Alternative Energy Harvesting Research Articles

Transparent spin thermoelectricity with enhanced energy conversion

Spin-thermoelectrics (STE) allows energy harvesting from the waste heat through the orthogonal relationship between the charge and heat flow, which offers large area scalability. Moreover, STE devices can be well adapted for transparent energy harvesting when a transparent magnetic insulator is exploited as a spin current source. Nevertheless, the transparent characteristics of STE devices have not been studied extensively so far. In this study, we show transparent characteristics of STE device based on thin films of Yttrium Iron Garnet (YIG)/Pt bilayers. Decreasing thickness of the Pt layer not only improves transmittance of visible light but simultaneously enhances the STE performance. The fabricated STE device of YIG (20 nm)/Pt (0.8 nm) exhibits a longitudinal spin Seebeck coefficient, SLSSE ≈ 7.04 μV/K, while sustaining over 80% transparency at λ = 700 nm. Our study shows the potential usage of STE as an alternative transparent energy harvesting, which could be adapted in various multi-purpose coatings.

Investigation of mechanical energy harvesting cycles using ferroelectric/ferroelastic switching

Piezoelectric energy harvesters have been widely developed in last decade due to their simplicity and practicality, but they suffer from low energy density. To increase the energy density, ferroelectric/ferroelastic switching could be an effective alternative energy harvesting approach. However, the nonlinearity and irreversibility of ferroelectric switching produces difficulty in establishing a stable working cycle. In this work, novel, practical and stable energy harvesting cycles using ferroelectric/ferroelastic switching are established and explored under quasi-static experimental conditions. A prototype device with a simple ‘sandwich’ configuration is tested. The results show that the cycle energy density can reach 11 mJ/cm3 under tensile loading and 3.2 mJ/cm3 under compression, demonstrating great potential for practical applications.

Bi-Triggering Energy Harvesters: Is It Possible to Generate Energy in a Solar Panel under Any Conditions?

In this review, the concept of a hybrid solar cell system, called all-weather solar cells, a new view on energy harvesting device design, is introduced and described in detail. Additionally, some critical economical, technological, and ecological aspects are discussed. Due to drastic global climate changes, traditional energy harvesting devices relying only on solar energy are becoming less adaptive, hence the need for redesigning photovoltaic systems. In this work, alternative energy harvesting technologies, such as piezoelectric and triboelectric devices, and photoelectron storage, that can be used widely as supporting systems to traditional photovoltaic systems are analysed in detail, based on the available literature. Finally, some examples of all-weather solar cells composed of dye-sensitized solar cells (DSSC) and silicon solar cells, often modified with graphene oxide or phosphors materials, as new perspective trends in nanotechnology are presented. Two types of solar cell triggers are analysed: (i) solar cells working during day and night (DSSC with phosphors materials), and (ii) solar cells working under sun and rain conditions (piezoelectric and triboelectric silicon or DSSC solar cells).

Tailoring mechanical energy harvesting performance of piezoelectric nanogenerator via intrinsic electrical conductivity of ferroelectrics

Piezoelectric-based mechanical energy harvesting has received tremendous attention as an alternative green energy harvesting technology. However, the magnitude of power generated in this process is extremely low pertaining to the low current response of piezoelectric energy harvesters. Although conducting fillers such as Ag nanowire, carbon nanotube, Cu nanorods, and so on, have used in conventional piezoelectric/polymer composite devices to increase scavenged power density, the achievement is not significant. Finding an alternative and efficient way of tailoring the energy harvesting is therefore highly appreciated. In this article, we introduce the concept of tuning intrinsic electrical conductivity of ferroelectric ceramics while preserving its ferroelectric/piezoelectric strength to enhance the energy harvesting performance of piezoelectrics. We implement this idea by developing an electron-doped (La-doped) Ba(Sn0.09Ti0.91O3) (BST:La) piezoceramic and further designing 0–3 type composite device with non-ferroelectric polydimethylsiloxane polymer. About three order of increase of intrinsic current density in the doped piezoceramic compared with that of undoped component leads to the scavenged power density enhancement ~10.5 times in the composite with the doped specimen as compared with that comprises of undoped piezoceramic (BST). Our approach opens up a new, convenient way to improve the power density of piezoelectric-based flexible energy harvesters.

