South Africa

The imperative to address traditional energy crises and environmental concerns has accelerated the need for energy structure transformation. However the variable nature of renewable energy poses challenges in meeting complex practical energy requirements. To address this issue the construction of a multifunctional large-scale stationary energy storage system is considered an effective solution. This paper critically examines the battery and hydrogen hybrid energy storage systems. Both technologies face limitations hindering them from fully meeting future energy storage needs such as large storage capacity in limited space frequent storage with rapid response and continuous storage without loss. Batteries with their rapid response (90%) excel in frequent short-duration energy storage. However limitations such as a selfdischarge rate (>1%) and capacity loss (~20%) restrict their use for long-duration energy storage. Hydrogen as a potential energy carrier is suitable for large-scale long-duration energy storage due to its high energy density steady state and low loss. Nevertheless it is less efficient for frequent energy storage due to its low storage efficiency (~50%). Ongoing research suggests that a battery and hydrogen hybrid energy storage system could combine the strengths of both technologies to meet the growing demand for large-scale long-duration energy storage. To assess their applied potentials this paper provides a detailed analysis of the research status of both energy storage technologies using proposed key performance indices. Additionally application-oriented future directions and challenges of the battery and hydrogen hybrid energy storage system are outlined from multiple perspectives offering guidance for the development of advanced energy storage systems.

One such technology is hydrogen-based which utilizes hydrogen to generate energy without emission of greenhouse gases. The advantage of such technology is the fact that the only by-product is water. Efficient storage is crucial for the practical application of hydrogen. There are several techniques to store hydrogen each with certain advantages and disadvantages. In gaseous hydrogen storage hydrogen gas is compressed and stored at high pressures requiring robust and expensive pressure vessels. In liquid hydrogen storage hydrogen is cooled to extremely low temperatures and stored as a liquid which is energy-intensive. Researchers are exploring advanced materials for hydrogen storage including metal hydrides carbonbased materials metal–organic frameworks (MOFs) and nanomaterials. These materials aim to enhance storage capacity kinetics and safety. The hydrogen economy envisions hydrogen as a clean energy carrier utilized in various sectors like transportation industry and power generation. It can contribute to decarbonizing sectors that are challenging to electrify directly. Hydrogen can play a role in a circular economy by facilitating energy storage supporting intermittent renewable sources and enabling the production of synthetic fuels and chemicals. The circular economy concept promotes the recycling and reuse of materials aligning with sustainable development goals. Hydrogen availability depends on the method of production. While it is abundant in nature obtaining it in a clean and sustainable manner is crucial. The efficiency of hydrogen production and utilization varies among methods with electrolysis being a cleaner but less efficient process compared to other conventional methods. Chemisorption and physisorption methods aim to enhance storage capacity and control the release of hydrogen. There are various viable options that are being explored to solve these challenges with one option being the use of a multilayer film of advanced metals. This work provides an overview of hydrogen economy as a green and sustainable energy system for the foreseeable future hydrogen production methods hydrogen storage systems and mechanisms including their advantages and disadvantages and the promising storage system for the future. In summary hydrogen holds great promise as a clean energy carrier and ongoing research and technological advancements are addressing challenges related to production storage and utilization bringing us closer to a sustainable hydrogen economy.

Healthcare facilities in isolated rural areas of sub-Saharan Africa face challenges in providing essential health services due to unreliable energy access. This study examines the use of hybrid renewable energy systems consisting of solar PV wind turbines batteries and hydrogen storage for the electrification of rural healthcare facilities in Nigeria and South Africa. The study deployed the efficacy of Hybrid Optimization of Multiple Energy Resources software for techno-economic analysis and the Evaluation based on the Distance from Average Solution method for multicriteria decision-making for sizing optimizing and selecting the optimal energy system. Results show that the optimal configurations achieve cost-effective levelized energy costs ranging from $0.336 to $0.410/kWh for both countries. For the Nigeria case study the optimal energy system includes 5 kW PV 10 kW fuel cell 10 kW inverter 10 kW electrolyzer and 16 kg hydrogen tank. South Africa's optimal configuration has 5 kW PV 10 kW battery 10 kW inverter and 7.5 kW rectifier. Solar PV provides more than 90% of energy with dual axis tracking yielding the highest output: 8889kWh/yr for Nigeria and 10470kWh/yr for South Africa. The multi-criteria decisionmaking analysis reveals that Nigeria's preferred option is the hybrid system without tracking. In contrast the horizontal axis weekly adjustment tracking configuration is optimal for South Africa considering technical economic and environmental criteria. The findings highlight the importance of context-specific optimization for hybrid renewable energy systems in rural healthcare facilities to accelerate Sustainable Development Goals 3 and 7.

South Africa has excellent conditions for renewable energy generation making it well placed to produce green hydrogen for both domestic use and export. In building a green hydrogen economy around export markets it will face competition from countries with equivalent or better resources and/or that are located closer to export markets (e.g. in North Africa and the Middle East) or have lower capital costs (developed markets like Australia and Canada). South Africa however has an extensive energy system with unserved electricity demand. The ability to trade electricity with the national grid (feeding into the grid during times of peak dedicated renewable energy supply and extracting from the grid during times of low dedicated renewable energy availability) could reduce the cost of producing green hydrogen by as much as 10–25 %. This paper explores the opportunity for South African green hydrogen producers presented by the electricity supply crisis that has been ongoing since 2007. It highlights the potential for a mutually reinforcing growth cycle between renewable energy and green hydrogen to be established which will contribute not only to the mitigation of greenhouse gas emissions but to the local economy and broader society.

