Integrated Energy Harvesting Research Articles

A 1500 Revolutions Per Minute 3D-Printed Bearing-Structural Triboelectric Nanogenerator for Self-Powered Intelligent Vehicle Monitoring System

Maintaining a high working frequency is critical one of technical solutions to the triboelectric nanogenerator (TENG) for improving its output power. Herein, we report a 3D-printed bearing-structural TENG (BS-TENG), which achieved a speed breakthrough of nearly 1500 rpm for the first time by 3D-printing diversified design whereby to enable even higher working frequency. Integrated BS-TENGs network can be utilized as both rotational energy harvester and self-powered high speed sensing system for vehicle temperature and speed real-time monitoring. It was vital that one unit delivers a peak power of 0.96 mW under an external load of 8 MΩ. Moreover, a capacitor of 1000 µF was charged by integrated energy harvester to achieve voltage of 4 V that just take nearly 80 s under rotational speed of 600 rpm. Furthermore, the results confirmed that the accuracy of the self-powered vehicle speed monitoring could more than 99% level under a wide range of 100 to 1500 rpm. This study not only presents a new approach for upgrading the working frequency of TENGs, but also provides new opportunities for TENGs in intelligent vehicle autonomous driving system.

Integrated photo-rechargeable supercapacitors formed via electrode sharing

Herein, we report integrated photo-rechargeable supercapacitors (IPSs) composed of the inverted organic solar cell (iOSC) and solid-state supercapacitor (SC), enabling a high-performance self-power pack. The iOSC serves as a self-power source while the SC functions as energy storage, and both share an indium-tin-oxide (ITO) electrode that affords improved charge propagation across the devices. Combining the energy harvesting and storage devices in this way significantly alleviates the limitations of each device. The power fluctuation of the iOSC can be reimbursed by the SC, thus allowing for a stable energy output. Moreover, the SC is frequently charged by the iOSC during the daytime, thereby greatly reducing the charging time and avoiding a complete discharge as well. When the SC of the IPS is charged by the iOSC under AM 1.5 G of illumination, the overall energy conversion-storage efficiency is ca. 2.27%. Our work provides an effective strategy for further study to fabricate a small, lightweight, portable/wearable self-power pack by integrating energy harvesting and energy storage devices into a single structure.

Microwatt power management: challenges of on-chip energy harvesting

IoT devices become more and more popular which implies a growing interest in easily maintainable and battery-independent power sources, as wires and batteries are unpractical in application scenarios where billions of devices get deployed. To keep the costs low and to achieve the smallest possible form factor, SoC implementations with integrated energy harvesting and power management units are a welcome innovation.On-chip energy harvesting solutions are typically only capable of supplying power in the order of microwatts. A significant design challenge exists for the functional blocks of the IoT-SoC as well as for the power management unit itself as the harvested voltage has to be converted to a higher and more usable voltage. Simultaneously, the power management blocks have to be as efficient as possible with the lowest possible quiescent currents.In this paper, we provide a look at on-chip microwatt power management. Starting with the energy-harvesting from RF power or light, we then show state-of-the-art implementations of ultra-low power voltage references and ultra-low power low-dropout regulator (LDO) designs.

Comprehensive evaluation of a photovoltaic energy harvesting system in smart clothing for mountain rescuers

A photovoltaic energy harvesting system has been developed for application in smart clothing for mountain rescuers. The generator has been assembled from flexible organic photovoltaic modules and integrated with a specially designed clothing. A power conversion and storage system has been prototyped, providing a USB standard output for supplying active clothing components or standalone devices. The clothing with the integrated energy harvester has been comprehensively tested in respect of both electrical performance and ergonomics. An electrical test methodology has been developed, based on the characteristics recorded in the field and their simulation in a laboratory. This enabled repetitive tests under identical real-life conditions. Ergonomic tests involved diverse physical activities performed by mountain rescuers, simulating their true operations, but conducted in a training room for the sake of standardisation. The prototype system has substantially extended the operating time of a realistic load (equivalent to a smartphone) by providing an extra 1.91 Wh of energy in the best case of irradiance in autumn and 0.77 Wh for a typical case with varying irradiance and temperature. Ergonomics ratings by end users have been good to very good and they have been generally in favour of using power harvesters integrated with their clothing.

