Ultra low power wireless and energy harvesting technologies — An ideal combination

Rapid developments of energy harvesting in the past decade have significantly increased the efficiency of devices in converting ambient free energy into usable electrical energy, thus offering opportunities to design energy autonomous systems nowadays. To achieve such energy autonomous systems, a good understanding of the harvesting capability from the source side strongly motivates the design of ultra low power (ULP) systems. In this paper, we focus on wireless body area networks (WBAN) applications and show that ULP wireless is the key technology to enable wireless autonomous transducer solutions (WATS). We first show that the current energy harvesters cannot provide sufficient power for a typical wireless sensor node based on off-the-shelf components. We then point out that the wireless module is the main component whose power consumption needs to be significantly reduced. To address this problem, we present a ULP wireless module that could satisfy the typical performance requirement of WBAN. Using this ULP wireless module, we demonstrate the feasibility of energy autonomous sensor nodes (i.e. WATS) with the current energy harvesting technology. Moreover, with this ULP module, we point out some new research trends on the miniaturization and cost reduction of energy harvesters. Therefore, we conclude that ultra low power wireless system is an ideal application for energy harvesting.