Design issues for energy harvesting enabled wireless sensing systems

Key technologies for the deployment of Wireless Sensor Networks are reduction of manufacturing and management cost. Even though many efforts have been made to reduce the price, size and power consumption of each sensor node, many architectural issues remain unsolved. We are developing a Wireless Sensor Networks platform relying on energy harvesting technologies. Solar cell is one of the most attractive power harvesters for Wireless Sensor Networks. However, when a solar cell is used in real environment, there are considerable variations of the amount of energy depending on the place. Our preliminary experiment shows that a solar cell placed at the window side of the office environment produced energy 100 times more than the one placed under the desk did. This large difference results from the locality of the environmental energy and thus there is a limitation to solve such a problem just with improvement of software. Instead, we are trying to fill these issues by the architectural design of the system and coordination of the nodes. In this paper, we show a concept of an energy transfer scheme which will be required to fill the energy differences between wireless sensor nodes.