The optimal thermo-optical properties and energy saving potential of adaptive glazing technologies

The development of dynamic building envelope technologies, which adapt to changing outdoor and indoor environments, is considered a crucial step towards the achievement of the nearly Zero Energy Building target. It is currently not possible to evaluate the energy saving potential of innovative adaptive transparent building envelopes in an accurate manner. This creates difficulties in selecting between competing technologies and is a barrier to systematic development of these innovative technologies. The main aim of this work is to develop a method for devising optimal adaptive glazing properties and to evaluate the energy saving potential resulting from the adoption of such a technology. The method makes use of an inverse performance-oriented approach, to minimize the total primary energy use of a building. It is applied to multiple case studies (office reference room with 4 different cardinal orientations and in three different temperate climates) in order to evaluate and optimise the performance of adaptive glazing as it responds to changing boundary conditions on a monthly and daily basis. A frequency analysis on the set of optimised adaptive properties is subsequently performed to identify salient features of ideal adaptive glazing. The results show that high energy savings are achievable by adapting the transparent part of the building envelope alone, the largest component being the cooling energy demand. As expected, the energy savings are highly sensitive to: the time scale of the adaptive mechanisms; the capability of the façade to adapt to the outdoor climatic condition; the difference between outdoor climatic condition and the comfort range. Moreover important features of the optimal thermo-optical properties are identified. Of these, one of the most important findings is that a unique optimised technology, varying its thermo-optical properties between a limited number of states could be effective in different climates and orientations.The present work has been developed in the framework of a PhD research project. The authors are grateful to EPSRC and Wintech Ltd. for funding the PhD. The authors are also grateful to the National Natural Science Foundation of China (No. 51408427) for their support.This is the final published version of the article. It was originally published in Applied Energy (Favoino F, Overend M, Jin Q, Applied Energy, 2015, 156, 1-15, doi:10.1016/j.apenergy.2015.05.065). The final version is available at http://dx.doi.org/10.1016/j.apenergy.2015.05.06

Principali reazioni termonucleari nelle stelle

L’elaborato si prefigge di dare una sommaria descrizione dei processi termonucleari che avvengono nelle strutture stellari, mostrandone le principali differenze e le condizioni in cui essi diventano rilevanti. Il primo capitolo si presenta come un’introduzione all’argomento, dando una definizione di stella e descrivendone in breve il ciclo vitale. Il secondo capitolo tratta i vari processi, partendo dall’analisi delle singole reazioni e passando a descrivere poi la catena protone-protone ed il ciclo CNO, nelle loro forme principali e nei loro rami secondari. Segue un’analisi del rate energetico ed una disamina dei processi successivi alla fase di sequenza principale. Il terzo capitolo conclude l’elaborato esaminando il caso delle supernovae, descrivendone sommariamente l’evento ed in processi termonucleari in esso rilevanti

Smart glazing in intelligent buildings : what can we simulate?

The integration of smart glazing and adaptive façade in buildings can lead to large performance improvements and added functionality compared to conventional static building envelope systems. This is achieved not only by embedding automatic/controllable (smart/active) switchable materials into the building envelope, but also including intelligence into the way the whole building is designed and operated.Desk studies and Building Performance Simulation can be used to support the design process of these technologies and of the building integrating them, as well as to support product development aimed at building integration of novel switchable glazing technologies. Although BPS tools traditionally lag behind the development of novel technologies and adaptive building envelope systems, therefore it is not always possible or easy to evaluate in an accurate and comprehensive way the performance of building integrated switchable glazing technologies, and in general adaptive facades.In this paper we outline the main requirements for BPS of smart glazing. These include user interface requirements, models availability, integration of physical domains, integration and customisation of control strategies. We analyse possible BPS tools that could be used and their main advantages and drawbacks, and describe the latest advances for more integrated simulation methodologies and tools, included an ad-hoc developed simulation tools which aims at overcoming the main limitation of traditional BPS tools

Thermo-chromic glazing in buildings: a novel methodological framework for a multi-objective performance evaluation

Abstract Transparent adaptive facade components can improve the energy performance and the indoor environmental quality of buildings. Nevertheless, their utilization is not widespread, due also to the lack of a robust methodology to comprehensively evaluate their potentialities and find out their most suitable applications. The present paper introduces a novel methodology to characterize the behavior of a transparent adaptive facade component, a thermo-chromic glazing, and predict its effects, through numerical simulations, on energy performance and visual comfort aspects. An experimental characterization on the thermo-chromic glazing was performed to determine its optical properties at the variation of its surface temperature. The component was found to be able to switch its visible transmittance between 0.71 and 0.13, and its solar transmittance between 0.65 and 0.28. The experimental results were used to feed the numerical model created on purpose to describe the adaptive behavior of the component. Finally, a numerical simulation campaign was performed to assess the effects of the thermo-chromic glazing on energy and visual comfort aspects of an enclosed office located in Turin. It was found that the thermo-chromic glazing reduced the overall energy performance compared to a static selective glazing, but it allows improving the visual comfort conditions within the space considered

Markups, intangible capital and heterogeneous financial frictions

This paper studies the interaction between financial frictions, intangible investment decisions, and markups at the firm level. In our model, heterogeneous credit constraints distort firms' decisions to invest in cost-reducing technology. The latter interacts with variable demand elasticity to generate endogenous dispersion across firms in markups and pass-through elasticities. We test the model's predictions on a representative sample of French manufacturing firms over the period 2004-2014. We establish causality by exploiting a quasi-natural experiment induced by a policy change that affected firms' liquidity. Our results shed new light on the roots of rising markups and markup heterogeneity in recent years

