Sustainable development systems are based on three pillars: economic development, environmental stewardship, and social equity [...] 

/pdf/energy-harvesting-and-energy-storage-systems-3mjm1slo.pdf

Energy Harvesting and Energy Storage Systems

Since sunlight is one of the most easily available and clean energy supplies, solar cell development and the improvement of its conversion efficiency represent a highly interesting topic. Superficial light reflection is one of the limiting factors of the photovoltaic cells (PV) efficiency. To this end, interfacial layer with anti-reflective properties reduces this phenomenon, improving the energy potentially available for transduction. Nanoporous materials, because of the correlation between the refractive index and the porosity, allow low reflection, improving light transmission through the coating. In this work, anti-reflective coatings (ARCs) deposited on commercial PV cells, which were fabricated using two different Linde Type A (LTA) zeolites (type 3A and 4A), have been investigated. The proposed technique allows an easier deposition of a zeolite-based mixture, avoiding the use of chemicals and elevated temperature calcination processes. Results using radiation in the range 470–610 nm evidenced substantial enhancement of the fill factor, with maximum achieved values of over 40%. At 590 and 610 nm, which are the most interesting bands for implantable devices, FF is improved, with a maximum of 22% and 10%, respectively. ARCs differences are mostly related to the morphology of the zeolite powder used, which resulted in thicker and rougher coatings using zeolite 3A. The proposed approach allows a simple and reliable deposition technique, which can be of interest for implantable medical devices.

/pdf/anti-reflective-zeolite-coating-for-implantable-3od2ipkj.pdf

Anti-Reflective Zeolite Coating for Implantable Bioelectronic Devices

A large number of autonomous devices is nowadays supported by renewable and green energy sources. A vital sub-circuit in such systems is the power converter circuit, which should efficiently transform and store the available energy. In order to obtain the maximum efficiency under varying energy conditions, various maximum power point tracking (MPPT) methods are used. In this work a complete harvesting module with battery management and MPPT is presented, suitable for a plethora of autonomous applications. A novel, low-complexity and ultra-low power consumption design is proposed, which offers very wide operating voltage and power range with high MPPT efficiency and very low power consumption. It can be combined with different harvesters, such as thermoelectric generators or photovoltaic panels and is able to work under widely varying energy conditions. As supported by experimental results, the proposed module covers a very wide working input power range, from 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> up to 4 W, as well as a very wide input voltage range, from 650 mV up to 2.8 V with 96.5% average MPPT efficiency and a total power consumption of 3.9 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> at 3.6 V. The module relies on an embedded ultra-low power microcontroller unit (MCU) to perform the power management and MPPT operations, which can also be used for extra tasks (e.g., sensor reading). Using the proposed module, an autonomous sensor node was built, able to acquire acceleration measurements, and wirelessly communicate with a remote user in order to send an alert or stream the acquired sensor data in real time. 

Wide-Range Light Harvesting Module for Autonomous Sensor Nodes

In this work, a DC-DC converter design package - chip methodology is proposed, aiming on the successful codesign of the on-chip DC-DC converter with the package wire bonds and the printed-circuit-board (PCB) parasitic elements. The proposed methodology enables rapid design cycle while providing high accuracy results, as bond wires and PCB traces are represented with SPICE equivalent circuit models extracted with 2.5D finite-element modeling. A light energy harvesting DC-DC boost converter, used as product vehicle, is designed and implemented in a 0.18 μm CMOS standard process. Measurements of the fabricated packaged chip show the significant contribution of the package and confirm the accuracy and design cycle speed-up of the proposed chip-package-board co- design methodology. 

Chip-Package-Board codesign Methodology for Energy Harvesting DC-DC Boost Converters

