Direct Electricity Generation Research Articles

Analog One-Cycle Control Strategy for Stable Battery Charging in Photovoltaic Systems

The growing adoption of photovoltaic systems for direct electricity generation from solar radiation has underscored the importance of efficient energy storage solutions. Batteries are the predominant method for storing energy from photovoltaic systems, especially for applications such as electric vehicle (EV) charging. However, these systems face significant challenges, particularly regarding battery longevity, as fluctuations in solar irradiation can lead to harmful voltage spikes. This paper introduces an Analog One-Cycle Control (OCC) strategy designed to mitigate these issues by stabilizing the battery voltage against varying input voltages. The proposed control scheme aims to enhance battery life by preventing damage caused by voltage overshoots. Experimental results demonstrate the effectiveness of the OCC strategy in maintaining steady-state conditions and optimizing power management.

Optimal design and economic analysis of a stand-alone integrated solar hydrogen water desalination system case study agriculture farm in Kairouan Tunisia

In the contemporary global discourse on environmental and developmental issues, the dual challenges of sustainable green energy and water supply stand paramount. These elements are vitally intertwined with the socio-economic vitality of the world. Notably, regions plagued by freshwater scarcity are increasingly turning to desalination which consists of a reliable and unconventional water source. The intersection of renewable energy with desalination and water purification processes presents a compelling synergy. This approach is particularly pertinent in areas where freshwater shortages coexist with abundant solar energy availability. Additionally, these technologies boast the advantage of low operational and maintenance costs. This paper delves into the design, optimization and financial analysis of a novel, standalone hybrid energy system, integrating photovoltaic and fuel cell technologies, for an agriculture farm situated in Kairouan, Tunisia. Unlike conventional systems, this model foregoes battery storage in favour of hydrogen storage, generated through water electrolysis powered by solar energy. This system harnesses solar energy for direct electrical power generation and hydrogen gas production. A segment of the generated electricity is allocated to electrolysis for green hydrogen production. In times of solar unavailability, the stored hydrogen is reconverted to electricity via a fuel cell. An intriguing aspect of this system is the utilization of saline well water, which, due to its high salt content, necessitates purification through desalination to prevent damage to the electrolysis unit and to render it suitable for agricultural irrigation.

Viability of low‐grade heat conversion using liquid piston Stirling engines

AbstractLiquid piston Stirling engines (LPSEs) are low‐cost, simple, maintenance‐free, and flexible external combustion engines with the potential to operate from low‐grade heat sources. This study reviews the major components, operations, and variants of LPSEs along with the mathematical models to assess their performance, which have been developed since the inception of LPSEs. Consequently, the technical feasibility of LPSEs in different applications is deduced from this complete systematic review, especially useful for both theoretical and applied researchers. The operation is based on a four‐stage Stirling cycle with most engines having three main components as per the findings of this study: the displacer columns, the regenerator, and tuning columns. The two main variants categorized by this study are the dry operating fluidyne and the wet operating thermofluidic. The accurate analyses of these engines are mostly within the spheres of experimental and numerical techniques since analytical mathematical models are difficult to develop owing to the complexity of the operating thermo‐physics. Pumping, cooling, and the direct generation of electricity are frequent applications of these engines reported in the literature. However, since their inception in 1969, these engines are yet to be commercialized owing to their low energy efficiency, power density, and reliability. The findings of this research conclude that LPSEs are essential for environment‐friendly pumping applications using low‐grade heat, especially in the irrigation sector of remote regions with limited access to electricity grids. Additionally, by replacing the electricity‐consuming status quo pumps, LPSEs ensure sustainability with minimal greenhouse gas emissions.This article is categorized under: Energy and Power Systems > Energy Management Sustainable Development > Energy‐Water‐Food Nexus Energy and Power Systems > Distributed Generation Sustainable Development > Goals

The Implementation of Waste Biomass Substrates as Feedstock for The Production of Bio-Electricity Through Microbial Fuel Cells (MFCS): A Short Review

