Darnell Group Presents Paper on Energy Harvesting at Semicon West

July 16, 2008 by Jeff Shepard

Bringing energy harvesting, thin-film batteries and portable fuel cells to commercialization was the subject of the morning Techxpot Emerging Markets session on Wednesday, July 16 at Semicon West. Among the six speakers were Jeff Shepard, President of Darnell Group, Jerry Ruddle, Executive Vice President with Advanced Cerametrics and Jarreth Solomon, Vice President with Solicore.

Shepard led off the session with a discussion of the different market strategies needed for successful introduction of energy harvesting devices and micro fuel cells. He noted that while micro fuel cells have been under development for many years and have yet to capture significant markets, much newer energy harvesting and thin-film battery devices are already capturing significant markets.

The problem for micro fuel cells has been a focus on inappropriate markets such as mobile phone handsets and laptop computers. A more recent trend for micro fuel cells to target portable auxiliary power applications has been successful in generating significant revenue opportunities for the devices.

"Both micro fuel cells and energy harvesting devices can find markets when they are used to replaced large numbers of batteries," Shepard observed. "For energy harvesting devices, that means applications such as wireless sensor networks with large numbers of nodes. For micro fuel cells, it is auxiliary or remote power applications where the need is for hundreds of watt-hours of continuous operation, and the fuel cell replaces many individual batteries; not small portable devices such as handsets or laptops."

The ability of Advanced Cerametrics’ flexible piezoelectric fiber composite transducers to harvest mechanical energy and convert it into electrical energy was detailed by Ruddle. He showed the ability of piezoelectric fiber composites to produce 500V(p-p) (at resonance frequency of 35 Hz, 0.9lbf) that can charge a 400µF capacitor to 50V in less than 4 seconds. The materials have been configured to yield a continuous 145mW of power.

Ruddle also showed the company’s unique Viscose Suspension Spinning Process (VSSP) for producing the fibers. VSSP combines two of the world’s oldest technologies, fiber spinning and ceramics with state-of-the-art chemistries. The resulting spun ceramics are lighter, stronger, flexible, and inexpensive compared to traditional ceramic solutions. Ceramic fibers can be woven, embedded, bonded or molded to user-defined shapes.

Turning to thin-film batteries, Solicore’s Solomon presented the latest developments related to the company’s Flexion line of lithium-polymer primary batteries. These solid state, polyimide-based batteries deliver standard capacities up to 50mAh, are 0.45mm thick and can withstand hot lamination of 135°C and 220psi lamination pressure used to produce smart cards. The paper-thin battery is capable of flexing and bending, making it suited to fit inside standard credit, debit and enterprise cards.

Solicore’s batteries can be configured to additional Smart Card platforms via a variety of sizes and capacities to meet the demands of different physical and power requirements. The Flexion battery has a shelf-life of three years (the typical life of a credit card) and enough capacity to power tens of thousands of secure card transactions.