Energy Scavenging Technologies Research Articles

Recent advancements in piezoelectric energy harvesting for implantable medical devices

Biomedical implantable devices like deep brain stimulators, implantable cardioverter-defibrillators and cardiac pacemakers are essential for treating the human heart and brain-related diseases. In the past few decades, a considerable amount of research has focused on improving bio-implant technologies. Conventional bio implant devices consist of an external generator like a battery to power the system, which requires replacement after a particular time. Therefore, in recent years, self-powered implants with various energy harvesting techniques have been proposed to avoid frequent surgery for battery replacement and to miniaturise the implant systems. However, the research communities have yet to explore all the limitations and possibilities of improvement on such energy-scavenging technologies, especially when the application is in vivo. Several aspects of recent developments in energy harvesting technologies feasible for biomedical implantable devices are reported systematically. A detailed review of piezoelectric energy harvester mechanism and miniaturisation, electric output and power management and biocompatibility of an energy harvester for implantable medical devices in vitro and in vivo environments. Furthermore, the piezoelectric energy harvester’s durability, packaging material, connection and evaluation criteria are discussed.

Thermoelectric Inks and Power Factor Tunability in Hybrid Films through All Solution Process.

Thermoelectric (TE) materials can have a strong benefit to harvest thermal energy if they can be applied to large areas without losing their performance over time. One way of achieving large-area films is through hybrid materials, where a blend of TE materials with polymers can be applied as coating. Here, we present the development of all solution-processed TE ink and hybrid films with varying contents of TE Sb2Te3 and Bi2Te3 nanomaterials, along with their characterization. Using (1-methoxy-2-propyl) acetate (MPA) as the solvent and poly (methyl methacrylate) as the durable polymer, large-area homogeneous hybrid TE films have been fabricated. The conductivity and TE power factor improve with nanoparticle volume fraction, peaking around 60–70% solid material fill factor. For larger fill factors, the conductivity drops, possibly because of an increase in the interface resistance through interface defects and reduced connectivity between the platelets in the medium. The use of dodecanethiol (DDT) as an additive in the ink formulation enabled an improvement in the electrical conductivity through modification of interfaces and the compactness of the resultant films, leading to a 4–5 times increase in the power factor for both p- and n-type hybrid TE films, respectively. The observed trends were captured by combining percolation theory with analytical resistive theory, with the above assumption of increasing interface resistance and connectivity with polymer volume reduction. The results obtained on these hybrid films open a new low-cost route to produce and implement TE coatings on a large scale, which can be ideal for driving flexible, large-area energy scavenging technologies such as personal medical devices and the IoT.

Direct Current Triboelectric Nanogenerators

AbstractThe triboelectric nanogenerator (TENG) as a promising energy scavenging technology has been utilized to convert ambient mechanical energy into electric energy for meeting ever‐increasing energy consumption and the need for sustainable energy in modern life. However, the electric energy generated by the conventional TENG based on coupling the contact electrification and electrostatic induction is pulsed alternating current, which requires rectification measures to obtain the direct current (DC) power suitable for storing and driving electronic equipment, resulting in the limitation of its portability and energy utilization efficiency. Through the use of new materials and structures, novel direct current triboelectric nanogenerators (DC‐TENGs) with constant DC output characteristics provide an intelligent solution. Here, the development of DC‐TENG is reviewed, focusing on the working mechanisms of DC‐TENG based on various strategies. The important factors affecting the outputs and the main applications of DC‐TENGs are summarized. Moreover, the possible challenges and future direction for DC‐TENGs are also discussed.

Water droplet impact energy harvesting with P(VDF-TrFE) piezoelectric cantilevers on stainless steel substrates

Harvesting energy from ambient environmental sources using piezoelectric transducers has seen a tremendous amount of interest from the scientific community in recent times. The practicality of energy scavenging technology looks set to see continued relevance, with decreasing power demands of electrical systems, such as wireless sensor networks, allowing such technology to progressively act as an energy source to drive and sustain them independently. In light of this, there is a growing opportunity for piezoelectric materials to prolong, or even replace, battery powered sensor systems positioned in remote or difficult to reach areas. It has been demonstrated that falling water droplets of millimetric-scale diameter can impart forces of over a thousand times their resting weight upon surface impact. As such, the potential for utilising piezoelectric transducers to drive sensor systems, by converting the kinetic impact energy of falling water droplets into useful electrical energy, is investigated. The key parameters that affect the efficiency of energy transfer between incident water droplets and piezoelectric cantilever structures made of stainless steel foil coated with the lead-free piezoelectric material P(VDF-TrFE) are investigated. A peak power output of 28 nJ achieved from the impact of a 5.5 mm diameter droplet upon a single energy harvesting transducer illustrated that, for droplets of diameter 3.1–5.5 mm impacting from heights between 0.5 and 2.0 m, it is desirable to utilise piezoelectric transducer beams of bending stiffness in the range of 0.067–0.134 N m−1 in order to achieve good energy transfer efficiency. Although the active electrode area was constrained in order to maintain consistency between samples, reducing the peak energy output, the achieved results correspond to a 15.9 J m−3 energy density, representing the significant energy transfer efficiency achievable through appropriate transducer mechanical tailoring to the excitation source.

