Harvest Waste Research Articles

SbSeI pyroelectric nanogenerator for a low temperature waste heat recovery

The low-grade waste heat, which constitutes majority of the total waste heat produced in industrial sector, is very difficult to be recovered. Pyroelectric materials have recently received a great attention for harvesting waste heat due to their ability to convert temperature fluctuations into an electrical energy. A simple, scalable and cheap fabrication method of pyroelectric nanogenerator (PENG) based on antimony selenoiodide (SbSeI) is presented for the first time. It involves a sonochemical synthesis of SbSeI nanowires and their high pressure (100 MPa) compression at room temperature into a bulk sample. Fabricated device has been subjected to thermal fluctuations, thereby generating an electric signal which has been highly correlated to the thermal input. SbSeI PENG has generated electric output up to 11 nA with power density of 0.59(4) μW/m2 upon exposure to heat-cool condition for a temperature variation from 324 K to 334 K. Presented paper reports also the temperature dependences of electric conductance and pyroelectric coefficient of compressed SbSeI nanowires, which has reached the maximum value of 44(5) nC/(cm2K) at 327 K.

Thermodynamic and economic analyses and multi-objective optimization of harvesting waste heat from a biomass gasifier integrated system by thermoelectric generator

Thermoelectric waste heat recovery systems (WHRSs) can be used appropriately to recover wasted heat from various industrial processes. In the current work, new thermodynamic modeling was developed to harvesting waste heat from an integrated system includes an externally fired gas turbine and a biomass gasifier by three thermoelectric WHRSs. The biomass system consisted a gas turbine cycle, an organic Rankine cycle (ORC) and a domestic water heater were first thermodynamically modeled, and then effects of adding thermoelectric WHRSs to different locations of the system were investigated. It is observed that first law efficiency of the system (η1) will become 17.11% (an increase of 0.35%) if the total output heat from the stack enters WHRSs. The efficiencies of the system can be increased from 16.76% to 17.93% by placing a WHRS on the condenser of ORC. Moreover, the operating parameters have a significant effect on the integrated system efficiency; the influence of increasing αGE on the efficiencies is in contrast to the effect of enhancing αcond. In addition, an economic assessment of integrating WHRSs with the biomass gasifier integrated system is conducted and the conditions are indicated under which the proposed system is profitable. Furthermore, the results of genetic algorithm based multi-objective optimization shows that with the use of γDU = 2 and γL,ORC=30 defined thermal efficiencies are at their optimum state.

Designing Thermally Actuated Bimorph as Energy Harvester

Abstract Microelectromechanical systems (MEMS) are micrometre-size systems that are capable of transforming electrical signals to mechanical signals. In this paper, the use of MEMS devices as a method for harvesting waste heat is explored. A background for the technology and methods is discussed and a method proposed for a working device based upon a thermally heated bimorph actuated by waste radiation alone is investigated. A chopper interrupts the radiant energy inducing an oscillation in the bimorph temperature and thus creates a mechanical motion which can be taken advantage of using piezoelectric materials. Difficulties in harvesting radiant energy with this method are highlighted and suggestions for non-passive energy generation are made based on the outlined principles.

Optimización de la capacidad de cogeneración mediante la adición de residuos de cosecha al bagazo en industria azucarera típica peruana

En este trabajo se realizó la evaluación energética de la mezcla apropiada de residuos de cosecha/bagazo de caña de azúcar, para mejorar la capacidad cogeneradora tanto de electricidad como de vapor para el proceso de producción de azúcar en una industria azucarera típica peruana. El Perú posee tradición en la industria azucarera caracterizado por su alta productividad de plantación de caña; el problema actual es la deficiente forma de cosecha de caña (pre-quemado de caña en campo) y, la obsolescencia de tecnología utilizada en el proceso de cogeneración.
 La metodología inicia con la cosecha mecanizada en área piloto de plantación de caña, seguido de los procesos de preparación y secado de los residuos de cosecha. Muestras de residuos se llevan al laboratorio para su caracterización fisicoquímica y energética a diferentes condiciones de humedad, obteniendo ratios de poder calorífico y contenido elemental. Se seleccionó la mezcla adecuada de residuos/bagazo que alimenta a la caldera para luego proceder a las pruebas energéticas de la Planta de Cogeneración.
 Como resultados se tiene un combustible mezcla residuos/bagazo optimizado (comparativamente a bagazo solo), en razón que: maximiza la eficiencia energética, minimiza costos de cogeneración, mejora la disponibilidad de caldera y disminuye la polución ambiental. La mezcla objetivo se logra a proporción volumétrica 1 a 4 con la que se obtiene: incremento de la producción eléctrica de 13 a 18 MW, incremento de eficiencia energética en 22.5% y reducción del costo de cogeneración en 19%.

