Green Energy Harvesting Research Articles

Electrical and Thermal Optimization of Energy-Conversion Systems Based on Thermoelectric Generators

Thermoelectric generator devices, which convert heat directly into electrical power, have a great potential for energy scavenging and green energy harvesting applications. The exploitation of such a potential requires a proper design of both the electrical circuit that drives the electrical load and the thermal part, in particular when the thermoelectric generator is coupled with the hot and cold heat sources through thermal resistances. We propose a straightforward approach to take into account both thermal and electrical issues, by means of an equivalent electric circuit model that can be solved with widely available simulator programs, such as SPICE. Our approach is shown to be effective for supporting the design and optimization of thermoelectric systems from the point of view of the output power and of the efficiency. In particular, with our model we are able to point out that thermal resistance matching optimizes the thermal fluxes only in first approximation. We also show that the electrical matching for the maximum output power must be carefully considered for each particular thermoelectric module and load condition.

Recent advances in cellulose-based flexible triboelectric nanogenerators

The combination of the functional materials developed by natural polymer cellulose and the triboelectric nanogenerators (TENGs) gives birth to the cellulose-based TENGs. The advent of this kind of green energy harvesting devices not only broadens the path of green new materials in the energy industry, but also gives more development potential to TENGs. Herein, recent research progress of cellulosic functional materials in the field of TENGs is systematically summarized, including the paper-based materials, micro/nano cellulose and cellulose derivatives for TENGs. Combined with the structure-property-application relationships of cellulose-based TENG, we consider the main aspects affecting the properties of each cellulose-based TENG and simultaneously discuss their corresponding potential applications. On this basis, from the optimization of cellulosic materials (triboelectric polarity, morphology and microstructure) and TENG’s structure, various strategies and methods to improve the electricity generation performance are also summarized. In view of the serious problems and challenges of cellulose-based TENGs in the aspects of processability, stability and application, we also proposal some effective countermeasures and more novel explorations. Finally, the research trend of cellulose-based TENGs and its future prospects as a kind of multi-functional green energy flexible equipment are presented. • The recent advances of cellulose-based functional materials in the field of TENGs are overviewed. • The strategies for adjusting structure-property-application of cellulose-based TENGs are analyzed in detail. • Key methods to improve the electricity generation performance of cellulose-based TENGs are summarized. • Effective measures and novel explorations are proposed to meet the challenges in processability, stability and application.

MXene based mechanically and electrically enhanced film for triboelectric nanogenerator

The development of triboelectric nanogenerator (TENG) technology which can directly convert ambient mechanical energy into electric energy may affect areas from green energy harvesting to emerging wearing electronics. And, the material of triboelectric layer is critical to the mechanical robustness and electrical output characteristics of the TENGs. Herein, a MXene enhanced electret polytetrafluoroethylene (PTFE) film with a high mechanical property and surface charge density is developed. The MXene/PTFE composite film was synthesized by spraying and annealing treatment. With the doping of MXene, the crystallinity of composite film could be tuned, leading to an enhancement in the tensile property of 450% and reducing the wear volume about 80% in the friction test. Furthermore, the as-fabricated TENG with this composite film outputs 397 V of open-circuit voltage, 21 µA of short-circuit current, and 232 nC of transfer charge quantity, which are 4, 6, and 6 times higher than that of the TENG made by pure PTFE film, respectively. Therefore, this work provides a creative strategy to simultaneously improve the mechanical property and electrical performance of the TENGs, which have great potential in improving device stability under a complex mechanical environment.

