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The latest buzz in the information technology industry regards "the Internet of things"—the idea that vehicles, appliances, civil-engineering structures, manufacturing equipment, and even livestock would have their own embedded sensors that report information directly to networked servers, aiding with maintenance and the coordination of tasks.Realizing that vision, however, will require extremely low-power sensors that can run for months without battery changes—or, even better, that can extract energy from the environment to recharge.Last week, at the Symposia on VLSI Technology and Circuits, MIT researchers presented a new power converter chip that can harvest more than 80 percent of the energy trickling into it, even at the extremely low power levels characteristic of tiny solar cells. Previous experimental ultralow-power converters had efficiencies of only 40 or 50 percent.Moreover, the researchers' chip achieves those efficiency improvements while assuming additional responsibilities. Where its predecessors could use a solar cell to either charge a battery or directly power a device, this new chip can do both, and it can power the device directly from the battery.All of those operations also share a single inductor—the chip's main electrical component—which saves on circuit board space but increases the circuit complexity even further. Nonetheless, the chip's power consumption remains low."We still want to have battery-charging capability, and we still want to provide a regulated output voltage," says Dina Reda El-Damak, an MIT graduate student in electrical engineering and computer science and first author on the new paper. "We need to regulate the input to extract the maximum power, and we really want to do all these tasks with inductor sharing and see which operational mode is the best. And we want to do it without compromising the performance, at very limited input power levels—10 nanowatts to 1 microwatt—for the Internet of things."The prototype chip was manufactured through the Taiwan Semiconductor Manufacturing Company's University Shuttle Program.Ups and downsThe circuit's chief function is to regulate the voltages between the solar cell, the battery, and the device the cell is powering. If the battery operates for too long at a voltage that's either too high or too low, for instance, its chemical reactants break down, and it loses the ability to hold a charge.To control the current flow across their chip, El-Damak and her advisor, Anantha Chandrakasan, the Joseph F. and Nancy P. Keithley Professor in Electrical Engineering, use an inductor, which is a wire wound into a coil. When a current passes through an inductor, it generates a magnetic field, which in turn resists any change in the current.Throwing switches in the inductor's path causes it to alternately charge and discharge, so that the current flowing through it continuously ramps up and then drops back down to zero. Keeping a lid on the current improves the circuit's efficiency, since the rate at which it dissipates energy as heat is proportional to the square of the current.Once the current drops to zero, however, the switches in the inductor's path need to be thrown immediately; otherwise, current could begin to flow through the circuit in the wrong direction, which would drastically diminish its efficiency. The complication is that the rate at which the current rises and falls depends on the voltage generated by the solar cell, which is highly variable. So the timing of the switch throws has to vary, too.Electric hourglassTo control the switches' timing, El-Damak and Chandrakasan use an electrical component called a capacitor, which can store electrical charge. The higher the current, the more rapidly the capacitor fills. When it's full, the circuit stops charging the inductor.The rate at which the current drops off, however, depends on the output voltage, whose regulation is the very purpose of the chip. Since that voltage is fixed, the variation in timing has to come from variation in capacitance. El-Damak and Chandrakasan thus equip their chip with a bank of capacitors of different sizes. As the current drops, it charges a subset of those capacitors, whose selection is determined by the solar cell's voltage. Once again, when the capacitor fills, the switches in the inductor's path are flipped."In this technology space, there's usually a trend to lower efficiency as the power gets lower, because there's a fixed amount of energy that's consumed by doing the work," says Brett Miwa, who leads a power conversion development project as a fellow at the chip manufacturer Maxim Integrated. "If you're only coming in with a small amount, it's hard to get most of it out, because you lose more as a percentage. [El-Damak's] design is unusually efficient for how low a power level she's at.""One of the things that's most notable about it is that it's really a fairly complete system," he adds. "It's really kind of a full system-on-chip for power management. And that makes it a little more complicated, a little bit larger, and a little bit more comprehensive than some of the other designs that might be reported in the literature. So for her to still achieve these high-performance specs in a much more sophisticated system is also noteworthy."Related products:XC7Z100-2FFG900IXC7Z010-1CLG400IA2F200M3F-1FGG256 