Microfluidic Pump Driven by Anisotropic Phoresis

Fluid flow along microchannels can be induced by keeping opposite walls at different temperatures, and placing elongated tilted pillars inside the channel. The driving force for this fluid motion arises from the anisotropic thermophoretic effect of the elongated pillars that generates a force parallel to the walls, and perpendicular to the temperature gradient. The force is not determined by the thermophilic or thermophobic character of the obstacle surface, but by the geometry and the thermophoretic anisotropy of the obstacle. Via mesoscale hydrodynamic simulations, we investigate the pumping properties of the device as a function of the channel geometry, and pillar surface properties. Applications as fluidic mixers, and fluid alternators are also outlined, together with the potential use of all these devices to harvest waste heat energy. Furthermore, similar devices can be also built employing diffusiophoresis or electrophoresis.

High-Efficiency Cryo-Thermocells Assembled with Anisotropic Holey Graphene Aerogel Electrodes and a Eutectic Redox Electrolyte.

Thermocells, capable of converting temperature-dependent electrochemical redox potentials into electrical power, can harvest waste or low-grade heat in an economical and continuous approach with zero carbon emission. However, the power density and conversion efficiency of thermocells are hindered by a narrow operation window and low ion conductivity of the electrodes, especially in freezing weather conditions. Herein, highly efficient cylindrical thermocells, working in a wide operation window of cold temperatures, are developed. A eutectic electrolyte consisting of formamide and water is formulated with a high ion conductivity, which is retained at a significantly extended lower limit of the operation window from conventional 0 to -40 °C. In parallel, an electrode material based on anisotropic holey graphene aerogel is synthesized with improved ion conductivity, especially at temperatures below 0 °C, due to its aligned graphene sheets and pores. By taking the advantages of both components, the power density and the Seebeck coefficient of a single-cylinder thermocell reaches an exceptionally high value, i.e., 3.6 W m-2 and 1.3 mV K-1 , respectively. Moreover, assembled thermocells in series packaging substantially enhance the voltage of the open-circuit, i.e., from 140 mV (1-cylinder thermocell) to 2.1 V (15-cylinder thermocells).

An Analysis Model Combining Gamma-Type Stirling Engine and Power Converter

Waste heat is a potential source for powering our living environment. It can be harvested and transformed into electricity. Ohmic heat is a common type of waste heat. However, waste heat has the following limitations: wide distribution, insufficient temperature difference (ΔT < 70 K) for triggering turbines, and producing voltage below the open voltage of the battery. This paper proposes an energy harvester model that combines a gamma-type Stirling engine and variable capacitance. The energy harvester model is different from Tavakolpour-Saleh’s free-piston-type engine [7.1 W at ΔT = 407 K (273–680 K)]. The gamma-type Stirling engine is a low-temperature-difference engine. It can be triggered by a minimum ΔT value of 12 K (293–305 K). The triggering force in the variable capacitance is almost zero. Furthermore, the gamma-type Stirling engine is suitable for harvesting waste heat at room temperature. This study indicates that 21 mW of energy can be produced at ΔT = 30 K (293–323 K) for a bias voltage of 70 V and volume of 103.25 cc. Because of the given bias voltage, the energy harvester can break through the open voltage of the battery to achieve energy storage at a low temperature difference.

Experimental study on the energy harvesting of a cooktop via thermoelectric module assisted with phase change material

AbstractThis article presents an effective method for harvesting waste heat from a household cooktop. The energy‐harvesting module contains a thermoelectric (TE) module, heat pipe module, and phase change material (PCM). The effects of TE modules, cooling mediums (air, water, and paraffin), and heat sink configuration and arrangement on the overall performance of the energy harvesting module are examined experimentally. It is found that the cooling process on the cold side of TE plays an essential role on the output voltage and system performance. By adding an air‐cooled heat sink, both output voltage and temperature difference can be moderately improved. Yet using a water‐cooled heat sink can improve the output voltage by about four times higher. Furthermore, the output voltage can be further promoted by using more efficient thermoelectric module. It appears that fewer fins incorporated with the PCM container filled with paraffin shows the optimal energy harvesting performance. Additionally, the recharging time for the full, medium, and low flame operation is tested with 3, 4, and 15 minutes, respectively, and the maximum recharging power of 7.25 W can be achieved with the highest energy storage of 523 mAh after operating 30 minutes.