A Review of Solar Energy Harvesting Electronic Textiles.

An increased use in wearable, mobile, and electronic textile sensing devices has led to a desire to keep these devices continuously powered without the need for frequent recharging or bulky energy storage. To achieve this, many have proposed integrating energy harvesting capabilities into clothing: solar energy harvesting has been one of the most investigated avenues for this due to the abundance of solar energy and maturity of photovoltaic technologies. This review provides a comprehensive, contemporary, and accessible overview of electronic textiles that are capable of harvesting solar energy. The review focusses on the suitability of the textile-based energy harvesting devices for wearable applications. While multiple methods have been employed to integrate solar energy harvesting with textiles, there are only a few examples that have led to devices with textile properties.

Energy harvesting for jet engine monitoring

Abstract Sensors that provide critical information about jet engine performance are widely installed on static components but are rarely found on rotors because of their inaccessibility and extremely high rotation speeds. We present a new monitoring method, integrating energy harvesting technology with wireless sensors to achieve real-time self-powered engine monitoring. Energy harvesters, used to generate power from ambient vibration, are sustainable alternatives to batteries for achieving self-sustained long-term operation of electronic devices. By utilising structural nonlinearity, force amplification mechanism, and the piezoelectric effect, we show a 22.52-g energy harvester capable of high power output (78.87 mW), broad working bandwidth (22.5 Hz), and strong reliability (2100 RPM). Our approach breaks limitations from wired connections that are weighty and vulnerable to failures. We theoretically and experimentally analyse the nonlinear responses and demonstrate the harvester by constantly lighting 112 LEDs and a self-powered wireless sensor system in a jet engine. This work paves a new way for developing future monitoring systems for advanced jet engines and other rotating machinery applications.

A chemically self-charging aqueous zinc-ion battery

Self-charging power systems integrating energy harvesting technologies and batteries are attracting extensive attention in energy technologies. However, the conventional integrated systems are highly dependent on the availability of the energy sources and generally possess complicated configuration. Herein, we develop chemically self-charging aqueous zinc-ion batteries with a simplified two-electrode configuration based on CaV6O16·3H2O electrode. Such system possesses the capability of energy harvesting, conversion and storage simultaneously. It can be chemically self-recharged by the spontaneous redox reaction between the discharged cathode and oxygen from the ambient environment. Chemically self-recharged zinc-ion batteries display an initial open-circuit voltage of about 1.05 V and a considerable discharge capacity of about 239 mAh g−1, indicating the excellent self-rechargeability. Impressively, such chemically self-charging zinc-ion batteries can also work well at chemical or/and galvanostatic charging hybrid modes. This work not only provides a route to design chemically self-charging energy storage, but also broadens the horizons of aqueous zinc-ion batteries.

Electrode Effects on Flexible and Robust Polypropylene Ferroelectret Devices for Fully Integrated Energy Harvesters.

This work presents a characterization study of the electrode interface in polypropylene ferroelectret nanogenerators. An emphasis is made on the comparison of carbon nanotube fiber electrodes with traditional metallic thin film electrodes. Multiple experiments were performed on samples with the same electrode dimensions for a range of applied pressures. Results showed higher open-circuit voltage peak values for the thin film metal electrodes, regardless of the applied pressure. Interestingly, the difference in short-circuit current values between metal and carbon nanotube-based fiber electrodes was not as significant. The carbon nanotube fiber electrode was further investigated by post-treating the fiber with acetone and comparing the results with untreated carbon nanotube film electrodes and thin film metal electrodes. In an effort to enable a monolithic integration of ferroelectret energy harvesters with flexible energy storage elements, this work also presents studies on generation and leakage of induced free charge in the electrodes of flexible ferroelectret energy harvesters. It was found the current leakage through parasitic elements is a faster process than dipole relaxation in the polypropylene film. Finally, an electrode reliability study shows no significant difference in the electrical output of the devices with metallic thin film electrodes after single folding but shows a significant deterioration after crumpling; meanwhile, these processes had no effect on the performance of similar devices with carbon nanotube fiber-based electrodes.

