Direct Electricity Generation Research Articles

Multifunctional Magnetic Nanocolloids for Hybrid Solar-Thermoelectric Energy Harvesting.

Present environmental issues force the research to explore radically new concepts in sustainable and renewable energy production. In the present work, a functional fluid consisting of a stable colloidal suspension of maghemite magnetic nanoparticles in water was characterized from the points of view of thermoelectrical and optical properties, to evaluate its potential for direct electricity generation from thermoelectric effect enabled by the absorption of sunlight. These nanoparticles were found to be an excellent solar radiation absorber and simultaneously a thermoelectric power-output enhancer with only a very small volume fraction when the fluid was heated from the top. These findings demonstrate the investigated nanofluid’s high promise as a heat transfer fluid for co-generating heat and power in brand new hybrid flat-plate solar thermal collectors where top-heating geometry is imposed.

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Direct electricity generation from water flow/evaporation, coined hydrovoltaic effect, has recently attracted intense interest as a facile approach to harvest green energy from ubiquitous capillary water flow or evaporation. However, the current hydrovoltaic device is inferior in output power efficiency compared to other renewable energy devices. Slow water evaporation rate and inefficient charge collection at device electrodes are two fundamental drawbacks limiting energy output efficiency. Here, we report a bioinspired hierarchical porous fabric electrode that enables high water evaporation rate, efficient charge collection, and rapid charge transport in nanostructured silicon-based hydrovoltaic devices. Such an electrode can efficiently collect charges generated in nanostructured silicon as well as induce a prompt water evaporation rate. At room temperature, the device can generate an open-circuit voltage (Voc) of 550 mV and a short-current density (Jsc) of 22 μA·cm-2. It can output a power density over 10 μW·cm-2, which is 3 orders of magnitude larger than all those reported for analogous hydrovoltaic devices. Our results could supply an effective strategy for the development of high-performance hydrovoltaic devices through optimizing electrode structures.

Applicability of Waste Engine Oil for the Direct Production of Electricity

New methods for the use of waste products as input for other technologies are a constant subject of research efforts. One such product is waste engine oil. Due to the constantly increasing number of motor vehicles in the world, the recycling or application of engine oils for energy production purposes is currently of considerable importance. This paper contains research regarding the analysis of the electro-oxidation potential of waste engine oil, and thus the possibility of using such oil as a material in fuel cells. The research demonstrates the basic possibility of the electro-oxidation of this oil emulsion on a platinum electrode in an acid electrolyte (aqueous solution of H2SO4). It was shown that in the temperature range of 20–80 °C, the electro-oxidation of the waste engine oil emulsion occurred for all emulsion concentrations (0.005%, 0.010%, 0.030%, and 0.060% of the reactor volume). The maximum current density obtained in the measurements was 21 mA·cm−2 at the temperature of 60 °C (0.030% waste oil and 0.5 M electrolyte). Although this value is small, it encourages further research on the use of used engine oil for the direct generation of electricity.

Thermoelectric generator (TEG) technologies and applications

• The state-of-the-art of thermoelectric generators is reviewed comprehensively. • The materials used in TEGs, Figure of Merit, improvement techniques are introduced. • Different configurations of experimental set-ups and prototypes are explored. • The performance of TEGs is investigated with different simulation software packages. Nowadays humans are facing difficult issues, such as increasing power costs, environmental pollution and global warming. In order to reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their capacity to transform thermal energy directly into electric power through the Seebeck effect. Due to the unique advantages they present, thermoelectric systems have emerged during the last decade as a promising alternative among other technologies for green power production. In this regard, thermoelectric device output prediction is important both for determining the future use of this new technology and for specifying the key design parameters of thermoelectric generators and systems. Moreover, TEGs are environmentally safe, work quietly as they do not include mechanical mechanisms or rotating elements and can be manufactured on a broad variety of substrates such as silicon, polymers and ceramics. In addition, TEGs are position-independent, have a long working life and are ideal for bulk and compact applications. Furthermore, Thermoelectric generators have been found as a viable solution for direct generation of electricity from waste heat in industrial processes. This paper presents in-depth analysis of TEGs, beginning with a comprehensive overview of their working principles such as the Seebeck effect, the Peltier effect, the Thomson effect and Joule heating with their applications, materials used, Figure of Merit, improvement techniques including different thermoelectric material arrangements and technologies used and substrate types. Moreover, performance simulation examples such as COMSOL Multiphysics and ANSYS-Computational Fluid Dynamics are investigated.