Self-powered nanosystems based on nanofuel cell

With the rapid progress in researches on nano-materials, a dramatically increasing number of nanoscale functional devices are developed, including nano-biosensors, nano-photoelectric sensors. Most of these nanoscale devices rely on external power supply to work sustainably. Although an energy storage unit is a choice for powering nanodevices, the large dimension of existed power sources has become one limited factor for the miniaturization of independently workable nanodevices. Therefore, a nanoscale power source capable of harvesting energy from the environment is an essential solution for building a “self-powered” nanosystem which is an integration of functional nanodevices and nano- enabled energy scavenging technologies. The successful development of such nanoscale power sources that match with nanodevices is significant for constructing self-powered nanosystems. The self-powered nanosystems will be widely used in industrial fields such as sensors networks, environmental and infrastructural monitoring, portable electronics, and healthcare. Referring to recent vigorously studies on exploiting self-powered nanosystems based on functional nanodevices and nano-batteries, it is obvious that the preparation of nano fuel cell is the key to the establishment of self-powered nanosystems. Fuel cells have many advantages over conventional batteries, such as high energy conversion efficiency, quick startup ability under low temperature, high energy density, and the feature of environmental friendly. What’s more, through the technical route of fuel cells, chemical and biochemical energy, the most abundant energy available in nature or in vivo biosystems, can be converted to electrical energy from fuels such as methanol and glucose, which is meaningful to the development of in vivo implantable nanosystems. Therefore, more and more attentions of the scientific community in fields of nanoenergy and nanosystems have been paid to the researches on micro and even nano scale miniaturization of fuel cells. Our group has done some studies on the proton exchange properties of single perfluorinated sulfonic acid resin (Nafion) nanowire, and on the nano proton exchange membrane fuel cells. We also have built a number of self-powered nanosystems based on such nano fuel cells. In this review article, we begin with the introduction to the proton exchange properties of Nafion nanowires, which is based on the works of our and other research groups. Then we briefly introduce nanofuel, nanobiofuel, hybrid nano biofuel cells, and self-powered nanosystems that are powered by these fuel cells, which represents a new self-powering approach in nanotechnology. We also briefly sum up the state of the art, point out confronting problems, and prospect possible trends in the researches on self-powered nanosystems. This work shows the feasibility of building self-powered nanosystems for biological sciences, environmental monitoring, defense technology and even personal electronics.

Energy Scavenging Technology and Components in WSN

With the evolution of modern technology wireless sensor nodes are finding a lot of applications in day to day life starting from smart home system to military surveillance. The primary building block of a wireless sensor network is a spatially distributed set of autonomous sensor nodes or motes. In order to design a wireless sensor network it is necessary to understand the structure and working of a sensor node. The sensor nodes can be considered as tiny battery powered computers that consists of a computing subsystem, communication subsystem, sensor subsystem, power subsystem. In this paper we review the features of these subsystems so that it is easy for the application developer to quickly understand and select the type of component for building customized sensor node platform. In this paper we have studied the features of different microprocessors and transceivers properties used in sensor nodes. We also study the classifications of sensors based on applications, the relevant sensor parameters, and different storage devices with their properties. This paper can be a ready reference to beginners interested in this field. One more major problem of wireless sensor network application that should be addressed is the limited lifetime of sensor nodes due to energy constraints. We also review how energy harvesting can increase the lifetime of a wireless sensor network and the possible methods that can be implemented for energy harvesting.

Energy Scavenging Device Based on Electric Field in Substations

Wireless sensor network has many advantages while energy supplying is a main limit. However, energy scavenging technology affords an efficient solution, especially in high voltage substations, there is swarmed with strong electromagnetic field, and the scavenging device based on electric field has an irreplaceable advantage. An equivalent mathematical model of the converter was established to study the energy harvesting effect. Another model of conditioning circuitry was further built to analyze the factors affecting charging current. Finally, several main factors and corresponding methods are analyzed to improve the energy scavenging efficiency.

Analysis and Optimization of Magnetic Energy Converters for Wireless Sensors in Substation

With the development of wireless sensor networks, energy supplying problem become critical. However, energy scavenging technology provides an efficient solution method, and it is the principal element for wireless sensors to facilitate on-site self-powering. A magnetic energy converter which can convert magnetic field energy to power is proposed when there is sufficient magnetic energy in substations. By modeling this converter, the inductive factor was defined to present energy harvesting capability and optimization was realized in terms of framework material, structural parameters and turns of coils. The research results present theoretical basis for optimal design of the energy scavenging devices.

Advances in Ultra-Low-Voltage Design

The idea of exploiting weak-inversion operation for low power, pioneered by Dr. Eric Vittoz in the 1960's, has led to many recent advances in sub-threshold circuit design, described in this paper by MIT's Anantha Chandrakasan and Joyce Kwong. In the near future, exciting new applications such as medical monitoring, toxic gas sensors and next-generation portable video gadgets in a number of systems will be powered by energy scavenging technologies that will require electronic circuits to operate with the utmost energy efficiency.