A parallel auto-adaptive topology for integrated energy harvesting system

This work presents a new topology for a thermal and RF energy harvesting system for integrated circuits. The system improves two circuit parameters: low start-up voltage and high-efficiency energy extraction. The high efficiency is achieved with a new parallel auto-adaptive DC-DC converter with a charge-pump based design to collect thermal energy. The low start-up voltage is possible with the assistance of a Radio-Frequency harvester circuit, resulting in a new hybrid energy harvesting architecture. The circuit was designed and fabricated with a CMOS 180 nm process, using an active area of 954 μm × 341 μm. The measurement results show an 87% peak efficiency with a maximum regulated output voltage of 2 V. The minimum operating input voltage is 250 mV without the start-up circuit and 30 mV with the RF start-up circuit at 33 KHz of switching frequency.

Researches on MEMS thermoelectric-photoelectric integrated energy harvester with metal heat sink

We propose a harvester based on the micro-electro-mechanical system (MEMS) and complementary metal-oxide-semiconductor (CMOS). The harvester has been integrated on a silicon substrate. In order to achieve an improved performance, the fabrication of the proposed harvester in this paper is amended to reduce the thermal resistance between the device and the environment. The device consists of two parts: thermoelectric and photoelectric. A metal heat sink made with gold is utilized at the centre of thermopiles to optimize the heat path and to enhance the thermal coupling between the harvest and surroundings. The output voltage and power are measured by a Keithley 2700. The results show that the output voltage factor and output power factor of the thermoelectric harvester are 0.5763 V cm−2·K−1 and 2.757 × 10−2 μW·cm−2·K−2, respectively. In addition, the photoelectric harvester is realized by back-contact technology. The light receiving surfaces can be both the top and bottom side, and the corresponding efficiencies of the photoelectric harvester are 5.446% and 0.2749%, respectively.

A narrow-band and ultra-low-power 433 MHz wake-up receiver

For the design of wireless sensor nodes (WSNs) the inclusion of a wake-up receiver becomes interesting as soon as an asynchronous bidirectional communication between the WSN and its host is mandatory, to e.g. reprogram the WSN or to trigger the delivery of data. For these purposes the use of the WSNs standard RF interface is not suitable in most cases, as the high power consumption of the same may drain the WSNs battery or overload the capabilities of an integrated energy harvesting module. To solve this principal conflict between flexibility and power consumption, we present the design and characterization of an ultra-low-power wake-up receiver. The concept is based on an optimized modulation/demodulation concept, to achieve a high RF sensitivity and narrow-band operation at the same time. The final device works in the license-free 433 MHz frequency band, with a high RF sensitivity of -63.4 dBm, an ultra-low power consumption of 8.7 µW, and with a low supply voltage of 2 V only.

An Integrated SiGe Based Thermoelectric Generator with Parabolic Trough Collector Using Nano HTF for Effective Harvesting of Solar Radiant Energy

An integrated thermoelectric generator (TEG) with the parabolic trough collector (PTC) for renewable power generation system has been investigated under different solar irradiations, heat transfer fluids (HTF) and TEG materials. In this research work, the idea of using a TEG for effective heat recovery from a solar collector is implemented in an innovative approach. The heat absorbed from PTC is supplied with the hot junction of the TEG and the cold junction being maintained less than surrounding temperature with cold water using an earthen pot surrounded by a thermocole. The temperature gradient between the hot and cold junction of TEG establishes the amount of power extraction. The high temperature absorption is enhanced by the use of synthetic HTF and nanofluids with nano particles (Alumina, Silica, TiO2 and CuO), which increases the effective harvesting of solar radiant energy. Moreover, the research work focuses to find the most efficient material for the hot and cold part of TEG. Silicon Germanium (SiGe) material for fabrication of TEG is suggested which has good ZT (figure of merit) values and electrical profile as compared to conventional Bismuth Telluride (Bi2Te3) under different solar irradiation conditions has been evaluated. The mathematical modelling of this proposed integrated energy harvesting system has been developed. The modelling and array configuration of TEG has been analysed with conventional Bi2Te3 and proposed SiGe materials. The performance of TEG with a PTC integrated system has been experimentally tested and the obtained results illustrate the better effective harvesting of solar energy for electrical power generation.

