DEVELOPMENT OF A PHOTOVOLTAIC VENTILATED FACADE -SMART SKIN- FOR THE CONTROL OF BUILDINGS THERMAL BUDGET

La necessità di sopperire al fabbisogno energetico degli edifici attraverso fonti rinnovabili gioca un ruolo fondamentale nell’attuale processo di decarbonizzazione. Nei paesi industrializzati essi possono infatti rappresentare fino al 40% della produzione totale di energia primaria, percentuale a cui l’implementazione di dispositivi fotovoltaici architettonicamente integrati può apportare una riduzione significativa. Nonostante il loro impiego stia aumentando considerevolmente, l’implementazione di pannelli con tecnologia LSC è ancora poco diffusa in questo tipo di strutture, seppur essi siano particolarmente indicati per l’integrazione architettonica. In questo lavoro è presentata la realizzazione di una Facciata Ventilata (VF) con ventilazione naturale, che integra un dispositivo LSC come componente esterna. Una VF è una struttura formata da due componenti, chiamate anche pelli, separate da un’intercapedine d'aria, che si basa sullo sfruttamento della radiazione solare per regolare il confort termico dell’edificio. La modellazione delle proprietà ottiche delle varie componenti della VF è perciò fondamentale per valutare le performance del sistema, in particolare quelle dell’LSC, che sono state modellate utilizzando Matlab. Le simulazioni hanno confermato che è possibile realizzare pannelli aventi dimensioni compatibili a quelle tipiche del settore edile, che sfruttino questa tecnologia, rendendone quindi possibile l’implementazione in questo tipo di strutture. Le proprietà ottiche dell’LSC (spettro di assorbimento, trasmissione e riflessione) sono state poi inserite in un modello agli elementi finiti sviluppato con il software COMSOL Multiphysics, il quale ha permesso di studiare le proprietà termiche dell’intera VF tramite il confronto con dati sperimentali. Le proprietà fisiche dei materiali sono state poi inserite in un secondo modello termico al fine di eseguire il retrofit di un tipico involucro edilizio. I risultati hanno dimostrato che una VF ideata in questo modo è effettivamente in grado ridurre il budget termico dell'edificio sia nella stagione estiva che in quella invernale. Infine, il confronto tra la trasmittanza termica della VF e i valori massimi prescritti dalla direttiva italiana, ha evidenziato un risultato promettente per una tesi di ricerca di tipologia “proof of concept”.Buildings can weigh up to 40% of the total primary energy requirements of industrialized countries. A wider deployment of renewable energy sources is therefore crucial to fulfill the increasing trend towards decarbonization, and several studies demonstrated that the integration of photovoltaic technology in building façades had a great potential in decreasing the building energy loads. In fact, the implementation of the so-called Building Integrated Photovoltaic devices is significantly increasing. However, there is still little implementation of Luminescent Solar Concentrators (LSC) panels in this type of structures, even though they could be a very promising technology to be installed in building façades. Here the realization of a natural Ventilated Façade (VF) integrating a LSC device as external pane is presented. A VF is the combination of two skins separated by an air cavity, and its working principle lies in the exploitation of solar radiation to create a thermal gradient between the outer and inner pane. The LSC optical properties were modeled with Matlab to describe the optical properties of this device (absorption, transmission, and reflection spectrum), and confirmed that LSC panels could be manufactured also with dimensions compatible with the typical ones of the building sector. The LSC optical properties were inserted in a finite element model developed with the software COMSOL Multiphysics, whose results were validated thanks to a comparison with experimental data. The obtained thermal and optical properties were then used in a new model created to perform the retrofit of a typical building envelope, which proved that this structure can be employed to decrease the building thermal budget in both summer and winter season. Finally, the VF thermal transmittance was compared to the maximum values prescribed by the Italian directive, confirming a promising result for a “proof of concept” research work

A Heat Pump-Based Multi-source Renewable Energy System for the Building Air Conditioning: The IDEAS Project Experience

The current paper presents the state-of-the-art of the ongoing IDEAS research project, funded under the Horizon 2020 EU framework programme. The project involves fourteen partners from six European countries and proposes a multi-source cost-effective renewable energy system for the decarbonisation of the building envelope. The system features a radiant floor fed by a heat pump for the building thermal management. The heat pump can exploit sun, air, and/or ground as thermal sources through the use of photovoltaic/thermal solar panels, air heat exchangers, and shallow ground flat-panel heat exchangers. Thermal energy storage is achieved by means of phase change materials spread along several system components, such as: radiant floor to increase its thermal inertia, solar panels for cooling purposes, ground to enhance soil thermal capacity. Within the project framework, a small- scale building, featuring a plethora of sensors for test purposes, and two large-scale buildings are meant to be equipped with the renewable energy system proposed. The small- scale building is currently in operation, and the first results are discussed in the present work. Preliminary data suggest that while multi-source systems coupled with heat pumps are particularly effective, it is complex to obtain suitable thermal energy storages on urban scale

