Quasi-self-powered Infrastructural Internet of Things: The Mackinac Bridge Case Study

Autonomous, continuous and long-term monitoring systems are required to prognosticate failures in civil infrastructures due to material fatigue or extreme events like earthquakes. While current battery-powered wireless sensors can evaluate the condition of the structure at a given instant of time, they require frequent replacement of batteries due to the need for continuous or frequent sampling. On the other hand, self-powered sensors can continuously monitor the structural condition without the need for any maintenance; however, the scarcity of harvested power limits the range at which the sensors could be wirelessly interrogated. In this paper, we propose a quasi-self-powered sensor that combines the benefits of self-powered sensing and with the benefits of battery-powered wireless transmission. By optimizing both of the functionalities, a complete sensor system can be designed that can continuously operate between the structure's maintenance life-cycles and can be wirelessly interrogated at distances that obviates the need for taking the structure out-of-service. As a case study, in this paper we present the design considerations involved in prototyping quasi-self-powered sensors for deployment on the Mackinac Bridge in northern Michigan, with a target operational life span greater than 20 years.