Advances in the development of power supplies for the Internet of Everything

AbstractThe Internet of Everything (IoE), which aims to realize information exchange and communications for anything with the Internet, has revolutionized our modern world. Serving as the driving force for devices in the IoE network, power supply systems play a fundamental role in the development of the IoE. However, due to the complexity, multifunctionality and wide‐scale deployment of diverse applications, power supply systems face great challenges, including distribution, connection, charging technologies, and management. In this review, some challenges and advances in the development of both power supply systems and their units are presented. In the overall system‐level field, establishing sustainable and maintenance‐free power supply systems through wireless connections, efficient power management and integrated energy harvesting and storage systems is highlighted. Additionally, the main performance metrics of power supply units are discussed, including energy density, service life, and self‐power ability. In addition, some directions of power quality assessment for both the system and unit levels of power supply systems are presented, aiming to provide insight into the future development of high‐performance power supply systems for the IoE.

Fully Integrated Low-Power Energy Harvesting System With Simplified Ripple Correlation Control for System-on-a-Chip Applications

This paper presents a fully integrated energy harvesting (EH) system that even includes an input capacitor and a simplified ripple correlation control (RCC) maximum power point tracking (MPPT) method for low-power system-on-a-chip applications. The proposed system implements the RCC block with a charge pump (CP) that can be integrated into the chip, instead of the inductive switching converter that is commonly used for conventional RCC methods. The CP changes the input impedance by changing the size of the flying capacitor to ensure system reliability. The simplified RCC method is implemented using a low-power analog divider operated in a subthreshold region. A test chip fabricated in a 180 nm CMOS process achieves over 95% MPPT accuracy with a very small input capacitor of 5 nF and a low quiescent current of 2.6 μA. The chip size of the entire system is 8 mm2, and the harvested power range is from 6 μ W to 1.4 mW.

A Novel Arch‐Shaped Hybrid Composite Triboelectric Generator Using Carbon Fiber Reinforced Polymers

With the diminution of energy sources and the need for using cleaner energy, alternatives must be found. In addition, the desire to supply energy to autonomous low‐power electronics has spurred interest in triboelectric materials. An arch‐shaped hybrid carbon fiber reinforced polymer (CFRP) composite triboelectric device is fabricated, which employs a curved upper copper electrode and a flat lower polyimide layer, both of which are combined with CFRP materials. This device can be used as a triboelectric energy harvesting source for self‐powered sensors that can be combined with fiber reinforced composite‐based structures. A voltage up to 300 mV is produced, which can charge a capacitor to 250 mV. The ability to combine triboelectric and CFRP materials provides a new approach to integrate energy harvesting into engineering structures and manufacture robust harvesting devices.

HYREP: A Hybrid Low-Power Protocol for Wireless Sensor Network

In this paper, a new hybrid routing protocol is presented for low power Wireless Sensor Networks (WSNs). The new system uses an integrated piezoelectric energy harvester to increase the network lifetime. Power dissipation is one of the most important factors affecting lifetime of a WSN. An innovative cluster head selection technique using Cuckoo optimization algorithm has been used in the designed protocol. The residual energy of the nodes and the distances to the sink were used in the threshold calculations, besides to take advantage of the relay node for communication. A hybrid method using the optimized routing protocol and the integrated energy harvester results in 100% increase in the network lifetime compared to recent clustering-based protocols. The simulations results using MATLAB indicate that energy consumption was been decreased by more than 40%.

Dual-Structured Flexible Piezoelectric Film Energy Harvesters for Effectively Integrated Performance.

Improvement of energy harvesting performance from flexible thin film-based energy harvesters is essential to accomplish future self-powered electronics and sensor systems. In particular, the integration of harvesting signals should be established as a single device configuration without complicated device connections or expensive methodologies. In this research, we study the dual-film structures of the flexible PZT film energy harvester experimentally and theoretically to propose an effective principle for integrating energy harvesting signals. Laser lift-off (LLO) processes are used for fabrication because this is known as the most efficient technology for flexible high-performance energy harvesters. We develop two different device structures using the multistep LLO: a stacked structure and a double-faced (bimorph) structure. Although both structures are well demonstrated without serious material degradation, the stacked structure is not efficient for energy harvesting due to the ineffectively applied strain to the piezoelectric film in bending. This phenomenon stems from differences in position of mechanical neutral planes, which is investigated by finite element analysis and calculation. Finally, effectively integrated performance is achieved by a bimorph dual-film-structured flexible energy harvester. Our study will foster the development of various structures in flexible energy harvesters towards self-powered sensor applications with high efficiency.