Optimal control and performance of photovoltachromic switchable glazing for building integration in temperate climates

The development of adaptive building envelope technologies, and particularly of switchable glazing, can make significant contributions to decarbonisation targets. It is therefore essential to quantify their effect on building energy use and indoor environmental quality when integrated into buildings. The evaluation of their performance presents new challenges when compared to conventional “static” building envelope systems, as they require design and control aspects to be evaluated together, which are also mutually interrelated across thermal and visual physical domains. This paper addresses these challenges by presenting a novel simulation framework for the performance evaluation of responsive building envelope technologies and, particularly, of switchable glazing. This is achieved by integrating a building energy simulation tool and a lighting simulation one, in a control optimisation framework to simulate advanced control of adaptive building envelopes. The performance of a photovoltachromic glazing is evaluated according to building energy use, Useful Daylight Illuminance, glare risk and load profile matching indicators for a sun oriented office building in different temperate climates. The original architecture of photovoltachromic cell provides an automatic control of its transparency as a function of incoming solar irradiance. However, to fully explore the building integration potential of photovoltachromic technology, different control strategies are evaluated, from passive and simple rule based controls, to optimised rule based and predictive controls. The results show that the control strategy has a significant impact on the performance of the photovoltachromic switchable glazing, and of switchable glazing technologies in general. More specifically, simpler control strategies are generally unable to optimise contrasting requirements, while more advanced ones can increase energy saving potential without compromising visual comfort. In cooling dominated scenarios reactive control can be as effective as predictive for a switchable glazing, differently than heating dominated scenarios where predictive control strategies yield higher energy saving potential. Introducing glare as a control parameter can significantly decrease the energy efficiency of some control strategies, especially in heating dominated climates.This work was conducted as part of a PhD research sponsored by UK EPSRC and Wintech Ltd. The authors acknowledge the support of the COST Action TU1403 – Adaptive Facades Network (www.adaptivefacade.eu) and the University of Sydney (IPDF fund). The experimental data used as an input in this work were partially supported by Regione PUGLIA (APQ Reti di Laboratorio, project “PHOEBUS” cod. 31) and by Italian Minister for Education and Research which funded the R&D program “MAAT” (PON02_00563_3316357 − CUP B31C12001230005). The devices were fabricated at the Center for Biomolecular Nanotechnologies of Istituto Italiano di Tecnologia and characterized in the laboratories of CNR-Nano in Lecce. The contribution of the fourth author to the work reported in this paper was supported by the Australian Research Council through its Future Fellowship scheme (FT140100130).This is the final version of the article. It first appeared from Elsevier at http://dx.doi.org/10.1016/j.apenergy.2016.06.107

Vacuum Insulation Panels: Analysis of the Thermal Performance of Both Single Panel and Multilayer Boards

The requirements for improvement in the energy efficiency of buildings, mandatory in many EU countries, entail a high level of thermal insulation of the building envelope. In recent years, super-insulation materials with very low thermal conductivity have been developed. These materials provide satisfactory thermal insulation, but allow the total thickness of the envelope components to be kept below a certain thickness. Nevertheless, in order to penetrate the building construction market, some barriers have to be overcome. One of the main issues is that testing procedures and useful data that are able to give a reliable picture of their performance when applied to real buildings have to be provided. Vacuum Insulation Panels (VIPs) are one of the most promising high performing technologies. The overall, effective, performance of a panel under actual working conditions is influenced by thermal bridging, due to the edge of the panel envelope and to the type of joint. In this paper, a study on the critical issues related to the laboratory measurement of the equivalent thermal conductivity of VIPs and their performance degradation due to vacuum loss has been carried out utilizing guarded heat flux meter apparatus. A numerical analysis has also been developed to study thermal bridging effect when VIP panels are adopted to create multilayer boards for building applications

Modelling and validation of a single-storey flexible double-skin façade system with a building energy simulation tool

Double skin facades are adaptive envelopes designed to improve building energy use and comfort performance. Their adaptive principle relies on the dynamic management of the cavity's ventilation flow and, when available, of the shading device. They can also be integrated with the environmental systems for heating, cooling, and ventilation. However, in most cases, the possible exploitation of the ventilation airflow is not fully enabled, as the adoption of only one or two possible airpath limits the possibility that this facade architecture offers, meaning that flexible interaction with the environmental systems cannot be planned. This work aims to develop, using an existing software tool for building energy simulation, a numerical model of a flexible double-skin facade module capable of fully exploiting the adaptive features of such an envelope concept by switching between different cavity ventilation strategies. Leveraging the "Double Glass Facade" component available in IDA ICE, a new model for a flexible double-skin facade module was developed, and its performance in replicating the thermophysical behaviours of such a dynamic system was assessed by comparison with experimental data collected through a dedicated experimental activity using one the outdoor test cells of the TWINS facility in Torino (Italy). The accuracy of the predictions of the new model for a flexible double-skin facade was in line with that obtained by the conventional "Double Glass Facade" component to simulate traditional double-skin facades. The mean bias errors obtained were lower than 1.5 degrees C and 4 W/m2, for air and surface temperature values and for transmitted long-wave or short-wave heat flux values, respectively. By establishing a new archetype model to study the performance and optimal integration of a large class of double-skin facade modules, including fully flexible ones, this work demonstrates the possibility of modifying existing models in building energy simulation tools to study unconventional building envelope model solutions such as adaptive facade systems