Concentrated Solar Power [CSP] technologies address one of the challenges associated with intermittent energy sources such as wind and solar by incorporating thermal energy storage [TES], allowing generation to be shifted to periods without solar resources, and providing backup energy during periods with reduced sunlight that can be caused by cloud cover. Furthermore, CSP's ability to operate on gas when TES runs out offers a base load and dispatchable renewable solution in the systems that use a gas generator as a backup, which in the future can rely on hydrogen. Enhancing optical efficiency is a key challenge in CSP technology development, which requires wirelessly controlling the exact aiming orientation of tens of thousands of heliostats within sub-milliradian accuracy, while optically monitoring the field from outside the optical path where a very high temperature is obtained. Another challenge is the minimal number of pixels designated to each heliostat, as the entire solar field is monitored simultaneously. Optical efficiency optimization is also challenging due to the inherent tradeoff between the Ground Cover Ratio (GCR) and the shading and blocking of the mirrors. The heliostat control method proposed in this paper is applicable to solar power tower technology. This study aims to improve the accuracy of the solar field's tracking under shading and blocking by presenting and implementing a novel tracking method and comparing it to prior art. The method is based on monitoring the reflection from a specular curved bar along the vertical and the horizontal edge of the heliostat (or mirror facet). According to the place of the sun's reflection, the deviation from the receiver is obtained. The results show that the triangulation method using a specular curved bar gives an accuracy of 0.8 mrad, which is superior to the prior art, considering shading and blocking. It also provides the best accuracy in the exploitation of pixels. This enhancement in efficiency will bring us closer to achieving 90–95 % availability of renewable electricity at the cost of gas. This advancement stands as a significant stride in our ongoing battle against climate change.

Lithium-ion batteries (LIBs) are the most advanced energy storage systems, meeting the current business, industrial and social demands. Two factors are currently driving the research in the batteries field: first is the constant demand for better performance, and the second is the urgent call to minimize the ecological impacts related to battery manufacturing, employment, and decommission. Biomaterials demonstrate complex and diverse structures and unique physicochemical properties that can be easily modified. These features are very advantageous for the preparation of lithium and Li-ion cell components. The adoption of biomaterials substantially benefits the development of a clean and sustainable battery industry. The main areas of implementing biomaterials in electrodes, separators, and binders for high-energy lithium and LIBs are identified, and the latest achievements in the fields are outlined in this work. While advanced development in the field of LIBs provides solid grounds to consider that the application of biomaterials has great potential, future implementation of such materials in commercial LIBs production is yet to be fully realized, and there is still a need for a large volume of research work. The main points of future work and perspective in this research area are outlined in this review.

CO2-containing synthesis gas is a relevant feedstock for the production of synthetic fuels using Fischer-Tropsch Synthesis. We report the role of CO2 in CO2, CO and H2 mixed feeds over a cobalt-based catalyst at 220 °C and 21 bar in a packed bed reactor. The C5+ selectivity remains above 78 % even for CO2-rich synthesis gas with 75 % CO2/(CO+CO2). Using 13CO2 isotopic labeling, the increase in methane selectivity is attributed to both CO and CO2 methanation, which is limited by maintaining a H2/CO outlet ratio below 10 and an outlet CO partial pressure above 0.2 bar, respectively. Operando modulated DRIFTS confirms a positive relationship between CO surface coverage and CO partial pressure. From DFT and microkinetic modeling, enhanced CO and CO2 methanation could be attributed to a lower CO surface coverage and a higher H2 surface coverage. This work identifies boundaries for efficient cobalt-catalyzed mixed-feed FTS for synthetic fuels production.

Ammonia (NH₃) is a vital chemical widely used in fertilizers, industry, and as a potential energy carrier. However, conventional ammonia production via the Haber-Bosch process is highly energy-intensive, consuming approximately 13.9 kWh per kg of nitrogen. Additionally, nitrogen-rich wastewater contributes to eutrophication and aquatic toxicity, necessitating sustainable recovery solutions. This study introduces an electrochemical membrane stripping (EMS) system incorporating hydrophobic, electrically conducting membranes (ECMs) to enhance ammonia recovery. By applying a controlled electric field and optimizing cathodic potential and crossflow velocity, the system efficiently transports ammonium (NH₄⁺) toward the cathodic membrane, where a localized pH shift converts it into free ammonia (NH₃), eliminating the need for chemical pH adjustment.

