Tunisia

Blending hydrogen into natural gas pipelines is a recent alternative adopted for hydrogen transportation as a mixture with natural gas. In this paper hydrogen embrittlement of steel pipelines originally designed for natural gas transportation is investigated. Solubility permeation and diffusion phenomena of hydrogen molecules into the crystalline lattice structure of the pipeline material are followed up based on transient evolution of internal pressure applied on the pipeline wall. The transient regime is created through changes of gas demand depending on daily consumptions. As a result the pressure may reach excessive values that lead to the acceleration of hydrogen solubility and its diffusion through the pipeline wall. Furthermore permeation is an important parameter to determine the diffusion amount of hydrogen inside the pipeline wall resulting in the embrittlement of the material. The numerical obtained results have shown that using pipelines designed for natural gas conduction to transport hydrogen is a risky choice. Actually added to overpressure and great fluctuations during transients that may cause fatigue and damage the structure also the latter pressure evolution is likely to induce the diffusion phenomena of hydrogen molecules into the lattice of the structure leading to brittle the pipe material. The numerical simulation reposes on solving partial differential equations describing transient gas flow in pipelines coupled with the diffusion equation for mass transfer. The model is built using the finite elements based software COMSOL Multiphysics considering different cases of pipe material; API X52 (base metal and nutrided) and API X80 steels. Obtained results allowed tracking the evolution with time of hydrogen concentration through the pipeline internal wall based on the pressure variation due to transient gas flow. Such observation permits to estimate the amount of hydrogen diffused in the metal to avoid leakage of this flammable gas. Thus precautions may be taken to prevent explosive risks due to hydrogen embrittlement of steel pipelines among other effects that can lead to alter safe conditions of gas conduction.

Green Hydrogen Microgrid System has been selected as a source of clean and renewable alternative energy because it is undergoing a global revolution and has been identified as a source of clean energy that may aid the country in achieving net-zero emissions in the coming years. The study proposes an innovative Microgrid Renewable hybrid system to achieve these targets. The proposed hybrid renewable energy system combines a photovoltaic generator (PVG) a fuel cell (FC) a supercapacitor (SC) and a home vehicle power supply (V2H) to provide energy for a predefined demand. The proposed architecture is connected to the grid and is highly dependent on solar energy during peak periods. During the night or shading period it uses FC as a backup power source. The SC assists the FC with high charge power. SC performs this way during load transients or quick load changes. A multi-agent system (MAS) was used to build a real energy management system (RT-HEMS) for intelligent coordination between components (MAS). The scheduling algorithm reduces energy consumption by managing the required automation devices without the need for additional network power. It will meet household energy requirements regardless of weather conditions including bright cloudy or rainy conditions. Implementation and discussion of the RT-HEMS ensures that the GHS is functioning properly and that the charge request is satisfied.

There is a growing interest in green hydrogen with researchers institutions and countries focusing on its development efficiency improvement and cost reduction. This paper explores the concept of green hydrogen and its production process using renewable energy sources in several leading countries including Australia the European Union India Canada China Russia the United States South Korea South Africa Japan and other nations in North Africa. These regions possess significant potential for “green” hydrogen production supporting the transition from fossil fuels to clean energy and promoting environmental sustainability through the electrolysis process a common method of production. The paper also examines the benefits of green hydrogen as a future alternative to fossil fuels highlighting its superior environmental properties with zero net greenhouse gas emissions. Moreover it explores the potential advantages of green hydrogen utilization across various industrial commercial and transportation sectors. The research suggests that green hydrogen can be the fuel of the future when applied correctly in suitable applications with improvements in production and storage techniques as well as enhanced efficiency across multiple domains. Optimization strategies can be employed to maximize efficiency minimize costs and reduce environmental impact in the design and operation of green hydrogen production systems. International cooperation and collaborative efforts are crucial for the development of this technology and the realization of its full benefits.

Tunisia's rapid industrial expansion and population growth have created a pressing energy deficit despite the country's significant yet largely untapped renewable energy potential. This study addressed this challenge by developing a comprehensive framework to identify and evaluate strategies for promoting green hydrogen production from renewable energy sources in Tunisia. A Strength Weakness Opportunity and Threat (SWOT) analysis incorporating social economic and environmental dimensions was conducted to formulate potential solutions. The Step-wise Weight Assessment Ratio Analysis (SWARA) method facilitated the weighting of SWOT factors and subfactors. Subsequently a multi-criteria decision-making approach employing the gray technique for order preference by similarity to ideal solution (TOPSIS-G) method (validated by gray additive ratio assessment (ARAS-G) gray complex proportional assessment (COPRAS-G) and gray multi-objective optimization by ratio analysis (MOORA-G) was used to rank the identified strategies. The SWOT analysis revealed "Strengths" as the most influential factor with a relative weight of 47.3% followed by "Weaknesses" (26.5%) "Threats" (15.6%) and "Opportunities" (10.6%). Specifically experts emphasized Tunisia's renewable energy potential (21.89%) and robust power system (12.11%) as primary strengths. Conversely high investment costs (11.2%) and political instability (7.77%) posed substantial threat. Positive socio-economic impacts represented a key opportunity with a score of 5.2%. As for the strategies prioritizing criteria production cost ranked first with a score of 13.5% followed by environmental impact (12.8%) renewable energy potential (12.0%) and mitigation costs (11.3%). The gray TOPSIS analysis identified two key strategies: leveraging Tunisia's wind and solar resources and fostering regional cooperation for project implementation. The robustness of these strategies is confirmed by the strong correlation between TOPSIS-G ARAS-G COPRAS-G and MOORA-G results. Overall the study provides a comprehensive roadmap and expert-informed decision-support tools offering valuable insights for policymakers investors and stakeholders in Tunisia and other emerging economies facing similar energy challenges.

