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The increasing demand for sustainable aviation fuels has prompted the exploration of hydrogen as a viable alternative for reducing carbon emissions in the aviation sector. The high gravimetric energy density of hydrogen makes it a promising candidate for future aviation fuel, offering significant potential to reduce the carbon footprint of air travel. While many articles on hydrogen aircraft design focus on the conceptual layout of fuel systems, they often lack critical details on the mass and size of key components and hydrogen boil-off during ground operation, which are vital for practical implementation. Through modeling and dynamic simulation analyses, this paper investigates the process of hydrogen fuel conditioning for gas turbines in aviation, focusing on the mass, sizing and performance of different components. The aircraft considered for this model consists of a 19-passenger with a 700 NM range that burns hydrogen in the GT directly. The sizing/design approaches of the most critical components, namely, the storage tank, heat exchanger, and pump are presented. The system-level analysis is presented for the flight mission profile. The parametric analysis is performed for a foam-insulated, storage tank with semihemispherical domes for the effects of ullage volume fraction, dormancy duration, and maximum storage pressure on gravimetric efficiency. Maximum efficiency occurs at low ullage fractions (0.05 0.1) and moderate tank pressures (4.0 5.0 bar). However, efficiency decreases with longer dormancy times. Liquid hydrogen is stored at 21 K and 1.5 bar, pressurized to 28 bar using a centrifugal pump consuming 1.47 kW at take-off. The hydrogen is then heated to the required combustor inlet temperature using a compact heat exchanger with an effectiveness of 0.5. The corrected gravimetric efficiency, considering the fuel conditioning system components, is 57% for a 2-hour dormancy and 53% for a 4-hour dormancy. A tank with gravimetric efficiency above 33% means that the combined mass of fuel and its storage will be lower than that of jet fuel. At 33%, the combined masses will be equal. Gravimetric efficiency of 57% is promising for a short and a medium hydrogen aircraft.

A predictive control strategy has been developed for photovoltaic-integrated venetian blind systems to balance indoor visual comfort and solar energy generation. The controller has been formulated as a model predictive control problem with an illuminance constraint of 100–200 lux and a four-step prediction horizon. The results have shown that the model predictive control with four-step prediction horizon has maintained indoor illuminance within the comfort range more effectively than both the single-step and fixed-angle configurations. Moreover, the total photovoltaic energy yield has been slightly higher while actuator oscillations have been significantly reduced. These findings have confirmed that extending the prediction horizon enhances both visual comfort stability and energy efficiency, demonstrating the potential of predictive control in smart, energy-positive façade systems.

Alternative aircraft and propulsion concepts are urgently required to improve the sus tainability of aviation across all segments. Hydrogen-powered designs eliminate the use of hydrocarbon fuels and offer benefits in terms of emissions. While the mass-specific energy of hydrogen is high, its volume-specific energy is very low; therefore, storage in the liquid phase at cryogenic temperatures is often considered. While several studies substantiated that such aircraft can be feasible, the tank design in general and its gravimetric efficiency specifically are critical aspects that have not been understood in sufficient detail. In particular, the influence of tank capacity on gravimetric efficiency is of interest. The objective of this paper is thus to expose select design trade-offs for hydrogen-electric aircraft with respect to liquid and gaseous tank design and tank dormancy across a wide range of tank sizes. The study is based on a survey of published prototype tank designs, physics-based modeling and simulation, empirical weight regressions, and a recent dormancy estimation method. Here, the explicit consideration of liquid hydrogen storage density on design metrics is a novelty. Three different hydrogen tank concepts of operation are introduced and ranges of tanks are sized accordingly. The best possible gravimetric efficiency is reported in charts as upper bounds of gravimetric efficiency. In the survey of published prototype tank designs, clear evidence for a strong influence of tank capacity on gravimetric efficiency was found for liquid storage. This major trend was exposed via computed design trend lines for the investigated concepts of operation. For gaseous storage, no such trend is found. Correlations of the trend lines are presented. It was also confirmed that additional trade-off of gravimetric efficiency against other, conflicting requirements is possible. Anewsuch parameter beyond pressure was identified for liquid tanks, ullage volume fraction (hydrogen storage density). Accordingly, it can often be beneficial for gravimetric efficiency to store cryogenic hydrogen at reduced density whenever tank dormancy is a design criterion. It was further found that for very large tank capacities this conflict of requirements between gravimetric and volumetric measures can disappear. Finally, the computed trend lines also suggest that, once hydrogen tanks are sufficiently matured on regional aircraft, it is very likely to reach a tipping point beyond which hydrogen-powered aircraft feasibility and benefits improve over kerosene as mission range increases, making hydrogen a superior fuel also for long-range aircraft.

