A wireless sensor node based on microbial fuel cell

In recent years there has been a widespread use of wireless sensor networks that found their application in complex systems where a lot of physical quantities have to be monitored. This nodes must deal with different physical quantities and must operate in different environments. In many applications the most critical aspect is the power supply, because frequently is possible to provide power supply by wires and sometimes the use of batteries is not an acceptable solution. This latter limitation occurs when the number of nodes is very high and/or the operation of battery substitution is very complex. Moreover, environmental requests for pollutant reduction and for renewable materials represents another limitation for the use power supply generation based on battery. For these reasons it can be useful to develop power sensor nodes which use energy harvested directly on the operation site, making the sensors energetically autonomous. In this paper we present an innovative sensor node based on Microbial Fuel Cells (MFCs). The implemented node proves the viability of MFC for the energy harvesting in sensor networks. This system uses the electric energy provided by the bacteria present in the soil as power supply for an ultra low power electronic system, based on a micro-controller equipped with a digital transceiver. The designed system is able to acquire data from a sensor and transmit them wirelessly. The scarcity of available energy and the limited voltages of the MFC require to design new schemes for the energy harvesting and the power supply, as well as new working modes which must satisfy the strong energy constraints.