All-Iron Ions Mediated Electron Transfer for Biomass Pretreatment Coupling with Direct Generation of Electricity from Lignocellulose

All-Iron Ions Mediated Electron Transfer for Biomass Pretreatment Coupling with Direct Generation of Electricity from Lignocellulose

A hybrid fuel cell system integrated with methanol steam reformer and methanation reactor

In this paper, a hybrid fuel cell system integrated with methanol steam reformer and methanation reactor is demonstrated. Methanol steam reformer employed in this system is to produce hydrogen-rich reformate in connection with a methanation reactor to reduce the carbon monoxide content effectively, and the reformate gas is sent into a low-temperature polymer electrolyte fuel cell for direct electric power generation. The optimum conditions (temperature, water to methanol ratio, and space velocity) for methanol steam reforming (MSR) reaction and methanation (MET) reaction are verified by experiments. A comparison between pure hydrogen, reformate surrogate, and actual reformate is performed. The results show that the power density of this hybrid system achieves 245.2 mW/cm2 while it achieves 268.8 mW/cm2 when employing pure hydrogen as the fuel. An alternative novel method to solve the problem of hydrogen storage and transportation is provided and the in-situ hydrogen production and utilizing through low-temperature fuel cell system is realized, which is helpful to accelerate the commercialization process of the fuel cell.

The Inverse Relationship between Metal-Enhanced Fluorescence and Fluorophore-Induced Plasmonic Current

In this work we investigate the relationship between metal-enhanced fluorescence (MEF) and fluorophore-induced plasmonic current (PC). This is accomplished through measurements of both radiative emission (MEF) and direct electrical current generation between discrete metal nanoparticles upon fluorophore excitation (PC). We have conducted these measurements on silver and gold nanoparticle island films, over a range of nanoparticle sizes and spacing in the films. We have observed an inverse relationship in the magnitude of MEF with PC, where larger and more closely spaced metal nanoparticles are found to result in increased PC and subsequently a decreased MEF. We attribute this effect to the relatively high capacitance and low charging energy of large and closely spaced particles, providing an outlet for plasmon relaxation in the form of electron flow and electrical current generation. These results are significant as they open potential for controlling for and the optimization of both MEF and PC.

High output voltage generation of over 5 V from liquid motion on single-layer MoS2

Water stores a large amount of clean energy in its dynamic forms. Owing to the wide availability of water and the rising demand for clean energy sources, the direct electricity generation from liquid motion by low-dimensional materials such as graphene has gained much interest. Electricity generation is induced by the motion of an electric double layer at the interface between the liquid droplet and solid surface. However, the output voltage with materials such as graphene is still limited to several hundred millivolts. In this report, we present a large-area single-layer MoS2 film grown by chemical vapor deposition as a nanogenerator, which is capable of generating a large output voltage of more than 5 V from the motion of an aqueous NaCl droplet. Our findings indicate that the high shunt resistance of MoS2 results in a large generated voltage. Furthermore, we demonstrate the possibility to scale up the MoS2 nanogenerator by arranging them in series and parallel connections, which respectively increase the output voltage and current, with a three-times increase with an array of three MoS2 nanogenerators. Our work opens the application of single-layer MoS2 for harvesting electricity from the dynamic movement of liquid, such as the capability to harvest ocean wave energy, which is also demonstrated here.

Use of abandoned oil wells in geothermal systems in Turkey

Human beings have been benefiting from geothermal energy for different uses since the dawn of civilization in many parts of the world. One of the earliest uses of geothermal energy was for heating and it was used extensively by Romans in Turkey. The Aegean region is favored with a large number of thermal springs known since ancient times. However, it was in the twentieth century that geothermal energy was first used on a large scale for direct use applications and electricity generation. The country’s installed heat capacity is 3322.3 MWt for direct use and 1347 MWe for power production. Also, many drilled wells to extract oil or natural gas were abandoned for various reasons in the southeast of Turkey. Some of the oil fields have heat content that can be used for geothermal energy. Some even have hot fluid in the reservoir. This paper presents an investigation into how to use geothermal energy in abandoned oil and natural gas wells. Methods used to generate geothermal energy from abandoned oil fields other than conventional geothermal energy production are examined. Downhole heat exchangers can be used to extract heat without producing geothermal fluid which decrease gas emissions to the atmosphere and energy need for reinjection, from the abandoned oil wells to generate electricity or direct use applications. Using this method, it is possible to use abandoned wells in southeastern Turkey where this energy improves the economy of the region.