Chemists at the University of Waterloo have developed a long-lasting zinc-ion battery that costs half the price of current lithium-ion batteries and could help enable communities to shift away from traditional power plants and into renewable solar and wind energy production.Professor Linda Nazar and her colleagues from the Faculty of Science at Waterloo made the important discovery, which appears in the journal, Nature Energy.The battery uses safe, non-flammable, non-toxic materials and a ph-neutral, water-based salt. It consists of a water-based electrolyte, a pillared vanadium oxide positive electrode and an inexpensive metallic zinc negative electrode. The battery generates electricity through a reversible process called intercalation, where positively-charged zinc ions are oxidized from the zinc metal negative electrode, travel through the electrolyte and insert between the layers of vanadium oxide nanosheets in the positive electrode. This drives the flow of electrons in the external circuit, creating an electrical current. The reverse process occurs on charge.The cell represents the first demonstration of zinc ion intercalation in a solid state material that satisfies four vital criteria: high reversibility, rate and capacity and no zinc dendrite formation. It provides more than 1,000 cycles with 80 per cent capacity retention and an estimated energy density of 450 watt-hours per litre. Lithium-ion batteries also operate by intercalation—of lithium ions—but they typically use expensive, flammable, organic electrolytes."The worldwide demand for sustainable energy has triggered a search for a reliable, low-cost way to store it," said Nazar, a Canada Research Chair in Solid State Energy Materials and a University Research Professor in the Department of Chemistry. "The aqueous zinc-ion battery we've developed is ideal for this type of application because it's relatively inexpensive and it's inherently safe."The global market for energy storage is expected to grow to $25 billion in the next 10 years. The bonus for manufacturers is they can produce this zinc battery at low cost because its fabrication does not require special conditions, such as ultra-low humidity or the handling of flammable materials needed for lithium ion batteries."The focus used to be on minimizing size and weight for the portable electronics market and cars," said Dipan Kundu, a postdoctoral fellow in Nazar's lab and the paper's first author. "Grid storage needs a different kind of battery and that's given us license to look into different materials."Water in the electrolyte not only facilitates the movement of zinc ions, it also swells the space between the sheets, like tiers of a wedding cake, giving the zinc just enough room to enter and leave the positive structure as the battery cycles. The electrode material's nano-scale dimensions and the battery's high-conductivity aqueous electrolyte also improve its cycling life and response times.Together with researchers at the Joint Center for Energy Storage Research in the U.S., Nazar's team is also investigating multivalent ion intercalation batteries based on Mg2+ in non-aqueous electrolytes. They were the first to report highly reversible Mg cycling in the TiS2 thiospinel and layered sulfides, which represent the first new highly functional Mg insertion materials reported in more than 15 years. Their papers appeared in Energy & Environmental Science and ACS Energy Letters earlier this year. 

If you want to save on your monthly electric bill and reduce your greenhouse gas emissions at the same time, you might buy a new, energy-efficient refrigerator. Or water heater. Or clothes dryer. But if you can only replace one of these, which will give you the biggest payback?You could try to figure that out by comparing the energy-use labels from your existing appliances with those of the models you might purchase—if you still have your old labels. Even then, the numbers may differ significantly from your actual usage, depending on factors such as age, condition, and your local climate. But soon, there could be a much easier way to figure out exactly how much power is being used by every appliance, lighting fixture, and device in your home, with pinpoint accuracy and at low cost, thanks to devices and software developed by researchers at MIT.The team's findings, developed over several years of intensive research, are described in a series of papers, including one published this week in the IEEE Sensors Journal, in a paper by MIT Professor of Electrical Engineering Steven Leeb and recent graduates David Lawrence MEng '16 and John Donnal PhD '16. Another paper from the team, which also includes as co-author James Paris PhD '13, is still in press.While many groups have worked on developing devices to monitor electricity use, the new MIT system has some key advantages over other approaches. First, it involves no complex installation: No wires need to be disconnected, and the placement of the postage-stamp-sized vibration sensors over the incoming power line does not require any particular precision—the system is designed to be self-calibrating. Second, because it samples data very quickly, the sensors