Conductive nanofilm/melamine foam hybrid thermoelectric as a thermal insulator generating electricity: theoretical analysis and development

Harvesting waste energy through thermoelectric has widely gained attention to aid green energy production. Current efforts are to take advantages of nanomaterials and nanosystems because of dramatic improvements in the performance. However, its cost-effectiveness in generating a 3D configuration for a large-area use is hindered by high production cost. To overcome the present challenges, we propose a flexible and lightweight thermoelectric developed on a melamine foam using a simple dip-dry technique to self-assemble conductive nanofilms in the scaffold. Different amounts of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) conductive nanofilms were variedly fabricated in the foam due to altered amounts of sodium dodecyl sulfate (SDS) surfactant from 0 to 5 wt%. Together with experimental results, a theoretical model was constructed to predict thermal and electrical conductivities, indicating the strong influence of SDS to the electrical conductivity. As a result, the highest nanofilm formation in the foam structure is achieved by adding SDS at 3 wt%. The figure of merit (ZT) of thermoelectric foam is about 0.006–0.007. Our first device was also demonstrated with output voltage of 1.1 mV (ΔT = 40 K). The present study could provide the design and optimization of a hybrid thermoelectric that can act as a simultaneous thermal insulator and power generator.

Thermoelectric GeTe with Diverse Degrees of Freedom Having Secured Superhigh Performance.

Driven by the ability to harvest waste heat into reusable electricity and the exclusive role of serving as the power generator for deep spacecraft, intensive endeavors are dedicated to enhancing the thermoelectric performance of ecofriendly materials. Herein, the most recent progress in superhigh-performance GeTe-based thermoelectric materials is reviewed with a focus on the crystal structures, phase transitions, resonant bondings, multiple valance bands, and phonon dispersions. These features diversify the degrees of freedom to tune the transport properties of electrons and phonons for GeTe. On the basis of the optimized carrier concentration, strategies of alignment of multiple valence bands and density-of-state resonant distortion are employed to further enhance the thermoelectric performance of GeTe-based materials. To decrease the thermal conductivity, methods of strengthening intrinsic phonon-phonon interactions and introducing various lattice imperfections as scattering centers are highlighted. An overview of thermoelectric devices assembled from GeTe-based thermoelectric materials is then presented. In conclusion, possible future directions for developing GeTe in thermoelectric applications are proposed. The achieved high thermoelectric performance in GeTe-based thermoelectric materials with rationally established strategies can act as a reference for broader materials to tailor their thermoelectric performance.

Performance comparison of thermoelectric generators using different materials

Abstract Thermoelectric generators (TEGs) are a promising device to harvest waste heat for power generation. Three material properties of TEGs, including the Seebeck coefficient, electrical resistivity, and thermal conductivity, are often considered as constants in the simulation. However, the performance of TEGs changes with different temperature. In this study, the performances, such as output power and efficiency of one constant property material and three temperature-dependent property materials are investigated numerically. The influences of the temperature difference, the temperature at the cold side surface, and current on the performance of the TEGs are analyzed. The predictions indicate that the output power of the TEGs deviate from the formula when their properties are temperature-dependent. In other words, the output power of the TEGs is not directly proportional to the temperature difference squared. The simulations also satisfy the result of self-consistency. In the case of the fixed temperature difference of 100 oC, when the temperature at cold side surface is lower, different performances of TEG are followed by different materials. The results also tell that one material whose ZT value increases with the rise in temperature has a similar trend in output power and efficiency to the constant-property material. However, another material that has the maximum value in the ZT curve has different trend in output power and efficiency from those of the constant-property material.

Modelling and analysis of a thermoacoustic-piezoelectric energy harvester

This paper proposes an energy harvester that can convert the acoustic power produced by a standing-wave thermoacoustic engine into electricity using a piezoelectric transducer. The proposed thermoacoustic-piezoelectric system may start producing electricity when sufficient heat input is supplied and large-amplitude thermoacoustic oscillations are generated. The stability of the thermoacoustic-piezoelectric energy harvester is analysed using a transfer matrix method based on linear thermoacoustic theory. Experimental results are presented to validate the predicted onset temperature difference across the stack and oscillation frequency. Subsequently, the acoustic field, viscous and thermal losses and acoustic power generation along the tube at the threshold condition are analysed. The present work also focuses on the effect of the temperature distribution of the system on the onset characteristics and the energy conversion process. In addition, a parametric study is performed to investigate the effect of the main geometrical and electrical parameters on the onset characteristics of the entire system. The analytical and experimental approaches developed in this study are useful for the design and optimization of thermoacoustic-piezoelectric engines for harvesting waste thermal energy in industrial applications.

