nanoPower Forum Points to Practical Energy Harvesting

May 19, 2009 by Jeff Shepard

The appearance of commercial energy harvesting and thin-film battery products was a consistent theme of the papers and exhibits at Darnell’s third-annual nanoPower Forum (nPF ’09). A growing variety of energy harvesting devices and thin-film batteries are now available for use in commercial applications. Among the companies highlighting products during nPF ‘09 were Adaptiv Energy, Advanced Cerametrics, Cymbet, Ferro Solutions, Infinite Power Solutions, Micropelt, Powercast, and others.

Adaptiv Energy presented the Joule-Thief™ vibration energy harvesting module. The module contains an energy harvesting beam based on AdaptivEnergy’s proprietary Ruggedized Laminated Piezo (RLP® technology, as well as proprietary energy collection and storage circuitry. The Joule-Thief module is claimed to be the highest output vibration energy harvesting device per unit weight and volume of any commercially available energy harvester. The module is designed to provide users with a choice of 3.6 Vdc or 1.8 Vdc output. Several energy storage options are available, allowing the storage capacity to be matched with the application.

Advanced Cerametrics demonstrated the Harvestor™ line of products that can provide perpetual electric power from vibration by means of a compact unit that harvests mechanical energy using piezoelectric fiber composites and proprietary power management circuits. This renewable power provides the microelectronics industry with a source of energy on the go (e.g. walking, flying, driving, riding, manufacturing, hauling, etc), and for stationary industrial and infrastructure applications where a perpetual power source is extremely valuable (e.g. wireless sensing and monitoring). The PFC (piezoelectric fiber composite) transducers are highly efficient and robust in creating electric power and actuation (compared to other piezoelectric products). Due to the high flexibility of PFCs, they are easy to design into products and systems.

New chip-scale power architectures were proposed by Cymbet in conjunction with the company’s EnerChip™ thin-film rechargeable batteries. Taking the concept of "distributed power" to its ultimate extreme, Grady proposed that energy sources be placed inside each IC on a board, providing instant power for surges of activity as well as isolation from surrounding transients and noise. Solid-state thin-film batteries such as the EnerChip can power ICs such as microcontrollers and real-time clocks via stacked dies or co-packaged in a multi-chip module format.

Just a week before nPF ’09, electronic components distributor Digi-Key Corp. and Cymbet announced that the companies have entered into a distribution agreement for the worldwide distribution of Cymbet’s EnerChip™ family of solid-state, rechargeable thin-film batteries and energy harvesting power storage modules.

For applications where battery replacement is costly, difficult or hazardous, Ferro Solutions demonstrated the VEH-360 Energy Harvester. The unit combines a compact generator that converts vibration to electricity with storage capacitors and a precision, regulated dc power supply. The VEH-360 delivers 3.3 Vdc and includes energy storage to ensure smooth power delivery even with an intermittent vibration source. It produces maximum power at 60 Hz. This vibration frequency is typically found in motors, compressors and generators in the power and process industries. VEH-360 can also be used in transportation, aerospace, and other environments to power equipment health monitoring, asset tracking, and wireless sensor systems.

Infinite Power Solutions (IPS) reported the ability to support a continuous discharge current measurement of 170mA at 25°C from a single micro-energy cell, 1 squarer-inch (25.4 x 25.4 x 0.17mm) in size. IPS also achieved a 100% depth of discharge (DoD) at 25°C for greater than 15,000 cycles at 9 C-rage with about 90% of their starting capacity maintained. As testing continues, IPS expects to achieve more than 20, Micropelt MPG-D751thermogenerator (3.5 x 4.5mm), power management circuitry, software user interface, radio and microcontroller. The device can handle multiple measurement signals + external sensor interface. It starts transmitting every second from 10°C delta T between heat source and room (3°C effective over TEG). The power capacity starts at 000 cycles with 100% DoD and 80% capacity retention and more than 100,000 recharge cycles with shallow cycling to 50% DoD.

Micropelt reported on the availability and performance of the TE-PowerTM RING, a thermally powered, embedded bearing monitor. The 25 x 60 x 30mm device includes a 1mW harvested. Next-generation devices will be chip-scale and designed for co-packaging with other circuit elements.

The Powercast P2100 (915MHz) RF power harvester measures 0.5 x 0.5 x 0.159" and produces up to 50mA of output. The P2100 is offered as standalone product or integrated with a supercapacitor from Cap-XX. When integrated, the P2100 charges the supercapacitor to about 1.2V. Supercapacitor cell voltage is limited by the voltage stability of the electrolyte; a low supply voltage allows the use of a single cell supercapacitor. This avoids the need for balancing between cells, no balancing circuitry, no current drawn by balancing circuit, reduced rate of supercapacitor ageing at lower voltage, and reduced leakage current at lower voltage.