Performance Optimization of Luminescent Solar Concentrators under Several Shading Conditions

The need of clean energy is constantly increasing, and Building Integrated PhotoVoltaic (BIPV) technologies represent valuable assets to expand even further the photovoltaic market. Thanks to BIPVs. a new concept of local electric microgrid will probably emerge as this kind of technology can turn buildings from energy wells to energy sources. Luminescent Solar Concentrator (LSC) panels are perfect to achieve this goal, indeed, contrary to standard flat PhotoVoltaic (PV) modules, they can be exploited in transparent or semi-transparent building façades. Thus, the purpose of this work was the optimization of the performance of LSC panels for BIPV applications. Being an application-oriented study, we paid particular attention to the scalability of the assembling process and the use of LSC slabs functionalized only with widely available organic commercial dyes and high-performance commercial silicon solar cells. The electrical and optical performance of the LSC panels were firstly simulated and then, once the most promising configurations were identified, the respective prototypes were assembled to compare the simulation results with the experimental measurements. These analyses were performed both under uniform illumination and in some relevant shading configurations typical for BIPV devices in operating conditions. The obtained results show that LSC panels that employ PV cells coupled with reflective films can yield a higher efficiency than a traditional system with cells placed along four sides

Review of Façade Photovoltaic Solutions for Less Energy-Hungry Buildings

Building-integrated photovoltaic technologies have considerable potential for the generation of onsite renewable energy. Despite this, their market penetration is in a relatively embryonic phase with respect to grounded or building-attached solutions, and they have limited commercial application. Their integration into building façades may represent a key asset in meeting the net-zero emissions by 2050 scenario, in particular for high-rise buildings in which the roof-to-façade ratio is unfavorable for the fulfillment of the energy load using only roof photovoltaic technology. Moreover, different façade orientations extend the production time throughout the day, flattening the power generation curve. Because of the present interest in BIPV systems, several researchers have conducted high-quality reviews focused on specific designs. In this work, various photovoltaic technologies and methods used to manufacture façade BIPV devices are reviewed with the aim of presenting researchers with the recent technological advancements and providing an overview of photovoltaic systems designed for different purposes and their applications rather than a detailed analysis of a specific technology. Lastly, future prospects and the limitations of building-integrated photovoltaic devices are presented

Novel building Integration Designs for increased Efficiencies in Advanced Climatically Tunable Renewable Energy Systems

Buildings play a significant role in the global energy balance. Typically, they account for 20-30% of the total primary energy requirement of industrialized countries, 40% in EU. Applying the proposed integrated RES to buildings is an important application for wider integration and deployment of renewable energy and to achieving our binding EU targets of at least a 40% reduction in greenhouse gas emissions (GHG) by 2030, compared to 1990 and at least 27% of renewable energy in EU. The IDEAS project will create an innovative building integrated renewable energy system (RES) which will cost effectively exceed current RES efficiencies, generating electricity, heat and cooling and optimised for multifamily, public and commercial buildings in different climatic conditions. The research aim is to create a novel low-cost building integrated RES maximizing the output tuneable for different climatic conditions through novel luminescent and geometric concentrator techniques leading to current solar system efficiencies being exceeded electrically. Thermally enhancement will be achieved using enhanced organic phase change materials (PCM) with a passive biomimetic heat transfer mechanism for heat storage and discharge. An electrically driven multi-source heat pumpHP system will then use the main energy sources at building scale (waste heat from the system, air and ground), to provide the input to an integrated underfloor heating and hot water system, and to manage the thermal energy storage. This building integrated RES will use advanced control techniques to maximize performance and electrical and thermal/cooling self-sufficiency in the building. The technology will be optimized and demonstrated for use in multi-family residential buildings, commercial and public buildings

Design of a Ventilated Façade Integrating a Luminescent Solar Concentrator Photovoltaic Panel

