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Energy harvesting using magnetostriction

Energy harvesting is the creation of off-grid electricity where it is needed using ambient energy, from sunshine to vibration or temperature difference. 

There are the very successful forms of energy harvesting and there are the basket cases of negligible commercial success – little more than research curiosities. 

IDTechEx Research has just completed a thorough look at the entire sector, building on over 6 years of prior research on the topic.   

We have found significant new progress in a number of technologies, including magnetostriction energy harvesting. First, let's look at the current progress with the more popular energy harvesting technologies. A full analysis of the whole subject is given in the new IDTechEx report, Energy Harvesting: Off-grid 

Renewable Power 2015-2025, which encompasses all forms of energy harvesting from microwatts to tens of kilowatts in power output and gives forecasts for the leading ones.   

Current successes   

Success currently lies in electrodynamics, which started with the humble bicycle dynamo and small wind turbine and progressed to a host of things from regenerative braking in vehicles to kites and floors generating electricity. 

For example, Pavegen, a supplier of tiles that generate electricity when stood on, even believe that it can one day use electrodynamics to make two millimetre carpet underlay that generates power from footfall.   

Low cost photovoltaic materials are starting to be taken seriously, such as perovskites, as covered in the IDTechEx Research report The Rise of Perovskite Solar Cells 2015-2025.   

Thermodynamics has a bright future powering sensors and adjusting heating radiator valves remotely followed by, many believe, creating electricity from vehicle engines. Transparent and flexible thermoelectrics have been demonstrated. 

IDTechEx expects thermoelectric energy harvesting to overtake piezoelectric energy harvesting in market value.   There is even a new probability that basket case energy harvesting methods may prove useful after all. Take magnetostriction as an example.   

Radically new magnetostriction   

Traditionally magnetostriction has come from brittle magnetic alloys that hum in a transformer. It has been noted that the reverse – their bending or compression – could in principle create electricity but that seems an unreliable, weak alternative to electrodynamics. 

However, in 2015, the materials scientists at the University of Maryland and Temple University in the USA have stumbled across a totally new phenomenon that may change all that. They have created potentially low cost "non Joulian" magnets that expand when being magnetised and think this may be key to widespread adoption of magnetostrictive energy harvesting. Whether that means we move from microwatts to watts or more remains to be seen.   

About 175 years ago, physicist James Prescott Joule (the same person after which the unit of work energy, the joule, is named) discovered magnetostriction, where iron-based magnetic materials minutely distort in shape, but not in volume, when placed in a magnetic field. 

Since then, it has been pretty much accepted that this was the way all magnetic materials behaved but the new work conducted on iron alloys (including iron-gallium, iron-germanium, and iron-aluminum) has resulted in the observation of a property never before encountered in magnetic materials: a change in volume whilst in the process of magnetisation. As this was fundamentally different to the phenomenon discovered by Joule, the new magnets are called "non-Joulian magnets."   

"Our findings fundamentally change the way we think about a certain type of magnetism that has been in place since 1841," says Dr Harsh Deep Chopra, Professor and Chair of Mechanical Engineering at Temple University. 

"We have discovered a new class of magnets, which we call 'Non-Joulian Magnets', that show a large volume change in magnetic fields. Moreover, these non-Joulian magnets also possess the remarkable ability to harvest or convert energy with minimal heat loss."   

To create these new magnetic materials, professor of materials science and engineering Manfred Wuttig, and Chopra heated certain iron-based alloys in a furnace to approximately 760º C for 30 minutes, then quickly cooled them to room temperature. 

Once cooled, the new materials demonstrated the non-Joulian behavior. In studying the newly formed materials under a microscope, the team was amazed to find tiny cell-like structures that appeared to be responsible for the strange non-Joulian magnetostriction they observed.   

"The response of these magnets differs fundamentally from that likely envisioned by Joule," said Professor Wuttig. 

"He must have thought that magnets respond in a uniform fashion. Knowing about this unique structure will enable researchers to develop new materials with similarly attractive properties."   


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