can pick up enough detailed information about spikes and patterns in the voltage and current that the system can, thanks to dedicated software, tell the difference between every different kind of light, motor, and other device in the home and show exactly which ones go on and off, at what times.Own your own dataPerhaps most significantly, the system is designed so that all of the detailed information stays right inside the user's own home, eliminating concerns about privacy that potential users may have when considering power-monitoring systems. The detailed analysis, including the potential for specialized analysis based on an individual user's specific needs or interests, can be provided by customized apps that can be developed using the MIT team's system.Tests of the system have showed its potential to save energy and greenhouse emissions—and even to improve safety. One installation at a military base used for training exercises revealed that large tents were being heated all day during winter months, even though they were unoccupied for most of the daytime hours—a significant waste of money and fuel (which, in a combat setting, could be an important logistical concern). Another test installation, in a home, found an anomalous voltage pattern that revealed a wiring flaw that caused some copper plumbing pipes to carry a potentially dangerous live voltage."For a long time, the premise has been that if we could get access to better information [about energy use], we would be able to create some significant savings," Leeb says. He and his students have been tackling the problem for more than 10 years and bit by bit have found ways to circumvent the daunting problems involved in achieving this basic task.First was the ability to monitor changes in voltage and current without cutting the main incoming power line to a home or business (an expensive process requiring a licensed electrician) or plugging every appliance into a special monitoring device. Other groups have attempted to use wireless sensors to pick up the very faint magnetic and electric fields near a wire, but such systems have required a complex alignment process since the fields in some places can cancel each other out. The MIT team solved the problem by using an array of five sensors, each slightly offset from the others, and a calibration system that tracks the readings from each sensor and figures out which one is positioned to give the strongest signal.Interpreting the data flowThe next trick was in figuring out how to analyze the reams of data flowing in from the high-speed sensors, in order to tease out which bits correspond to current and voltage, and how that information could be used to identify "signatures" of specific appliances. This is possible because every motor or device has distinctive characteristics as to exactly how fast and how much the voltage varies, or spikes, at the moment the device switches on, or as it operates. After extensive testing in the lab, in homes, at the Fort Devens Army base outside Boston, and aboard the U.S. Coast Guard cutter Spencer, the team was able to develop a catalog of such signatures, to identify each kind of electrical load.And finally, given the prodigious amount of raw data generated by the system, the team had to figure out how to extract the useful information and display it in a way that would make it easy for people to make decisions about energy investments. They developed an interface that allows users to "zoom in" on specific time segments, revealing enough data to tell when a refrigerator turns on or off, or goes into its defrost cycle, or how often a water heater is switching on and off during the day."A bunch of major players have gotten into, and out of, this field," says Leeb, including giants like Google and Microsoft. But now, he says, the MIT team has solved the key issues and come up with a practical and very powerful system. One of the major insights they had was that keeping most of the data within the home and sending only small subsets out into the cloud for processing solved two problems at once: It eliminated the privacy concerns of using such a system, and it eliminated the huge bandwidth and data transmission costs that would be required if the raw data was sent to a central facility.Once the system is developed into a commercial product, Leeb says, it should cost only about $25 to $30 per home. "We're trying to lower the barriers to installation," says co-author John Donnal, and this noncontact sensor is simple enough for most home users to install on their own. "It just goes on with a zip tie," he says.William Singleton, an engineer at the U.S. Army Fort Devens Base Camp Integration Laboratory, who was not involved in this research, says this work "is an excellent example of how theoretical scientific and mathematical principles can be brought to bear on real world, practical, problem-solving applications." By using the MIT team's sensing system, he says, "significant potential savings in fuel, water, and equipment maintenance can be realized. This will provide increased options for the battlefield commander in accomplishing his mission, reduce the overall base camp logistics footprint, and ultimately save lives of warfighters involved in base camp sustainment and resupply." 

