TIB Open Publishing
Not a member yet
1994 research outputs found
Sort by
Impact of AlOx Capping Layer Thickness for Edge Passivation of TOPCon2 Shingle Solar Cell
Full text linkThis work aims at understanding the short circuit current density losses observed on TOPCon² solar cells after AlOx layer deposition and annealing. This process is the most considered for edge passivation of shingle solar cell, who suffer from heavy edge recombination losses after cutting procedures. Our solar cells feature Transparent Conductive Oxide (TCO) layers at the front and rear sides, on top of which the AlOx edge passivation layer is deposited during Atomic Layer Deposition (ALD) process. We focus on the effect of the AlOx layer thickness and the annealing conditions on the optical and electrical properties of the front AlOx/TCO stack. It is found that annealing of thick AlOx layers induce an increase of free carriers’ concentration in the TCO layer, resulting in additional parasitic absorption. Thinner AlOx layer and/or cooler annealing condition would limit this phenomenon, however rising a compromise with the shingle edge passivation goal. Indeed, we see that applicated on the TOPCon² shingle solar cells, less current density loss comes along lower edge passivation level
Iron-Doped Magnesium Aluminosilicate Transparent Glass-Ceramics. Mg-Petalite or Spinel Nanocrystals? Competing Mechanisms
Full text linkTransparent glass-ceramics based on Fe2+:Mg-petalite and/or Fe2+:MgAl2O4 nanocrystals were obtained from the initial glass by single and two-stage heat-treatments at temperatures from 800 to 1000 °C. ZrTiO4 and spinel crystallized during the DSC scan up to 1000 °C. Spinel nanocrystals 9-12 nm in size also appeared during single and two-stage heat-treatments at temperatures of 850 - 1000 °C. Mg-petalite crystallites ~30 nm in size evolved in the narrow temperature range from 850 to 900 °C during single-stage holding periods. A maximum fraction of Mg-petalite crystallized at 850 °C. Once formed, Mg-petalite is preserved upon further heating and holding even at 1000 °C for 6 h. Mg-petalite and spinel transformed into sapphirine and highly siliceous residual glass during heating at 1100 °C. Competing crystallization mechanisms are discussed. In materials with a weakly developed liquid-liquid phase-separated structure, crystallization of Mg-petalite from the magnesium aluminosilicate glass predominates, and spinel becomes an additional phase. Spinel crystallizes as the main phase from glasses with the developed liquid-liquid phase-separated structure. Its crystallization is accompanied by the formation of highly siliceous glass, from which Mg-petalite crystallization is impossible. Intense absorption band with maximum at ~1.9 μm due to fourfold coordinated Fe2+ ions in spinel nanocrystals is used as a spectral indicator of spinel formation. Glass-ceramics are relevant for the development of saturable absorbers intended for lasers operating at 1.6-2.4 μm
On Computation of Lyapunov Exponents by QR Methods with Error Control for Semi-Linear DAEs
Full text linkIn this paper, we propose and analyze numerical methods for computing Lyapunov exponents of semi-linear differential-algebraic equations (DAEs), leveraging smooth QR factorizations and Runge-Kutta (RK) methods with error control and automatic step size selection. We demonstrate how both discrete and continuous QR approaches efficiently approximate Lyapunov exponents by simultaneously solving semi-linear DAEs and their linearized counterparts. The paper details the underlying algorithms, error analysis, and numerical integration techniques, focusing on half-explicit RK (HERK) and explicit singly diagonal implicit RK (ESDIRK) methods. We also provide implementation details and present numerical experiments to illustrate the efficiency of these methods
Validation of Solar Extinction Model at Plataforma Solar de Almería
Full text linkSolar extinction should be one of the most important factors to select the best locations for solar tower plants. The optical path between the heliostats and the receiver (slant range, SR) very often exceed 1 km. This distance could involve many particles in the atmosphere, which absorb and scatter the reflected solar radiation. Therefore, it is necessary to know the radiative losses due to solar extinction at the location and to have models rigurously validated with experimental data. At PSA there is a database with more than 6 years of solar extinction measurements. These data have been obtained thanks to a solar extinction measurement system developed by The Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT). This database allowed the development of a Typical Solar Extinction Year (TSEY). This TSEY presented an average annual solar extinction value of 6 ± 2 % for a measurement distance of 741.63 m. With this amount of data a model to estimate solar extinction has been validated at PSA. The input data used were the aerosol optical depth (AOD) and the SR. For this purpose, average daily extinction values were estimated with a model. From this new simulated database, a synthetic TSEY was developed in order to compare it with the experimental TSEY. In both cases, the average annual solar extinction values were in agreement with the value of 6 ± 2 % (741.63 m). By this way, the model has been validated and it could be used to estimate solar extinction worldwide
