Renewable and energy efficiency breakthroughs turn science fiction into fact
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| Dr. Swades K. Chaudhuri operates the microbial fuel cell developed by the Geobacter Project. The fuel cell uses the bacteria, Rhodoferax ferrireducens, which harvests electrons from the medium very efficiently because it attaches directly to the electrode. (Photo courtesy of the Geobacter Project) |
The generation that grew up on science fiction movies promising personal jet packs and robot servants has high hopes for science, even if our dreams have shifted to the less glamorous, but more critical, goals of environmentally friendly energy and reduced U.S. dependence on imported fossil fuel. Some recent advances in existing technologies bring those goals closer, either through alternative fuel source development or more efficient energy use.
Tap water power could replace batteries for small electric needs
Generating energy from flowing tap water may sound like science fiction, but a research team at the University of Alberta, Edmonton, Canada claims it's possible. According to professors Daniel Kwok and Larry Kostiuk, the natural electrokinetic properties of liquid such as ordinary tap water produce energy when pumped through tiny microchannels. "This discovery has a huge number of possible applications," said Kostiuk.
The key to electrical power generation is to create a sustainable electrical charge separation, which occurs at solid-liquid interfaces. When a liquid, like water, comes into contact with a non-conducting solid, the solid surface becomes charged with a thin layer. This region, known as the electric double layer, ranges from several nanometers to a few micrometers thick. The research team constructed a solid-liquid interface with microchannels comparable with the thickness of the EDL and forced the liquid through the channels, transporting the net charges in the EDL downstream.
When an external electric circuit is added by placing electrodes at the ends of the channel, electrical energy is extracted as current flows between the electrodes. The work of pushing the liquid through the channel is the source of that energy. Although the power generated from a single channel is extremely small, millions of parallel channels increase the power output, said the developers.
While the new clean alternative energy source could eventually rival wind and solar power, it would need huge bodies of water to work on a commercial scale. The most promising applications for "microhydropower" are in electronics and microelectronic devices. "This technology could provide a new power source for devices such as mobile phones or calculators, which could be charged up by pumping water to high pressure," said Kostiuk.
So, in the future, you may be charging your pocket communicator—er, cell phone—at the kitchen sink, instead of the electrical outlet.
Efficient microbial fuel cell turns sugar into electricity
Or perhaps you would rather use sugar to charge up your cell phone battery. The Geobacter Project has developed a fuel cell powered by a bacterium that converts sugar into electricity with more than 80-percent efficiency.
Microbial fuel cells have been around for a while, but the device built by researchers at the University of Massachusetts—Amherst differs in two crucial ways. "We are harvesting a much higher percentage of the electrons available," said Microbiology Professor Derek Lovley. "Typically, the efficiency is of 10 percent or less."
The researchers immersed a graphite electrode into a solution containing glucose and the bacteria, Rhodoferax ferrireducens. The microbes attached to the electrode and began to feed on the sugar, producing electrons that were collected by the electrode and flowed to an external circuit. Once the glucose was fully consumed, the researchers replaced the solution, and electricity production rapidly resumed.
Previous versions of microbial fuel cells required chemicals to help transport electrons from the medium containing the bacteria to the electrode. The so-called "mediators" are expensive and toxic, and have to be refueled frequently in the cell. The microbe Lovley and researcher Swades Chaudhuri isolated from marine sediments from Oyster Bay, Va., doesn't require a mediator because it attaches directly to the electrode.
Finding a microbe that efficiently harvests electrons and doesn't need a mediator represents a major advance in microbial fuel cell technology. Applications for hardworking Rhodoferax ferrireducens could range from powering handheld devices to producing electric energy on a larger scale from sugars found in waste material—even in sewage in remote communities.
Nanotechnology applications show promise for energy industry
Bacteria aren't the only tiny units with big energy savings potential. Scientists from Research Triangle Institute in North Carolina believe that nanotechnologies can lead to more efficient and reliable refrigerators and air conditioners.
RTI developed a nanometer-scale thermoelectric film that can heat and cool and convert heat to energy with unprecedented speed and efficiency. A module with just one square centimeter of the material can provide 700 watts of cooling under a nominal temperature gradient.
At a recent American Chemical Society meeting, the RTI research team unveiled a prototype device containing a semicondutor chip that consists of about 1,000 layers of the material. "This is the first nonscale material-based device that can achieve a cooling effect suitable for everyday functions like refrigeration or power production," claimed team leader Rama Vankatasubramanian.
Functioning as a heat pump in laboratory tests, the postage stamp-sized prototype cooled a block of solid steel from 79 degrees to 64 degrees in about two minutes, much faster than a conventional refrigerator. The performance approached the cooling efficiency of current thermoelectric devices, but in a much smaller package. With ongoing improvements, researchers believe the device can increase its efficiency by two to three times.
The new devices may initially serve as tiny heat pumps that could spot-cool microprocessors or communication lasers, said Venkatasubramanian, adding, "We can imagine the possibility of replacing most of the mechanical refrigerators and air-conditioning systems with chlorofluorocarbon-free, solid-state, no-moving-parts—and therefore reliable—electronic heat pump technology."
Induction cooking combines high performance, energy efficiency
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This electric induction range, developed by Luxine, Inc. with support from the Electric Power Research Institute, generates a high frequency, alternating current magnetic field to cook at record energy efficiency. (Photo courtesy of EPRI)
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As fascinating and promising as these developments are, they don't mean much to the average consumer looking for ways to save money and energy at home. On the other hand, an electric kitchen range that uses magnetic induction to provide superior cooking performance at record energy efficiency might be very interesting indeed. Luxine, Inc. of Malibu, Calif., with support from the Electric Power Research Institute, has developed a new generation of more reliable, high performance, commercial and residential induction ranges.
Induction ranges generate a high frequency, alternating current magnetic field to heat an iron-based cooking pan through a ceramic-glass cooking surface. Because the energy transfers through the ceramic top, the cooking surface stays cool, while efficiency is very high—92 percent, including the energy to heat the pan. Actual cooking efficiency is 95 percent.
In comparative performance tests of several gas, electric and induction ranges, the Luxine unit was 92 percent energy efficient, compared to 72 percent for the radiant electric range. The residential gas range rated 47 percent, while the commercial gas range had an energy efficiency of only 30 percent. A 3.5-kW Luxine induction range boiled 20 pounds of water in about 15 minutes, virtually the same time as a 5.1-kW electric resistance coil.
The secret to induction ranges is that all the energy goes into the pan through direct energy transfer of electricity through a magnetic field to the cooking pan. No energy is wasted to heat an electric coil or a ceramic cooking surface. As soon as the pan is removed, no further energy radiates into the kitchen. Cooler kitchens use less electricity for air conditioning and ventilation, resulting in additional energy and cost savings.
The Luxine Power technology is only available through four major commercial equipment manufacturers. However, the company is working with Viking Range to introduce the concept to the residential market. Luxine Chief Executive Officer Nick Bassill anticipates that Luxine Power technology will be available to consumers in early 2004.
It may not be quite the same as having a robot servant to cook dinner, but the money saved on your electric bill could be put away for that jet pack you've had your eye on.