Research challengeElectrical harvesting is the conversion of freely available ambient energy such as vibrations into electrical power. This power can then be used to supply low-power, autonomous electronic semiconductor systems such as wireless sensor networks used in the energy, transport, aeronautical and military sectors.Energy harvesters can be used to replace batteries in wireless devices reducing the maintenance costs of replacing the millions of batteries that are thrown away each year and enabling these wireless sensors to be placed in inaccessible and hazardous locations.Research at Southampton is leading the way in developing devices that can turn these vibrations into useable energy in a cost-effective, user-friendly way.ContextIn the future energy harvesting is set to play a significant role in the powering of autonomous electronic systems and wireless sensor networks around the globe. Our solutionSouthampton’s research team has been working for more than 15 years on a solution to our growing energy needs. Since their research began they have produced the world’s first piezoelectric vibration energy harvester and high efficiency electromagnetic energy harvesters. Their work has placed them at the forefront of vibration energy harvesting research internationally.Today they continue to lead the research into realising the full potential of vibration energy harvesting.What was the impact?Southampton’s research has spearheaded the development of a multi-million pound industry and enabled large-scale deployment of wireless sensors in the rail network and other industry.In 2004 the Southampton team commercialised its research by launching the spin out company Perpetuum. The company is a global leader in vibration energy harvesting and has already attracted almost £10m in venture capital. It has developed the world’s first practical electromagnetic micro-generator that is capable of delivering enough power to transmit large amounts of data. This wireless sensor system is already monitoring the condition of bearings on hundreds of UK and European trains to improve rail safety and reduce maintenance costs. Its generators have also been used by Shell to help monitor the condition of its gas field equipment in Norway.Southampton’s research has also helped develop international standards, influenced the decisions of funding bodies and raised the profile of energy harvesting among industry and the wider public.  

Learn how to reduce your electricity bill by using the latest kind of energy monitorIn today’s data-centric, energy-conscious age, seeking to reduce your electricity bill and greenhouse gas emissions is quite common. But if you’re trying to decide which device to switch to an energy-efficient mode, how can you figure out which uses the most energy? Trying to compare products’ energy use labels is often fruitless and overly complex, as those actual figures vary depending on how old a product is and how your local climate fares, among other things. However, thanks to MIT’s research and software, a much easier method for determining how much power each device uses is approaching.While developing devices to screen electricity use is not new, MIT’s plans of a stamp-sized energy monitor have some ideal advantages. Involving no complicated installation, the process doesn’t require disconnected wires, and you don’t have to be overly careful when placing sensors over an incoming power line. The system is designed as self-calibrating and processes comprehensive information about voltage and current patterns. Such detailed readings allow one to differentiate every kind of light, motor, and device in the home to determine when certain products are used.MIT’s system is also arranged so that all of this specific information remains within the home and does not run at risk of someone else accessing your power. The research team is also developing customized apps that could provide in-depth analysis of a user’s specific power-related needs. These apps could help the entire system become even more useful, as tests of it have proven successful. Testing has also shown when heating is excessive, as seen with an installation at a military base where large tents were heated during the day despite usually being empty at that time.“For a long time, the premise has been that if we could get access to better information [about energy use], we would be able to create some significant savings,” said Steven Leeb, MIT professor of Electrical Engineering and one of the research paper’s authors. The required information has grown more attainable as the years go by, firstly needing the skill to supervise changes in voltages and current without disabling main power lines to a home or connecting each appliance to a monitoring device. Systems that previously tried to use wireless sensors for determining faint magnetic and electric fields had dubious performance because fields would cancel out each other. MIT found a solution by applying an array of five offset sensors and a calibration system that determines the strongest sensor signal.With this sensor system in place, MIT researchers then had to find a way to analyze data flooding in from the sensors. Because every energy appliance has different performing speeds and voltage variances, a database of these differences is key to understanding products. MIT was able to develop such a catalog of appliances’ “signatures,” then having to display the data in a decipherable way. The team created an interface that permits users to “zoom in” on time segments and explore things such as when a fridge turns on and how often a water heater switches on and off.MIT plans to develop the system commercially, only pricing it at about $25 to $30 per home. As the device is a non-contact sensor, someone could even install it without any outside help. William Singleton, an engineer at the U.S. Army Fort Devens Base Camp Integration Laboratory who wasn’t involved in the experiments, said the system is “an excellent example of how theoretical scientific and mathematical principles can be brought to bear on real world, practical, problem-solving applications. Significant potential savings in fuel, water, and equipment maintenance can be realized.”Source:TechXplore , New Atlas         By Kristen Perrone