Lessening the Burden of Power

E-mail Barbara Goode

You've probably imagined what you could do with sensors that are completely independent not only of communications lines but also of power lines. Plenty of suppliers have also contemplated this and have made intriguing progress in battery development and energy harvesting, as recent news reports demonstrate.

In the realm of energy scavenging, the U.K. company Perpetuum recently launched a vibration energy harvester to power sensors, microprocessors, and transmitters capable of sending large amounts of data from many types of industrial equipment. The PMG7 high-performance microgenerator, now available to OEMs, sensor manufacturers, and end users, converts kinetic energy from the vibration of equipment running at mains frequency (50 or 60 Hz) into electrical energy. It can generate up to 5 mW, which is enough to power a wireless transmitter sending up to 6 KB of critical data every few minutes, or smaller amounts of data, such as a temperature reading, several times a second. It can operate in most industrial environments and at minimal vibration levels (25 mg). It simply screws into place or can be held by magnets.

According to Perpetuum CEO Roy Freeland, "No competitive offering has come close to this level of performance in terms of the amount of data that can be sent or the conditions under which it will operate reliably."

Battery Developments
Other work is in the realm of R&D, and concerns battery technologies. Oak Ridge Micro-Energy, for instance, has developed a new rechargeable thin-film lithium-ion battery that can operate at high temperatures. Based on a new anode-cathode combination, the company's prototypes were cycled at a record high temperature of 170°C (338° F). Conventional rechargeable lithium-ion batteries cannot be cycled at temperatures much above 60°C, and most batteries work best at room temperature; operation at high temperatures dramatically decreases battery performance and the life. The Oak Ridge thin-film battery can also be recharged and suffers only a minor decrease in performance over time at high temperatures.

According to Mark Meriwether, president and CEO, "This battery could open up many new markets for our thin-film batteries in diverse areas, such as downhole and other sensors that operate in harsh environments, backup of high-temperature nonvolatile memory, and semiconductor diagnostic wafers."

And Rutgers University has granted mPhase Technologies the right to test its lithium-based alternative chemistries for a prototype nano-structured battery. "The mPhase nano-structured battery promises to significantly change the storage battery industry," says Seth Tropper, technology commercialization consultant for Rutgers Office of Corporate Liaison and Technology Transfer (OCLTT)

In another announcement, mPhase reported that the microscopic structure designs of its prototype battery and magnetometer demonstrate resiliency to shock and acceleration. The batteries survived a high acceleration test at 12,000 g, conducted at Picatinny Arsenal, the Army's foremost munitions research facility. The test paves the way for developing small guided munitions.

Batteries for Military Application
Several other developments were made with military applications in mind, too. According to recent press, sensors are becoming increasingly important for military operations. In many of these scenarios, battery maintenance is undesirable or impossible.

Neah Power Systems, Inc. is working to extend its patented fuel-cell technology, based on porous silicon electrodes, to power sensors for military, portable electronics, and homeland security applications. "Most fuel cells require air to react with the methanol fuel to produce electricity," said Dan Rosen, PhD, chairman of Neah Power Systems. "Neah uses liquid electrolytes that enable them to be configured to either use air or run as a closed system in applications where you don't want your sensor and its fuel cell to be detected. Many sensors are buried or run under water. Neah anticipates that this extension of its fuel cell design will meet the needs for many such applications."

And finally, MTI MicroFuel Cells Inc. (MTI Micro) says it has achieved an energy density of more than 1.3Wh per cc of fuel on a 30 W laboratory test unit. This significant achievement represents more than a 30% increase in fuel efficiency and is an important technical milestone as MTI Micro moves forward in developing its award-winning Mobion fuel cell technology for a range of applications targeted for the military market.

"We recognize what our military customers need—a rugged, light, compact power-pack that can work in most operational environments and run longer than batteries," said Juan Becerra, vice president of market and business development for MTI Micro. "We are focused on developing products that can meet those requirements and improve the mobility and effectiveness of our soldiers."

For high-power applications, MTI Micro's direct methanol fuel cell (DMFC) system, Mobion-30, is being designed to produce up to 30 W of continuous power in a portable, lightweight, energy-rich power-pack, allowing deployed soldiers to use portable electronic devices for much longer periods of time. The Mobion-30 may help reduce military operational and logistics costs of tracking, shipping and disposing of millions of batteries.

In the low-power military space, MTI Micro's Mobion-1 is designed to produce 1 W of continuous power and is intended for applications with minimal power needs but continuous, unattended run-time.

Very Exciting
"The latest accomplishments in fuel cell efficiency by MTI Micro are very exciting to AFRL," said William Cook, senior engineer at the Air Force Research Laboratory Information Directorate.

Actually, the accomplishments of all these organizations—and others pursuing power advancements—are very exciting for all types of sensor applications. Devices that can operate without batteries larger than themselves—and that need little or no battery maintenance—will open up all sorts of opportunity. Let's see what happens next.

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