Energy Harvesting in Immersed Tunnel for Powering Wireless Sensor Nodes for Corrosion Monitoring

Collecting data from corrosion sensors in reinforced concrete structures demands intensive labor work, therefore measurements are only performed occasionally. A low-cost Wireless Sensor Network/Node (WSN) will eliminate the need for manual work and allow for continuous measurements if needed. For a distributed WSN over a large area, a concerning issue is how to power such devices. This paper, therefore, investigates the use of a reinforced concrete battery for powering WSNs. Results obtained from a real-world immersed tunnel, which has hundreds of electrochemical based corrosion sensors embedded into the reinforced concrete structure, shows that sufficient energy can be harvested from the sensors, to perform wireless transmission of corrosion data to a base-station. With an open circuit potential of 975 mV, the maximum harvested output power is
$12.4~\mu \text{W}$
, while the minimum measured output power is
$1~\mu \text{W}$
. The results also show that
$8.82~\mu \text{W}$
, with an open circuit potential of 727 mV, can be directly harvested from the reinforcement steel itself. Due to the fact that the steel volume can work as a large battery anode, a longer lifetime for the energy source is expected. Furthermore, we show that the harvested energy from the corrosion sensors will induce a galvanic corrosion rate of only
$3.7~\mu \text{m}$
/year, when transmitting the corrosion data once a month. This indicates that there is no risk to the structural integrity when using this energy source.