Lignocellulosic biomass plays a pivotal role in sustainable energy production, with a focus on indirect biomass fuel cells (IDBFC) and direct biomass fuel cells (DBFC). IDBFCs require the initial conversion of biomass into simpler forms like sugars, biogas, syngas, or biocharfor subsequent electricity generation. In contrast, DBFCs offer a more direct approach, generating electricity from biomass without intermediate steps. Lignocellulosic biomass, composed of cellulose, lignin, and hemicellulose, has diverse applications, from bioethanolto direct electricity generation. However, the complex composition of lignocellulosic compounds, including carbon, hydrogen, oxygen, phosphorus, nitrogen, and sulfur, poses challenges for efficient enzymatic hydrolysis, a crucial factor in achieving high power density inMicrobial Fuel Cells (MFCs). MFCs use microorganisms to convert substrates into electricity, influenced by factors like substrate degradation rate, circuit resistance, electron transfer rates, proton mass transfer, electrode materials, and operational conditions. The selection of proper electrode materials is vital for optimising MFC performance. At the heart of MFC performance are electricigens, microorganisms facilitating electron transfer from biomass to the anode through direct or indirect mechanisms. Direct electron transfer (DET), relying on physical contact between microorganism membranes and the anode, is preferred for its efficiency and eco-friendliness. The paper also explores the importance of nutrient supplements (macro and micro) in enhancing bio-methane production and process stability in agro-industrial biogas mono-digestion plants. Nutrient balance significantly affects microbial generation time, degradation rates, and gas production in anaerobic digestion processes. In conclusion, understanding the intricate interplay between lignocellulosic biomass energy fuel cells, electricigens, and their performance factors is crucial for advancing sustainable energy production. MFCs show promise in utilising sludge and various waste biomasses, positioning them as practical, reliable, and versatile power sources in the evolving landscape of renewable energy technologies.
 Keywords: Lignocellulosic waste, bioenergy, microbial fuel cells (MFCs), electricigens

An Aqueous Redox Flow Battery Using CO2 as an Active Material with a Homogeneous Ir Catalyst.

For the application of CO2 as an energy storage material, a H2 storage system has been proposed based on the interconversion of CO2 and formic acid (or formate). However, energy losses are inevitable in the conversion of electrical energy to H2 as chemical energy (~70% electrical efficiency) and H2 to electrical energy (~40% electrical efficiency). To overcome these significant energy losses, we developed a system based on the interconversion of CO2 and formate for the direct storage and generation of electricity. In this paper, we report an aqueous redox flow battery system using homogeneous Ir catalysts with CO2-formate redox pair. The system exhibited a maximum discharge capacity of 10.5 mAh (1.5 Ah L-1), capacity decay of 0.2% per cycle, and total turnover number of 2550 after 50 cycles. During charging-discharging, in situ fluorescence X-ray absorption fine structure spectroscopy based on an online setup indicated that the active species was in a high valence state of Ir4+.

An Aqueous Redox Flow Battery Using CO2 as an Active Material with a Homogeneous Ir Catalyst**

AbstractFor the application of CO2 as an energy storage material, a H2 storage system has been proposed based on the interconversion of CO2 and formic acid (or formate). However, energy losses are inevitable in the conversion of electrical energy to H2 as chemical energy (≈70 % electrical efficiency) and H2 to electrical energy (≈40 % electrical efficiency). To overcome these significant energy losses, we developed a system based on the interconversion of CO2 and formate for the direct storage and generation of electricity. In this paper, we report an aqueous redox flow battery system using homogeneous Ir catalysts with CO2‐formate redox pair. The system exhibited a maximum discharge capacity of 10.5 mAh (1.5 Ah L−1), capacity decay of 0.2 % per cycle, and total turnover number of 2550 after 50 cycles. During charging‐discharging, in situ fluorescence X‐ray absorption fine structure spectroscopy based on an online setup indicated that the active species was in a high valence state of IrIV.