Thermodynamic evaluation of SOFC-GT hybrid power and cooling system

ABSTRACT Amongst various energy conversion systems, the fuel cell based direct energy conversion system appears to have good potential to mitigate the environmental impact along with being an alternate source for power generation. Fuel cells are quite attractive due to their capability to produce electricity directly without producing any harmful emissions in the environment. However, there exists ample scope for optimal utilization of energy interactions in it. Present work deals with the parametric investigation of the considered configuration of the solid oxide fuel cell (SOFC) and gas turbine (GT) hybrid system coupled with a refrigeration cycle for yielding power and cooling together. The hybrid power and cooling system rely upon the SOFC for direct electricity generation along with shaft work from the GT. For better energy utilization, it is proposed to utilize the GT exhaust energy for steam generator and running the vapor absorption refrigeration system to meet the power generation and cooling requirements, respectively. Novelty of this work lies in the effective energy utilization by integration of cooling with power in SOFC-GT hybrid system. Here thermodynamic modeling of the considered hybrid power and cooling system has been carried out based on the first law of thermodynamics. The computer simulation of SOFC-GT hybrid power and cooling system is used for studying the effect of different parameters on the cycle performance. Here maximum efficiency of 64.74% is found at 6 cycle pressure ratio, 1400 K turbine inlet temperature and 288 K ambient temperature.

Numerical integration of solar, electrical and thermal exergies of photovoltaic module: A novel thermophotovoltaic model

Over the years, there have been efforts to understand the thermodynamics of solar cells so that the physics can be better improved. Heat generation in photovoltaic (PV) modules (which contain solar cells for direct electrical energy generation) has been acknowledged in many literatures as a key power degradation parameter. At the moment, an accurate modeling of photovoltaic power generation requires a computational iterative model since the output voltage of a PV creates a transcendental equation. This study uses code-based model (CBM) which allows user defined codes to implement a novel integration of solar, electrical and thermal exergies of photovoltaic module in order to create a thermophotovoltaic model. After integrating the proposed model in MATLAB, parametric studies were carried out to understand how changes in temperature and solar radiation affect the electrical and thermal exergy flows during power generation. Interestingly, results show that heat is essential for power generation although it should not exceed the critical value beyond which the voltage would start deteriorating. At 290 K, the electrical exergy flow of the 45 W PV module used in this study was 41.46 J/s and the overall improvement in exergy could be up to 51% if the waste heat generated is utilised for useful thermal work. The energy and exergy efficiencies of the PV module were initially the same but the energy efficiency degraded because of the reduction in the open circuit voltage (Voc) as temperature increased. Lastly, insights from this study is purposed to increase the understanding of how electrical and thermal exergy flow pattern in the PV module can be managed to either stabilise its temperature through cooling and surface treatment or facilitate its heat recovery for photovoltaic-thermal applications.

Toward CO2 utilization for direct power generation using an integrated system consisting of CO2 photoreduction with 3D TiO2/Ni-foam and a photocatalytic fuel cell

An integrated system consisting of CO2 photoreduction with 3D TiO2/Ni-foam and a PFC for direct electricity generation.

Solar energy-A look into power generation, challenges, and a solar-powered future

Sun is an inexhaustible source of energy capable of fulfilling all the energy needs of humankind. The energy from the sun can be converted into electricity or used directly. Electricity can be generated from solar energy either directly using photovoltaic (PV) cells or indirectly using concentrated solar power (CSP) technology. Progress has been made to raise the efficiency of the PV solar cells that can now reach up to approximately 34.1% in multi-junction PV cells. Electricity generation from concentrated solar technologies has a promising future as well, especially the CSP, because of its high capacity, efficiency, and energy storage capability. Solar energy also has direct application in agriculture primarily for water treatment and irrigation. Solar energy is being used to power the vehicles and for domestic purposes such as space heating and cooking. The most exciting possibility for solar energy is satellite power station that will be transmitting electrical energy from the solar panels in space to Earth via microwave beams. Solar energy has a bright future because of the technological advancement in this field and its environment-friendly nature. The biggest challenge however facing the solar energy future is its unavailability all-round the year, coupled with its high capital cost and scarcity of the materials for PV cells. These challenges can be met by developing an efficient energy storage system and developing cheap, efficient, and abundant PV solar cells. This article discusses the solar energy system as a whole and provides a comprehensive review on the direct and the indirect ways to produce electricity from solar energy and the direct uses of solar energy. The state-of-the-art procedures being employed for PV characterization and performance rating have been summarized. Moreover, the technical, economic, environmental, and storage-related challenges are discussed with possible solutions. Furthermore, a comprehensive list of future potential research directions in the field of direct and indirect electricity generation from solar energy is proposed.