Quaternary Heusler alloys a future perspective for revolutionizing conventional semiconductor technology

Computational methods are infallible in predicting the ground state and numerous other properties of materials. There have been copious efforts to design high spin-polarized ferromagnetic materials for utilizing the electron spin to revolutionize conventional electronics. Our investigation relies on designing new quaternary half-metallic Heusler alloys CoFeXSn (X = Ru, Zr, Hf, Ta) with 100% spin polarization and high magnetic moment. Also, we have analyzed the effect of 3-d and 4-d transition metal electrons on electronic structures, mechanical and thermoelectric properties. The origin of the half-metallic gap and magnetism is conferred in detail using schematic representation. Mechanical parameters elucidate the brittle, ductile, and anisotropic nature of alloys. Based on the criteria of mechanical stability the alloys CoFeRuSn, and CoFeTaSn exhibit ductile nature whereas CoFeZrSn, and CoFeHfSn evinces brittle nature. The various elastic parameters authenticate the mechanical stability of the alloys. In addition to this, the thermoelectric parameters affirm the possible application of these materials in green energy harvesting.

Towards Bio-Hybrid Energy Harvesting in the Real-World: Pushing the Boundaries of Technologies and Strategies Using Bio-Electrochemical and Bio-Mechanical Processes

Sustainable, green energy harvesting has gained a considerable amount of attention over the last few decades and within its vast field of resources, bio-energy harvesters have become promising. These bio-energy harvesters appear in a wide variety and function either by directly generating energy with mechanisms similar to living organisms or indirectly by extracting energy from living organisms. Presently this new generation of energy harvesters is fueling various low-power electronic devices while being extensively researched for large-scale applications. In this review we concentrate on recent progresses of the three promising bio-energy harvesters: microbial fuel cells, enzyme-based fuel cells and biomechanical energy harvesters. All three of these technologies are already extensively being used in small-scale applications. While microbial fuel cells hold immense potential in industrial-scale energy production, both enzyme-based fuel cells and biomechanical energy harvesters show promises of becoming independent and natural power sources for wearable and implantable devices for many living organisms including humans. Herein, we summarize the basic principles of these bio-energy harvesting technologies, outline their recent advancements and estimate the near future research trends.

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.

Optimizing the Artificial Lighting in a Smart and Green Glass Building-integrated Semi-Transparent Photovoltaics: A Multifaceted Case Study in Egypt

Numerous increases in CO2 emissions are recognizable nowadays. Consequently, building integrated photovoltaics (BIPV) glows up as a trendy future solution. BIPVs are introduced by substituting one of the building components with a green energy harvesting source seeking for sustainability. Herein, we propose a BIPV techno-economic feasibility by utilizing in-Lab fabricated semi-transparent solar cells as a glass interface. Three alternatives have been taken into consideration with proposing on-roof Photovoltaic (PV) system (alternative #1) and semi-transparent solar cells working as glass interfaces (alternative #2) while keeping the governmental grid as a reference alternative (alternative #3). Daylight simulations and electric lighting loads optimization are investigated showing an overall energy budget per alternative. An optimum alternative with an overall excess energy of around 88 MWh as annual energy production was reached, while satisfying 100% of the targeted electrical loads. Levelized cost of energy (LCOE) is demonstrated as an economic parameter to evaluate the three proposed alternatives.

Bio-waste sunflower husks powder based recycled triboelectric nanogenerator for energy harvesting

Sunflower seed is a popular food, but plenty of bio-waste sunflower husks are discharged into the world. If this bio-waste trash can be recycled, it will be reduced not only environmental pollution but also the waste of resources. In this paper, a triboelectric nanogenerator (SFP-TENG) based on a bio-waste sunflower husk powder is proposed and its open-circuit voltage, short circuit current, and instantaneous power are archived as 488 V, 28.5μA, and 1200μW, respectively, under the frequency of 10 Hz with the excitation force of 58 N. The proposed SFP-TENG can harvest the biomechanical energy from the human body’s daily motions. The fabricated SFP-TENG device is capable of lighting up 153 commercial LEDs. Furthermore, the SFP-TENG device is also tested under various humid environments such as 38, 49, 60, 79, and 89% relative humidity. Additionally, it can power up microelectronic devices such as calculator and stopwatch. Hence, we are sure that the proposed device can promote cost-effective and eco-friendly green energy harvesting through recycling bio-wastes as sunflower husk.

