Watermill principle applied to energy harvesting for sensor nodes in underground environments

This paper describes an energy harvesting solution for a wireless sensor node based on the watermill principle. This solution has been conceived to be employed for the realization of monitoring infrastructures to be deployed in underground water lines like aqueducts or drainage systems. In particular, this solution has been developed to be employed in a Wireless Sensor Network for the monitoring of the 'Bottini' (the ancient medieval aqueduct) running under the streets of the Historic Centre of Siena, Italy. Through the proposed harvesting system the sensor nodes are able to operate autonomously for long spans of time, allowing the real time remote monitoring of critical environmental parameters that are crucial for the preservation of this cultural site. The power generation system includes a waterwheel exploiting the water flow of the aqueduct to drive an electric motor, and a power control system, in order to manage the power accumulation and the energy consumption of the sensor node. The operation of the whole architecture has been tested in laboratory in order to prove the effectiveness of the solution and its possible use in the real scenario.