Energies

In this study, we synthesized pure and cobalt-doped NiTiO3 perovskite nanostructures using a sol–gel method and characterized them to investigate the impact of cobalt incorporation on their photocatalytic hydrogen production under UV light. XRD analysis confirmed the formation of the hexagonal ilmenite structure, with lattice parameters increasing with cobalt doping, indicating the substitution of larger Co2+ ions onto smaller Ni2+ sites. Raman spectroscopy revealed a decrease in the intensity of active modes, suggesting crystal structure distortion and oxygen vacancy generation. UV-vis spectroscopy showed a decrease in bandgap energy from 2.24 to 2.16 eV with cobalt doping up to 5%, enhancing UV light absorption. SEM and TEM images revealed nanoparticle agglomeration, while cobalt doping did not significantly alter particle size up to 5% doping. Photoluminescence spectroscopy revealed an initial increase in PL intensity for NiTiO3-1%Co, followed by a systematic decrease with higher cobalt concentrations, with NiTiO3-10%Co exhibiting the lowest intensity. Photocatalytic experiments demonstrated a remarkable improvement in hydrogen evolution rate with increasing cobalt doping, with NiTiO3-10%Co exhibiting the highest rate of 940 μmol∙g−1·h−1, a 60.4% increase compared to pure NiTiO3. This enhanced performance is attributed to the substitution of Co2+ on Ni2+ sites, the modification of electronic structure, the suppression of electron–hole recombination, and the creation of surface catalytic sites induced by cobalt incorporation. The proposed mechanism involves the introduction of Co2+/Co3+ energy levels within the NiTiO3 bandgap, facilitating charge separation and transfer, with the Co+/Co2+ redox couple aiding in suppressing electron–hole recombination. These findings highlight the potential of cobalt doping to tune the properties of NiTiO3 perovskite for efficient hydrogen production under UV light.

The need to globalize and implement the fourth industrial revolution has led to increased interest in research on renewable energy harvesting equipment. Wind and solar have been the fastest growing sources of energy and have been used to reduce our dependency on fossil fuels for energy. The Savonius wind turbine is an attractive option for regions with high turbulence intensity and low wind speeds due to its advantages over other small-scale vertical-axis wind turbines. These advantages include its simple design, satisfactory performance at lower speeds, and ability to turn independent of the wind flow direction. However, Savonius wind turbines face several challenges. The most significant one being the negative torque generated during operation. This negative torque is caused by the interaction between the exhaust air and the returning blade, thus reducing efficiency, as the turbine has to overcome this additional force. To improve on the efficiency, various assessments and optimization techniques have been employed. These focus on the geometric parameters of the Savonius wind turbine as well as installation augmentation techniques. This article reviews and reports on several combinations of parametric performance-influencing adjustments and power augmentation techniques applied to Savonius wind turbines. The article concludes by proposing future research directions.

Anaerobic digestion (AD) is an effective technology for the sustainable management of organic agricultural waste, producing both biogas and nutrient-rich digestate. This study aims to review and evaluate different methods for obtaining valuable products from digestate, with a focus on innovative and sustainable approaches. The main objectives are to identify effective technologies for the recovery of nutrients and organic matter, assess their environmental and economic impact and outline the challenges and prospects in this area. The review covers established techniques (with a technology readiness level (TRL) of six to nine, indicating their maturity from pilot to full scale) such as struvite precipitation and ammonia stripping, which are very effective in recovering nitrogen and phosphorus from digestate and converting it into valuable biofertilizers. Struvite, for example, offers an option for slow-release fertilizers that reduces dependence on synthetic fertilizers. A comparative analysis shows that ammonia stripping can efficiently capture nitrogen and produce fertilizer without harming the environment. New methods, such as microalgae cultivation, use digestate as a nutrient source for the production of biofuels and bioplastics, contributing to renewable energy and sustainable material production. The study also examines composting and vermicomposting, where digestate is converted into nutrient-rich soil conditioners that significantly improve soil health and fertility. The production of biochar through pyrolysis is highlighted for its benefits in improving soil properties and sequestering carbon, providing a dual benefit for waste management and climate change mitigation. Membrane technologies, including ultrafiltration (UF) and reverse osmosis (RO), are being investigated for their effectiveness in nutrient recovery, despite challenges such as membrane fouling and high operating costs. The study highlights the potential of these valorization processes to improve the sustainability and economic viability of AD systems and to align with circular economy principles. The results suggest that the continuous optimization of these technologies and the integration of recycling processes are crucial to overcome existing challenges and realize their full potential.

In connection with the growing requirements regarding the quality and continuity of energy supply and the dynamic development of renewable energy sources, the need for a thorough analysis of factors affecting power and energy losses and the effectiveness of the MV network increases. One of the biggest challenges in managing power networks is the problem of load asymmetry. Load asymmetry can lead to numerous adverse phenomena, such as increased power losses, deterioration of the quality of energy supplied, and an increased risk of network failure. Despite various research on this issue, there is still a need for a more accurate understanding of mechanisms leading to the development of methods of minimizing these phenomena. The relationships describing power losses in lines and power transformers are widely known. However, most published analyzes assume the same load on each phase. If the asymmetrical load of the line already appears, such analysis is not based on the data of actual lines and applies to a homogeneous line with equal load along its entire length. Therefore, the authors decided to modify the method of calculating power losses so that they can be determined in a branched line loaded in many points, with knowledge of the current flowing into the line, its length, and the number of acceptances. This method allows for the determination of power losses in an innovative way, taking into account line load asymmetry. The use of relationships commonly available in the literature to determine power losses leads to errors of 5.54% (compared to the actual, measured losses). Taking into account both the asymmetry and multi-point loading in the method proposed by the authors allows us to limit this error to 3.91%. To estimate the impact of asymmetry on power losses in lines and power transformers, the authors performed field tests in the selected medium voltage power network. The increase in power losses determined on their basis caused by the asymmetry of the load currents obtained values from 0.03% to 4.78%. Using generally known methods of reducing asymmetry, these losses can be avoided, and therefore the energy transmission costs may be reduced, and the greenhouse gas emissions might be lowered.

The operation of the utility grid is being reshaped by the continuous addition of distributed energy resources and advanced metering infrastructure, which challenge existing grid control strategies. Some utilities deploy advanced distribution management systems (ADMS) to assist with the consolidation of various applications and to augment situational awareness in response to the new power delivery dynamics. An ADMS is an integrated software platform that provides utilities with a way to enhance their reliability, control, and optimization with advanced applications, such as volt/VAR optimization (VVO). A VVO application could serve as a vehicle to deliver cost savings by providing the utility with a method to reduce rates by controlling the voltage and decreasing the energy usage in their service territory. Some utilities are reluctant to integrate an ADMS, because it is a significant investment that requires approval from the public regulatory commission and/or their customers. This paper evaluates the impact on VVO performance when using a lower-quality network model supplemented with additional measurements, which could provide an implementation for cost savings. The results show that a better model quality would provide the highest energy savings; however, some level of telemetry is necessary in all scenarios to prevent voltage exceedances.