Giant Nernst effect and field-enhanced transversal zNT in ZrTe5

Thermoelectric materials can recover electrical energy from waste heat and vice versa, which are of great significance in green energy harvesting and solid state refrigerator. The thermoelectric figure of merit (zT) quantifies the energy conversion efficiency, and a large Seebeck or Nernst effect is crucial for the development of thermoelectric devices. Here we present a significantly large Nernst thermopower in topological semimetal ZrTe5, which is attributed to both strong Berry curvature and bipolar transport. The largest in-plane S_xy (when B//b) approaches 1900 {\mu}V/K at T=100K and B=13T, and the out-of-plane S_xz (when B//c) reaches 5000 {\mu}V/K. As a critical part of z_N T, the linearly increased in-plane S_xy and resistivity \r{ho}_yy regard to B induces an almost linear increasing transversal z_N T without saturate under high fields. The maximum z_N T of 0.12 was obtained at B=13 T and T= 120K, which significantly surmounts its longitudinal counterpart under the same condition.

Energy Efficient Throughput Aware Traffic Load Balancing in Green Cellular Networks

With the augmentation of affordable multimedia wireless gadgets, the ubiquitous availability of the internet access, and the rapid pace of mobile traffic motivate research towards fifth generation (5G) communications to realize energy-efficient cloud radio access networks (C-RAN) with guaranteed quality of experience. Exploiting green energy harvesting for powering the C-RAN substantially alleviates the energy procurement from the utility grid, carbon footprint, and operational expenses. In this paper, we propose a new dynamic point selection coordinated multipoint (DPS CoMP) based load balancing paradigm emphasizing achievable throughput and energy efficiency (EE) by reducing utility grid consumption from a network level perspective. This paper investigates the radio efficiency, EE, and average on-grid energy saving addressing the key challenges of tempo-spatial dynamics of traffic intensity and renewable energy (RE) generation under a wide range of network setup. Endeavoring load balancing technique strives a balance in network utilities such as green energy utilization and user association based on BS coordination technique in a cluster. Provision of cell sleep approach is contemplated for further energy saving by turning off lightly loaded base stations (BSs) during low traffic arrivals. The proposed CoMP based load balancing algorithm proficiently manages resource block allocation to the new users and elevated the energy efficiency over the conventional location and traffic centric mechanisms. Extensive system-level simulations manifest that the suggested framework enables an adjustable trade-off between radio efficiency and EE, and saves 22% on-grid power consumption and increases EE index by 32%. Afterward, an exhaustive comparison of the proposed method with the existing schemes is pledged for further validation highlighting sustainable 5G wireless systems.

Scalable thermoelectric fibers for multifunctional textile-electronics

Textile electronics are poised to revolutionize future wearable applications due to their wearing comfort and programmable nature. Many promising thermoelectric wearables have been extensively investigated for green energy harvesting and pervasive sensors connectivity. However, the practical applications of the TE textile are still hindered by the current laborious p/n junctions assembly of limited scale and mechanical compliance. Here we develop a gelation extrusion strategy that demonstrates the viability of digitalized manufacturing of continuous p/n TE fibers at high scalability and process efficiency. With such alternating p/n-type TE fibers, multifunctional textiles are successfully woven to realize energy harvesting on curved surface, multi-pixel touch panel for writing and communication. Moreover, modularized TE garments are worn on a robotic arm to fulfill diverse active and localized tasks. Such scalable TE fiber fabrication not only brings new inspiration for flexible devices, but also sets the stage for a wide implementation of multifunctional textile-electronics.

Recent Progress in Hybridized Nanogenerators for Energy Scavenging.

