TIB Open Publishing
Not a member yet
1994 research outputs found
Sort by
Echo-LLM Evidence-Checked Hierarchical Ontology
Full text linkLarge language models can draft ontologies, but unverified extraction yields hallucinated triples—producing plausible yet incorrect facts. EchoLLM is a text-only, evidence-grounded pipeline for ontology construction. Candidate triples are first extracted with an instruction-following LLM. A hybrid retriever (BM25 + dense) gathers sentence-level evidence for each triple. Natural language inference then tests whether the evidence entails the triple; only entailed, lexically consistent hypotheses are accepted, and all decisions are logged. Accepted entities are embedded and clustered to induce classes and a lightweight hierarchy; rdfs:comment is generated from supporting text. The result is a validated triple set and an initial ontology suitable for bootstrapping domain knowledge graphs. The construction design favors high precision which requires no domain-specific rules, and surfaces failure modes (extraction, retrieval, verification). This enables authors and subject-matter experts to build trustworthy knowledge graphs quickly while keeping model and cost choices flexible
Development of a Concentrating Optics System for a Photoelectrochemical Hydrogen Reactor
Full text linkGreen hydrogen is expected to play a crucial role in achieving net-zero carbon emissions. By supporting the development of photoelectrochemical (PEC) hydrogen production, the technology’s advantages in terms of scalability, low-cost materials, and reduced transmission losses can be utilised. This study presents the design, construction and characterisation of concentrating optics for on-sun testing with a PEC reactor. The optical design incorporates refractive primary optics (linear Fresnel lenses) and reflective secondary optics (stepped lightguide) to produce a scalable line-concentrating system. Ray tracing simulations predicted an optical concentration ratio (OCR) and optical efficiency of 12.5 and 51.3%, respectively. However, experimental testing revealed lower performance, with maximum OCR and optical efficiency of 5.8 and 23.8%, respectively. The greatest contributor to the discrepancy is found to be heightened stray losses in the demonstrated system. The results highlight the importance of precise manufacturing to reliably produce superior optical performance. Despite high losses and sensitivity to misalignment, the optics were successfully coupled with the PEC reactor to produce hydrogen in subsequent on-sun tests, the results contributing to an extended study investigating the up scaling of PEC reactor technology
Optimal Design of Hybrid Solar Power Systems: A Case Study in the Chinese Market
Full text linkThe global energy industry is shifting towards a net-zero energy system to achieve climate neutrality, leading to significant growth in distributed renewable energy generation. This reshapes market dynamics and presents challenges in balancing supply and demand, increasing the risk of midday oversupply and variability in renewable generation, potentially compromising grid reliability. Concentrated solar power (CSP) offers a viable solution for grid decarbonization by integrating large-scale renewables and providing ancillary services like peak shaving and load shifting, frequency control, and energy storage, complementing the intermittent supply of photovoltaics (PV). The synergy between low-cost PV and dispatchable CSP fosters a resilient and sustainable system. Demonstration projects, especially in China, emphasize the relevance of hybrid CSP systems. CSP plants are built alongside large-scale PV installations to address the growing challenges associated with the electrical grid. The study explores hybridizing high-performance collectors, specifically Ultimate Trough (UT) collectors using molten salt as a heat transfer fluid, with PV to identify optimal solar field sizing and operational strategies. The techno-economic optimization framework integrates in-house cost models with thermodynamic and optical models derived from the System Advisor Model (SAM). A case study in Shichengzi, China, evaluates a hybrid CSP + PV plant with integrated thermal storage. High-performance collectors and better synergy in UT and PV production profiles lead to a 17% and 35% reduction in the power purchase agreement (PPA) price compared to conventional large aperture troughs not optimized for molten salt operation and linear Fresnel devices. This research supports informed decision-making and design solutions for sustainable and economically viable renewable energy production
Salt Tank Testbed: a Test Site Designed to Replicate Floor Buckles Observed in Commercial TES Tanks
Full text linkA test site has been designed and is under construction to replicate the buckling failure observed in several in-service storage tanks for nitrate salts operating up to 565°C. In commercial tanks multiple factors have been identified that influence the floors susceptibility to buckling, including: the as-manufactured shape of the floor, high compressive stresses due to thermal gradients and/or friction, fluid inventory and absolute temperature. Based on extensive modeling analysis it was determined that similar buckles can be reproduced in a scaled test tank (approximately 9x smaller than a representative commercial tank design). To buckle the scaled tank a radial thermal gradient is generated in the tank with a low fluid level, the fluid level is then increased while maintaining the thermal gradient; based on the modeling results just one of these cycles can plastically deform the tank floor. The test site which is under con-struction is designed to replicate this damaging cycle at lower temperatures. The goal of test-ing will be to reproduce this damaging cycle and buckle the scaled test tank floor, allowing proper model validation and a methodology for comparing different tank designs at a smaller (and less costly) scale
Dynamic Wind Loading of Heliostats: Efficient Simulation of Resonance Effects for Heliostat Cost-Optimization
Full text linkA method for the design of heliostats considering dynamic wind loads is presented. The transient FEM simulation is based on a CAD model of the heliostat and a pressure distribution time series measured in a wind tunnel. In order to minimise the calculation times, a simplified FEM model is used first to determine the period in which the maximum deformations occur. The stresses can then be determined for this period using a more precise model
Advanced Drone-Based Alignment Measurements for Parabolic Trough Collectors: Optical Inspection of Solar Field Installation
