An Adaptive Energy-Management Framework for Sensor Nodes with Constrained Energy Scavenging Profiles

Modern energy harvesting systems for WSNs involve power scavenging sources, rechargeable batteries, and supercapacitors. Typical energy-management systems calculate/predict the remaining energy stored in a node, and associated actions are dispatched involving the networking protocols. However, long-term characteristics of the mentioned hardware components are typically neglected preventing the achievement of very long maintenance-free lifetimes (e.g., >5 years) for the nodes. In this work, a systematic analysis of this problem is provided, and an open energy-management framework is proposed which promotes (a) the nontraditional combination of primary cells, supercapacitors, and harvesting systems, (b) the concept of a distributed system inside a node, and (c) the adoption of the dual duty-cycle (DDC) operation for the WSNs. The DDC's core component is a cross-layer protocol implemented as an application-layer overlay which maintains the operation of the network under very high energy efficiency. Its trade-off is the reduction of the network throughput. Therefore, the DDC system has mechanisms that dynamically switch the WSN operational mode according to application's needs. Detailed guidelines are provided in order to allow the implementation of the solution on existing WSN platforms. The energy efficiency of the low duty-cycle mode of the solution is demonstrated by simulated and empirical results.