SummaryAs the world's demand for alternative energy increases, the development of green energy harvesters becomes ever more important. As a result, the creation of triboelectric (TENG), piezoelectric (PENG), and pyroelectric nanogenerators, electromagnetic generators (EMG), solar cells, and electrochemical cells is attracting interest in an effort to convert mechanical, thermal, magnetic, solar, and chemical energy into electricity. In order to take advantage of the ambient energies from our surrounding environment, the design of hybridized generator units that can simultaneously scavenge energy in a variety of forms continues to develop. These systems are being considered to satisfy the energy needs of a range of electronic devices and adapt to a variety of working environments. This review demonstrates the latest progress in hybridized nanogenerators in accordance with their structure, operating principle, and applications. These studies demonstrate new approaches to developing hybrid techniques and novel assemblies for efficiently harvesting environmental energy from a number of sources.

Thermoelectric Energy Harvesters: A Review of Recent Developments in Materials and Devices for Different Potential Applications.

The thermoelectric effect encompasses three different effects, i.e. Seebeck effect, Peltier effect, and Thomson effect, which are considered as thermally activated materials that alter directions in smart materials. It is currently considered one of the most challenging green energy harvesting mechanisms among researchers. The ability to utilize waste thermal energy that is generated by different applications promotes the use of thermoelectric harvesters across a wide range of applications. This review illustrates the different attempts to fabricate efficient, robust and sustainable thermoelectric harvesters, considering the material selection, characterization, device fabrication and potential applications. Thermoelectric harvesters with a wide range of output power generated reaching the milliwatt range have been considered in this work, with a special focus on the main advantages and disadvantages in these devices. Additionally, this review presents various studies reported in the literature on the design and fabrication of thermoelectric harvesters and highlights their potential applications. In order to increase the efficiency of equipment and processes, the generation of thermoelectricity via thermoelectric materials is achieved through the harvesting of residual energy. The review discusses the main challenges in the fabrication process associated with thermoelectric harvester implementation, as well as the considerable advantages of the proposed devices. The use of thermoelectric harvesters in a wide range of applications where waste thermal energy is used and the impact of the thermoelectric harvesters is also highlighted in this review.

Origami triboelectric nanogenerator with double-helical structure for environmental energy harvesting

Triboelectric nanogenerators (TENGs) based on contact electrification and electrostatic induction have emerged as promising green and clean energy harvesting devices. Its most unique property is that it can harvest low-frequency waste mechanical energy from the environment to electricity with high conversion efficiency. To improve the output power of TENGs, a lot of efforts have been done on fabrication of textured contact surface which leads to higher fabrication cost. In this work, inspired by the origami technology, we have designed a novel double helix structure TENGs (dh-TENG) with low cost and ease fabricating process. The dh-TENG can switch from 2D to 3D freely and significantly improve the output performance of TENG. Several factors, such as the input frequency, resistive load together with various structural parameters, were systematically investigated; the working mechanism of the dh-TENG was studied by using the COMSOL software. The experimental results show that the maximum output power of the dh-TENG reaches 0.58 mW when the external load resistance is 20 MΩ, which can fully power electronic devices such as capacitors and LEDs. These findings provide useful guidance for optimizing the performance of dh-TENGs for practical applications in self-powered systems and portable mobile electronic products, especially on soft electronics and wearable electronics.

A novel and stable way for energy harvesting from Bi2Te3Se alloy based semitransparent photo-thermoelectric module

