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ENERGY HARVESTING

ENERGY HARVESTING
By John Reed

Opening a new range of possibilities for military systems.

28 Apr 11. The term ‘energy harvesting’ is generally defined as the conversion of ambient energy to electricity in order to power small or mobile devices. As a part of the much broader green revolution it is specifically concerned with rationalising the need for batteries in such devices, by harnessing a range of sources including heat, light and movement. Current activity in the energy harvesting market embraces specific techniques for harvesting movement, heat and light, and extends to include the development of harvesting tolerant electronics, biobatteries and supercabatteries (ultracapacitors). This brief overview will focus on those developments considered most likely to offer relatively near-term benefits to the defence community.

Mature Technology

The probability is that evolving military requirements for energy harvesting will lie at the ‘top end’ of what is already a substantial mature market – albeit still characterised by first generation solutions. A report from IDTechEx, “Energy Harvesting 2010-2020” forecasts a market of over two billion dollars in 2016 for harvesting elements, excluding power storage and electronic interfaces. The authors project sales of 10 billion energy harvesting devices in 2020 with harvesting on wireless sensors accounting for only a modest part of this number but with sophistication that may justify premium pricing. Such sophistication is evident in an ITT wireless module that gathers information from sensors on critical equipment in a manufacturing arena and enables manufacturing equipment problems to be identified and addressed before they impact production. Harvesting is via vibration of the machines, conditioned and then stored in thin film batteries. This energy powers processors that collect and process critical information and transmit it to a computer every five seconds where it is analysed and can notify the process owner of changing conditions. The wireless system is powered by the energy generated by the process itself which simplifies the installation and rollout of new network nodes to every machine.

Military Requirements

In the near term it is likely that portable military equipment could provide the economies of scale sought by manufacturers and users alike. Military demands for portable power sources have historically been met by adapting mature technology. Advances in technology for applications in the commercial marketplace have been successfully migrated to the military but arguably the diversity of equipment and the managerial realities of logistic processes have kept the military user behind the developmental curve. Batteries are typically only used once per mission – if only to minimise the risks of battery failure. One visible outcome is that the estimated cost of shipping batteries to US Army units in Afghanistan is put at between $3,000 to $4,000/KwH.

Typically, operational experience drove the US Army Power Source Roadmap towards a set of objectives that envisaged the provision of hybrid batteries for use by the ‘future warfighter’ complemented by wearable re-fuellable sources that might be based on fuel cell, microturbine or thermal electric technology.

In practice many legacy systems were characterised by features that did not readily lend themselves to radical changes in technology. The extent of the problem may be gauged from the fact that that the weight that soldiers are customarily required to carry is usually 50-60kg of which batteries account for 10-25kg. Moreover in 2007 US Army medics were called upon to treat a total of 257,000 orthopaedic injuries – a high proportion of which had ‘load-associated’ origins.

Ergonomics, Textiles and Energy Harvesting

The planned introduction of a new generation of Future Soldier Systems has provided opportunities to reassess the equipment required to enhance the situational awareness of

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