The growing interest in sustainable aviation has highlighted liquid hydrogen (LH2) as a promising alternative to conventional fuels. This study develops a systems level, conceptual approach to size and assess the key elements of an LH2 fuel system for a short-range commercial aircraft with operational and geometric characteristics similar to those of the Airbus A220-300. A configuration with two fuselage mounted tanks (front and aft), providing a total fuel capacity of approximately 4 t of LH2, is considered. A modeling framework is developed by coupling a tank sizing model with a one-dimensional distribution system model to evaluate key physical phenomena influencing system performance, including pressure losses, thermal behavior and overall weight impact, along the fuel path from the storage tanks to the engine interfaces under steady operating conditions. The architecture reflects typical safety and redundancy requirements for hydrogen systems, while remaining sufficiently simple to serve as a preliminary, low fidelity sizing tool at conceptual design level. The predicted fuel system mass is compared against several empirical mass correlations from the literature, providing an initial consistency check for the modelled architecture. The resulting framework provides a structured, low fidelity methodology for assessing LH2 storage and main distribution architectures and for identifying key design drivers and tradeoffs relevant to aircraft level integration.
This work concerns thermal energy storage in the medium-temperature range (100 – 250 °C), which is typical of parabolic-trough concentrating solar power (CSP) systems. Within this context, the use of phase change materials (PCMs) has been drawing attention in recent years as a promising technology. A class of PCMs suitable for the specific temperature range are sugar-alcohols and, among those, meso-erythritol (melting point: 118 °C) has been selected here as a such representative compound. Both experimental and computational methods are being used, whereby the experimental part of the work is carried out in a pilot facility, which is a hydraulic loop integrating a 100 L cylindrical storage tank. This is loaded with 200 hollow spherical containers (capsules) of 7.5 cm diameter made of steel, containing the PCM and forming a packed-bed arrangement. This offers a large surface area allowing for good heat transfer between the storage medium and the circulating heat transfer fluid, which is here a thermal oil (Therminol). For the computational work, a packed-bed model is used, considering the tank as a porous medium consisting of two phases (fluid and PCM) thermally interacting with each other and the continuous solid phase approach is used for the PCM, with suitable treatment of the phase-change in the energy equation. The model is validated and used for comparisons with preliminary experiments for the charging of the tank showing good agreement. Subsequently, a parametric investigation is carried out based on the model, by considering additional values of the main thermal-hydraulic parameters, such as oil flow rate and inlet temperature, and their effect on the melting rate and the charging efficiency are investigated. For a period of 8 hours, typical of a daily cycle of operation of a solar energy system, the evolution of the phase change process is evaluated from the numerical results for all parameters considered. It is shown for which values of these parameters the melting process can not be completed within the chosen time period and, thus, careful selection is needed when designing a storage system based on the given storage concept for optimum utilization of the harvested solar energy.
The notion of "Energy Data Spaces" is gaining traction as a revolutionary framework within the energy industry, promoting the seamless integration, sharing, and analysis of data among various stakeholders. Endorsed by the European Commission Energy Data Spaces are designed to establish a cohesive digital ecosystem where data from diverse sources, including energy producers, consumers, and grid operators, can be collaboratively leveraged to streamline energy management and boost operational efficiency. This paper delves into the core principles, structural design, and prospective applications of Energy Data Spaces, emphasizing their pivotal role in fostering innovation and sustainability in the energy sector. We present a reference implementation of an Energy Data Space, highlighting the key features that must be addressed, such as data privacy, security, and standardization challenges. Our findings demonstrate that this framework successfully enables secure, interoperable data exchange across heterogeneous systems, as validated through our collaboration with the Electricity Authority of Cyprus (EAC). The results indicate that providing stakeholders throughout the energy data value chain with an Analytics Catalogue of adaptable AI services significantly optimizes grid operations and demand-side management.
Beam-down concentrating solar systems consist of two successive reflections. Compared to the conventional concentrated configurations, there are two concentrators, and the receiver is on the ground level. In the present study, a beam-down linear Fresnel reflector is investigated in optical terms. The collector is a conventional flat plate receiver. Two different secondary concentrators are examined and compared based on their optical performance. Both the secondary concentrators are hyperboloidal, intending to enhance the optical performance. The first concentrator examined has a parabolic shape. The second concentrator examined consists of flat segments, which are designed based on the parabolic profile of the previous parabolic secondary concentrator, aiming to reduce the configuration’s construction cost. The major objective of this work is to conduct an optical analysis of the proposed configurations and calculate the optical performance, the incident angle modifier, and the intercept factor for various incident angles. The maximum value for optical efficiency was calculated at 68.6% and refers to the flat-segmented design, a promising value for a concentrating solar system.