In this research, due to the present pandemic of COVID-19, we are proposing a stable and fixed semitransparent photo-thermoelectric cell (PTEC) module for green energy harvesting. This module is based on the alloy of Bismuth Telluride Selenide (Bi2Te3Se), designed in a press tablet form and characterized under solar energy. Here, both aspects of solar energy i.e., light and heat are utilized for both energy production and water heating. The semitransparent PTEC converts heat energy directly to electrical energy due to the gradient of temperature between two electrodes (top and bottom) of thermoelectric cells. The PTEC is 25% transparent, which can be varied according to the necessity of the utilizer. The X-ray diffraction of material and electric characterization of module i.e., open-circuited voltage (VOC) and Seebeck coefficient were performed. The experimental observations disclose that in the proposed PTEC module with an increment in the average temperature (TAvg) from 34 to 60 °C, results in the rise of VOC ∼ 2.4 times. However, by modifying the size of heat-absorbing top electrode and by increasing the temperature gradient through the addition of water coolant under the bottom electrode, an uplift in the champion device results in as increment of VOC ∼5.5 times and Seebeck coefficient obtained was −250 μV/0C, respectively. Results show that not only the selection of material but also the external modifications in the device highly effective the power efficiency of the devices. The proposed modules can generate electric power from light and utilize the penetrating sunlight inside the room and for the heating of the water which also acts as a coolant. These semitransparent thermoelectric cells can be built-in within windows and roofs of buildings and can potentially contribute to green energy harvesting, in situations where movement is restricted locally or globally.

Self‐Assembly of Porous Microstructured Polydimethylsiloxane Films for Wearable Triboelectric Nanogenerators

AbstractTriboelectric nanogenerator (TENG), a green energy harvester, can harvest mechanical energy from human motion to electric energy to be applied in wearable electronics and sensor network. Porous materials played an important role in enhancing electric performance of TENG. In this paper, Azobisisobutyronitrile (AIBN) is used as a self‐reactive agent to modify Polydimethylsiloxane (PDMS) to form a self‐assembled porous structure (PDMS‐N10 film) through the difference in temperature between PDMS pre‐curing and AIBN decomposition. The PDMS‐N10‐based TENG exhibits a 2.5‐fold and 2.7‐fold improvement in output voltage and current as compared with PDMS without modification respectively. In addition, 116 light‐emitting diodes could be lighted up and 22 µF capacitor is charged. The TENG is also used as a sensor or trigger device for sensing the movements of elbow, knee, wrist, or finger, which can be applied in wearable devices because of the flexibility and durability as well as low cost.

Vapor solid phase grown hierarchical CuxO NWs integrated MOFs-derived CoS2 electrode for high-performance asymmetric supercapacitors and the oxygen evolution reaction

Designing and exploring a simple, novel, and smart synthetic concept to fabricate highly efficient and dual-function electrode material at an optimum cost for green energy harvesters has been a long-standing challenge. Herein, for the first time, we investigated a simple and smart concept to fabricate dual-function vapor solid phase grown copper oxide nanowires (CuxO NWs) integrated metal-organic frameworks-derived (MOFs) hollow and porous cobalt sulfide (CuxO NWs@CoS2) hybrid nanostructures as an effective binder-free electrode for supercapacitors and the OER. When utilized as an electrode material for supercapacitors, the CuxO NWs@CoS2 hybrid electrode displayed an ultrahigh specific capacity of 331.6 mAh/g (volumetric capacity of 2.46 mAh/cm3) with an outstanding rate capability of 67% even at a high current density of 50 mA/cm2; moreover, the electrode possessed a long-term durability of 100.2% after 10,000 cycles. An all-solid-state asymmetric device (CuxO NWs NWs@CoS2//Fe2O3/rGO aerogels) delivered a specific energy density of 49.8 Wh/kg. In addition, the oxygen evolution activity of the CuxO NWs@CoS2 electrode was also investigated and the electrode demonstrated superior catalytic properties compared to other formulations. This investigation emphasizes a novel synthetic approach and its multifunctional applicability in energy storage and generation devices.