Uncovering the energy-carbon-water footprint of waste rubber recycling: Integrated environmental and economic perspectives

The commitment to waste management has gained increasing momentum as global waste generation continues to skyrocket and threaten the environment. However, detailed assessments and clear insights remain absent to address the global waste utilization conundrum. This study evaluated the impact-oriented energy, carbon, and water (ECW) footprints of three typical scenarios for a waste recycling activity (i.e., waste rubber recycling) from environmental and economic dimensions, and explored key factors, nexus characteristics, and optimization measures. Results indicated that the rubber powder as an asphalt modifier scenario had a 93% greater environmental impact and 87% higher economic cost compared with the pyrolysis and reclaimed rubber production scenarios. Key processes, such as direct processes, electricity generation, and transportation, were identified as the major contributors to the ECW footprints, with the internal costs of raw materials, equipment, and taxes coupled with the external costs of human health dominating the economic impact. The nexus analysis results highlighted the urgent need to optimize the energy system for waste rubber recycling. Greening the production process revealed the benefits, with natural additives mitigating 85% of the environmental burden and 97% of the external costs compared with conventional additives. Industrial green microgrids, clean energy generation, proximity waste management, and electrified transportation were explored to foster sustainable optimization of waste rubber recycling systems. Moreover, a joint tax-subsidy mechanism for rubber production-recycling systems can stimulate recycling-oriented product design and increase the motivation to recycle waste rubber.

ACCESSIBLE SOLAR ENERGY TECHNOLOGY FOR DOMESTIC APPLICATIONS IN THE UK: EDGE SOLAR

AbstractRenewable energy is increasingly used and promoted. In the UK, for example, large scale renewable energy farms have been used to supply electricity with great effect. Given the large number of homes, there is considerable impact to be made by small scale residential renewable energy systems. Despite solar panels being the most common form of residential renewable energy technology, only 4% of buildings in the UK support solar technology of any kind. For direct electricity generation, silicon-based photovoltaic (PV) arrays are the most utilised, and when used in a residential setting, they are typically mounted on the sloped roofs. This is where the problem lies. The technology comes with a high cost, and there is further financial burden of installation and maintenance, making solar energy inaccessible for many UK homeowners. This paper presents a research and design innovation project to make PV technology more accessible in the UK. Edge Solar, the innovative, affordable, new PV system concept for UK homes may become a promising solution to significantly improve the accessibility to the PV technology and renewable energy at the household level in the UK and beyond with further development and commercialisation.

An approach for sizing a PV–battery–electrolyzer–fuel cell energy system: A case study at a field lab

Hydrogen is becoming increasingly popular as a clean, secure, and affordable energy source for the future. This study develops an approach for designing a PV–battery–electrolyzer–fuel cell energy system that utilizes hydrogen as a long-term storage medium and battery as a short-term storage medium. The system is designed to supply load demand primarily through direct electricity generation in the summer, and indirect electricity generation through hydrogen in the winter. The sizing of system components is based on the direct electricity and indirect hydrogen demand, with a key input parameter being the load sizing factor, which determines the extent to which hydrogen is used to meet seasonal imbalance. Technical and financial indicators are used to assess the performance of the designed system. Simulation results indicate that the energy system can effectively balance the seasonal variation of renewable generation and load demand with the use of hydrogen. Additionally, guidelines for achieving self-sufficiency and system sustainability for providing enough power in the following years are provided to determine the appropriate component size. The sensitivity analysis indicates that the energy system can achieve self-sufficiency and system sustainability with a proper load sizing factor from a technical perspective. From an economic perspective, the levelized cost of energy is relatively high because of the high costs of hydrogen-related components at this moment. However, it has great economic potential for future self-sufficient energy systems with the maturity of hydrogen technologies.

Simulation of Thermosyphon Rankine Engine

The increasing global energy demand has led to other alternative ways of harvesting energy from renewable resources. This energy cause less environmental pollution and deterioration of humans' health. Thermosyphon Rankine engine (TSR) is a concept used for direct electrical power generation from low-grade heat sources. In this project, an extended investigation on previous experimental done was conducted through a simulation approach using Computational Fluid Dynamic (CFD) analysis to simulate a two-phase flow, phase change occurred during evaporation and condensation processes inside the thermosyphon under different power inputs of 245 W, 552 W, and 984 W. Also the water was used as a working fluid. The volume of fluid (VOF) technique was used to model the phase change using ANSYS FLUENT software. The simulation investigated temperature profile, water volume fraction, and velocity. Then, CFD predicted temperature profile was compared with the previous experimental data, and percentage error was calculated. Compared to the experimental one, CFD predicted temperature profile was higher than the experimental one due to mechanical losses during experimentation. Meanwhile, the model managed to simulate vapor bubbles and nucleate boiling during phase change. It showed that the VOF model with the in-built evaporation-condensation model developed by Lee only simulated nucleate boiling at the interphase between water and vapor phase during evaporation and condensation processes.

