ENEA Research Centre Research Articles

Self-Cleaning Solar Mirror Coatings: From the Laboratory Scale to Prototype Field Tests

In this study, a low-cost, scalable and robust process is proposed as an innovative method for coating solar mirrors with a self-cleaning, transparent in the full solar range and versatile material based on auxetic aluminum nitrides, previously obtained at the laboratory scale. This work presents the scaling-up of the fabrication process from the laboratory to prototypal scale and the preliminary results of outdoor self-cleaning solar mirror field tests in the demonstrative concentrating solar power (CSP) plant ENEASHIP located in Casaccia (Rome) ENEA Research Center. Prototypes with a size of 50 × 40 cm have shown stability in external conditions: no coating degradation occurred during the test campaign. Their washing restores the initial reflectance affected by soiling and the self-cleaning performance allows for the utilization of a reduced quantity of water for cleaning operations with respect to the uncoated glass of back surface mirrors. A similar self-cleaning AlN coating could be utilized on other solar components affected by soiling, such as the glass envelopes in heat-collecting elements, PV panels and other parts where a self-cleaning performance combined with an optical one is required.

Innovative Power Generation Technologies for Improved Household Energy Delivery and Sustainable Future: Classical Solutions from ENEA Research Centre, Trisaia Italy

The present communication is focused predominantly on important R&D solutions relevant to renewable energy technologies covering the following: (i) Innovative heat transfer fluid and thermal storage technology based on a molten salt mixture developed by ENEA for large-scale heat storage. The system uses a parabolic trough collector, compared with diathermic oil, which allows higher operating temperature, resulting in significant benefits to the plant’s operation, safety and the environment. (ii) The world’s first solar disk powered by air micro turbine developed by ENEA. (iii) An innovative steam-explosion prototype plant installed at ENEA for the pre-treatment of lignocellulosic biomass and the fractionation of bio components to generate ethanol from lignocellulosic material using hemicellulose and lignin. (iv) The production of hydrogen-enriched biogas using steam as the gasification agent, which helps in obtaining nearly nitrogen-free product gas and with a high calorific value of around 12 MJ/Nm3 dry gas and a high percentage of hydrogen (up to 55%) while using steam as the gasifying agent in the presence of a catalyst. (v) A rotary kiln plant, with the main purpose being to develop and optimize a thermo-chemical process to convert used rubber tyres so as to recover material and energy, as well as other solid products, with high value-added “Activated carbon” and synthesis gas.

Modeling and optimization method for Battery Energy Storage Systems operating at variable C-rate: A comparative study of Lithium technologies

Lithium-Ion (Li-Ion) batteries are widely used for energy storage applications in microgrids systems. A real time estimation of static and dynamic conditions of the battery pack, such as the remaining capacity or the aging effects, is fundamental for these applications, where it is necessary to ensure stability and reliability in the power supply. Since the internal state of each cell cannot be directly measured, a model-based estimation algorithm has to be implemented to further describe the performance of the whole battery pack. This work proposes a simplified version of the equivalent circuit model capable of describing the behavior of Battery Energy Storage Systems (BESS) for microgrid applications. To create an accurate model based on experimental data, data relating to different Lithium technologies of storage systems located in ENEA Research Centre Casaccia were collected. Each BESS was subjected to discharge cycles operating at variable C-Rate, in order to carry out the same parameters identification process and analyze the behavior of the different technologies. The results demonstrate that the electrical parameters obtained for a specific C-rate and for the same BESS technology can be used for discharges carried out at the same power but on different days, showing a robustness of the proposed model in terms of reduced RMSE between the experimental and the simulated curves.

Thermal-hydraulic assessment of Once-Through Steam Generators for EU-DEMO WCLL Breeding Blanket primary cooling system application