Route towards sustainable smart sensors: ferroelectric polyvinylidene fluoride-based materials and their integration in flexible electronics.

With the advent of the Internet of Everything (IoE) era, our civilization and future generations will employ an unimaginable complex array of electronics and sensors in daily life. Ferroelectric polymers represent a core group of materials supporting the fast development of IoE, and their functionality, straightforward processing and unmatched versatility make them prime candidates for integration in multifaceted devices. Since they are highly selective, highly responsive, highly scalable, self-powering and compatible with flexible and stretchable substrates, they can be easily integrated with various electronics into numerous stand-alone objects and even into skin as sensors for monitoring diverse mechanical, thermal and vital parameters. They can also be used in combination with other sensor materials for harvesting waste energy from mechanical and thermal sources, for data storage and for actuation. This article reviews the up-to-date accomplishments in the ferroelectric polymer field, with focus on materials involving polyvinylidene fluoride (PVDF), and also discussed both their current advancement and future growth in the development of sustainable systems.

The Effect of Solvent on the Seebeck Coefficient and Thermocell Performance of Cobalt Bipyridyl and Iron Ferri/Ferrocyanide Redox Couples

The conversion of thermal energy to electricity using thermoelectrochemical cells (thermocells) is a developing approach to harvesting waste heat. The performance of a thermocell is highly dependent on the solvent used in the electrolyte, but the interplay of the various solvent effects is not yet well understood. Here, using the redox couples [Co(bpy)3][BF4]2/3 (bpy=2,2′-bipyridyl) and (Et4N)3/(NH4)4Fe(CN)6, which have been designed to allow dissolution in different solvent systems (aqueous, non-aqueous, and mixed solvent), the effect of solvent on the Seebeck coefficient (Se) and cell performance was studied. The highest Se for a cobalt-based redox couple measured thus far is reported. Different trends in the Seebeck coefficients of the two redox couples as a function of the ratio of organic solvent to water were observed. The cobalt redox couple produced a more positive Se in organic solvent than in water, whereas addition of water to organic solvent resulted in a more negative Se for Fe(CN)6 3−/4−. UV-vis and IR investigations of the redox couples indicate that Se is affected by changes in solvent–ligand interactions in the different solvent systems.

Harvesting waste heat energy by promoting H+-ion concentration difference with a fuel cell structure

Energy consumption continues to rise as society develops worldwide. Meanwhile, a lot of energy is wasted in the form of heat from various devices and systems. Here we report a new power generator, which works based on a difference in H+-ion concentration in a fuel cell structure and produces electricity by harvesting waste heat. The device works via the following three successive processes: H2 is oxidized at anode to H+ ions, the H+ ions then penetrate through a phosphoric acid-treated polybenzimidazole (PBI-PA) membrane and finally the H+ ions get reduced to H2 at cathode with electrons coming through external circuit from the anode. This system generates electricity at a current density of 21 mA cm−2 and a power density of 1.03 mW cm−2 at 170 °C. The cell's thermoelectric conversion efficiency at 170 °C is 13.72%, which is higher than typical values reported for many common thermoelectric materials in low temperature regimes. This innovative approach may allow for efficient generation of electricity from waste heat.

A Conceptual Review of Green Neighbourhood Adaptive Model for Urban Living

Green Neighborhood can be defined as a neighborhood area that meets the needs of peoples’ daily activities and allows communities to control pollution, save energy, increase employment, decrease crime rates, develop friendships, practice on-site renewable energy methods and preserve agricultural and environmentally sensitive areas. In such an environment, people make easy access to their home, workplaces, public facilities, transit facilities and green spaces within a comfortable walking scale. The guidance is aimed at assisting local authorities and agencies to implement five (5) selected green neighborhood initiatives; Provision of Pedestrian Walkway, Provision of Bicycle Lane, rainwater Harvesting System, Waste Composting and Community Farming.Keywords: green neighbourhood; environment; community; comfortableeISSN 2398-4295 © 2019. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open-access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. http://dx.doi.org/10.21834/ajbes.v4i15.167

Manipulation of p-/n-Type Thermoelectric Thin Films through a Layer-by-Layer Assembled Carbonaceous Multilayer Structure.