Solar thermal energy plays a vital role in the transition toward sustainable and energy-efficient heating solutions. Among the available technologies, flat plate collectors (FPCs) remain one of the most widely adopted systems for low-temperature applications (≤120℃), including residential water heating, industrial process heat, and district heating. Enhancing the thermal performance of large-scale FPCs is essential to improve efficiency, reduce energy losses, and ensure adaptability across diverse climatic conditions. This study presents a computational fluid dynamics (CFD) thermo-hydraulic analysis of riser tubes in a large-scale flat plate collector (FPC) using ANSYS Fluent. Three riser lengths (4.45 m, 5.45 m and 6.45 m) are examined with regard to temperature distribution, hydraulic behavior, and energy and exergy performance. An aqueous solution of 50% (w/w) glycol enters the risers at 15 °C with a velocity of 0.4 m/s, while non-uniform heat fluxes of 750 and 100 W/m2 are considered on the sun-facing and shaded sides. For riser lengths of 4.45 m, 5.45 m and 6.45 m, the CFD simulations indicate outlet temperatures of 89.63 °C, 96.81 °C and 103.61 °C, corresponding to thermal efficiencies of 74.1%, 77.0% and 79.4% and exergy efficiencies of 8.0%, 9.6% and 11.1%, respectively. Fully developed laminar flow is observed, with pressure drops (2.7–3.56 kPa) and low pumping power demands. To ensure numerical reliability, a mesh-independence study was carried out for the 5.45 m riser. Refining the grid from 6.5 × 105 to 7.43 × 105 cells changed the outlet temperature by less than 0.2%; therefore, Mesh 2 was adopted for all simulations. Taken together, the mesh-independence analysis and the comparison with monitoring data support the reliability of the numerical model. Overall, the longest riser provides the highest energy and exergy performance but operates close to the stagnation temperature range (100–120 °C), reducing safety margins. The intermediate 5.45 m riser emerges as the most balanced configuration, combining high thermal and exergy efficiencies with more moderate outlet temperatures and hydraulic losses; it is therefore recommended for real-world deployment in large-scale FPC systems.
Luminescent Solar Concentrators (LSCs) have recently attracted attention for their dual role in boosting solar energy efficiency and enhancing greenhouse cultivation, offering a sustainable solution for agriculture and photovoltaics. The aim of this work is the synthesis and application of a new luminescent material as an LSC in greenhouses. Boron carbon oxynitride (BCNO) was synthesized and characterized as a new material with enhanced luminescent properties that could be useful in greenhouses to improve plant growth. The emission maximum of BCNO is located at 450 nm; therefore, it provides a targeted light increase at the first photosynthetically active peak of chlorophyll. Specifically, spectroscopic and structural studies were carried out to develop and optimize the material as a film, with the ultimate goal of depositing it on plastic surfaces that are commonly used in greenhouses. The BCNO film absorbs harmful UV light and converts it into strong blue light. The results were encouraging as they showed that the BCNO material, due to its high emission in the blue, can be used as LSCs in agriculture. The evaluation of BCNO as a solar concentrator was achieved in a small greenhouse with hydroponic lettuce crops. Two greenhouses were constructed, one of which had the BCNO material as a cover for the plastic shell. Compared to the control greenhouse, plants grown under the BCNO-coated cover exhibited a maximum increase of 16% in shoot fresh weight and 15% in dry biomass. Furthermore, total chlorophyll content was enhanced by up to 8.12%, while leaf gas exchange parameters showed notable improvements, with photosynthetic rates and stomatal conductance increasing by 7.34% and 11.11%, respectively compared to the control. These results indicate that materials such as BCNO are highly promising for optimizing and maximizing greenhouse crop yields.