The increasing trend towards decarbonization requires the reduction of the environmental impact of the building sector that currently accounts for approximately 40% of the total CO2 emissions of European countries. Even though Luminescent Solar Concentrator (LSC) panels could be a very promising technology to be installed in urban environments, there is still little implementation of LSC panels in building façades. Here, the realization of a Ventilated Façade (VF) integrating an LSC device as an external pane is presented and a preliminary numerical and experimental investigation is used to evaluate the interaction between the different structure components. Thanks to the realization of a dedicated mock-up finite element method, models are calibrated and validated against experimental measurements, showing a good correspondence between simulated and measured data. Moreover, the electrical characterization of the LSC panel confirms that large area devices can be used as an external skin of VF, reporting a photovoltaic efficiency of 0.5%. The system’s thermal and optical properties (estimated thanks to the software COMSOL Multiphysics) encourage the continuation of the research by considering different technologies for the VF internal skin, by scaling up the case study, and by running the simulation of an entire building considering winter and summer energy demands

ANGELS (ANodi in GErmanio nanoporoso per batterie al Litio per applicazioni aeroSpaziali)

Il progetto ANGELS (ANodi in GErmanio nanoporoso per batterie al Litio per applicazioni aeroSpaziali) vede come proponente l’Università di Ferrara nella veste del gruppo coordinato dal prof. Vincenzi insieme alla Fondazione Bruno Kessler di Trento, l’Istituto Italiano di Tecnologia di Genova e l’Università di Cagliari. Questo progetto proseguirà una collaborazione già in atto da un paio d’anni tra questi enti, oggetto del lavoro di un dottorando la cui borsa è cofinanziata da Unife e FBK. Questa collaborazione ha permesso di sviluppare un anodo innovativo per batterie al litio in grado di fornire prestazioni fino a tre volte superiori rispetto agli attuali anodi in commercio, che usano come materiale attivo la grafite, invece del germanio utilizzato in questo progetto. Il livello tecnologico attuale corrisponde a un TRL3 mentre l’obiettivo del bando ASI sarà quello di arrivare ad un livello TRL4, avendo come settore di riferimento quello degli accumulatori per applicazioni aerospaziali. Dato il potenziale interesse industriale dell’invenzione, è stata anche iniziata la procedura per il deposito di un brevetto italiano, sempre coordinato dall’Università di Ferrara, attraverso l’Ufficio di trasferimento Tecnologico. Il budget del progetto e la suddivisione dei fondi tra i partner è riportato nella tabella seguente, in cui viene indicato il cofinanziamento a carico dei vari partner e il finanziamento a carico di ASI, che risulta essere il 65% del valore totale del progetto, come indicato espressamente nel bando. Il cofinanziamento dell’Università di Ferrara avverrà esclusivamente attraverso ore uomo mentre il finanziamento erogato da ASI per il suddetto progetto corrisponde al 100% di quanto chiesto nella sottomissione del progetto

Design of a color neutral non‐patterned photovoltaic window based on luminescent solar concentrator

The necessity to fulfil buildings energy demand with different energy sources lead to an increasing integration between building components and renewable energy sources. The development of new BIPV technologies requiring less silicon solar cells for active area is particularly interesting especially from a circular economy perspective. This work describes the design of five neutral color photovoltaic windows based on large area (0.61 m2) luminescent solar concentrators, which were developed by the University of Ferrara and Eni S.p.A and were installed at the Eni “Renewable, New Energies and Material Science Research Centre” in Novara (Italy). The prototypes show a visible transmittance of 38.5% which represents an improvement with respect to commercial semi-transparent photovoltaic technologies, moreover the evaluation of the window colorimetric properties highlights a color rendering index equal to 93.0, thus ensuring an excellent illumination quality of the building indoor. The panel electrical performance was measured indoor, at the end of the assembly process, and on-site, showing a power production ranging from 1.2 W to 2.8 W and an efficiency between 0.23% and 0.48% depending on the illumination condition and the background reflectivity. Although the generated power is limited, it is already sufficient to power stand-alone small appliances and smart systems

Porous Germanium Anode for Li-Ion Batteries

In this work we have presented the results of our novel binder free anodic material made of porous Germanium. The anodes are realized in a two-step process: firstly, a thin Germanium layer is deposited using a plasma enhanced chemical vapour deposition technique; then a nanometric porous matrix is realized through an electrochemical etching process. The anodes have been tested in prototype coin type cells, using metallic Lithium as counter and reference electrode. The electrochemical performances, as well as some morphologic characterizations have been presented. The anodes realized and whose results have been presented have been able to perform hundreds of charge and discharge cycles at very high C-rates, retaining a stable capacity of more than 950 mAh/g even at currents as high as 5C (considering 1C as 1600 mA/g), which is 2.5 times the theoretical capacity of the actual standard anodic material, which is Graphite