Solar Heat for Commodity Production: Mapping and Comparison With Fossil Fuel and PV
Full text linkA systematic assessment of concentrated solar thermal (CST) energy and its levelized cost of heat (LCOH) is essential to demonstrate the global potential of CST-energy for decarbonizing industrial heat demand – especially, since time is running out to tackle climate change and a significant part of industrial heat demand can be covered with CST as solar heat for industrial processes (SHIP). For this study, CST-LCOH in dependence of the DNI (direct normal irradiance) are obtained from literature as the annual energy yield changes with DNI and thus, the LCOH changes accordingly. These are mapped for Spain and compared locally with fossil fuel- as well as PV-based heat. A sensitivity analysis is performed for CST-LCOH, varying it by ±10 %, and including an implementation of CO2-taxes of 0, 50 and 100 €/t CO2 for the fossil fuels coal and natural gas. In all cases, if a renewable source is cheaper than fossil fuels, it is overwhelmingly CST. The margin for CST-energy, obtained as the difference of fossil fuel price with CST-LCOH, divided by CST-LCOH and which can also be interpreted as the relative margin from CST-LCOH to -price, reaches in the extreme case 139 % for fossil fuel prices in 2022 and a CO2-tax of 100 €/t CO2
Torque in the Rotation Axis of a Parabolic Trough Solar Collector due to Wind Loads
Full text linkParabolic trough collector (PTC) solar plants are susceptible to episodes of high speed sustained wind or gusts, which can affect their performance due to aerodynamic loads on the collector. In some collector configurations, the axis of rotation of the collector is directly connected to the flexible joint of the collector, so that torque is also transmitted to the rotation and expansion assembly installed at the end of the solar collector assembly. To obtain accurate measurements of the effect of the wind on the axis of rotation of a PTC, a torque sensor and an inclinometer were mounted at the end of a PTC at the Plataforma Solar de Almería (PSA) (Spain). A series of tests were carried out with different wind speeds and directions to verify the performance of the measurement system in dealing with the structural deformation of PTCs due to wind loads
Assessment of Self-Dispatch Strategy in a Concentrating Solar Power System: Impact Analysis on the Chilean Spot Electricity Market
Full text linkThis study investigates the technical and economic impacts of self-dispatch strategies on Concentrated Solar Power (CSP) plants in Chile’s spot electricity market. The PySAM simulation tool was used to model three dispatch scenarios—Marginal Cost-Responsive Dispatch, Daytime Mandated Dispatch, and Continuous Base Load Dispatch—to assess their effects on energy production, load factors, and financial outcomes at the Crucero and Cardones substations. The findings indicate that the Marginal Cost-Responsive Dispatch strategy optimizes revenue by aligning energy generation with periods of higher market prices. This strategy mitigates the adverse financial impacts of zero-marginal-cost periods, which undermine the viability of more rigid approaches like Daytime Mandated Dispatch. Economic analysis shows that only the Marginal Cost-Responsive Dispatch consistently covers annualized capital expenditures (CAPEX), particularly at lower CAPEX levels. In contrast, the alternative scenarios fail to achieve financial sustainability due to forced generation during low-value periods. Consequently, these results underscore the crucial role of dispatch flexibility in enhancing the economic performance of CSP plants. The study suggests that market regulations should be revised to encourage strategies that enable CSP plants to dynamically respond to market conditions, supporting the broader integration of CSP technology into Chile’s energy market. Such adjustments are crucial for advancing the country’s decarbonization goals. Future research should focus on further developing advanced self-dispatch algorithms and hybrid CSP systems to optimize economic outcomes in increasingly dynamic market environments
Current Progress of Activities at EU-SOLARIS ERIC: The European Research Infrastructure Consortium for CSP Technologies
Full text linkAn ERIC, established by a decision of the European Commission, is a legal entity possessing legal personality and full legal capacity acknowledged across all EU Member States. Its primary role is to establish and operate a research infrastructure on a non-economic basis.