Once-Through Steam Generators (OTSGs) were recently selected to be installed in the Primary Heat Transfer Systems (PHTS) related to EU-DEMO WCLL Breeding Blanket (BB). Referring to the Balance of Plant Direct Coupling Design (BoP-DCD) option, these components are used to deliver the thermal power removed from the two principal blanket subsystems, i.e. First Wall (FW) and Breeder Zone (BZ), to the Power Conversion System (PCS).OTSG design foresees a vertical component with primary water moving downward inside tube bundle and secondary fluid flowing throughout shell in counter current. The latter moves firstly downwards through the annular downcomer and then goes up in the central riser, where it boils up to super-heated steam conditions. Then, it is deflected by the upper tubesheet, flows again downwards along the steam downcomer and exits through the laterally connected steam nozzles.In the last years, as part of the research activities associated to the Work Package Balance of Plant (WPBoP), a detailed analysis of the steam generator, aimed at deeply understanding the main thermal-hydraulic aspects characterizing its performances during the pulsed regime of DEMO normal operations, was performed. To fulfil this scope, a complete model of the component was prepared by using the best-estimate system code RELAP5/MOD3.3, selected to be also the reference design verification tool.During operations, OTSG experiences full-load and low-load alternative phases with rapid transitions from one another. The steam generator capability to follow such load variations avoiding the occurrence of instabilities in the component was studied. The computational activity carried out was a preliminary thermal-hydraulic characterization of the component conceptual design during both pulse and dwell phases. The feedbacks of this analysis were also fundamental for the conceptualization of the steam generator mock-up to be installed in the planned STEAM facility that will be built at the ENEA Research center of Brasimone.

Design of a Prototypical Mock-Up for the Experimental Investigation of WCLL First-Wall Performances

A large research effort is currently ongoing within the framework of the EUROfusion consortium for the study and design of a water-cooled lithium–lead (WCLL) breeding blanket (BB). This concept will be tested in ITER through the installation of a test blanket module (TBM) and it is one of the two candidates adopted as driver BBs in DEMO. In this framework, at the ENEA research centre of Brasimone, the realization of the experimental platform, W-HYDRA, is envisaged. The platform is dedicated to the support of the development of WCLL BB and ITER TBM and the investigation of the DEMO balance of plants. One of the most important experimental infrastructures is the water-loop facility, the aim of which is to provide water at a high pressure and temperature (PWR conditions), with a sufficient mass-flow rate and power for the experimental testing of BB and TBM components. The facility will be equipped with a vacuum chamber and an electron beam gun for the reproduction of high surface heat flux on plasma-facing components. In the present work, the design of a prototypical mock-up (MU) of the WCLL BB first wall is described. The MU is used to investigate the thermal, hydraulic and structural behavior of the current first-wall design under relevant heat loads at the expected operational conditions. The delineation of the main experimental test’s features and the instrumentation needed is assessed in the paper. A preliminary CFD calculation on the prototypical MU and the computational results are also presented.

Downscaling of Hourly Climate Data for the Assessment of Building Energy Performance

In Italy, the calculation of the energy needs of buildings has been mainly based on quasi-steady state calculation procedures. Nowadays, the increasing interest in more detailed energy analysis for high-efficiency buildings requires more accurate calculation methods. In this work, starting from the hourly data of UNI 10349, the downscaling of a typical meteorological year was carried out by applying different mathematical and physical models for the main climate variables considered in the energy balance of a building to be used in dynamic simulation tools. All results were validated with one-minute measurements observed at the ENEA Research Centre in Rome, Italy. The results showed an MBE% of 0.008% and RMSE% of 0.114% using the interpolation spline method for the temperature, while, for the global horizontal irradiance, applying the novel sinusoidal–physical interpolation method showed an MBE% of −0.4% and an RMSE% of 31.8% for the 1 min observation data. In this paper, an easily implemented novel model for downscaling solar irradiance for all sky conditions that takes into account the physical aspects of atmospheric phenomena is presented.

Set up and test of an anticoincidence system for the detection of radioactive xenon by gamma spectrometry system

The aim of this work is based on the optimisation of a gamma spectrometry system in anticoincidence for the detection of noble gases, in particular the radioactive isotopes of xenon. These four radionuclides are of particular interest for the Comprehensive Nuclear Test-Ban Treaty (CTBT). The Laboratory of the ENEA Research Centre of Brasimone, where the experimental apparatus has been set up to carry out the measurements of 131mXe, 133Xe, 133mXe and 135Xe, is able to provide, if necessary, data and analysis on noble gases. The apparatus provides for the sampling of outdoor air, the passage through filters and in activated carbons maintained at cryogenic temperatures to allow xenon absorption. Finally, gas extraction and xenon volumes are analyzed by means of gas chromatography and a thermal conductivity detector. At the end of the extraction an aluminium cylinder containing radioxenon is analyzed by high resolution gamma spectroscopy using a High Purity Germanium Detector P-type. The signals produced by the interaction of cosmic rays with the crystal have been recognized as the main cause of the increase of the detector background because they give rise to the Compton continuum and, as a result, they affect the value of the minimum detectable activity (MDA). In order to overcome this effect, a system in anticoincidence has been developed using two plastic scintillators, placed over the shielding of the HPGe detector, which send pulses recording within a time delay window located in the germanium multichannel analyzer: at the time the signal arrives from the scintillator, the gate blocks data acquisition to avoid recording pulses generated by cosmic radiation. For both configurations of the system (with and without the anticoincidence apparatus operating) the energy, and efficiency calibrations have been carried out using a certified multigamma-ray calibration source to assess the performance.