Under optimal conditions, the EMS system achieved 88 % ammonia recovery with a high flux of 37 ± 1.45 g m⁻² d⁻¹, representing a 33.5 % improvement over conventional methods. Mass balance analysis confirmed electromigration as a key transport mechanism, leading to a threefold increase in ammonia concentration at the membrane surface. Additionally, the system demonstrated high energy efficiency, with a specific energy consumption of 2 ± 0.15 kWh per kg of nitrogen, making it a cost-effective alternative for liquid fertilizer production.

As a proof-of-concept, the EMS system was successfully tested on real municipal wastewater, highlighting its practical viability. However, further research is needed to assess long-term stability, scalability, and integration with wastewater treatment infrastructure. This study demonstrates EMS as a promising technology for sustainable nitrogen recovery, supporting circular economy initiatives.

The metal organic framework (MOF) MIP-177(Ti) is under the spotlight for its robust photo-response and stability. This MOF can be synthesized in forms: MIP-177(Ti)-LT (LT: low temperature) and MIP-177(Ti)-HT (HT: high temperature). The MIP-177(Ti)-LT version comprises of Ti₁₂O₁₅ units interconnected by 3,3′,5,5′-tetracarboxydiphenylmethane (mdip) ligands and interconnecting formate groups. Upon high temperature treatment, MIP-177(Ti)-LT loses its formate groups, thus rearranging into a continuous 1-D chain of Ti₆O₉ units leading to the MIP-177(Ti)-HT. Based on this 1-D connected structure, one should expect a higher catalytic activity of MIP-177(Ti)-HT. Nevertheless, the hydrogen evolution reaction photoactivity assessment clearly indicates the opposite. Combining transient IR measurements (TRIR), TAS and DFT/TD-DFPT calculations unveils the reasons for this situation. The TRIR measurements evidence that the photoinduced electrons are located in the inorganic part, while the holes are in the mdip ligand. The longer lifetime of MIP-177(Ti)-LT is mapped onto a slower decay of the Ti–O related peaks. A reversible change in the coordination of the carboxylate groups from a bidentate to a monodentate coordination is observed only in MIP-177(Ti)-LT. Complementary DFT and TD-DFPT simulations demonstrate a higher electron delocalization on the inorganic part for MIP-177(Ti)-LT (hence, enhanced mobility and slower recombination), thus explaining its superior photocatalytic activity.

A novel approach for modeling hypergolic ignition is presented, validated, and used to successfully predict ignition delay times for a hybrid rocket propellant configuration. This configuration employs a hypergolic additive (sodium borohydride) that allows two non-hypergolic reactants (polyethylene and hydrogen peroxide) to gain hypergolic capabilities. The model considers multiple phases and multiple species, heterogeneous and homogeneous chemical reactions, mass transfer between phases, and heat transfer. The transient behavior of the various chemical and thermal properties involved in hypergolic ignition is studied. In addition, a parametric investigation is conducted to predict ignition delay times as functions of multiple variables such as additive loading, oxidizer concentration, and initial propellant temperatures, among others. The results are presented in the form of ignition delay time contour maps. The heat release rate is shown to be controlled mostly by hypergolic chemical reactions. Gas homogeneous reactions only take place during the last portion of the ignition process and are the ones responsible for ultimately leading to a gas thermal runaway. The proper inclusion of the vaporization and pyrolysis of the propellants is found to be crucial since these determine the formation of a gas phase, where ignition is achieved. It is found that the vaporization of the liquid oxidizer is the controlling mass transfer mechanism for the hybrid rocket configuration considered. The model successfully predicts the minimum hypergolic additive loading and the range of oxidizer-to-fuel ratios required for ignition. It is found that the optimal oxidizer-to-fuel ratio leading to the shortest ignition delay time is mostly a function of additive loading. In addition, it is found that pressure, propellant initial temperature, and oxidizer concentration, have a major influence on ignition delay times and that they barely affect the optimal oxidizer-to-fuel ratio. The presented model, although evaluated for the hybrid rocket configuration, is considered to be applicable for any hypergolic propellant configuration.