In the present work, a focused analysis of the cost-components distribution of a low-enthalpy Rankine cycle using supercritical carbon dioxide (sCO2) as the working fluid is made. This investigation aims to evaluate the cost distribution of the main sCO2 components and identify the most cost-intensive elements to support future techno-economic assessments of low-enthalpy power plants. More specifically, the present work explores the utilization of a low-enthalpy geothermal field located in the Sidirokastro area, in Serres region in Greece, for approximately 250 kW of power generation, with a maximum geothermal water source temperature of 78 °C. To estimate the thermodynamic performance of this specific geothermal field, a thermodynamic model was developed, modelling a transcritical Rankine cycle using sCO2 as the working fluid. The thermodynamic model was developed using the Cape Open to Cape Open (COCO) simulator and incorporated the most recent available data describing the geothermal source properties and typical performance characteristics of the main thermodynamic cycle components. Furthermore, the Peng-Robinson equation of state was used, to estimate the thermophysical properties of sCO2. For the calculation of the low-enthalpy power plant, a preliminary assessment of the purchase cost of the main components of the geothermal power plant was performed, based on the most updated correlations from international literature. These correlations connect the equipment purchase cost to the key operational parameters, such as the power output and the UA value (the product of the overall heat transfer coefficient and the heat exchanger surface area). To improve the accuracy of the calculation of the UA parameter in the power plant heat exchangers, detailed sub-models for the geothermal heat exchanger and the water condenser were used. These models allow to properly capture the effect of the CO2 thermophysical properties variations to the calculation of the logarithmic mean temperature difference and thus, to the UA parameter value. The analysis of the results led to the identification of the most important components of the geothermal power plant from a cost-intensive point of view. More specifically, the condenser and the geothermal heat exchanger, accounted for over 55% of the total cost, with the water condenser cost corresponding to 32.44% and the one of the geothermal heat exchanger to 23.05%. These findings provide valuable insights for future techno-economic analyses aiming at the evaluation and optimization of the performance of low-enthalpy geothermal power plants.
Rocks and sediments are composite materials comprising multiple mineral (or other solid) phases, with fluid phases (air, water, hydrocarbons) or ice filling the pore spaces. Two key thermogeological parameters, used in the design of ground source heating and cooling (GSHC) and geothermal systems are (i) volumetric heat capacity (a scalar quantity) and (ii) thermal conductivity (a tensor). The bulk volumetric heat capacity of a composite material, being a scalar quantity, can simply be calculated as the weighted arithmetic mean of the components. Many proposals have been made for the estimation of bulk thermal conductivity from the conductivities of a rock or sediment’s components, and no single proposal is universally satisfactory. A variety of proposed algorithms have been examined for monomineralic systems (quartz or calcite + water + air). A weighted geometric mean of the components of a geological material generally provides a good (but not perfect) estimator of bulk thermal conductivity, but tends to perform poorly in dry, porous materials. A semi-empirical “Kersten-Johansen” approach seems a good estimator of thermal conductivity of porous sandy materials at varying states of compaction and saturation; its applicability to lithified rocks and non-silicate lithologies has yet to be demonstrated.
As the fraction of global energy consumption derived from renewable energy sources continues to increase, solar energy is the one among the others with the largest growth in usage. Despite its advantages, which include cost-effectiveness and the ability to be used in a wide range of applications, there are some factors that play a significant role in the total energy production of a photovoltaic system. Some of them are the tilt and orientation of the solar panels and the shadows generated. This work aims to conduct simulations of photovoltaic systems to be installed on a building of the laboratories of Mechanical Engineering at the Polytechnic Campus of the National Technical University of Athens. The building is characterized by a gross rooftop area of about 2000 m2. In this study, the Skelion software, a plugin in the environment of Sketchup, is used. Initially, using the dimensions of the building based on the calculation from three-dimensional rendering maps from Google Earth, as well as observation and measurement of dimensions on-site, the design of the building and the surrounding area is completed. Subsequently, an analysis of certain parameters is carried out, such as the type of photovoltaic panel, the shading on the surfaces, and the optimal tilt and orientation of the panels, aiming at the optimal utilization of solar energy potential. In addition to the above, certain scenarios for the placement of photovoltaic panels both on the roof of the building and on its sides are examined. Lastly, based on the results, an economic analysis and comparison are carried out to find the system with the optimal energy performance that will be as profitable as possible. As a result, the maximum annual energy production, in accordance with the acceptable energy efficiency of the solar panels, was found to be 247 MWh, with the maximum rate of losses due to shading being equal to 10%. Furthermore, the net present value of the specific scenario rises to 20 k€ and the payback period was calculated to be 10 years.
