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A sustainable power source to meet the needs of energy requirement is very much essential in modern society as the conventional sources are depleting. Bioenergy, hydropower, solar, and wind are some of the well-established renewable energy sources that help to attain the need for energy at mega to gigawatts power scale. Nanogenerators based on nano energy are the growing technology that facilitate self-powered systems, sensors, and flexible and portable electronics in the booming era of IoT (Internet of Things). The nanogenerators can harvest small-scale energy from the ambient nature and surroundings for efficient utilization. The nanogenerators were based on piezo, tribo, and pyroelectric effect, and the first of its kind was developed in the year 2006 by Wang et al. The invention of nanogenerators is a breakthrough in the field of ambient energy-harvesting techniques as they are lightweight, easily fabricated, sustainable, and care-free systems. In this paper, a comprehensive review on fundamentals, performance, recent developments, and application of nanogenerators in self-powered sensors, wind energy harvesting, blue energy harvesting, and its integration with solar photovoltaics are discussed. Finally, the outlook and challenges in the growth of this technology are also outlined.

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Abstract-The comparative evaluation based on the power speed density of several types of portable Permanent Magnet Generator (PMG) considered for agricultural applications is presented. These generators are purposely designed to be used in agriculture sectors and thereby it should be of lightweight, small in size and ease to use. Six different generator topologies are developed for investigation of such purposes. A number of design parameters are considered to analyze the performance characteristics for each type of developed PMG. Based on the power speed density factor that is used to describe better generator performance, the suitable PMG for the agricultural application is identified through a comprehensive evaluation.

With their highly robust nature and simple design, switched reluctance machines are finding their way into numerous modern day applications. However, they produce oscillatory torque that generates torque ripple and mechanical vibrations. A double rotor structure to maximize the flux linkage and thereby increase the torque generating capability is proposed. As the machine operates close to saturation, the torque computation depends heavily on the energy conversion as the rotor rolls over the stator for a fixed pole pitch. The flux linkage characteristics are highly non-linear, hence estimation of the magnetic and mechanical parameters is extremely cumbersome. Magnetic circuit analysis by interpretation of the number of flux tubes using integration techniques at different positions of the machine to develop the flux linkage characteristics of the double rotor structure is presented. Computation of the inductances during the movement of rotor from unaligned to aligned is crucial in determining the generated torque. Relevant equations of calculations for inductance and flux linkages in the aligned, partially aligned and unaligned positions are computed. The partially aligned computation is based on the average on two intermediate positions, namely the 1/4th aligned and 3/4th aligned conditions. The static torque characteristics based on the energy conversion principles are used to compute the torque value. Results from simulation and experiments used for performance evaluation of the proposed flux tube analysis for computation of the electro-magnetic torque are presented. OPEN ACCESSEnergies 2012, 5 4009

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The rise in the number of electric vehicles used by the consumers is shaping the future for a cleaner and energy-efficient transport electrification. The commercial success of electric vehicles (EVs) relies heavily on the presence of high-efficiency charging stations. This article reviews the design and evaluation of different AC/DC converter topologies of the present status and future implementation plans for DC fast-charging infrastructures. The design and evaluation of these converters are presented, analysed, and compared in terms of output power, component count, power factor, and total harmonic distortion effectiveness and reliability. This paper also evaluates the architecture, merit, and demerits of AC/ DC converter topologies for DC fast-charging stations. Based on this analysis, it has found that the Vienna rectifier is the best suitable converter topology for the high-power DC fast-charging infrastructure (> 20 kW), thanks to its low current ripples, low output voltage ripples, high efficiency, high power density, and high reliability. The paper focuses specifically on different topologies of Vienna rectifier topologies on Level-3 DC fast-charging stations which direct to less CO 2 emissions in electric vehicle charging stations, thus contributing to sustainable development goals of climatic action.

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