Adaptive Contention Window MAC Protocol in a Global View for Emerging Trends Networks

Massive tremendous amount of miniaturized wireless Internet of Things (IoT) devices are widely employed in many fields such as industrial production, social life, public (and defense) security and management of human society. The limitation of node device's energy capacity is the bottleneck issue of these network systems. MAC protocol is a key communication protocol for such sensor nodes which both rationally saves energy (an alternative to energy harvesting way) and improves the performances of the wireless sensor networks. There are complex tradeoff optimization relationships between the size of contention window and energy consumption, delay and collision, in which too large or too small contention window value cannot make the network performance optimal. This paper firstly gives an optimization algorithm for the size of the contention window through theoretical analysis, which can achieve a compromise between energy consumption (i.e. alternative energy harvesting) and delay. Then, a global view based adaptive contention window (GV-ACW) MAC protocol is proposed to further reduce latency and improve alternative energy harvesting. The GV-ACW MAC protocol adopts the optimized size of contention window in the near sink area to meet the functional requirements of data forwarding, while in the far sink area, the size of contention window is larger than it required by node for data transmission so as to reduce the latency and thereby improve the network performance as a whole. The theoretical analysis and experimental results show that, comparing with previous MAC protocol, GV-ACW protocol can realize effective alternative energy harvesting which resulting increasement of the network lifetime by 6% and reduce the network delay by 15%.

SMART ENERGY HARVESTING AND SEVERE WEATHER ALERT SYSTEM

Life in the rural coastal communities in the Philippines depicts poverty. This poverty is due to the lack of direct energy access and frequent destruction of livelihood lead by severe weather such as storms and typhoons. To help these communities to become sustainable the researchers provided a solution to enable alternative energy access to these communities as well as severe weather early warning. This research implements a hybrid alternative energy harvesting system using an attachable solar and wind energy apparatus for community use;; farther--time early warning for severe weather through weather APIs with a real--time atmospheric analysis and prediction for a short--time early warning;; and a handheld lantern for fishermen that allows them to receive farther and short--time alerts. The system is integrated into The Things Network through LoraWAN™ which allows administrators to monitor the energy stored and weather conditions as well as communicating with the lanterns at a longer and more reliable network.

Conducting polyaniline decorated in-situ poled Ferrite nanorod-PVDF based nanocomposite as piezoelectric energy harvester

PVDF-metal oxide based piezo-nanocomposite is an promising substitute of flexible nanogenerator. Herein, a ternary nanocomposite system Zinc Ferrite nanorod/Polyvinylidenefluoride (PVDF)/Polyaniline (PANI) nanochains was presented as alternative energy harvesting material. The inherent problem of low short-circuit current and high internal resistance of the nanocomposite was minimised by introducing a third phase cost-effective conducting supplementary filler, PANI nanochain.PANI assist to overcome the local dielectric dissimilarity by easy formation of conduction pathways via delocalization of π-electrons present in the benzene ring and reduce the internal resistance of composite. Besides, it serves the role of dispersing agent by floating nanofillers throughout the volume and improves the homogeneity of filler distribution. Additionally, PANI reinforces composite with respect to stress accumulation and modulates the release behaviour by entangling with nanofillers by means of Van Der Waals force and helps to stabilize the polar PVDF. This lead to an improvement in electro-mechanical response and piezo-response behaviour of nanocomposite. The nanocomposite exhibits a ∼42 V ac open circuit voltage and short circuit current density ∼0.85 μA/cm2with an overall increase in power density 35% compare to its binary metal-oxide/PVDF nanocomposite counterpart in response to single finger tapping and releasing. The generated power was utilized to illuminate twenty six number of red LEDs without any external energy storage unit. Also, the nanocomposite could charge up a commercial capacitor (10 μF) within 115 s which can be used for alternative powersource in self-powered devices and sensors.

Thermionic-Thermoradiative Converters

A thermionic-thermoradiative converter (TITRC) is established by combining the concepts of the thermionic emission and thermoluminescence, where the main irreversible losses are considered. The TITRC utilizes simultaneously electron and photon fluxes and converts directly a part of them into electricity, which enables a significant enhancement on the heat transfer and performance of the TITRC. Compared with either the thermionic energy generator or the thermoradiative device, the TITRC possesses advantages of higher power output and conversion efficiency in an extended temperature range. When the emitter in the TITRC is operated at 1500 K and Ag-O-Cs is used as the collector, the maximum power density and efficiency of the proposed TITRC can reach up to 0.301 Wcm $^{-2}$ and 22.5%, respectively. This letter can benefit the optimal design of the TITRC, and shed light on developing the ongoing research of the alternative energy harvesting devices.