Recently, with the miniaturization of electronic devices, problems with regard to the size and capacity of batteries have arisen. Energy harvesting is receiving significant attention to solve these problems. In particular, the thermoelectric generator (TEG) is being studied for its ability to harvest waste heat energy. However, studies on organic TEGs conducted thus far have mostly used conductive polymers, making the application range of TEGs relatively narrow. In this study, we fabricated organic TEGs using carbonaceous nanomaterials (i.e., graphene nanoplatelet (GNP) and single-walled carbon nanotube (SWNT)) with polyelectrolytes (i.e., poly(vinyl alcohol) (PVA) and poly (diallyldimethyl ammonium chloride) (PDDA)) via layer-by-layer (LbL) coating on polymeric substrates. The thermoelectric performance of the carbonaceous multilayer structure was measured, and it was confirmed that the thermoelectric performance of the TEG in this study was not significantly different from that of the existing organic TEG fabricated using the conductive polymers. The 10 bilayer SWNT thin films with polyelectrolyte exhibited a thermopower of −14 μV·K−1 and a power factor of 25 μW·m−1K−2. Moreover, by simply changing the electrolyte, p- or n-type TEGs could be easily fabricated with carbonaceous nanomaterials via the LbL process. Also, by just changing the electrolyte, p- or n-type of TEGs could be easily fabricated with carbonaceous nanomaterials with a layer-by-layer process.

Standard and figure-of-merit for quantifying the performance of pyroelectric nanogenerators

Pyroelectric nanogenerators have emerged as an effective approach for the energy of the new-era, the era of internet of things, with a great potential for harvesting waste heat energy. Here, we present the figure-of-merit for quantifying the output of a pyroelectric nanogenertor. The charge-voltage cycle during temperature cycling has been experimentally performed on a PVDF film and PZT ceramic material. Output energy of 2.53 μJ per cycle and 2.59 mJ per cycle is presented at temperature cycling of 23 K (from 300 to 323 K) and 8 K (from 300 to 308 K) for the PVDF and PZT, respectively. The practicability of the derived figure-of-merit as a universal standard for pyroelectric nanogenerator is further experimentally confirmed and compared with previous results. We believe that it could be useful for optimizing the performance of pyroelectric nanogenerators from both material and structural aspects as well as estimating the generated electricity based on maximum temperature cycling.

Co-P Diffusion Barrier for p-Bi2Te3 Thermoelectric Material

(Bi0.25Te0.75)2Te3 (p-Bi2Te3) is thermoelectric material that can harvest waste heat into useful electric power. A severe reaction between p-Bi2Te3 and Sn-based solder decreases the reliability of thermoelectric modules. Sn/p-Bi2Te3 and Sn3.0Ag0.5Cu (SAC305)/p-Bi2Te3 with and without electroless Co-P at the interfaces were investigated in this study. Without a Co-P layer, brittle SnTe, Sn3Sb2, and Bi precipitates formed at the interface. A thin layer of SnTe after reflow results in growth of a layer-type Sn3Sb2 instead of a strip-like Sn3Sb2. The addition of a Co-P layer to both systems successfully inhibited the formation of brittle intermetallic compounds. Shear test results confirmed that the Co-P diffusion barrier also effectively increased the joint strength.

Bioinspired Design of Vascular Artificial Muscle

AbstractRecently, liquid crystal elastomers (LCEs) have drawn much attention for its wide applications as artificial muscle in soft robotics, wearable devices, and biomedical engineering. One commonly adopted way to trigger deformation of LCEs is using embedded heating elements such as resistance heating wires and photothermal particles. To enable the material to recover to its unactuated state, passive and external cooling is often employed to lower the temperature, which is typically slow and environmentally sensitive. The slow and uncontrollable recovery speed of thermally driven artificial muscle often limits its applications when even moderate cyclic actuation rate is required. In this article, inspired by biology, a vascular LCE‐based artificial muscle (VLAM) is designed and fabricated with internal fluidic channel in which the hot or cool water is injected to heat up or cool down the material to achieve fast actuation as well as recovery. It is demonstrated that the actuation stress, strain, and cyclic response rate of the VLAM are comparable to mammalian skeletal muscle. Because of the internal heating and cooling mechanism, VLAM shows a very robust actuating performance within a wide range of environmental temperatures. The VLAM designed in this article may also provide a convenient way to harvest waste heat to conduct mechanical work.