China
Africa
Explore chapters and articles related to this topic
Energizing and Powering Microsystems
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
The fundamental drawback of microscale sources is that limited space constrains energy and power to miniscule levels. What is worse, technologies that store more energy unfortunately suffer from lower power densities, and vice versa. To illustrate this latter point, consider that a capacitor, which responds quickly to changing loads, supplies high power per unit volume, but only for a short while because energy density is low. A fuel cell of equivalent dimensions, on the other hand, which incidentally requires additional time to respond, stores more energy but sources less power, as the Ragone plot of Figure 1.3 corroborates graphically [3]. For this reason, Li ions are popular in cellular phones, laptop computers, digital cameras, and other mobile products, because they represent what amounts to a balanced alternative, with not only moderate energy and power densities but also intermediate speed. Super- or ultracapacitors feature comparable tradeoffs plus additional cycle life. Additionally, the voltage range of supercapacitors extends to zero, below the headroom limit of a circuit under which drawing energy is less probable, which means that the circuit may not leverage some of the energy stored in the capacitor.
Restoration: Nanotechnology in Tissue Replacement and Prosthetics
Published in Harry F. Tibbals, Medical Nanotechnology and Nanomedicine, 2017
Improvements in energy storage through nanoengineered supercapacitors and hypercapacitors, aerocapacitors, and conductive polymers [174], coupled with lower power requirements for nanoengineered electronics, allow room for great improvements in size and capability of embedded devices, allowing very small implantable devices to perform electrostimulation in selected points of the nervous, sensory, and neuromuscular system. Such devices may make it practical for increased use of implanted electrostimulation for bone and tissue grafts, and to stimulate function in the endocrine system and other organs.
The Prospect of Energy-Harvesting Technologies for Healthcare Wireless Sensor Networks
Published in Daniel Tze Huei Lai, Rezaul Begg, Marimuthu Palaniswami, Healthcare Sensor Networks, 2016
The supercapacitor, in short supercap, is another electrochemical energy system other than batteries that has been increasing its presence in powering wireless sensor nodes. There are several reasons for this phenomenon. One reason is that the supercap is very scalable, and its performance scales well with its size and weight. Another reason is that the supercap has many desirable characteristics that favour the operations of the sensor nodes such as high power density, rapid charging times, high cycling stability, temperature stability, low equivalent series resistance (ESR) and very low leakage of current (Flipsen 2004). Supercapacitors have much higher peak power density than other energy storage devices like batteries and fuel cells. This means that supercaps can deliver more electrical power than batteries and fuel cells within a short time. The peak power densities of supercaps are well above 1000 W/kg, whereas the power densities of all types of batteries are in the range of 60 to 200 W/kg, and fuel cells are even lower, below 100 W/kg. Hence, for burst power operation, supercaps are a better choice than batteries and fuel cells. Conversely, batteries have much higher energy storage capacities than supercaps. This means that batteries can deliver electrical power for a longer period of time as compared to supercaps. The peak energy densities of all types of batteries are in the range of 20 to 200 Wh/kg, whereas the power density of supercap is below 10 Wh/kg. Hence, for sustaining the extended operational lifetime of wireless sensor nodes, relying solely on supercaps might not be suitable due to their very low energy density as compared to other energy storage devices. Research to increase the energy storage density of both batteries and supercaps has been conducted for many years and continues to receive substantial focus (Blomgren 2002). While these technologies promise to extend the lifetime of wireless sensor nodes, they cannot extend it indefinitely.
Stimuli-responsive graphene-incorporated multifunctional chitosan for drug delivery applications: a review
Published in Expert Opinion on Drug Delivery, 2019
Sahar Gooneh-Farahani, M. Reza Naimi-Jamal, Seyed Morteza Naghib
Supercapacitor with a unique structure is the technology for energy storage. This structure (with the ability to save high energy) is a good candidate to replace the battery. Supercapacitors have high power density, fast charging and discharging, long lifetime and cyclic stability used in various fields such as medical or military equipment, security and information systems such as backup storage, lasers, power supplies, UPS sensitive computers, electrification networks, and turbines [269]. Different materials are used to create high-performance supercapacitors such as porous carbon, carbon nanotubes, graphene, transition metal oxide, and conducting polymers [270–272]. Between these materials, carbon-based supercapacitors are widely considered due to their large surface area and relatively high density. The carbon-based supercapacitors, like graphene, have low energy density and high price. In order to increase the energy density, carbon materials are combined with transition metal oxide and conductive polymers. Graphene can be a great candidate for fabricating supercapacitor electrode due to its exceptional properties such as large surface area, excellent electrical properties, high conductivity, and thermal properties. The development of graphene-based electrode as an energy storage device especially high-performance supercapacitor has expanded recently [273,274]. Electronic properties of graphene material are increased through the doping of heteroatoms such as N and B, for example, nitrogen-doped graphene improves electrochemical performance. The use of the NH3 atmosphere as the N source for nitrogen doping creates a different concentration and uniformity of N in the graphene synthesis by the method CVD or chemical oxidation or graphite exfoliation [275,276]. CS is a renewable biopolymer with low production cost containing nitrogen groups that can be introduced as a heteroatom to the graphene network, which results in the distribution and doping of nitrogen in a uniform manner at a low cost and less consumption of time and energy [277,278].