Hydro power plants are among the most mature technologies for power production. To optimally manage possible overgeneration from non-programmable renewable energy sources, such as photovoltaic power plants and wind power plants, a Pumped Hydro Storage (PHS) plant can be employed as both a storage device (pumping mode) and a power production technology (turbine mode). To this aim, this paper deals with the optimization of the sizing and operation of a PHS plant that interacts with a power generation system consisting of different power production technologies. The national power production system and electric energy demand of Sweden are used as a case study and a PHS plant is sized and managed to fit conventional hydraulic sites as well as abandoned mines to be used as reservoirs. First, this paper develops a methodology suitable to identify the optimal size and operation strategy of the PHS plant, by means of the simultaneous use of two algorithms: surrogate modeling optimization algorithm and mixed integer linear programming algorithm. Then, this paper analyzes different present and future scenarios of electricity production, demand, and cost, in order to assess the energy and economic feasibility of PHS plants. The analyses carried out in this paper demonstrate that PHS plants are highly recommended with high overgeneration from photovoltaic power plants or wind power plants. This situation is a likely scenario thanks to green energy transition strategies. The return on investment of the most cost-effective solutions in the future scenarios ranges from 8.5 % to 11.6 %. In all the investigated scenarios, the results indicate that PHS is mainly employed to meet domestic electricity demand.

Positive energy districts (PEDs) generate morerenewable energy than they consume, but annual netpositivebalances often obscure significant hourly supplydemandmismatches, creating a last 20% challenge. Thispaper addresses this critical challenge by proposing aninteroperable digital platform integrating multi-objectiveoptimization, digital twins, and blockchain P2P trading toalign generation, storage, and demand response on anhourly basis. The optimization employs complementarycentralized and iterative decomposed frameworks, cooptimizinggeneration, storage, and loads. Preliminaryanalyses from seven European pilot sites suggest thattransparent coordination and trusted transactions are essentialfor closing the final shortfall. The analyses suggestsignificant improvements in local self-consumption(up to a 15% increase during peak hours) and a reductionin grid reliance. This offers a scalable roadmapfor grid-connected PEDs aiming for optimal local selfconsumption.

The aviation industry is undergoing a significant transformation as it seeks to align with global sustainability goals, particularly the ambition to achieve net-zero carbon emissions by 2050. Conventional aircraft, which rely on fossil fuels, are responsible for a substantial portion of global greenhouse gas emissions. As a result, there is an urgent need to develop alternative propulsion systems that minimize carbon footprints. Hybrid electric aircraft, powered by a combination of hydrogen, fuel cells, and battery systems, represent one of the most promising pathways toward sustainable aviation. Hydrogen is a clean energy carrier with the potential to significantly reduce emissions. However, the integration of these technologies presents significant thermal management challenges, which must be addressed to ensure safe and efficient operation. This study presents the modeling and simulation of a thermal management system (TMS) designed for hybrid electric aircraft powered by liquid hydrogen (LH2), fuel cells, and battery systems. It addresses these challenges by developing a TMS model that efficiently regulates the temperature of the fuel cells, batteries, and associated electronic components while maintaining overall system performance. The proposed system employs a multi-loop architecture, combining active and passive cooling techniques, such as liquid cooling and heat exchangers with liquid hydrogen as heat sink which is typically stored in a tank at cryogenic temperatures (similar to 20 K). The effectiveness of the TMS is evaluated under a single mission scenario. A pipe diameter of 45 mm was found optimal, balancing pump power and system weight. Coolant mass flow reduces by 48.67% from take-off to cruise, with the fuel cell route dominating at 78.15% (take-off) and 94.43% (cruise).