This paper contributes to the field of analytic and semi-analytic solutions for optimal power flow problems involving storage systems. Its primary contribution is a rigorous proof establishing the uniqueness of the “shortest path” optimal solution, a key element in this class of algorithms, building upon a graphical design procedure previously introduced. The proof is constructed through five consequential lemmas, each defining a distinct characteristic of the optimal solution. These characteristics are then synthesized to demonstrate the uniqueness of the optimal solution, which corresponds to the shortest path of generated energy within defined bounds. This proof not only provides a solid theoretical foundation for this algorithm class but also paves the way for developing analytic solutions to more complex optimal control problems incorporating storage. Furthermore, the efficacy of this unique solution is validated through two comparative tests. The first one uses synthetic data to benchmark the proposed solution in comparison to recent reinforcement learning algorithms, including actor–critic, PPO, and TD3. The second one compares the proposed solution to the optimal solutions derived from other numerical methods based on real-world data from an electrical vehicle storage device.

The community is exploring sustainable alternatives for grid-scale energy storage. Besides lithium-ion batteries (LIBs), such technologies with a focus on sustainability aspects offer only a limited solution for grid-scale energy storage. Rechargeable metal-air batteries (MABs) based on affordable abundant multivalent metal anodes in aqueous medium provide promising theoretical metrics, such as volumetric capacity, but do not completely fulfill their potential when scaled from lab to commercial products. Both the metal anode and the air cathode need to be addressed: corrosion, hydrogen evolution reaction (HER) during charging, and passivation all diminish the anode's effective volumetric energy density and shelf life, while the air cathode's challenges include sluggish kinetics, low efficiency, and poor stability. Nevertheless, this Perspective highlights iron-air MABs as an appealing sustainable alternative for grid-scale energy storage, since iron is abundant and affordable, recyclable, has multielectron reversible redox activity, historically rich experience in production and processing, and is safe to handle. Given that further research will be directed to exploring the composition and design of electrolytes and electrodes, it may lead to advances in scaling and commercialization, as well as reducing the environmental impact of secondary batteries utilized for grid-scale energy storage in the next decades.

The increasing global energy demand necessitates the development of sustainable electrochemical energy technologies. Anion-exchange membrane fuel cells (AEMFCs) present a promising alternative to proton-exchange membrane fuel cells (PEMFCs) due to their ability to utilize platinum-group metal (PGM)-free catalysts, which significantly reduce costs and resource dependency. In this work, we prepare various PGM-free catalysts for the oxygen reduction reaction (ORR) via an ionothermal synthesis using cyclodextrin and magnesium nitrate. The synthesis conditions were optimized and the electrocatalysts were investigated with both physical and electrochemical characterization techniques. The catalysts’ ORR performance was assessed using rotating disk electrode (RDE) measurements and single-cell AEMFC tests. The optimized FeNC-CD3 catalyst exhibited a half-wave potential of 0.90 V vs RHE in 0.1 M KOH in the RDE test and a peak power density of 599 mW cm⁻² in an AEMFC, showcasing its potential as a viable alternative to conventional Pt-based cathode catalysts. This work highlights the critical role of hierarchical porosity in enhancing the ORR activity and paves the way for the development of cost-effective and efficient AEMFC technology.

Outdoor shade, as a vital environmental asset of heat stress reduction, has long been evading systematic treatment in theory and practice. Yet, to become an effective climatic tool to address urban heat, outdoor shade has to be systematically quantified, mapped, and managed. The spatial Shade Index (SI) we have developed in the past allows us to describe on a simple scale from 0 to 1 the extent to which the cumulative effect of solar radiation at ground level is blocked during a typical spring or summer day. By calculating an average SI for each street segment, open space, or any other spatial unit of interest in a city, it is possible to produce maps that present the shade hierarchy of the city’s main pedestrian spaces, allowing for a quick and easy comparison of their shading quality. Recently, we have managed to develop a computationally efficient method for producing high-resolution urban shade maps in a relatively short time by processing digital surface models, tree canopy contour maps, and official spatial land use layers. With experience gained from generating shade maps for 15 cities, it is now possible to conclude that shade mapping can only be the first step in a more complex procedure of prioritising shading actions across a city. In each of the mapped cities, the high number of street segments or open spaces with poor shading conditions made it impossible to allocate enough municipal resources to bring each and every one of them to a reasonable level of spatial shading. A shade map and the SI it assigns to each spatial unit thus become only the starting point of evidence-based policy negotiations that bring to the table other climate-related considerations, including public health, social equity, promotion of public transport travel, and increasing the appeal of commercial streets. The presentation will provide examples of the application of shade maps in real-life planning tasks in different cities, including as the basis for developing strategic urban forestry plans. It will also expand on the underlying differences and discrepancies in historical urban planning concepts and resource allocation preferences that shade maps expose, given that outdoor shade in its entirety is always, even inadvertently, the product of urban planning and design decisions.