High-Sensitivity Thomson Spectrometry in Experiments of Laser-Driven Low-Rate NeutronLess Fusion Reactions

The aneutronic 11B(p, α)2α fusion reaction driven by the interaction of high-energy lasers with matter has become a popular topic of research, since it represents a potential long-term goal alternative to the most studied deuterium-tritium reaction. However, the detection of the typical ionic products, especially alpha particles, of this low-rate fusion reaction is a challenging issue, due to their low flux. One of the diagnostic devices that can be implemented in laser-driven proton-boron fusion experiments is a Thomson spectrometer (TS), which is capable of detecting and discriminating ions according to their mass-to-charge ratio (A/Z, where A is the mass number and Z is the atomic number of the ions). In this work, we report on the ultimate test of a TS, which was designed and developed at the ENEA Research Centre in Frascati, Italy, in the context of a p + 11B fusion experiment. Our device—designed to have high sensitivity and a robust shielding against electromagnetic pulses (EMPs)—was implemented at the PALS laser facility (∼700 J in ∼350 ps pulses) at a distance of 367 mm from the laser-plasma interaction point. We analyse here the measured signals obtained with our device, focusing on the assessment of their signal-to-background ratio. Despite the presence of strong EMPs and background radiation at such a short distance from the laser-irradiated target, the TS proved to be suitable for effectively detecting protons and heavier ions stemming from the plasma source.

Optimal design and management for hydrogen and renewables based hybrid storage micro-grids

In an energy sustainability perspective, the renewables penetration is expected to importantly increase over the next decade, requiring modifications in the current electric system in terms of flexibility and reliability. In this respect, storage systems will play a central role and the production of green hydrogen is seen as a promising solution for both short-term and seasonal storage.In this context, the aim of this paper is the development of a methodology for the optimal design of hybrid storage micro-grids based on renewables and hydrogen and the definition of an optimal management strategy in a perspective of hydrogen employment as seasonal storage. In detail, an optimization code – based on mathematical models for each component and on specifically developed optimization strategies for the management of the components interaction – will be presented and applied to a case study. The code optimizes the sizes of the integrated electrolyzer and fuel cell, based on an objective function that maximizes the storage efficiency. It has been applied to the S.A.P.I.E.N.T.E. micro-grid installed at the ENEA Research Centre near Rome (Italy) – composed of photovoltaic panels, batteries, heat pump and thermal storage systems – obtaining the optimal design of the hydrogen section to be integrated as seasonal storage strategy. Furthermore, a parametric analysis on the battery size has been performed. The application of the developed optimization routine resulted in the introduction of a 3.7 kW electrolyzer and 4 kW fuel cell coupled with 36 kWh of battery capacity, enabling a total hydrogen production of about 87.5 kg (corresponding to 1159 kWh of electricity produced during the thermal year).

DTT: A Challenging Framework for a Sound Superconducting Magnets Design

At the ENEA's research center of Frascati, the DTT (Divertor Tokamak Test) facility is currently under construction. The activity of this experimental nuclear fusion reactor, will be focused on the optimization of the power exhaust management in view of DEMO. The project has been started during year 2015, when also the superconducting magnet system has been initially designed, basing on the available inputs coming from physics and on the desired goals for the machine. At present, the coils engineering design has almost been completed and the production of crucial components, such as the superconducting strands, conductors and toroidal field coils, have already been started. For the remaining superconducting elements, the engineering design is being finalized and other tenders are going to be launched soon. The result is a compact and flexible tokamak, with highly demanding requirements in terms of superconducting and structural performances, sometime close to the intrinsic mechanical limits of the adopted materials. Tight constraints on time, budget and resources forced the design team to walk through a complex path in these years for reaching a sound and satisfactory design of the complete magnet system. In fact, it was not possible to rely entirely on state-of-the-art and already assessed superconducting technologies, as was initially assumed. In particular, the trade-off between limiting the R&D phase and extending the performance demonstrated in other projects to the specific DTT requirements, pushed the team to take some risks, while providing a robust and fully performing magnet system design.