Direct Electricity Generation Mediated by Molecular Interactions with Low Dimensional Carbon Materials—A Mechanistic Perspective

AbstractNext‐generation off‐the‐grid electronic systems call for alternative modes of energy harvesting. The past two decades have witnessed the evolution of a wide spectrum of low dimensional carbon materials with extraordinary physical and chemical properties, ideal for microscale electrical energy storage and generation. Tremendous progress has been made in harnessing the energy associated with the interactions between these nanostructured carbon substrates and the surrounding molecular phases, subsequently converting them into useful electricity. This review summarizes the important theoretical and experimental milestones the field has reached to date, and further classifies these energy harvesting processes based on underlying physics, into five mechanistically distinct classes—phonon coupling, Coulombic scattering, electrokinetic streaming, asymmetric doping, and capacitive discharging. With a special mechanistic focus, the authors hope to resolve the fundamental attributes shared by this diverse array of molecular scale energy harvesting schemes, offer perspectives on key challenges, and ultimately establish design principles that guide further device optimization.

Simultaneous effective sludge stabilization and direct electricity generation by merging microbial fuel cell (MFC) and Fered-Fenton reactor: An experimental study

Harvesting bioenergy from waste materials has fascinated noticeable attention in recent decades. In this respect, it is expected that the recovery of sustainable energy from sewage sludge will become more and more of interest. Improving the efficiency of currently utilized methods and removing their limitations are the main issues that investigations have been concentrated on them. In this study, a novel package has been designed and experimentally investigated. The main purpose of the current study is attaining an effective system which would be able to effectively stabilize the sewage sludge in considerably low retention times simultaneous with direct electricity generation. Therefore, a two-chamber microbial fuel cell (MFC) and an electrochemical advanced oxidation process (EAOP) reactor (based on Fered-Fenton process) have been merged to each other to reach this goal and the performance of the package has been modeled and optimized by response surface methodology (RSM). Also, the optimal conditions of the package's performance have been determined. The accuracy of the proposed models have been confirmed by various experiments and evaluating the related literature. According to the results, the package demonstrated its best performance when the pHEAOP, IEAOP, the retention time, Tpackage, [Fe2+]/[H2O2], and [H2O2] are 4, 1500 mA/cm2, 4 h, 35 ᵒC, 0.75 and 1500 mg L−1, respectively. In this condition, the package generated 5700 mW m−3 as the maximum generated electrical power density and more than 75% as the VSS removal efficiency.

Prospects in bioelectrochemical technologies for wastewater treatment.

Bioelectrochemical technologies are emerging as innovative solutions for waste treatment, offering flexible platforms for both oxidation and reduction reaction processes. A great variety of applications have been developed by utilizing the energy produced in bioelectrochemical systems, such as direct electric power generation, chemical production or water desalination. This manuscript provides a literature review on the prospects in bioelectrochemical technologies for wastewater treatment, including organic, nutrients and metals removal, production of chemical compounds and desalination. The challenges and perspectives for scale-up were discussed. A technological strategy to improve the process monitoring and control based on big data platforms is also presented. To translate the viability of wastewater treatment based on bioelectrochemical technologies into commercial application, it is necessary to exploit interdisciplinary areas by combining the water/wastewater sector, energy and data analytics technologies.