Photo-thermo-electric modeling of photon-enhanced thermionic emission with concentrated solar power

Photon-enhanced thermionic emission (PETE) is an advanced technology that combines both the photoelectric and the thermionic effects synergistically into a single device for direct electricity generation. However, its industrial-level application is still missing partly due to the lack of advanced models to analyze its operating characteristics and to understand the synergistic mechanism. Herein, we develop a numerical model of PETE by fully considering the optical, the electrical and the thermodynamic aspects with one-dimensional steady-state continuity equations of carriers in the semiconductor cathode. A hybrid PETE-Stirling cycle system is also proposed to yield an output power density of 162.65 kW/m 2 with 32.8% conversion efficiency. The PETE conversion efficiency keeps ∼20% with the optimal electron affinity increases from 0.5 to 1.14 eV as solar concentration ratio varies from 100 to 500. The cathode thickness should be optimized by considering both solar absorption and photon enhancement, where the thickness range of 0.78–1.52 μm is obtained for 50–500 suns. The interelectrode gap is also found to significantly affect the PETE performance by regulating both the space-charge effect and near-field radiation, where the range of 0.5–2 μm is recommended. This work can serve as a foundation to understand the working mechanism of PETE converters and provide guidelines for the performance evaluation. • Numerical models are developed for photon-enhanced thermionic emission converters. • Coupled effects of optical, electrical and thermodynamic fields are fully considered. • Characteristics of the converter for various scenarios are analyzed in detail. • A hybrid system is proposed with a 162.65 kW/m 2 power density and a 32.8% efficiency.

Thermo-hydro-mechanical modeling of an enhanced geothermal system in a fractured reservoir using carbon dioxide as heat transmission fluid- A sensitivity investigation

Geothermal energy has the potential to support direct heat usage and electricity generation at a low carbon footprint. Using carbon dioxide (CO2) as a heat transfer fluid can allow us to achieve a negative carbon energy solution. This study assess the geothermal energy extraction potential from a discretely fractured reservoir using CO2. The geothermal energy extraction process is a coupled thermo-hydro-mechanical (THM) mechanism, and the geomechanical stresses involve thermoelasticity and poroelasticity. This study demonstrates a fully coupled THM mechanism for enhanced geothermal system (EGS) operations. A large number of parameters are involved in the THM mechanism, and therefore, it becomes difficult to assess the key operating parameters to have better-operating efficiency. We identified 22 input parameters that control the THM mechanism. Therefore, a sensitivity analysis is performed to investigate the relative importance of these parameters that concentrates on three key objective parameters: thermal breakthrough time, mass flux and overall energy recovery. The important parameters controlling these three objective parameters are matrix permeability and fracture aperture whereas wellbore radius has an impact on mass flux and total energy recovery. All the parameters are ranked in order of their importance during an EGS operation.

Comparative Life Cycle Assessments of Photovoltaic Thermal Systems with Earth Water Heat Exchanger Cooling

Photovoltaic (PV) technology is a commercially established technology for direct generation of electricity using solar energy. However, one drawback of this technology is that its electrical efficiency decreases with increase in panel temperature beyond standard surface temperature of 25°C. To maintain the panel surface temperature, photovoltaic thermal (PV/T) cooling technology with earth water heat exchanger (EWHE) could be a suitable solution for the arid and semi-arid regions. The current paper discusses a comparative Life Cycle Analysis (LCA) of the standalone PV and PV/T systems coupled with EWHE cooling for the conditions of Pilani, Rajasthan, India. The main purpose of the study is to evaluate environmental performance analysis for forced cooling (PV/T+EWHE). Environmental performance of the system was evaluated through cradle-to-grave LCA which was carried out by using Umberto NXT software. The life cycle assessment showed that PV, PV/T and EWHE devices consumes large amount of energy during fabrication and installation process. It was also found out that PV/T+EWHE system has huge environmental impacts, in various midpoint and endpoint impact categories, as compared to normal PV system. But on the other hand, the electrical energy performance was better for PV/T+EWHE system as compared to normal PV system. Finally, it was concluded that, large PV/T+EWHE based power plants would be more sustainable in terms of environmental and energy performance.