Alumina Based Electrode for Stable and Improved Supercapacitor Applications

This work describes the preparation of an Al2O3 electrode material for a performing and stable supercapacitor. The electrode was prepared by a DC thermal plasma plant installed at ENEA Research Centre of Portici. The structures and morphologies of samples were characterized by SEM, XRD, TG, and FT-IR. Al2O3 electrode electrochemical characteristics were performed in a sulphuric acid solution electrolyte. Cyclic Voltammetry (CV) technique was carried out. The results show that Al2O3 exhibits a good specific capacitance. Furthermore, after 10000 cycles, 98% of the initial capacitance was maintained.

Hydrodynamics and transport processes in porous materials under terawatt laser irradiation

Porous materials have many applications for laser-matter interaction experiments related to inertial confinement fusion. Obtaining new knowledge about the properties of the laser-produced plasma of porous media is a challenging task. In this work we review the development and the validation of the MULTI-FM code, by discussing the theoretical model on which the code is based, its implementation and the experiments on which the code has been tested. The experiments have been performed with the ABC laser located in the ENEA Research Center in Frascati.

Analysis of the temperature distribution in the pin bundle of the CIRCE facility

In this paper, a CFD analysis of the Fuel Pin Simulator (FPS) of the CIRCE-HERO facility built at the ENEA research centre in Brasimone was performed. STAR-CCM + code was used with the purpose of reproducing steady-state and transient experimental conditions adopting LBE as working fluid. RANS and URANS simulations were performed comparing the calculated temperature trends with the experimental data. In particular, the FPS average outlet temperature was monitored for the transient case and an exhaustive study of the heat transfer between the FPS and the pool during the transient was carried out. The impact of the involved heat transfer phenomena on the FPS energy balance was studied from a quantitative point of view and the relevant difference in terms of thermal inertia between pool and FPS component was pointed out.

Structural Assessment Procedure of the Toroidal Field Magnet System for the Divertor Tokamak Test

The Divertor Tokamak Test facility (DTT) is an experimental tokamak machine to be built in Frascati, Italy, at the ENEA research center. During its development, the DTT has gone through several design iterations. Developing a rigorous finite-element methodology to evaluate the performance of all its components has thus been a critical part of the verification phase of each new update. This work summarizes the assessment procedure that currently supports the design of the Toroidal Field magnet system, including the superconducting winding pack (Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn), the casing structure and all of the inter-coil structures. Given the high complexity of the 3D structure to reproduce, we implemented some modeling simplifications to solve the problems. Here we describe the finally adopted methodology next to all the motivations we examined to make sure the results were sound and reliable from an engineering point of view.

X-ray imaging of bio/medical samples using laser-plasma-based X-ray sources and LiF detector

This contribution to ECPD2019 is dedicated to the memory of Anatoly Faenov. During a period of approximately thirteen years 1994–2006, Anatoly and his wife Tatiana Pikuz (simply “Tania” for friends), accepting the frequent invitations of the National Institute for Nuclear Physics (INFN) and of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), cooperated with many Italian research laboratories dedicated to EUV and soft X-ray generation, spread in different towns (L'Aquila, Frascati, Milano, Padova, Pisa, Roma, etc.). In spite of the fact that they could stay in Italy only about one or two months per year, their activity was so intense that more than 50 peer- reviewed publications were generated from their experimental and theoretical work (just considering only the results obtained at L'Aquila and Tor Vergata—Rome Universities and at the ENEA Research Center of Frascati), without mentioning the cultural atmosphere that they stimulated in the field of Science and Humanity. The numerous experimental spectra obtained at ENEA by means of their spherically bent mica spectrometers, together with the corresponding theoretical simulations performed in Moscow, allowed to study the changing role of different excitations mechanisms for various plasma conditions, and to characterize at best the ENEA laser-plasma source for different applications: polychromatic and monochromatic micro-radiography of dried biological samples at 1 keV, soft X-ray contact microscopy (SXCM) of living cells in the water-window spectral region, spectroscopy of hollow atoms, etc. In this memorial paper, the main results of biological samples imaging on lithium fluoride (LiF) detectors, obtained with the ENEA and Tor Vergata University laser-plasma sources, are presented. In particular, the improvement of the micro-radiography and of the SXCM techniques obtained after moving from photoresist detectors and photographic films to lithium fluoride (LiF) detectors are discussed, for both dried and wet biological samples.

