Why harvesting is essential

The last two decades have witnessed the rapid development of miniaturized portable electronics now widely found in daily life and industry. However, the resulting power demands are challenging for battery technologies and form a critical part of the compromise between lifetime, stability, capacity, and the practical requirements of limited size for power sources.

Therefore, energy harvesting transducers, which can turn ambient forms of energy into useful electrical power, have become attractive as an alternative or supplement to batteries in portable, remote, and implantable devices.

Harvesting solutions

Given the ubiquitous presence in nature and artificial structures of mechanical vibrations, electromechanical energy harvesters using mechanical or kinetic energy created by vehicles, human motion, ocean waves, wind, and fluids, have been widely investigated.

There are various transduction mechanisms for converting mechanical/kinetic energy to electrical energy, including piezoelectric, electromagnetic, electrostatic, and triboelectric approaches. Among these methods, piezoelectric energy harvesting has become widespread.

Potential of ferroelectrics

Ferroelectric materials provide another promising material for energy harvesting. Non-linear dielectric hysteresis arising due to ferroelectric or ferroelastic switching of demains can cause a much greater flow of charge than piezoelectric transduction.

However, the challenges of nonlinearity, fatigue degradation and the difficulty of driving an electrical cycle by stress have limited any real use.

Researchers at Oxford have developed an energy harvester using ferroelectric/ ferroelastic switching that:

• Delivers greater energy per cycle than piezoelectric
• Operates at frequencies typical of structural and mechanical vibrations
• Is relatively simple/inexpensive to build and operate

Overall this overcomes many of the drawbacks of previous energy harvesting solutions and provides a real workable solution.

Commercialisation

Opportunities to license or further develop this technology are available. There may be particular applicability in industries with large vibrational energy creation, such as the automotive industry.