All-iron ions mediated electron transfer for biomass pretreatment coupling with direct generation of electricity from lignocellulose

A coupled process of biomass pretreatment for increasing cellulose digestibility and direct conversion of biomass to electricity has been developed with ferric or ferricyanide ions as the anode electron carriers, and Fe(NO3)3 activated by HNO3 as the cathode electron carriers. Pretreated substrates are subjected to enzymatic hydrolysis for release of fermentable sugars, while the pretreatment liquor is employed as anolyte for electricity generation in a liquid flow fuel cell (LFFC). Pretreatment of sugarcane bagasse with 2 M FeCl3 in anode reactor removes ∼ 100% hemicelluloses and obtains 76% enzymatic glucan conversion (EGC), while pretreatment with 0.1 M K3[Fe(CN)6] in 0.5 M KOH achieves 78% lignin removal, 95.8% EGC and 85.1% xylan conversion. From 1000 g bagasse, 171.3 g fermentable sugars is produced with co-generation of 101.4 W·h electricity based on FeCl3 pretreatment, while 519 g fermentable sugars and 28.9 W·h electricity are obtained based on K3[Fe(CN)6] pretreatment.

Engineered nanomaterials in microbial fuel cells – Recent developments, sustainability aspects, and future outlook

Microbial fuel cells (MFCs) have recently emerged as green technology for the direct electricity generation from polluted (waste)water loaded with organic and inorganic contaminants. Despite the remarkable progress in applying MFCs to deal with different types of (waste)water, several issues, including the power density, durability, and costs of the electrode materials, are still to be tackled towards the commercialization of these technologies. The present manuscript provides a critical review of the recent advances and existing challenges in applying engineered nanomaterials (ENMs) to optimize the properties and performance of MFCs. The main advantages of the application of ENMs in the structure of MFCs are to provide a high specific surface area (SSA) for the electrodes, promote the electron transfer and oxygen reduction reactions, thereby representing a high level of biocompatibility for the adhesion of microbial communities, and being durable and cost-effective, especially when fabricated from natural resources. The sustainability aspects of ENMs-based MFC technologies and recommendations for future studies towards the development of sustainable nanomaterials-enabled developments of MFCs are discussed.

Zinc and Aluminum Phthalocyanine Modified Carbon Nanotubes; Preparation and Characterizations

In this work, two elements were developed. The first is Multi walled carbon nanotubes-zinc phthalocyanine (ZnPcs). In addition, there was also a development of the multi walled carbon nanotubes-aluminium phthalocyanine hybrid materials. The multi-walled carbon nanotubes were under treated with nitric combined with the sulfuric acid before being mixed with phthalocyanines to de-build the effects. Drop-casting hybrid materials to slides of the glass and interdigitating electrodes from their dimethylformamide solution have been done. The perfect hybridization owing to π-π interaction was discovered. This discovery was assisted by two elements. The first is the ultraviolet-visible absorption spectroscopy. Moreover, another element that played a vital role in this discovery is Fourier Transform Infrared Spectroscopy. The hybrid films were tested for current-voltage measurements and direct electrical conductivity. This work has also examined how temperature affects direct electrical conductivity and power generation.

An Overview on the Conversion of Forest Biomass into Bioenergy

Biomass plays a crucial role in mitigating the concerns associated with increasing fossil fuel combustion. Among various types of biomass, forest biomass has attracted considerable attention given its abundance and variations. In this work, an overview is presented on different pathways available to convert forest biomass into bioenergy. Direct use of forest biomass could reduce carbon dioxide emissions associated with conventional energy production systems. However, there are certain drawbacks to the direct use of forest biomass, such as low energy conversion rate and soot emissions and residues. Also, lack of continuous access to biomass is a severe concern in the long-term sustainability of direct electricity generation by forest biomass. To solve this problem, co-combustion with coal, as well as pelletizing of biomass, are recommended. The co-combustion of forest biomass and coal could reduce carbon monoxide, nitrogen oxides, and sulfide emissions of the process. Forest biomass can also be converted into various liquid and gaseous biofuels through biochemical and thermochemical processes, which are reviewed and discussed herein. Despite the favorable features of forest biomass conversion processes to bioenergy, their long-term sustainability should be more extensively scrutinized by future studies using advanced sustainability assessment tools such as life cycle assessment, exergy, etc.