Full text linkA novel drone-based measurement method for the automatic quality check of the field assembly of parabolic trough collectors has been developed. The module as well as receiver alignment of entire parabolic trough loops can be measured using commercially available drones equipped with a visual camera and RTK (real time kinematic) positioning. The measurement principle is based on the geometric relations between aperture edges of the parabolic trough collector and the absorber tube line, which both are measured seamlessly along the collector using robust edge detection algorithms. The measurement method replaces hook-rod based measurements of the receiver alignment and total-station based measurements of the module alignment in a fast and fully automated way while keeping high measurement resolution and accuracy. Due to its speed and versatility to measure receivers with and without protective foil and with the collector in arbitrary orientation, the measurement method can be applied in all project phases ranging from solar field construction over commissioning to operation. The paper presents the progress in the development of the method and the results of the validation measurements performed at the parabolic trough collector loop of the molten salt test platform (EMSP) in Évora, Portugal
Simulation of a Hybrid Concentrated Solar and Biomass-Fuelled Trigeneration System for Residential Applications
Full text linkSolar technologies stand out as effective solutions for decarbonising the building sector. Among them, Concentrated Solar Power (CSP) systems offer the advantage of delivering flexible and dispatchable power. However, hybridisation with other renewable energy sources is often pursued to extend the operational hours. Therefore, this study investigates the complementarity of solar energy with biomass combustion within a small-scale hybrid trigenerative plant. More precisely, the proposed system consists of a 240 kWth peak thermal power Linear Fresnel Reflectors solar field combined with a 130 kWth back-up biomass boiler to supply heat to a 20 kWel/100 kWth Organic Rankine Cycle (ORC) unit for the provision of cooling, heating and electric power to 10 apartments. The hybrid plant also integrates thermal energy storage tanks and a battery energy system to increase the solar energy self-consumption and reduce the intervention of the grid. The performance of the hybrid system is analysed through an advanced simulator developed by the authors in MATLAB/Simulink considering the components’ inertia. The results reveal an increment in solar energy self-consumption achieved by exploiting the low solar irradiance to bring the latent heat thermal energy storage into its melting range, thereby extending ORC operation into nighttime hours. More precisely, the system meets the entire annual thermal demand for space heating, cooling and domestic hot water through renewable sources, consuming 2.25 tons of biomass. Electric demand coverage, instead, reaches up to 81% with the inclusion of a 60 kWhel battery energy storage system
Demonstration of a Proof-of-Concept Integrated Skip Hoist-Thermal Energy Storage System
Full text linkThis paper presents the design, construction, and preliminary testing of an innovative skip-hoist particle lift (PL) integrated with a multi-layered cylindrical thermal energy storage (TES) system for particle-based concentrated solar power (CSP) applications. The skip-hoist PL, constructed with stainless steel for high-temperature compatibility, was seamlessly integrated with two TES bins on a 22-m concrete tower. Preliminary testing at ambient temperature confirmed the system’s operational feasibility, paving the way for high-temperature testing and the proposed 1.3 MWe pre-commercial scale-up in Waad Al-Shamal, Saudi Arabia
Optical, Structural, and Electrical Properties of TeO2 – Na2O – NaX Glasses (X = Cl, Br, I): Roles of Crucible Materials and Halides
Full text linkAlkali tellurite glasses, which offer a broad glass-forming region along with large halide solubility, are excellent candidates as transparent conductive materials. TeO2 – Na2O – NaX (X = Cl, Br, I) glasses with halogen contents X ranging from 0 to 6 at. % (in total at. % of constituting elements Te, Na, O, and X) are investigated. Au crucibles alter their optical properties through the formation of inhomogeneously distributed gold nanoparticles. In contrast, alumina crucibles, despite undergoing a more severe dissolution, result in minor changes of the glasses’ structural and electrical properties. The electrical conductivity of such mixed anion glasses hinges on the mobility of the charge carriers (Na+ ions), and thus (i) on the bond strength of the Na-X bonds involved, as well as (ii) on the free volume within the glass network and consequently on the size of the anions. Accordingly, the electrical conductivity is found independent on the substitution rate for small halogens (X = Cl, Br), but increases up to threefold for large halogens (X = I)
Thermo-Optical Set-Up to Investigate Non-Isothermal Glass-Metal Contact
Full text linkThe development of innovative mold materials and coatings for glass forming, relies on a profound understanding of the interaction between glass melt and the respective metallic or oxidic surface. In order to revise the existing theories on sticking temperatures and viscosities, a new thermo-optical setup was constructed that enables the investigation of the non-isothermal bonding behavior of glass melts on different substrates. A glass gob is generated in an upper furnace at temperatures of up to 1200 °C and is then poured onto an individually heated substrate (the respective contact material) at temperatures similar to container glass forming. The resulting movement of the gob at pouring and on the substrate is observed with a high-speed camera. The set-up was tested with a soda lime silicate glass melt in contact with various metallic, carbon-based and ceramic materials. Sticking temperatures for the different materials were determined and compared to the results found in literature. Contact temperatures at which sticking occurs varied significantly with the investigated material. A critical interface temperature (respectively viscosity of 108.8 Pas) as obtained by previous researchers could not be found, instead the temperature range for sticking was almost 200 K. Some materials resisted sticking even at temperatures up to 600 °C with the interface viscosity being below 108.8 Pas. Interestingly, those substrates also showed non-wetting behavior in previous heating micros-copy trials, suggesting that wettability plays a more important role for sticking than assumed so far