(Invited) Smart Textile for Energy Harvesting and Self-Powered Sensing Applications

Since the introduction of the first expounded triboelectric nanogenerator (TENG) in 2012, the theoretical and practical aspects of the TENG have been researched as an alternative energy harvesting technology to convert mechanical energy into electricity efficiently. Numerous self-powered sensing systems have adopted the TENG as a power source to further explore its versatile applications toward different targets. In this study, we employed a TENG to replace a traditional power supply for synthesizing different metallic nanoparticles using an electrochemical approach. Carbon fibers were adopted as the conductive substrates to grow the metallic nanoparticles, where the size and density of the nanoparticles on carbon fibers can be controlled by the electric output of the TENG. Additionally, we demonstrated that the as-prepared carbon modified and integrated with the TENG to construct a wearable self-powered sensing system exhibited significant selectivity and sensitivity toward lactate detection. Furthermore, the design of the sensing unit was favorable regarding its adaptability and flexibility to fit human body shapes and postures. As demonstrated in this study, the as-prepared self-powered sensing system could detect the lactate concentration in human perspiration, which can be an ideal wearable device for end users who seek real-time monitoring of their physical condition. This study concludes with a proposal for noninvasive biosensors, which provide boundless potential for future cross-field applications. References T-H. Chang, Y.-W. Peng, C.-H. Chen, T.-W. Chang, J.-Y. Wu, J.-C. Hwang, J.-Y. Gan and Z.-H. Lin, Nano Energy 2016, 21, 238–246.T-W. Chang, C.-W. Wang, C.-H. Chen, Y.-C. Li, C.-L. Hsu, H.-T. Chang and Z.-H. Lin, Nano Energy 2016, 22, 564-571.C.-H. Choi, P.-W. Lee, Y.-H. Tsao and Z.-H. Lin, Nano Energy 2017, In Press (https://doi.org/10.1016/j.nanoen.2017.10.064).

Utilization of self-powered electrochemical systems: Metallic nanoparticle synthesis and lactate detection

Since the introduction of the first expounded triboelectric nanogenerator (TENG) in 2012, the theoretical and practical aspects of the TENG have been researched as an alternative energy harvesting technology to convert mechanical energy into electricity efficiently. Numerous self-powered sensing systems have adopted the TENG as a power source to further explore its versatile applications toward different targets. In this study, we employed a TENG to replace a traditional power supply for synthesizing different metallic nanoparticles using an electrochemical approach. Carbon fibers were adopted as the conductive substrates to grow the metallic nanoparticles, where the size and density of the nanoparticles on carbon fibers can be controlled by the electric output of the TENG. Additionally, we demonstrated that the as-prepared carbon modified and integrated with the TENG to construct a wearable self-powered sensing system exhibited significant selectivity and sensitivity toward lactate detection. Furthermore, the design of the sensing unit was favorable regarding its adaptability and flexibility to fit human body shapes and postures. As demonstrated in this study, the as-prepared self-powered sensing system could detect the lactate concentration in human perspiration, which can be an ideal wearable device for end users who seek real-time monitoring of their physical condition. This study concludes with a proposal for noninvasive biosensors, which provide boundless potential for future cross-field applications.

A Computational Simulation of Using Tungsten Gratings in Near-Field Thermophotovoltaic Devices

Near-field thermophotovoltaic (NFTPV) devices have received much attention lately as an alternative energy harvesting system, whereby a heated emitter exchanges super-Planckian thermal radiation with a photovoltaic (PV) cell to generate electricity. This work describes the use of a grating structure to enhance the power throughput of NFTPV devices, while increasing the energy conversion efficiency by ensuring that a large portion of the radiation entering the PV cell is above the band gap. The device contains a high-temperature tungsten grating that radiates photons to a room-temperature In0.18Ga0.82Sb PV cell through a vacuum gap of several tens of nanometers. Scattering theory is used along with the rigorous coupled-wave analysis (RCWA) to calculate the radiation energy exchange between the grating emitter and the TPV cell. A parametric study is performed by varying the grating depth, period, and ridge width in the range that can be fabricated using available fabrication technologies. It is found that the power output can be increased by 40% while improving the efficiency from 29.9% to 32.0% with a selected grating emitter as compared to the case of a flat tungsten emitter. Reasons for the enhancement are found to be due to the enhanced energy transmission coefficient close to the band gap. This work shows a possible way of improving NFTPV and sheds light on how grating structures interact with thermal radiation at the nanoscale.