Pumped hydro storage (PHS) is the most mature and widely used technology for large-scale energy storage. Hydropower plants are in fact also employed for this aim. However, most hydraulic sites suitable for this purpose have been already exploited. Therefore, the use of abandoned mines represents an alternative solution to take advantage of the availability of underground volumes as hydro storages. This paper investigates the potential of PHS plants integrated within a power generation system that comprises both programmable (e.g., hydropower and nuclear power plants) and non-programmable (e.g., wind and solar power plants) energy systems. All systems are connected with the power grid. To this purpose, this paper develops a methodology aimed at identifying the optimal sizing of the PHS plant as well as the optimal operation of the whole power generation system at Country level, with the goal of minimizing the imported energy. The methodology is validated by using Sweden as the case study, to assess the energy and economic feasibility of PHS plants in 2050. Different future scenarios of electricity production, demand, and cost are analyzed. The analyses carried out in this paper demonstrate that PHS plants are highly recommended if the cost of imported energy is expected to increase. In such a scenario, PHS is mainly employed to meet domestic electricity demand.

This chapter resumes the main special features of Tesla turbines, encompassing the state-of-the-art both at modelling and experimental levels, and discussing the fundamentals of its principle of operation. Differently from all other types of dynamic machines, Tesla turbines exchange work thanks to frictional forces instead of pressure forces.

Interests in small-scale turbomachinery are gaining momentum, particularly around waste heat recovery using Organic Rankine Cycle (ORC), energy harvesting, pico-hydro, refrigeration and heat pumps and small-scale power generation. These applications demand to have economical, simple construction, and reasonably efficient machines. The performance of bladed turbomachine at a small scale is poor mainly due to viscous losses and relatively large clearances. In some cases, like ORC, it requires a lubrication system, making it complex and costly. Bladeless or Tesla turbomachinery is seen as one of the solutions for these applications due to its simple construction and cost-effectiveness. However, the experimental efficiency of the bladeless turbines/compressors is found in the low region, <40%. In this article, the performance of a bladeless turbine is investigated using a vaneless volute configuration, making the turbine stator-less (vaneless volute) and bladeless (vaneless rotor). This study presents numerical and experimental performance investigation with a volute as a stator of the bladeless rotor. Three-dimensional (3D) Numerical results show very promising performance of the turbine with total to static efficiencies calculated above 65%. In the second part of the article, turbine prototype components, assembly, and test setup are discussed. Experimental maximum efficiency of 41.5 +/- 0.88% at 3.5kg/s@5000rpm and power of 915W is obtained. This is the highest recorded efficiency for the Tesla turbine in peer-reviewed research. The overall turbine performance from 3D numerical simulation with ventilation and mechanical losses is compared with experimental results. This work demonstrates that the proposed stator-less/volute configuration provides an efficient way for bladeless or Tesla turbines, particularly for low-head applications.

This book aims at providing the reader with up-to-date knowledge about Tesla turbine features, mechanical design, and performance characteristics. A Tesla machine, in general, is characterised by the absence of rotating blades, therefore it is also called bladeless or boundary layer machine. In this book, suitable numerical approaches for the fluid-dynamic analysis are described, with practical examples related to physical prototypes designed, built and operated by the Authors. Interest in small scale turbines is growing mainly for energy efficiency and power recovery in a variety of applications. Considering small scales, conventional bladed turbines impose manufacturing limitations, lower performance and higher cost, which hinder their implementation. Tesla bladeless turbomachines are being re-discovered due to many advantages such as their simple design and ease of manufacturing with acceptable performance, especially for small-scale power generation and energy harvesting. To contribute to the spread of efficient and viable Tesla turbines (or expanders), this book presents holistic design guidelines to Tesla turbines, encompassing geometrical definition of Tesla rotor, of Tesla stator, of Tesla rotor-stator-casing assembly, providing practical correlations to take into account various loss mechanisms, and discussing the optimal design point definition for such type of century-aged but always young turbines.