It is likely that blending hydrogen into natural gas grids could contribute to economy-wide decarbonization while retaining some of the benefits that natural gas networks offer energy systems. Hydrogen injection into existing natural gas infrastructure is recognised as a key solution for energy storage during periods of low electricity demand or high variable renewable energy penetration. In this scenario natural gas networks provide an energy vector parallel to the electricity grid offering additional energy transmission capacity and inherent storage capabilities. By incorporating green hydrogen into the NG network it becomes feasible to (i) address the current energy crisis (ii) reduce the carbon intensity of the gas grid and (iii) promote sector coupling through the utilisation of various renewable energy sources. This study gives an overview of various interchangeability indicators and investigates the permissible ratios for hydrogen blending with two types of natural gas distributed in Tunisia (ANG and MNG). Additionally it examines the impact of hydrogen injection on energy content variation and various combustion parameters. It is confirmed by the data that ANG and MNG can withstand a maximum hydrogen blend of up to 20%. The article’s conclusion emphasises the significance of evaluating infrastructure and safety standards related to Tunisia’s natural gas network and suggests more experimental testing of the findings. This research marks a critical step towards unlocking the potential of green hydrogen in Tunisia.

The decarbonization of hard-to-abate industries is crucial for keeping global warming to below 2◦C. Green or renewable hydrogen synthesized through water electrolysis has emerged as a sustainable alternative for fossil fuels in energy-intensive sectors such as aluminum cement chemicals steel and transportation. However the scalability of green hydrogen production faces challenges including infrastructure gaps energy losses excessive power consumption and high costs throughout the value chain. Therefore this study analyzes the challenges within the green hydrogen value chain focusing on the development of nascent technologies. Presenting a comprehensive synthesis of contemporary knowledge this study assesses the potential impacts of green hydrogen on hard-to-abate sectors emphasizing the expansion of clean energy infrastructure. Through an exploration of emerging renewable hydrogen technologies the study investigates aspects such as economic feasibility sustainability assessments and the achievement of carbon neutrality. Additionally considerations extend to the potential for large-scale renewable electricity storage and the realization of net-zero goals. The findings of this study suggest that emerging technologies have the potential to significantly increase green hydrogen production offering affordable solutions for decarbonization. The study affirms that global-scale green hydrogen production could satisfy up to 24% of global energy needs by 2050 resulting in the abatement of 60 gigatons of greenhouse gas (GHG) emissions - equivalent to 6% of total cumulative CO2 emission reductions. To comprehensively evaluate the impact of the hydrogen economy on ecosystem decarbonization this article analyzes the feasibility of three business models that emphasize choices for green hydrogen production and delivery. Finally the study proposes potential directions for future research on hydrogen valleys aiming to foster interconnected hydrogen ecosystems.

In this study the electrolysis of water by using ammonium chloride (NH4Cl) as an electrolyte was investigated for the production of hydrogen gas. The assembled electrochemical cell consists mainly of twenty-one stainless-steel electrodes and a direct current from a battery ammonium chloride solution. In the electrolysis process hydrogen and oxygen are developed at the same time and collected as a mixture to be used as a fuel. This study explores a technic regarding the matching of oxyhydrogen (HHO) electrolyzers with photovoltaic (PV) systems to make HHO gas. The primary objective of the present research is to enable the electrolyzer to operate independently of other energy origins functioning as a complete unit powered solely by PV. Moreover the impact of using PWM on cell operation was investigated. The experimental data was collected at various time intervals NH4Cl concentrations. Additionally the hydrogen unit consists of two cells with a shared positive pole fixed between them. Some undesirable anodic reaction affects the efficiency of hydrogen gas production because of the corrosion of anode to ferrous hydroxide (Fe(OH)2). Polyphosphate Inhibitor was used to minimize the corrosion reaction of anode and keep the efficiency of hydrogen gas flow. The optimal concentration of 3M for ammonium chloride was identified balancing a gas flow rate of 772 ml/min with minimal anode corrosion. Without PWM conversion efficiency ranges between 93% and 96%. Therefore PWM increased conversion efficiency by approximately 5% leading to a corresponding increase in hydrogen gas production.