Thermo-economic analysis of a direct supercritical CO2 electric power generation system using geothermal heat

Thermo-economic analysis of a direct supercritical CO2 electric power generation system using geothermal heat

Direct Current Electricity Generation from Dynamic Polarized Water–Semiconductor Interface

Liquid electricity generator and hydrovoltaic technology have received numerous attentions, which can be divided into horizontal movement generator and vertical movement generator. The horizontal movement generator is limited for powering the integrated and miniaturized energy chip as the current output direction is depending on the moving direction of the water droplet, which means a sustainable and continuous direct-current (DC) electricity output can be hardly achieved because of the film of limited length. On the other hand, the existing vertical movement generators include triboelectricity or humidity gradient-based liquid electricity generator, where the liquid or water resource must be sustainably supplied to ensure continuous current output. Herein, we have designed an integratable vertical generator by sandwiching water droplets with semiconductor and metal, such as graphene or aluminum. This generator, named as polarized liquid molecular generator (PLMG), directly converts the lateral kinetic energy of water droplet into vertical DC electricity with an output voltage of up to ~1.0 V from the dynamic water-semiconductor interface. The fundamental discovery of PLMG is related to the non-symmetric structure of liquid molecules, such as water and alcohols, which can be polarized under the guidance of built-in field caused by the Fermi level difference between metal and semiconductor, while the symmetric liquid molecules cannot produce any electricity on the opposite. Integratable PLMG with a large output power of ~90 nW and voltage of ~2.7 V has been demonstrated, meanwhile its small internal resistance of ~250 kilohm takes a huge advantage in resistance matching with the impedance of electron components. The PLMG shows potential application value in the Internet of Things (IoTs) after proper miniaturization and integration.

A flexible and wearable epidermal ethanol biofuel cell for on-body and real-time bioenergy harvesting from human sweat

Flexible and wearable epidermal biofuel cells (BFCs) that are worn on skin for the direct electricity generation from human perspiration are perceived to be a most enticing and promising next-generation energy source for addressing the on-body energy-harvesting challenge of wearable electronics. Previously reported epidermal BFCs are only focused on the utilization of human endogenous substances ( i.e ., glucose or lactate that can be produced by human body) in sweat as the biofuels for power production. Given the substances diversity in human body, some exogenous substances (that cannot be produced by body) are abundant in sweat in certain daily situations, however, their utility for epidermal bioenergy harvesting has been ignored so far. In the present work, we propose the first example of a flexible and wearable epidermal microfluidic human exogenous substance ethanol/oxygen BFC for the simultaneous sweat sampling and sweat bioelectricity generation on skin of individuals who drink alcohol. Certain actual situations that were associated with alcohol absorption and elimination in human body were considered and investigated for skin-on, continuous in situ sweat ethanol bioenergy generation in controlled environments. Such non-invasive flexible and wearable epidermal ethanol BFC expands the scope of human sweat-derived biofuels from endogenous substances to exogenous ones and holds great promise for the skin-worn and real-time bioenergy harvesting from human perspiration, which may open up a new challenge and approach to explore the human sweat for bioenergy conversion. We demonstrated the first example of a flexible and wearable epidermal microfluidic human exogenous substance ethanol/oxygen biofuel cell through a skin-worn, real-time in situ fashion to harvest the continuous electrical power from alcohol drinkers’ perspiration in different real-life scenarios. • The first example of a flexible and wearable epidermal human exogenous substance ethanol biofuel cell. • The simultaneous sweat sampling and sweat bioelectricity generation on skin of individuals who drink alcohol. • Certain actual situations were considered and investigated for skin-on, continuous in situ sweat ethanol bioenergy generation.