||Tracking the position of humans within a building usually implies significant infrastructure investment; also devices are usually too high in weight and volume to be integrated into garments. We propose a system that relies on existing infrastructure (and therefore requires little infrastructure investment) and is based on a sensor that is low cost, low weight, low volume and can be manufactured to have similar characteristics to everyday clothing (flexible, range of colours). The proposed contribution to this area is based on solar modules. This paper investigates their theoretical and practical characteristics in a simplified scenario. Forward motions on the large scale up to 10m long as well as small scale motions related to the human body on the spot of less than 10cm are investigated. Models with accuracy in the centimetre range have been achieved. The case that energy harvesting technology could be used for both sensing and providing power is thus strengthened.