Under the initiative of Spain, France, Germany, and Cyprus as Members, with Portugal as an Observer, a European Research Infrastructure Consortium (ERIC) has been formed. This consortium, named "European Solar Research Infrastructure for Concentrated Solar Power" (EU-SOLARIS ERIC) is established in accordance with Council Regulation (EC) No. 723/2009 of 25 June 2009.
The establishment of an ERIC was sanctioned by the European Commission, as evidenced in Commission Implementing Decision (EU) 2022/2297 of 19 October 2022 [1]. The inaugural assembly of the EU-SOLARIS ERIC took place at the CIEMAT Headquarters in Madrid on 12th January 2023. During this gathering, the General Assembly was officially convened, and the Statutes along with other governing documents were formally endorsed. At the time of composing this document, negotiations for the accession of three additional countries—Greece, Turkey, and Italy—are underway.
This paper summarizes the R&D activities carried out during this first year of the ERIC, particularly, we describe the new projects achieved
Evaluating the Potential of Solar Heat Production for the Food and Beverage Industry in Cyprus From 2024 to 2035
Full text linkThe increasing heat demand in Cyprus\u27 F&B industry presents an opportunity to leverage the abundant solar resources of the country as a sustainable alternative to fossil fuels for industrial processes. To project the final energy consumption (FEC) of the national F&B industry from 2024 to 2035, the GDP (PPP) is used as an exogenous variable. A regression model is obtained with an adjusted correlation coefficient (R²) of 85.8%. For the projections, two economic growth scenarios are considered (positive, PEG, [+3%] and negative, NEG, [−1.5%]), combined with two scenarios for solar technology deployment (business-as-usual, BAU, [2%] and large, LTD, [20%]). Additionally, dynamic simulations in TRNSYS are conducted to estimate the annual yield of a model SHIP plant using Parabolic Trough Collectors. The modelled system, consisting of a total collector area of 660 m² and a thermal storage of 30 m³, yielded 4,320 MJ/m² of thermal energy. It was found that solar energy could uptake between 10% and 28% of the FEC for the NEG and PEG scenarios, respectively. Moreover, the solar heat potential ranged between 85 TJ and 444 TJ, which represents between 19,780 m² and 102,800 m² of solar collectors, respectively. Lastly, the projections also analyse the reduction of GHG emissions in 2035 compared with the baseline year (2023), where the NEG-LTD scenario achieved a reduction of 71%; meanwhile, the PEG-BAU scenario presented an increment of 25% in the GHG emissions
A Novel Exponential Continuous Learning Rate Adaption Gradient Descent Optimization Method
Full text linkWir stellen zwei neuartige, schnelle, gradientenbasierte Optimierungsalgorithmen mit dynamischer Lernrate vor. Die Grundidee besteht darin, die Lernrate α an die jeweilige Situation anzupassen, wobei vor allem orthogonale benachbarte Gradienten angestrebt werden. Die Methode weist eine hohe Erfolgsquote und eine schnelle Konvergenzrate auf und ist in viel geringerem Maße auf manuell eingestellte Hyperparameter angewiesen, wodurch sie eine größere Universalität bietet. Sie skaliert linear (der Ordnung O(n)) mit der Dimension und ist rotationsinvariant, wodurch bekannte Einschränkungen überwunden werden. Die Methode wird in zwei Varianten, C2Min und P2Min, mit leicht unterschiedlicher Steuerung vorgestellt. Ihre beeindruckende Leistung wird durch Experimente mit mehreren Benchmark-Datensätzen (von MNIST bis Tiny ImageNet) im Vergleich zu den hochmodernen Optimierern Adam und Lion.We present two novel, fast gradient based optimizer algorithms with dynamic learning rate. The main idea is to adapt the learning rate α by situational awareness, mainly striving for orthogonal neighboring gradients. The method has a high success and fast convergence rate and relies much less on hand-tuned hyper-parameters, providing greater universality. It scales linearly (of order O(n)) with dimension and is rotation invariant, thereby overcoming known limitations. The method is presented in two variants C2Min and P2Min, with slightly different control. Their impressive performance is demonstrated by experiments on several benchmark data-sets (ranging from MNIST to Tiny ImageNet) against the state-of-the-art optimizers Adam and Lion