Power-Management Techniques for Wireless Sensor Networks and Similar Low-Power Communication Devices Based on Nonrechargeable Batteries

Despite the well-known advantages of communication solutions based on energy harvesting, there are scenarios where the absence of batteries (supercapacitor only) or the use of rechargeable batteries is not a realistic option. Therefore, the alternative is to extend as much as possible the lifetime of primary cells (nonrechargeable batteries). By assuming low duty-cycle applications, three power-management techniques are combined in a novel way to provide an efficient energy solution for wireless sensor networks nodes or similar communication devices powered by primary cells. Accordingly, a customized node is designed and long-term experiments in laboratory and outdoors are realized. Simulated and empirical results show that the battery lifetime can be drastically enhanced. However, two trade-offs are identified: a significant increase of both data latency and hardware/software complexity. Unattended nodes deployed in outdoors under extreme temperatures, buried sensors (underground communication), and nodes embedded in the structure of buildings, bridges, and roads are some of the target scenarios for this work. Part of the provided guidelines can be used to extend the battery lifetime of communication devices in general. 1. Introduction Energy harvesting has been an intensive research area in wireless sensor networks (WSNs). However, for many important WSN scenarios, such energy option is not feasible, and specific power-management strategies are necessary for WSN nodes that are powered by nonrechargeable batteries. For instance, when extreme temperatures are involved, the charging process of rechargeable cells is strongly impacted, as empirically demonstrated in our work. The behavior observed in Figure 1 for a specific node was repeated by many others and the network was impacted for many periods of consecutive days. Figure 1: Even with sufficient solar irradiation in some days, the efficiency of the recharging process of two NiMH cells (1.5？V nominal voltage each) is drastically impacted by extreme low temperatures (<0°C). Also, the efficiency of a solar panel, in particular a small one, is strongly impacted by snow and ice. Also, buried nodes used in wireless underground sensor networks [1] and nodes embedded inside the walls of buildings [2], in the roads, or in the internal structures of a bridge, typically cannot employ rechargeable cells. On the other hand, when nonrechargeable batteries (or primary cells) are considered for WSNs, a high operational cost is usually expected [3]. This is typically the case even for very low duty-cycle WSN