Vibration Energy Harvesters Enable Wireless Sensor Network

June 28, 2013. MicroGen Systems Inc. has announced that vibration energy harvesting BOLT Power Cells enabled a live wireless sensor network (WSN) using Linear Technology’s Dust Networks LTC5800-IPM SmartMesh IP mote-on-chip at the Sensors Expo and Conference exhibition in Rosemont, IL, June 5-6, 2013. The Linear mote was powered by MicroGen’s piezoelectric Micro Electro Mechanical Systems (piezo-MEMS) vibrational energy harvester or micro-power generator (MPG) technology.

The Linear WSN consisted of four motes; WSN software enebled efficient power-managed communication. The self-powered motes were enabled by electronic shakers set at typical industrial vibrations levels of 120 Hz and an acceleration level of 0.2 g. MicroGen placed vibration powered motes at the Linear booth and at the X-FAB MEMS Foundry booth. These motes were on the order of 20 to 30 meters away from MicroGen’s booth. This was the first fully MEMS energy-harvesting-powered WSN completed by a commercial company.

Inside MicroGen’s BOLT Power Cell is a small semiconductor MEMS chip fabricated using similar techniques as the computer chip industry. This chip is a ~1.0 cm² piezo-MEMS MPG containing one end-mass loaded microcantilever containing a piezoelectric thin film. As the MPG’s cantilever bends up and down due to the external vibrational force it produces AC electricity. At resonance the AC power output is maximized, where it is ~100 µW at 120 Hz and ≥ 0.1 g, and ~900 µW at 600 Hz and ≥ 0.5 g.

The AC electricity is efficiently converted to DC using Linear Technology’s LTC3588-1 piezoelectric energy-harvesting AC/DC converter. After the energy is scavenged it is temporarily stored on a 300-µF capacitor. The output of the Power Cell ranges from 25-500 µW at 3.3 VDC, depending upon configuration and frequency. The BOLT Power Cell is intended to enable a wireless sensor mote from many different manufacturers.

The bottom-line is that the BOLT Power Cell is simply a battery replacement unit that uses vibrational energy instead of chemical energy produced by environmentally unfriendly materials. The intent is to eliminate or extend the lifetime of primary cells or rechargeable batteries in WSN industrial and building applications, where the labor to frequently change batteries is cost prohibitive for a WSN to be installed. Power Cells will be offered at 50/60 Hz harmonics between 100 and 1,500 Hz. MicroGen’s MPGs and Power Cells are sensitive to low levels of acceleration. At G-levels < 0.1 to 0.5 g (depends upon frequency) at a specific industrial signature frequency, the Power Cell will enable the WS mote attached. In volume the MPG and Power Cell production cost are estimated be on the order of $0.50 and $1.00 each, respectively.

Joy Weiss, president of the Dust Networks product group at Linear Technology, stated, “I am pleased to see the progress that MicroGen is bringing to energy harvesting to enable self-powered SmartMesh wireless sensors.”

Linear Technology’s Boston Design Center’s Director, Sam Nork, added, “MicroGen’s demonstration of its piezo-harvesting chip integrated with Linear Technology’s LTC3588 piezo conversion chip is a perfect match to efficiently produce DC electricity for WSN applications.”

MicroGen’s CEO, Robert Andosca, stated, “We are very pleased that we were able to show a low-cost energy harvester solution to enable Linear Technology’s SmartMesh wireless motes. Our goal is to provide piezo-MEMS harvesters in a form-factor that can be used by all wireless sensor products currently on the market. Our BOLT Power Cell is the first example of doing so with a commercial MEMS-based energy harvesting generator component.”

MicroGen unveiled its BOLT product line at the Sensors Expo in June. MicroGen plans to announce the availability of the products late summer 2013. Initially, MicroGen will offer MPGs and BOLT Power Cells at frequencies 100, 120, and 600 Hz. For extra energy storage, plug-in BOLT Energy Cells will be available with a 22-mF Panasonic ultracapacitor, a 50 µA-hr Cymbet solid-state battery, or a 7.0 mA-hr Panasonic rechargeable coin cell.

MicroGen is bringing to market a suite of products based on its proprietary piezo-MEMS platform technology at the X-FAB Silicon Foundries AG (www.xfab.com) production facility located north of Hamburg, Germany. MicroGen’s first piezo-MEMS component is a small (volume is < 1.0 cm³) vibrational energy harvester, or MPG. The MPG is the heart of MicroGen’s BOLT Power Cell DC power source. These low-cost, long-lifetime products scavenge otherwise wasted ambient vibrational energy and will replace or extend the lifetime of batteries in wireless sensor and other microelectronic applications.

MicroGen’s primary target markets are the industrial and building markets (for example, process automation, machinery monitoring, lighting control, HVAC, and smart utility metering). Longer term, the secondary market is transportation systems (for example, planes, trains, and automobiles; civil infrastructure monitoring; and asset tracking).

MicroGen located in Rochester, NY, developed its core piezoelectric platform technology at Cornell University (www.cnf.cornell.edu).

www.microgensystems.com

Linear Technology has been designing, manufacturing, and marketing a broad line of high performance analog integrated circuits for major companies worldwide for over three decades.

www.linear.com

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