The device is a magneto-electric-coupled magneto-mechano-electric (ME MME) energy converter that can produce mW power in a 300μT field and operate below 100μT.
“Output power from ≤50μT magnetic fields is sufficient to operate a digital clock without charging a capacitor”, according ‘Maximizing power generation from ambient stray magnetic fields around smart infrastructures enabling self-powered wireless devices’, a paper published in Energy & Environmental Science.
IoT infrastructures devices is a potential application. 50μT was at ~200mm from a mains-powered appliance.
The device, around 40mm square and fixed at one edge, is a cantilever made from sheets of a magneto-strictive material (Fe85B5Si10 Metglas) and PZT piezoelectric material, expoxied together, with a permanent magnet stuck to the free end.
The magneto-strictive material converts the magnetic field into force which bends the structure in time to the 50 or 60Hz field, and the piezoelectric converts this bending to electricity. Meanwhile the permanent magnet is pushed back and forth by directly by the alternating field. Up to 80V peak-to-peak was produced in a 300μT field.
Beam bending from the permanent magnet in the applied field (MME) produces most of the output voltage, with the magneto-strictive material (ME) contributing ~16%, according to theoretical analysis.
“The beauty of this research is it uses known materials, but designs the architecture for basically maximising the conversion of the magnetic field into electricity,” said Priya. “This allows for achieving high power density under low amplitude magnetic fields.”
Source: electronicsweekly