Cognitive Relaying With Wireless Powered Primary User

Integrating energy harvesting into cognitive radio networks can promisingly sustain the operations of energy-limited terminals and improve the spectral efficiency. Traditionally, secondary users (SUs) are normally assumed to harvest energy from the transmissions of primary users (PUs). In contrast, we consider an alternative scenario with a PU harvesting energy from its access point (AP) and SUs, and propose a cognitive relaying scheme. Each time block is divided into two periods. In the first period, AP transfers wireless energy to PU, and meanwhile, an SU and its relay cooperatively transmit secondary data using peak powers, where the resultant interference can help boost the amount of energy harvested by PU. In the second period, PU transmits data to AP using the harvested energy, and meanwhile, SU and its relay continue to cooperatively transmit secondary data using controlled powers under the interference constraint at AP. We analyze the throughput of both the two systems and reveal the impacts of key parameters. Numerical results show that our scheme can greatly improve the system spectral efficiency while satisfying the interference constraint of PU.

A 1.02 μW Battery-Less, Continuous Sensing and Post-Processing SiP for Wearable Applications.

Improving system lifetime and robustness is a key to advancing self-powered platforms for real world applications. A complete self-powered, battery-less, wearable platform requires a microwatt-power system-on-chip (SoC), operating reliably within this budget, capable of surviving long periods without charging, and recovering from power loss to its previous state. To meet these requirements, we designed a wireless sensing heterogeneous system-in-package (SiP) containing an ultra-low power (ULP) SoC, a non-volatile boot memory (NVM), and a 2.4 GHz frequency shift key (FSK) radio, all integrated with custom ULP interfaces. The SoC includes a fully integrated energy harvesting platform power manager (EH-PPM) to power the SiP and other commercial sensors. The EH-PPM is designed for small loads and powers the SoC and peripherals while drawing very low operating current. The SoC also includes a digital system data-flow for sensing applications, an analog front end for ECG signal acquisition, and a cold-boot management system (CBMS) for boot and recovery from the NVM. The CBMS enables integration of the SoC with the ULP NVM to create a wearable formfactor, self-powered system capable of recovery from power loss. The SoC also includes a radio interface tightly integrated with a compression accelerator to efficiently communicate with the FSK transmitter and reduce the FSK's transmission time. This tight integration between accelerators on the SoC and peripherals is another feature that reduces the system's power consumption by reducing the code size and number of memory accesses required to perform an operation. The SoC consumes 507 nW average power while running free-fall detection, 519 nW average power while measuring ambient temperature, and 1.02 μW during continuous ECG monitoring and post-processing.

A design framework for realizing multifunctional wings for flapping wing air vehicles using solar cells

Long flight durations are highly desirable to expand mission capabilities for unmanned air systems and autonomous applications in particular. Flapping wing aerial vehicles are unmanned air system platforms offering several performance advantages over fixed wing and rotorcraft platforms, but are unable to reach comparable flight times when powered by batteries. One solution to this problem has been to integrate energy harvesting technologies in components, such as wings. To this end, a framework for designing flapping wing aerial vehicle using multifunctional wings using solar cells is described. This framework consists of: (1) modeling solar energy harvesting while flying, (2) determining the number of solar cells that meet flight power requirements, and (3) determining appropriate locations to accommodate the desired number of solar cells. A system model for flapping flight was also developed to predict payload capacity for carrying batteries to provide energy only for power spikes and to enable time-to-land safely in an area where batteries can recharge when the sun sets. The design framework was applied to a case study using flexible high-efficiency (>24%) solar cells on a flapping wing aerial vehicle platform, known as Robo Raven IIIv5, with the caveat that a powertrain with 81% efficiency is used in place of the current servos. A key finding was the fraction of solar flux incident on the wings during flapping was 0.63 at the lowest solar altitude. Using a 1.25 safety factor, the lowest value for the purposes of design will be 0.51. Wind tunnel measurements and aerodynamic modeling of the platform determined integrating solar cells in the wings resulted in a loss of thrust and greater drag, but the resulting payload capacity was unaffected because of a higher lift coefficient. A time-to-land of 2500 s was predicted, and the flight capability of the platform was validated in a netted test facility.