Protein Gel Phase Transition: Toward Superiorly Transparent and Hysteresis‐Free Wearable Electronics

AbstractThe next generation of wearable electronics for health monitoring, Internet‐of‐Things system, “interface‐on‐invisible,” and green energy harvesting require electrically conductive material that is superiorly transparent, negligibly hysteretic, industrially feasible, and highly stretchable. The practical potential of ionic hydrogel is challenged with obvious hysteresis and a limited sensing range due to relative delamination and viscoelastic performance. Herein, a novel liquid conductor, termed as egg white liquid, is developed from self‐liquidation of egg white hydrogel, and the liquid not only inherits the designed architecture from a hydrogel predecessor but also achieves comparable conductivity (20.4 S m−1) to the ionic hydrogel and ultrahigh transparency (up to 99.8%) . Moreover, the 3D‐printed liquid–elastomer hybrid exhibits excellent conformability, remarkable sensitivity with negligible hysteresis (0.77%), and the capability of monitoring human motions and dynamic moduli is further demonstrated. The liquid nature inspires a gesture‐controlled touchless user interface for front‐end electronic systems. Furthermore, mechanical energy harvesting and pressure sensing are evidenced by exploiting this liquid conductor into a triboelectric nanogenerator. Notably, the as‐prepared liquid via subsequent phase transition possessing superior transparency, ultralow hysteresis, economic benefit, and unique liquid phase may potentially fuel the development of a new class of wearable electronics, human–machine interface, and clean energy.

Waste capacitor: A fresh approach to detect and remove Cr(VI) from water and making it an energy harvesting material

The large scale amplification of industrial discharge in the modern era is resulting in widespread water pollution, especially from various industrial effluents and wastewater containing heavy metals, posing a severe threat to our environment. In order to combat such problems, this work aims on Multifunctional Fluorescent Nano-Sensor (MFNS) mediated simultaneous detection and removal of hexavalent chromium from real life wastewater which further converts it into an energy harvesting material, namely, “Waste capacitor”. This smart material can detect the presence of the targeted heavy metal (Cr(VI)) in the wastewater and can entrap it by using a facile adsorption process. Thereafter, it will change its microstructure which further enhances its dielectric properties. Morphology, microstructure and optical properties of the synthesized material have been studied thoroughly and a turn-off based fluorescence sensing has been reported herein. Photoinduced electron transfer (PET) based fluorescence quenching is mainly responsible for this sensing mechanism. The selectivity and sensitivity of the material during fluorescence sensing have also been studied by using standard Stern-Volmer method showing that the synthesized material is tremendously selective and sensitive towards the specific target ion. High surface area with slit-like porous structure enhances the adsorption based removal of the contaminant. Nearly 76% of contaminants have been removed by using this smart material. After adsorbing specified target, this MFNS changes its microstructure and results in superior dielectric constant with a minimal tangent loss. Tremendous sensitivity (in nM range), selectivity towards the specific contaminant and adsorption of toxic heavy metal and converting it into a green energy harvesting material (waste capacitor) makes this smart multifunctional material a real waste to wealth converter.

Modeling and Analysis of Thermoelectric Energy Harvesting System with High-Gain Power Converter

In recent years, the green energy harvesting system using thermoelectric generator for generating electrical power from waste heat has rapidly been increased. This research work investigates the theoretical modeling of single thermocouple, thermoelectric module (TEM) and TEM with high-gain power converter. This study develops a MATLAB-Simulink model for a single thermocouple and TEM to predict the P–I and V–I performance curves. The TEMs are subjected to a varying ΔT in many waste heat-generating applications. Such impact on a varying ΔT is analyzed from the comparison of a P–I and V–I performance curve obtained under two different ΔT conditions. Moreover, a TEM along with a high-gain power converter, to boost the output voltage to meet the load requirement, is modeled in a MATLAB-Simulink. The simulation analysis of P–I and V–I performance curves of a TEM for a ΔT of 95 °C and 135 °C is compared with the experimental results to validate the practical feasibility of the proposed model. A large voltage conversion ratio of 17 with an efficiency of 91.5% is obtained from the power converter. Hence, the proposed system can employ to power the DC micro-grid systems. Also, a 2.35-V input-voltage and 40.4-V load-voltage prototype of high-gain power converter with TEM has been tested in laboratory to validate the performance.