Interplay Between Surface and Morphology: Bio-Nano-Composites for Energy Harvesting

Immobilization of large biological molecules on solid substrates or into hierarchical composite material is of significant importance for scientific and engineering communities developing alternative energy harvesting technologies using bio-, enzyme-, microbial and biomimetic materials. Advances associated with functional materials based on bio-nanocomposite and nanobiomaterials require detailed information about the composition, physical and chemical structure of the interface.Characterizing the interface between immobilized biomolecules and a transducer is crucial for understanding spatial distribution and ordered orientation of biocatalysts. X-ray Photoelectron Spectroscopy (XPS) is a powerful technique allowing estimation of the elemental and chemical composition of the upper 10 nm of a surface and has been demonstrated to be a powerful tool to quantify the amount of protein immobilized or adsorbed during enzyme immobilization.In multicomponent heterogeneous functional systems related to this discussion, one has to be able to differentiate between multiple enzymes, between enzyme and other organic based constituents of composites, such as electrodes, polymers, etc., and to determine interactions between constituents in the composite, such as hydrogen bonding.Despite challenges, we are showing that XPS is a powerful analytical method for characterization of bio-inorganic and bio-organic composite multicomponent materials. Through carefully designed experiments, involving selection of reference materials that constitute part of the composite and individual relevant mixtures of those, constraining curve fits using information obtained from the references and cross-correlation between elemental speciation, it is possible to distinguish between chemically similar biological compounds in the matrix of organic or inorganic materials. Formation of intermolecular secondary bonds between proteins/peptide and inorganic matrix, structure of layered systems are types of analytical problems that XPS can address when enough care is taken.[1]The structure of ultrathin BOD film immobilized by LbL approach including elemental and chemical composition of layer-by layer assembly and relative thickness of adsorbed layers was studied by Angle-resolved XPS (ARXPS). The high resolution C 1s spectrum of the GA treated carbon electrode (CE), pure PEI and BOD, and 2L layer-by-layer samples are presented in Figure 1. A pure BOD has a unique peak at 288.5 eV in the C 1s high-resolution spectrum due to the presence of COOH/N-C=O types of species. A unique peak at 287.5 eV is observed for CE+PEI sample.Unique peaks within C 1s XPS spectra for each component of layer-by-layer assemblies can be used to distinguish individual layers on the electrode surface between each other. Angle-resolved XPS is used to follow ultrathin layer-by-layer formation. The layers are not discrete, but rather some intermixing occurs. The change in thickness of BOD/PEI bi-layer determined through the overlayer model confirmed collapse of order in the system for layers larger than 2.In addition to chemical composition, the morphology of the components involved in the functional energy harvesting devices, such as supports, catalysts, membranes, electrode, GDLs, etc. is critically important for the function of the relevant components.Approaches in extracting morphological information out of SEM images at a variety of scales will be discussed. Figure 2 shows the approach in multi-step filtering of SEM images to obtain roughness and porosity measures representing different scales. [2]Effect of morphology on current density of modified PTFE electrodes is displayed in Figure 3. The more of large pores is present the smaller the resistance and the higher the current density. Structure-to-property relationship between surface composition as extracted by XPS, morphological information as provided by SEM and performance characteristics, such as, for example, electrochemical performance and bacteria attachment, allows for accelerated targeted material design.[1] K. Artyushkova, P. Atanassov, ChemPhysChem,14(10), 2013, 2071-2080, DOI: 10.1002/cphc.201300037.[2] K. Artyushkova, S. Pylypenko, M. Dowlapalli, P. Atanassov, RSC Advances, 2 (2012) 4304-4310.

Ambient RF Energy Harvesting in Urban and Semi-Urban Environments

RF harvesting circuits have been demonstrated for more than 50 years, but only a few have been able to harvest energy from freely available ambient (i.e., non-dedicated) RF sources. In this paper, our objectives were to realize harvester operation at typical ambient RF power levels found within urban and semi-urban environments. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken from outside all of the 270 London Underground stations at street level. Using the results from this survey, four harvesters (comprising antenna, impedance-matching network, rectifier, maximum power point tracking interface, and storage element) were designed to cover four frequency bands from the largest RF contributors (DTV, GSM900, GSM1800, and 3G) within the ultrahigh frequency (0.3-3 GHz) part of the frequency spectrum. Prototypes were designed and fabricated for each band. The overall end-to-end efficiency of the prototypes using realistic input RF power sources is measured; with our first GSM900 prototype giving an efficiency of 40%. Approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using our four prototypes. Furthermore, multiband array architectures were designed and fabricated to provide a broader freedom of operation. Finally, an output dc power density comparison was made between all the ambient RF energy harvesters, as well as alternative energy harvesting technologies, and for the first time, it is shown that ambient RF harvesting can be competitive with the other technologies.