Power Generation from a Radiative Thermal Source Using a Large-Area Infrared Rectenna

Electrical power generation from a moderate temperature thermal source by means of direct conversion of infrared radiation is important and highly desirable for energy harvesting from waste heat and micropower applications. Here, we demonstrate direct rectified power generation from an unbiased large-area nanoantenna-coupled tunnel diode rectifier, called a rectenna. Using a vacuum radiometric measurement technique with irradiation from a temperature-stabilized thermal source, a generated power density of 8 nW/cm$^2$ is observed at a source temperature of 450C for the unbiased rectenna across an optimized load resistance. The optimized load resistance for the peak power generation for each temperature coincides with the tunnel diode resistance at zero bias and corresponds to the impedance matching condition for a rectifying antenna. Current voltage measurements of a thermally illuminated large-area rectenna show current zero crossing shifts into the second quadrant indicating rectification. Photon-assisted tunneling in the unbiased rectenna is modeled as the mechanism for the large short-circuit photocurrents observed where the photon energy serves as an effective bias across the tunnel junction. The measured current and voltage across the load resistor as a function of the thermal source temperature represents direct current electrical power generation.

Modeling assisted evaluation of direct electricity generation from waste heat of wastewater via a thermoelectric generator

The thermal energy represents a significant portion of energy potential in municipal wastewater and may be recovered as electricity by a thermoelectric generator (TEG). Converting heat to all-purpose electricity by TEG has been demonstrated with large heat gradients, but its application in waste heat recovery from wastewater has not been well evaluated. Herein, a bench-scale Bi2Te3-based waste heat recovery system was employed to generate electricity from a low temperature gradient through a combination of experiments and mathematical modeling. With an external resistance of 7.8 Ω and a water (hot side) flow rate of 75 mL min−1, a maximum normalized energy recovery of 4.5 × 10−4 kWh m−3 was achieved under a 2.8 °C temperature gradient (ΔT). Model simulation indicated a boost in both power output and energy conversion efficiency from 0.76 mW and 0.13% at ΔT = 2.8 °C to 61.83 mW and 1.15% at ΔT = 25 °C. Based on the data of two-year water/air temperature obtained from the Christiansburg Wastewater Treatment Plant, an estimated energy generation of 1094 to 70,986 kWh could be expected annually with a saving of $163 to $6076. Those results have revealed a potential for TEG-centered direct electricity generation from low-grade heat towards enhanced resource recovery from wastewater and encouraged further exploration of this approach.

Understanding the Mechanisms of Photosynthetic Electron Transport for Energy Conversion Applications

Light energy can be harnessed using photosynthesis for either direct generation of electricity or production of energy rich fuels such as ethanol, propanol, butanol of hydrogen in photo-bioelectrochemical cells (1). A photo-bioelectrochemical cell (PBEC) based on natural photosynthesis is composed of an anode containing a photo-biocatalyst such as photosystem II, thylakoid membrane, or whole cell microorganism such as cyanobacteria coupled with an enzymatic cathode. With the help of light, the photo-biocatalyst on the anode oxidizes water to generate electrons and protons. On the cathode, enzymes such as laccase or bilirubin oxidase are employed to catalyze the reduction of oxygen and protons to water. When such anodes are coupled with cathodes containing enzymes such as hydrogenase or nitrogenase, the system generates hydrogen. In either case, water and light are the only raw materials used to generate electricity or hydrogen. The photo-biocatalysts on the anode utilize the photosynthetic light reactions to generate electrons and deliver them to the anode via either direct or mediated electron transfer. The electron transfer mechanisms of the light reactions determine the pathways for electron delivery to the anode, which in turn determines the photocurrent density, stability and overall conversion efficiency of the process. This talk will overview our research over the years on the understanding of the photosynthetic light reactions and the underlying pathways through which the electrons are channeled to the anode.

Direct Electricity Generation from Dissolved Cellulosic Biomass in an Alkaline Fuel Cell

AbstractCellulose, which accounts for more than half of the carbon content in plants, has become a popular feedstock for biofuel production. In this work, direct electricity generation from dissolved cellulosic biomass in an alkaline fuel cell is explored without energy‐intensive process. The effect of different cellulose dissolution solvents on the electricity production is investigated. Results show dissolution treatment can remarkably affect the fuel cell performance. When NaOH/urea/thiourea is chosen as a solvent, the specific capacity of cellulose is about sixfold higher than that using only NaOH as solvent. The limiting current density and the maximum power density reach 0.85 mA cm−2 and 0.07 mW cm−2, respectively. This power density surpasses those of any existing biotic or abiotic designs. Electrochemical characterizations demonstrate that the remarkable activity improvement towards the cellulose oxidation reaction in NaOH/urea/thiourea aqueous solution is due to the lower charger transfer resistance and higher energy transfer efficiency.