The widespread adoption of renewable energy technologies requires adaptable and replicable energy storage solutions tailored to diverse climatic conditions. This paper presents a comprehensive study on the replication potential of a compact hybrid energy storage solution, called MiniStor across various European sites. The MiniStor system integrates solar photovoltaic-thermal (PVT) and solar thermal collectors, a thermochemical (TCM) reactor using an ammonia cycle, a heat pump with phase change material (PCM) storage, and a battery for electrical energy management in buildings. Its core innovation, the TCM reactor stores heat through reversible ammonia-calcium chloride reactions, providing heating during winter and cooling during summer. To assess its broader applicability, the system’s replication potential was evaluated across various European climates and residential typologies, focusing on single-family homes. Simulation, based on specific meteorological and building data, demonstrated that MiniStor can effectively operate across diverse regions demonstrating significant potential for RES integration across Europe, with renewable energy coverage ranging from 32% to over 88% depending on location for the worst-case scenario. This work contributes to accelerating the large-scale integration of renewable energy storage solutions in the built environment across Europe.
A dynamic model was developed in TRNSYS® software package to simulate the thermal behavior of a single family house in Spain during a year. The model takes into consideration the characteristics of the building (orientation, insulation, thermal zones, etc.), heating and cooling devices, weather conditions and electric grid usage. Additionally, the model incorporates occupancy profiles, lighting, heat producing devices and infiltration to estimate thermal loads and photovoltaic production. So, with the utilization of the model, a characterization of the thermal and photovoltaic systems is accomplished, which can be used for the assessment of potential coupling with individual models of thermal energy storage solutions and comparison of cases with and without storage. As a result, the investigation of load shift strategies together with the exploitation of the photovoltaic energy source, will be feasible if the required input becomes available. According to the model, the annual thermal demands are 1618 kWh for space heating, 2358 kWh for space cooling and 1671 kWh for domestic hot water. The total electricity consumption of the heat pump and all circulating pumps is 1273 kWh, while the photovoltaic array produces 6512 kWh per year.
Mine water, a product primarily from pyritic weathering in coal mining regions, alongside oxidative weathering of other minerals, has caused destructive changes in water chemistry, sediment chemistry, and biological communities globally. Younger and Wolkersdorfer (2004) detail the impacts of mining on the freshwater environment. This study looks back to over twenty years of data collected in the coal-bearing region of Ohio showing impairments suggested by Younger and Wolkersdorfer (2004). This study focused on correlations between water and sediment chemistry and its impact on aquatic biology in the coal mined areas of four watersheds that have been severely, moderately, and lightly impacted by acid mine drainage. Sediment and water chemistry collected over a number of years at 62 sites have been correlated with a metric of biological health, specifically that of benthic macroinvertebrates. The study results suggest that contaminants including Al, Fe, and Mn in the water column are the most likely stressors to impede biological recovery supporting the findings of Younger and Wolkersdorfer (2004).
The mining industry invests a lot of money and effort in excavating and maintaining large underground networks of interconnected void spaces. This brings a unique opportunity to future engineer and minimize capital costs of mine water geothermal projects, which have wide global potential. This paper provides an update on the state-of-art in mine water driven energy utilization and, using the example of the Upper Silesian Coal Basin (USCB), Poland, presents a simple and fast method for assessment of geothermal project viability based on availability of six categories of nearby energy receptors: single-family housing, multi-family housing, services and large-area retail, office space, large-scale public buildings, active mining sites, and large-scale production plants. Results indicate a high potential for success of mine-water geothermal projects in the highly urbanised USCB. However, the coal mining industry in Poland is in decline so there is a strong tendency to avoid any kind of investment in innovation. The authors argue that this approach, although understandable, is short-sighted, as it overlooks opportunities to promote use of low-carbon energy resources, and create a post-closure “after-life”, or support mining communities, sustaining the cultural identity of mining regions. Given that land use categorization and weighting in our method can be adjusted for local or regional conditions, it is readily applicable for assessment of project viability at any prospective mine water geothermal location across the world.
Paul Younger, to whose memory this issue is dedicated, was an early advocate of a geothermal energy renaissance in the north of England. This paper offers background to the experience gained with the Eastgate BH1 and Eastgate BH2B boreholes, focused on exploring the geothermal potential of the Weardale Granite, followed by what has subsequently become known as the Newcastle Science Central Deep Geothermal Borehole (NSCDGB), which found a sequence of (presumed) Fell Sandstones. These efforts represent not only a legacy piece of the energy infrastructure in the UK, but also a legacy of Paul Younger. While the NSCDGB has not been developed using conventional geothermal methods, it has proved invaluable in providing data and a modelling test-bed for the geothermal potential of northern England and it is hoped that in future years it can serve as a testing facility for deep geothermal research. Research carried out as part of the recently concluded NetZero GeoRDIE has confirmed that it could still be converted to a Deep Borehole Heat Exchanger (DBHE), with an indicative total continuous heat yield of >50 kW for a lifetime of 25 years if repurposed to c.920 m depth.
