing, which proved to be the case.” In theory, this method would allow a cup of sugar to power a 60-watt light bulb for 17 hours, but Lovley said the device needs improvement before it can be used commercially. “There are still issues with getting a high enough voltage and converting the sugar to electricity fast enough,” he said. “Although the process is highly efficient, it is slow. In addition, as the process is right now, we’re not talking about a lot of power. It’s barely enough to run a calculator, but we did it using unpolished graphite as a receptor. There are almost certainly better electroactive materials.” Adds Lovley, “The other thing that limits this is that the microorganisms have to attach to the surface of the receptor, so we’re working with polymer scientists, such as Tom Russell at UMass Amherst, to find a receptor with a maximally uneven surface, so more microbes can attach to it. I don’t want to give the impression that it’s ‘Back to the Future,’ where we stuff a banana in the engine and go, but it’s a pretty good leap from where microbial fuel cells were before.” The technology could also be used in environments where it is difficult or costly to charge the batteries, or in poor, remote communities, where the electrodes could be adapted so that they use carbohydrate waste from farm animals or sewage to power batteries for running refrigerators and stoves.
The transportation of particle-laden fluids through piping systems is a critical process in many industries. And every year, thousands of dollars are expended in the repair of pipes damaged by erosion and blockages caused by solid particles, which tend to settle along the bottom of pipes as the carrier fluids are pumped through. In past, most designers would simply spec higher velocities to move slurries, but this required higher energy expenditures. Other fixes included armoring pipe bends, which also increased costs; induction mixers that would wear out or, themselves, cause blockages; and helical ribs or vanes, which are also subject to erosion, or cause turbulence and energy losses. At the University of Nottingham in England, Professor Nick Miles and his team have patented “Swirl in Pipes” technology, in which an internal twist in a pipe lifts solid particles upwards as fluids are pumped under high pressure. This configuration unsettles the particles, reducing general wear (particularly in bends) and blockages that disrupt flow. A gradual swirl reduces wear without significant increase of turbulence in the system; with no sudden changes to the flow, pressure drop is reduced and liquids don’t require high velocity pumping. The technology also serves gases, with application potential for oil, gas, mining, and food and beverage industries.
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A 177 km underground power line that started commercial operation in early October 2002 is supplying about 220 MW of power to as many as 120,000 Southern Australian households. The MurrayLink Interconnector consists of two DC cables buried 1.2m deep, extending from Redcliff in Victoria to Berri in South Australia. At each end is a converter station that converts the AC into DC and vice versa. The longest of its kind in the world to date, the transmission is carried out using HDVC Light technology from ABB, Norwalk, CT. Tougher environmental concerns are placing heavy restrictions on right-of-ways for building new overhead transmission lines and for the construction of new generating plants. Conventional HVDC technology transmits electricity over long distances via overhead transmission lines or submarine cables, also interconnecting separate power systems where traditional AC connections cannot be used. Capitalizing on these benefits, HVDC Light interconnects two power grids, with power exchange between the networks very easily controlled and measured, while improving the feasibility to connect small-scale, renewable power generation plants such as wind, solar, hydro and tidal, to the main AC network. As a voltage source converter, HDVC Light uses pulse width modification to generate the fundamental voltage. If there is a surplus of generating capacity in one of the grids, it can be shared with the other. With the HVDC Light converter, the polarity does not change when the power flow changes, according to ABB. Instead, the current direction changes, making it easy to use a converter as a building block in a multi-terminal system. The HVDC Light cable, an extruded polymer cable for HVDC transmissions, can work in deepwater or with dynamic floating platforms. In a platform-to-platform design, platforms of different frequencies (e.g., 50 and 60 Hz) can be combined, optimizing operations.
Sugars can be converted to electricity with efficiency much higher than previously known, according to researchers at the University of Massachusetts Amherst, in the October issue of
Nature Biotechnology. Professor Derek Lovley and postdoctoral researcher Swades Chaudhuri have discovered a microorganism,
Rhodoferax ferrireducens, is capable of stable, long-term electricity production by oxidizing carbohydrates. The organism transfers electrons directly onto an electrode as it metabolizes sugar into electricity, producing carbon dioxide as a byproduct. Because sugars are a substantial component of many types of waste and carbohydrate-rich crops, such as corn (a renewable energy source), carbohydrates could become economical alternatives to fossil fuels in the production of electricity, according to Lovley. “There’s been a lot of interest in microbial fuel cells trying to covert sugar into electricity,” Lovley observes. “But in the past, they’ve converted 10 percent or less of the available electrons, and we’re up over 80 percent. And previous attempts to convert carbohydrates to electricity have required an electron shuttle, or mediator, which is typically toxic to humans.”
Rhodoferax does not require a mediator because it attaches directly to the surface of the electrode. “That’s one of the big advances,” said Lovley. “People have done it without a mediator before, but their recovery of energy was less than 1 percent. Moreover, not having to use toxic elements is an obvious advantage in creating electricity. In the end, the electrons in the fuel cell are transferred to oxygen, so what we are really doing is putting a wire in between the microbe and the oxygen and harvesting this electron flow that otherwise would just go directly to oxygen.” The downside, however, is that it is a slow process. That cup of sugar could take weeks to digest. Still, a slow but steady trickle of electricity can be used to charge up a battery, which can then discharge large amounts of power when needed. The organism isolated in Lovley’s UMass Amherst lab came from aquifer sediments in Virginia during a U.S. Department of Energy study. “We found it had the unique ability to oxidize sugars with the reduction of iron oxides,” Lovley said. “This was of interest to us because last year we reported in Science that another group of iron reducers, known as Geobacter, could transfer electrons to electrodes. We reasoned that Rhodoferax might be able to do the same thing, which proved to be the case.” In theory, this method would allow a cup of sugar to power a 60-watt light bulb for 17 hours, but Lovley said the device needs improvement before it can be used commercially. “There are still issues with getting a high enough voltage and converting the sugar to electricity fast enough,” he said. “Although the process is highly efficient, it is slow. In addition, as the process is right now, we’re not talking about a lot of power. It’s barely enough to run a calculator, but we did it using unpolished graphite as a receptor. There are almost certainly better electroactive materials.” Adds Lovley, “The other thing that limits this is that the microorganisms have to attach to the surface of the receptor, so we’re working with polymer scientists, such as Tom Russell at UMass Amherst, to find a receptor with a maximally uneven surface, so more microbes can attach to it. I don’t want to give the impression that it’s ‘Back to the Future,’ where we stuff a banana in the engine and go, but it’s a pretty good leap from where microbial fuel cells were before.” The technology could also be used in environments where it is difficult or costly to charge the batteries, or in poor, remote communities, where the electrodes could be adapted so that they use carbohydrate waste from farm animals or sewage to power batteries for running refrigerators and stoves.
Slurry piping.