Modeling and analysis of hybrid energy storage systems for wireless sensor networks

Abstract

Various energy harvesting technologies have been employed to extend the lifetime of wireless sensor networks. However, the network lifetime is still limited by the cycle life of rechargeable batteries (RBs) for the traditional RB-only storage system. Alternatively, supercapacitors (SCs) have extremely long cycle life-on the order of millions of cycles. A hybrid storage system combining RB and SC can leverage the complementary strengths of RB and SC and therefore significantly extend the lifetime of wireless sensors. This paper presents a generalized model of energy harvesting and hybrid storage system in order to evaluate the performance of hybrid energy storage systems (HESS) with different energy source and consumer profiles. Since high energy conversion efficiency is desired for most energy harvesting systems in addition to the lifetime, the system performance is analyzed in terms of two metrics: wireless sensor lifetime and energy conversion efficiency. A tradeoff is usually observed between the two performance metrics. However, under certain circumstances some specific HESS configurations can outperform the RB-only storage system in terms of both metrics. The results also suggest that an adaptive HESS that dynamically configures the storage devices based on the energy source and consumer profiles may have better performance comparing with a fixed HESS configuration.