If you've ever removed the battery from a laptop, then you will know that it constitutes quite a large percentage of the total weight of the computer. Well, if you think you've got it tough lugging that laptop battery around, consider the plight of infantry soldiers – they have to carry multiple batteries to power devices such as weapons, radios, and GPS equipment, and they have to do so for hours at a time, often under very harsh conditions. Attempts to lighten the 45 to 70 kg (99 to 154 lb) loads typically carried by soldiers currently include the use of fuel cells, li-ion batteries woven into their clothing, and autonomous pack horse-like vehicles. Now, UK researchers are adding their two pence-worth, by developing wearable solar and thermoelectric power systems.

The Solar Soldier project is being led by the University of Glasgow, in collaboration with Loughborough, Strathclyde, Leeds, Reading and Brunel Universities.

The idea is that during daylight hours, robust solar photovoltaic cells would generate electricity, while at night, thermoelectric devices would do so by harnessing the temperature difference between the soldiers' bodies and the cool outside air. As with the previously-mentioned lithium batteries, it is possible that both systems could be woven into the soldiers' clothing. It's also possible that heat created in the energy-collection processes could be stored or otherwise utilized by the system.

Incorporation of "advanced energy storage devices" would ensure that electricity was continuously available.

It is hoped that the weight of the system will be up to fifty percent less than the total battery weight currently carried by soldiers. If it works as hoped, it will also allow troops to spend more time time away from their bases, as they won't have to return to recharge their batteries. The researchers even believe that the thermoelectric system, which will absorb energy across the electromagnetic spectrum, might make troops less visible to infra-red night vision equipment.

"We aim to produce a prototype system within two years," said Professor Duncan Gregory of the University of Glasgow. "We also anticipate that the technology that we develop could be adapted for other and very varied uses. One possibility is in niche space applications for powering satellites, another could be to provide means to transport medicines or supplies at cool temperatures in disaster areas or to supply fresh food in difficult economic or climatic conditions".

Funding for the Solar Soldier project is being supplied by the Engineering and Physical Sciences Research Council (EPSRC), with support from the Defence Science and Technology Laboratory (Dstl). The project is scheduled for completion in December 2011.