Energy Harvester Design
Magnetostrictive Energy Harvesting
Galfenol and other magnetostrictive materials have traditionally been used to convert electrical energy into mechanical energy using the Joule Effect. Magnetostrictive materials can also be used in the reverse, the Villari Effect, converting mechanical energy into electrical energy. By utilizing this reversible characteristic, Galfenol-based devices can “harvest” vibrational energy from vibrations and convert it to useful electrical energy. Typical areas of application include industrial equipment such as pumps or motors, structures such as buildings or ships, and oil wells (drilling or producing).
Traditionally vibrational energy harvesting has been achieved using piezoceramic materials or via magnetic induction. Galfenol offers several advantages over these other vibrational energy harvesting methods. Galfenol is very manufacturable and can be easily produced in a variety of shapes and sizes. Galfenol is also a strong and durable material with a high Curie Temperature, meaning that is can work and survive in very harsh environments. Finally, Galfenol can harvest energy over a broad frequency range (> 15 Hz half-power bandwidth) which is a limitation of many other vibrational energy harvesters. All of these factors demonstrate Galfenol’s potential as an important materials for vibrational energy harvesting.
Proof-of-Concept Energy Harvesting Devices
ETREMA has developed system level energy harvesting devices, including the energy harvester component and the companion electronics needed to regulate and store the power. Below are descriptions of three proof-of-concept devices and the electronics ETREMA developed under DOD funded SBIR grants to highlight the capabilities of Galfenol as an important energy harvesting material.
The Bolt Energy Harvester was designed to work alongside supports for industrial equipment. The Bolt is compact (< 35 cm3) with the Galfenol welded to threaded stainless steel end pieces for easy installation. The Bolt works in both tension and compression and has produced 75 mW of power (35 lbs rms input) over a vibrational frequency range between 175 – 400 Hz.
The X-Spring Energy Harvester was designed to be placed directly in the load path for industrial equipment. The Galfenol is mounted within a titanium spring element, designed to match the stiffness of the equipment support. The entire package is < 200 cm3 with a predicted output power of ~ 2 mW. The X-Spring also exhibits a large operational frequency bandwidth of 110 Hz.
The Magnetically Amplified Energy Harvester was designed to provide a non-contact method of harvesting energy from industrial equipment. A permanent magnet and/or a magnetic material are attached to the vibration source and the end of a Galfenol beam. The magnetic force amplifies the displacement of the beam up to 9x which increases the power output of the Magnetically Amplified Energy Harvester. This device generated up to 9 Volts of electric potential, which was enough to power a small wireless transmitter as described in the companion electronics sections. The half-power bandwidth for this devices ranges from 15 – 35 Hz, depending on beam length
Companion Electronics Design
ETREMA has also developed companion electronics for vibrational energy harvesters to deliver a full wireless sensor system. The companion electronics include power management and storage, a sensor, and a wireless transmitter. ETREMA used a Microchip MRF24J40MA radio to demonstrate the capabilities of the power management and storage system and our vibrational energy harvester. Using the Magnetically Amplified Energy Harvester, described above, ETREMA was able to transmit a data package every 10 s requiring 5 mW of power to be available to accomplish this. Combining ETREMA’s expertise in both Galfenol-based energy harvesters and developing system level solutions, ETREMA can provide an energy harvesting device, complete with power management and storage electronics, capable of powering a sensor and wireless transmitter.
ETREMA has developed several proof-of-concept energy harvesting systems for powering wireless sensors. TdVib is currently looking for industrial partners to further this effort and provide energy harvesting solutions to power wireless sensor networks.
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