A large number of autonomous devices is nowadays supported by renewable and green energy sources. A vital sub-circuit in such systems is the power converter circuit, which should efficiently transform and store the available energy. In order to obtain the maximum efficiency under varying energy conditions, various maximum power point tracking (MPPT) methods are used. In this work a complete harvesting module with battery management and MPPT is presented, suitable for a plethora of autonomous applications. A novel, low-complexity and ultra-low power consumption design is proposed, which offers very wide operating voltage and power range with high MPPT efficiency and very low power consumption. It can be combined with different harvesters, such as thermoelectric generators or photovoltaic panels and is able to work under widely varying energy conditions. As supported by experimental results, the proposed module covers a very wide working input power range, from 40 μW up to 4 W, as well as a very wide input voltage range, from 650 mV up to 2.8 V with 96.5% average MPPT efficiency and a total power consumption of 3.9 μW at 3.6 V. The module relies on an embedded ultra-low power microcontroller unit (MCU) to perform the power management and MPPT operations, which can also be used for extra tasks (e.g., sensor reading). Using the proposed module, an autonomous sensor node was built, able to acquire acceleration measurements, and wirelessly communicate with a remote user in order to send an alert or stream the acquired sensor data in real time.

https://ieeexplore.ieee.org/ielx7/6287639/9668973/09739712.pdf

Wide-range light harvesting module for autonomous sensor nodes

Integrated DC - DC converter design methodology for design cycle speed up

This work introduces a light harvesting system with battery management. In contrast to relevant solutions that operate in limited ranges, the proposed system covers a wide operating input power range from 10 uW up to 300 mW. Specifically, experimental results highlight that, combined with a 73 × 94 mm flexible light harvester, it can harness light in a range from 50 LUX (indoor lighting) up to 120,000 LUX (outdoor lighting). The introduced system consists of a boost converter and an ultra-low power microcontroller (MCU). The MCU performs Global Maximum Power Point Tracking (GMPPT), using a resistor-free time-based input power sensing method, to calculate the input power of the converter, which does not interfere with the operation of the boost converter. The efficiency of the GMPPT system was evaluated with detailed experimentation, where we achieved 99.75% average GMPPT tracking efficiency while consuming only 73.5 uW at 4.2 V.

73.5 uW Indoor-Outdoor Light Harvesting System with Global Maximum Power Point Tracking

This work presents an ultra-low-power CMOS supercapacitor storage unit suitable for a plethora of low-power autonomous applications. The proposed unit exploits the unregulated voltage output of harvesting circuits (i.e., DC-DC converters) and redirects the power to the storage elements and the working loads. Being able to adapt to the input energy conditions and the connected loads’ supply demands offers extended survival to the system with the self-startup operation and voltage regulation. A low-complexity control unit is implemented which is composed of power switches, comparators and logic gates and is able to supervise two supercapacitors, a small and a larger one, as well as a backup battery. Two separate power outputs are offered for external load connection which can be controlled by a separate unit (e.g., microcontroller). Furthermore, user-controlled parameters such as charging and discharging supercapacitor voltage thresholds, provide increased versatility to the system. The storage unit was designed and fabricated in a 0.18 um standard CMOS process and operates with ultra-low current consumption of 432 nA at 2.3 V. The experimental results validate the proper operation of the overall structure.

An Ultra-Low-Power CMOS Supercapacitor Storage Unit for Energy Harvesting Applications

Earthquake monitoring has always been a vital application for human safety. This work proposes an implementation of an instrumentation node for earthquake monitoring that combines the recent advances in portable instrumentation systems (e.g. IoTs), along with the latest development in MEMS sensors. The focus is on creating a measuring node optimal for such a case study, meaning high accuracy measurements, smart and adaptive functionality and minimal energy consumption.

Earthquake instrumentation node with MEMS sensors

The paper proposes a simple and low-cost technique of a power measuring system for the characterization and evaluation of harvesters, harvesting circuits or switching converters. The system is a lab instrument and it can measure the power that is drawn from or provided to it, by measuring the time duration for a specific voltage difference to occur on a capacitor of known capacitance (V-T). This way, it is easier to measure low power values in comparison with the most straightforward method that depends on voltage and current measurements. The system is using only commercially available discrete components and is optimized for measuring power in the uW range with uW accuracy as supported with experimental results. It was tested to compare different solar harvesting circuits and to measure the available power levels for various light intensities.

Konstantinos Kozalakis

Papers

Integrated DC - DC converter design methodology for design cycle speed up

73.5 uW Indoor-Outdoor Light Harvesting System with Global Maximum Power Point Tracking

An Ultra-Low-Power CMOS Supercapacitor Storage Unit for Energy Harvesting Applications

Earthquake instrumentation node with MEMS sensors

Energy harvesting circuits power measuring system