The transition to sustainable energy systems is crucial in reducing greenhouse gas emissions and increasing energy efficiency. This paper synthesizes insights from industrial experts and academic researchers on the challenges, opportunities and solutions of integration of thermal energy storage (TES) in industrial energy systems. These insights were gathered during an international expert workshop on TES, organized by the European Energy Research Alliance as part of the Joint Program on Energy Efficiency in Industry (EERA-JP EEIP) on November 7th, 2023, discussing a white paper on industrial thermal energy storage. This paper provides a comprehensive overview of the current state and future potential of TES technologies. Demonstrating technology benefits, continuing material development, improving economic feasibility, enhancing system flexibility, developing innovative business models, fostering policy supports, and facilitating knowledge transfer are believed to be essential for the successful adoption of TES technologies in industry.
Much of Paul Younger’s work focused on nature-based solutions that addressed environmental problems, especially relating to removal of contaminants from minewaters. Enhanced Rock Weathering (ERW) has emerged during the last few years as a new paradigm, taking advantage of natural processes of rock weathering to remove CO2 from the atmosphere. This approach makes use of existing infrastructure in mining and processing silicate rocks, especially those used as aggregates in the construction industry. Weathering of silicate minerals has long been known to influence the Earth’s atmospheric CO2 content, and the process of ERW artificially enhances this by crushing the rock to increase its reactive surface area, prior to application to soils. The key challenges include verification of claims for CO2 removal, and scaling up production to meet the need to remove billions of tonnes of CO2 globally. Although multidisciplinary, these challenges are similar to those associated with widespread deployment of passive minewater treatment systems, and are addressed using sound knowledge of mineralogy and geochemistry.
Brain metastases are ten times more common than primary brain tumors and pose a significant clinical challenge. How brain metastatic tumor cells adapt to the unique and hostile brain microenvironment remains unclear. Astrocytes, the most abundant glial cells in the brain, are emerging as key mediators regulating the development of brain metastases. Initially anti-metastatic, astrocytes are reprogrammed by tumor-derived signals, transitioning into a pro-metastatic phenotype. Here, we review the roles of astrocytes in brain metastasis and describe the evidence for their phenotypic plasticity, the basis of astrocyte-tumor interactions, and potential therapeutic strategies targeting these processes.
The key features of Professor Paul Younger’s work on Underground Coal Gasification (UCG) linked to Carbon Capture and Storage (CCS) are summarised, with particular reference to his work on protecting potable water aquifers from contamination by the by-products of in-situ gasification and on his development of a technical basis for secure storage of captured carbon dioxide (CO2) in UCG cavities. A review of recent developments in the UCG field is presented, noting that the scale and international reach of demonstration projects has diminished over the intervening years and that the locus of research activity has moved to China and other Asian countries in which coal use continues at high levels. The importance in a climate-constrained world of a robust method of capturing and storing the CO2 produced by UCG activity is highlighted. Developments in CCS linked to the UCG process itself are reviewed and a brief summary is provided of the present state of CCS technology more generally.
Paul Younger was an outstanding geologist born and bred in the northeast of England and although he spent time away, his geological umbilical firmly fixed him in the region encompassing the counties of Northumberland and Durham their cities, towns and pit villages; an area for which the geology underpinned the industrial and social development. The linkage between geology and industry is commonly reflected in the groundwater of area and it was this that first stimulated Paul into research. He became a hydrogeologist. But Paul recognised that there is more to adit water outflow than solutes. The water told another story, one of heat below the surface, copious amounts of it. The warm and tepid waters encountered by Paul in the region set him thinking about geothermal energy. In 2004 he became the first person in 20 years to drill a dedicated geothermal appraisal well in the UK at Eastgate in Weardale. He followed up with a second well in Eastgate in 2010 and a third in central Newcastle in 2011. Paul was passionate about the energy transition and saw geothermal energy as a vast resource, easily won and one which could affect a fundamental change in the way we heat our homes and places of work. Sadly, Paul did not live to see the UK National Geothermal Centre formed in 2024. It is nonetheless a product of his vision.
