Storage-Less and Converter-Less Photovoltaic Energy Harvesting With Maximum Power Point Tracking for Internet of Things

Abstract

Energy harvesting from natural environment gives range of benefits for the Internet of Things. Scavenging energy from photovoltaic (PV) cells is one of the most practical solutions in terms of power density among existing energy harvesting sources. PV power systems mandate the maximum power point tracking (MPPT) to scavenge the maximum possible solar energy. In general, a switching-mode power converter, an MPPT charger, controls the charging current to the energy storage element (a battery or equivalent), and the energy storage element provides power to the load device. The mismatch between the maximum power point (MPP) current and the load current is managed by the energy storage element. However, such architecture causes significant energy loss (typically over 20%) and a significant weight/volume and a high cost due to the cascaded power converters and the energy storage element.This paper pioneers a converter-less PV power system with the MPPT that directly supplies power to the load without the power converters or the energy storage element. The proposed system uses a nonvolatile microprocessor to enable an extremely fine-grain dynamic power management (DPM) in a few hundred microseconds. This makes it possible to match the load current with the MPP current. We present detailed modeling, simulation and optimization of the proposed energy harvesting system including the radio frequency transceiver. Experiments show that the proposed setup achieves an 87.1% of overall system efficiency during a day, 30.6% higher than the conventional MPPT methods in actual measurements, and thus a significantly higher duty cycle under a weak solar irradiance.

Development of an Indoor Photovoltaic Energy Harvesting Module for Autonomous Sensors in Building Air Quality Applications

“…Therefore the supercapacitor almost stays in the steady state during each period in IoT experiments. The 2.4 µA dynamic leakage current of the IPEHPM (which has also been confirmed by a Keithley source-meter) makes the IPEHPM an ultra-low power consumption design with the total power consumption no larger than 4.2V × 2.4 µA = 10.1 µW, which is much lower than 140 µW consumed by the MPPT control part alone in [21].…”

“…PV energy harvesting approaches for powering applications have been compared to this work in Table IV in terms of the adoption of functional blocks of DC-DC convertor, MPPT and illumination restrictions. Compared to other powering applications, such as powering indoor low-power system with MPPT [14], using assumption of fixed indoor illumination to exempt MTTP [26] and the "storage-less and converter-less" strategy with MPPT for powering the IoT [21], the simple charger power management scheme employed in the newly designed IPEHPM provides a DC-DC convertor-free and MPPT-free solution, enabling powering IoT nodes using PV energy harvesting at all indoor illumination conditions with the minimum power consumption. Fig.12 (refer to time from 8 to 22 hours) is slightly nonlinear.…”

“…The impedance matching needs to be implemented for example by a voltage controlled oscillator (VCO) to continuously tune the switching frequency of a capacitor to adjust the load impedance (R= 1/(f×C)) of the PV energy harvester. As a result, MPPT power comsumption reported in [21] is 140 µA, which is relatively large when compared to the 160 µW maximum power produced by the adopted PV at 200 lux.…”

Internet of Things: A Scientometric Review

“…The third most growth topic was energy efficiency with 154 documents, and China and Italy as leading countries with 18 and 17 publications, respectively. Energy efficiency as an application for IoT is related in this data set with the following topics: smart buildings [128][129][130], energy harvesting [131][132][133], and RFID [134,135]. Social networks (or Social media) is another application for IoT, with 117 documents, and Italy as the leading country with 23 publications.…”

Graceful Performance Modulation for Power-Neutral Transient Computing Systems

“…The major benefit of Hibernus is that only one checkpoint is saved per power interruption, so the overheads of the scheme are much lower than for other reported works. A similar approach is recently proposed in [27] that shuts down or hibernates the microcontroller in response to the external power availability.…”