Software Controlled Low Cost Thermoelectric Energy Harvester for Ultra-Low Power Wireless Sensor Nodes

Abstract

General hardware architecture of an energy-harvested wireless sensor network node (EH-WSN) can be divided into power, sensing, computing and communication subsystems. Interrelation between these subsystems in combination with constrained energy supply makes design and implementation of EH-WSN a complex and challenging task. Separation of these subsystems into distinct hardware modules simplifies the design process and makes the architecture and software more generic, leading to more flexible solutions. From the other hand, tightly coupling these subsystems gives more room for optimizations at the price of increased complexity of the hardware and software. Additional engineering effort could be justified by a smaller, cheaper hardware, and more energy-efficient a wireless sensor node. The aim of this paper is to push further technical and economical boundaries related to EH-WSN by proposing a novel architecture which-by tightly coupling software and hardware of power, computing, and communication subsystems-allows the wireless sensor node to be powered by a thermoelectric generator working with about 1.5 • C temperature difference while keeping the cost of all electronic components used to build such a node below 9 EUR (in volume).

An Input Power-Aware Efficiency Tracking Technique With Discontinuous Charging for Energy Harvesting Applications

“…This result can be shown mathematically by first multiplying I OUT-avg in (8) and V OUT in (9) to find the output power as shown in (11). Following that, the power losses in (4) and 10, as well as P OUT in (11), are substituted into the PCE equation in (5). The resulting PCE for discontinuous charging is shown in (12).…”

“…For many applications, it is not necessary to sense ambient power frequently. This is because WSN nodes only turn on briefly to sense and transmit data, and remain in standby for the rest of the time [11], [12], [31]. Hence, average power losses due to the sensing operation are negligible, as seen in the simulation results in Section V. Finally, this sensing method requires that the input be disconnected from the converter during the time required to sense the current.…”

“…Many wearable WSNs define their communication protocol using the IEEE 802.15.4 standard for low data-rate, lowpower, and low-complexity short-range radio frequency transmissions [5]. One example is the GreenNet protocol [11], [19]. In this section, the proposed technique is applied to the GreenNet-based WSN implementation described in [11] for indoor environments, to show how it enables energy autonomy in a scenario where that would not be possible otherwise.…”

“…One example is the GreenNet protocol [11], [19]. In this section, the proposed technique is applied to the GreenNet-based WSN implementation described in [11] for indoor environments, to show how it enables energy autonomy in a scenario where that would not be possible otherwise.…”

“…1, consume tens of mA when active. Hence, WSN nodes typically remain in sleep mode for more than 99% of the time, allowing the average power to approach values consumed during sleep [11]. For example, the WSN in [12] consumes 10.27mW and 29.52mW during sensor polling and radio transmission, respectively.…”