Given the economic industrial and environmental value of green dihydrogen (H2) optimization of water electrolysis as a means of producing H2 is essential. Binders are a crucial component of electrocatalysts yet they remain largely underdeveloped with a significant lack of standardization in the field. Therefore targeted research into the development of alternative binder systems is essential for advancing performance and consistency. Binders essentially act as the key to regulating the electrode (support)–catalyst–electrolyte interfacial junctions and contribute to the overall reactivity of the electrocatalyst assembly. Therefore alternative binders were explored with a focus on cost efficiency and environmental compatibility striving to achieve desirable activity and stability. Herein the alkaline hydrogen evolution reaction (HER) was investigated and the sluggish water dissociation step was targeted. Controlled hydrophilic poly(vinyl alcohol)-based hydrogel binders were designed for this application. Three hydrogel binders were evaluated without incorporated electrocatalysts namely PVA145 PVA145-blend-bPEI1.8 and PVA145-blend-PPy. Interestingly the study revealed that the hydrophilicity of the binders exhibited an enhancing effect on the observed activity resulting in improved performance compared to the commercial binder Nafion™. Notably the PVA145 system stands out with an overpotential of 224 mV at−10 mA·cm−2 (geometric) in 1.0 M KOH compared to the 238 mV exhibited by Nafion™. Inclusion of Pt as active material in PVA145 as binder exhibited a synergistic increase in performance achieving a mass activity of 1.174 A.cm−2.mg−1 Pt in comparison to Nafion™’s 0.344 A.cm−2.mg−1 Pt measured at−150 mV vs RHE. Our research aimed to contribute to the development of cost-effective and efficient binder systems stressing the necessity to challenge the dominance of the commercially available binders.

In recent years the utilization of aluminium (Al) Al alloys and their composite powder and anode encourages the generation of green hydrogen through hydrolysis and water splitting electrolysis with zero emissions. As such in this study the development and characterization of Al Al alloys and Al-based composite powder and compacted Al composites for clean hydrogen production using hydrolysis and water splitting processes were reviewed. Herein based on the available literature it is worth mentioning that the incorporation of active additives such as h-BN Bi@C g-C3N4 MoS2 Ni In Fe and BiOCl@CNTs in the Al-based composites using ball milling melting smelting casting and spark plasma sintering technique remarkably improved the rate of hydrogen evolution and hydrogen gas conversion yield particularly during hydrolysis of Al-water reaction. Again Al-based electrodes with improved electrical conductivity notably results in better water splitting electrolysis as well as fast chemical reaction in achieving hydrogen gas production at low energy consumption with efficiency. Though notwithstanding the significance of Al Al alloy and Al-based composite hydrogen generation performances there are still some challenges associated with the Al-based materials for hydrogen production via hydrolysis and water electrolysis. For example the low current density and poor electrochemical properties of Al which on the other hand results in long induction time high overpotential and cost remains a gap to bridge. Hence the authors concluded the review study with recommendations for future improvement of Al-based composite electrodes on hydrogen production and sustainability via hydrolysis and water electrolysis. Thus the study will pave the way for further research on clean hydrogen energy generation.

The escalating global energy demand has intensified research into sustainable hydrogen production particularly through water splitting. A highly promising avenue involves photocatalytic water splitting which leverages readily available earth-abundant materials to generate clean hydrogen from water using only renewable energy sources. Among the various catalytic materials investigated metal-organic frameworks (MOFs) have recently attracted considerable interest. Their tunable porosity high crystallinity as well as the customisable molecular structures position them as a transformative class of catalysts for efficient and sustainable photocatalytic hydrogen generation. This review examines MOFs detailing their structural characteristics unique properties and diverse synthetic routes. The discussion extends to the various composite materials that can be derived from MOFs with particular emphasis on their application in photocatalytic hydrogen production via water splitting. Furthermore the review identifies current challenges hindering MOF implementation and proposes modification strategies to overcome these limitations. The concluding section summarises the presented information and future perspectives on the continued development of MOF composites for enhanced photocatalytic hydrogen production from water.

Liquid organic hydrogen carriers (LOHCs) are a promising class of hydrogen storage media in which hydrogen is reversibly bound to organic molecules. In this work we focus explicitly on cyclic LOHCs (both homocyclic and heterocyclic organic compounds) and their catalytic dehydrogenation. We clarify that other carriers (e.g. alcohols like methanol or carboxylic acids like formic acid) exist but are not the focus here; these alternatives are discussed only in comparative context. Cyclic LOHCs typically enable safe ambient-temperature hydrogen storage with hydrogen contents around 6–8 wt%. Key challenges include the high dehydrogenation temperatures (often 200–350 °C) catalyst costs and catalyst deactivation via coke formation. We introduce a comparative analysis table contrasting cyclic LOHCs with alternative carriers in terms of hydrogen density operating conditions catalyst types toxicity and cost. We also expand the catalyst discussion to highlight coke formation mechanisms and the use of mesoporous metal-oxide supports to mitigate deactivation. Finally a techno-economic analysis is provided to address system costs of LOHC storage and regeneration. Finally we underscore the viability and limitations of cyclic LOHCs including practical storage capacities catalyst life and projected costs.