Sandpit: The Solar Soldier

In this age of stealth jets, nuclear munitions and guided weapons the infantryman still remains the most important weapon system. It is the infantryman who looks in the foxhole or immobilized tank to establish that the enemy is defeated. Wars end when soldiers beat down the door, not bombs. Against enemies who shelter in difficult terrain where military vehicles cannot operate easily (inaccessible to so called 'medium' and 'heavy' forces) and hide behind civilians, it is the infantryman who will effectively utilise the resource available to overcome the enemy. The infantryman has similar power requirements and expectations to his civilian counterpart, albeit his equipment is different and the environment in which he operates is far more challenging and hostile. The critical difference is that, to the soldier, loss of portable power might place his life at risk. Without power for communications, GPS, thermal imagers and other portable surveillance equipment, he is left blind and deaf to all but his immediate environment; cut off from the wider network and consequently vulnerable.Unfortunately, today soldiers heavily rely on batteries for power requirements which constitute up to 25% of their overall load (including lethal, survival, and communication). This effectively reduces their manoeuvrability, operational range and adds a significant weight and stress burden. The situation not only limits their capabilities and but also increases competition for key resources such as food and ammunition. Increasing technical capability will only increase the demand for power (it is projected that power demand will increase ten-fold by 2020).Therefore, there is a pressing need for making batteries that powers soldiers' portable electronic equipment, as light as possible. Advances in technology must be directed to eliminate, or at least greatly reduce the need for batteries. Numerous solutions such as miniature fuel cells and ammonium borate based hydrogen generators are currently under consideration. However, it is clear that most of these investigated technologies do not provide an energy sustainable solution. In addition, novel solutions must meet criteria of light-weight, flexibility, climate resistance, robustness, improved energy density/extended life, improved ergonomics and reduced encumbrance. Recognising the nature of the challenge we propose an integrated device that couples photovoltaic cells (PV) with thermoelectric (TE) power. This project will develop an integrated photovoltaic and thermoelectric power generation device on flexible substrates which work in all weather conditions. The final aim is to incorporate this flexible power generating device into the uniform of infantryman allowing IR masking capability.

In specific terms, it will be the infantryman who would initially benefit from development of the integrated PV-TE device. During the design of this project we have carefully considered the lack of known existing activity in this area and the potential benefit to infantryman and military applications. In the longer term, new research and development opportunities will open up in the area of PV and TE for exploitation in particular in civilian appliances. In the short term the UK armed forces, particularly the soldiers in the battle field would palpably benefit from the project outcome. Initially, and as it develops from fledgling status and matures, it could be that the technology is best suited to small scale, lower power applications as a minor component of the power management of a modern infantryman (for example, embedded in equipment, the helmet or small sections of the armour and uniform of the soldier). This is where the balancing with existing energy storage technologies is important as is the power (and thermal) management. More substantial power may subsequently be harvested/generated from large surface area/high temperature gradient applications utilizing large flexible substrates (the idea of a tent surface patched with PV-TE to harness solar light and heat or even the ability to capture heat, convert and store energy when needed from conflagrations, for example). The technology on a small to medium scale developed for the military arena is likely to be transferable to security/policing and in civilian markets, portable electronics and domestic appliances. In the medium to long term, if one is able to produce large quantities of the materials in a controlled, cheap way and manufacture economically, the ramifications for sustainable power generation are enormous. One might capture incident sunlight and waste heat in automotive and other transport settings to power onboard (auxiliary) systems ( remove or diminish the need for lead-acid batteries in cars, increase fuel efficiency etc). Ultimately, one might even envisage autonomous small-medium scale power supplies used in conjunction with renewables such as wind and battery stores to provide power for buildings or small communities. In this context, we must not forget the fact that that the carbon footprint of the proposed integrated PV-TE device is significantly smaller than existing devices and many other would be alternatives Beyond the device itself and its interfacing, the work also has the potential for making significant impact in the scientific development of nonlinear (and fast) control methods, and their application. The approach to nonlinear control design and application to energy harvesting is novel, and is motivated by the structure of important problems arising in the real world. There is potential for significant impact in the field chosen for experimental evaluation: harvesting energy. However, the results of the project will be generic and are believed to be widely applicable. The main innovative aspects in terms of the thermal management include the thermodynamic cycle for the whole system, which combines PV, TE, electricity and thermal storage devices, and transport phenomena across the length scales (from the energy carrier scale - photons, phonons, atoms/molecules, to thin films and superlattice, and to the bulk), In addition, recovery of energy from electricity charge / discharge processes and its transformation into power is another novel aspect.