Laser Scanners for High-Quality 3D and IR Imaging in Cultural Heritage Monitoring and Documentation

Digital tools as 3D (three-dimensional) modelling and imaging techniques are having an increasing role in many applicative fields, thanks to some significative features, such as their powerful communicative capacity, versatility of the results and non-invasiveness. These properties are very important in cultural heritage, and modern methodologies provide an efficient means for analyzing deeply and virtually rendering artworks without contact or damage. In this paper, we present two laser scanner prototypes based on the Imaging Topological Radar (ITR) technology developed at the ENEA Research Center of Frascati (RM, Italy) to obtain 3D models and IR images of medium/large targets with the use of laser sources without the need for scaffolding and independently from illumination conditions. The RGB-ITR (Red Green Blue-ITR) scanner employs three wavelengths in the visible range for three-dimensional color digitalization up to 30 m, while the IR-ITR (Infrared-ITR) system allows for layering inspection using one IR source for analyses. The functionalities and operability of the two systems are presented by showing the results of several case studies and laboratory tests.

Laser Irradiated Foam Targets: Absorption and Radiative Properties

An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminum targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target.

Thermal and mechanical characterization of panels made by cement mortar and sheep’s wool fibres

Green building and environmental sustainability are two important concepts for technicians and engineers. Among natural materials, usually considered as waste, sheep wool plays a fundamental role.This paper is intended to learn more about the potential of these fibres inserted in cement mortar panels, investigating both the insulation properties and mechanical strength, trying to achieve an optimal compromise between these two aspects.Therefore, in the laboratory of materials ENEA Research Centre Trisaia, several panels with different percentages of sheep wool were manufactured, tested and characterized according to technical standards.

Dry deposition models for radionuclides dispersed in air: a new approach for deposition velocity evaluation schema

In the framework of a National Research Program funded by the Italian Minister of Economic Development, the Department of Energy, Information Engineering and Mathematical Models (DEIM) of Palermo University and ENEA Research Centre of Bologna, Italy are performing several research activities to study physical models and mathematical approaches aimed at investigating dry deposition mechanisms of radioactive pollutants. On the basis of such studies, a new approach to evaluate the dry deposition velocity for particles is proposed. Comparisons with some literature experimental data show that the proposed dry deposition scheme can capture the main phenomena involved in the dry deposition process successfully.

Comparative analysis of data-driven methods online and offline trained to the forecasting of grid-connected photovoltaic plant production

Actual technology improvements are contributing to DC and AC micro grid diffusion characterized by renewables photovoltaic and storage systems. Photovoltaic technologies have the advantage of a capillary distribution, but they are characterized by an intrinsic variable behavior due to continuously changing weather conditions. This drawback can be overcome by an appropriate temporal and energetic match among photovoltaic generation and storage capacity, so increasing micro grids reliability and efficiency levels. An accurate forecast of photovoltaic production can contribute to smooth photovoltaic systems intermittency problems so supporting generation and storage balance.Many different forecasting algorithms have been proposed in literature to provide long, medium and short-term predictions of photovoltaic production. A criterion for selection among them is not a priori and it is not uniquely identifiable. In this paper, the attention is focused on eleven data-driven models to obtain 12h ahead forecast, also including some models not usually used in solar field but successfully employed in other expertise fields. This study addresses simple linear models, as Multiple Linear Regression, nonlinear models, such as Classification And Regression Tree, Model Tree M5, Extreme Learning Machines, weighted k-Nearest Neighbors, Multivariate Adaptive Regression Spline, Support Vector Machines, Bayesian Regularized Neural Networks and ensemble methods, as Random Forests, Cubist and Extreme Gradient Boosting. The goal is to compare methods characterized by different complexity levels to understand if a higher complexity model can provide better performances. Furthermore, the considered forecasting methodologies are compared applying two different training methodologies (online and offline) to identify the most performing training mode. The application of optimization algorithms permits to identify optima parameters and the optimum training dataset length for each model. After the optimization step, a statistical analysis is carried out to compare methods forecasting performances for the production of a 1kWp photovoltaic plant installed at the ENEA Research Center of Portici. The case study results demonstrate promising forecasting performances applying the online training mode. Among all studied methods, Support Vector Machines, M5 and the Cubist can assure minima prediction errors and satisfying accuracy with optima dataset lengths. Cubist and M5 represent the best performing models since they are able to minimize prediction errors both in case of optima and minima training datasets.