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

Shape morphing solar shadings: a review

This paper provides an overview of available innovative shape morphing building skins and their design principles. In particular, the proposed review deals with comfort-related issues associated with dynamic solar shading devices, building integration of smart materials, and morphological analyses related to the most recent shape morphing solar skins. In the first part of the paper, an introduction to the typologies of movement in architecture, its concept and application are presented. An explanation of biomimetic principles together with an overview of user's response to dynamic shading devices is also provided. This is followed by the description of the design principles for shape morphing solar shadings with particular focus on energy and comfort aspects, smart materials and biomimetic principles for efficient movements. A review of most recent developments on the topics of comfort, users' response and control of dynamic shading devices, is presented and summarized in a comparison table. The main technical and mechanical properties of the most diffused smart materials (Shape Memory Alloys, Shape Memory Polymers and Shape Memory Hybrids) that can be used for innovative shape morphing solar skins are illustrated in detail and compared. Biomimetic principles for efficient movements complete this part of the work. The principles illustrated in the previous part of this paper are then used to critically analyse the most recent examples of building integrated shape morphing shadings

Expanding the applicability of daytime radiative cooling: Technological developments and limitations

Daytime radiative cooling is regarded as the gold promise of future sustainable building energy systems and a breakthrough in the fight against local climate change. Despite the fervid research interest, most literature reports exceptional theoretical performances under ideal, desert-like conditions, but overlooks the cooling impairment that occurs under low atmospheric transparency (cloudy, humid, polluted conditions) and reduced sky access (packed urban contexts). Power recovery and stabilization call for decoupling of incoming and outgoing radiation at equal wavelengths. Enhanced directionality and high-contrast, broadband asymmetric transmission have been recently proposed to expand the applicability of radiative coolers over a wider spectrum of climates, weathers and terrains. This review offers itself as a first, timely synthesis of the current technological arena. Physical principles, materials and designs, collected from a variety of applicative fields, are detailed and discussed in terms of performance and feasibility, to inspire the transition into sustainable building cooling, worldwide. Major grey areas and serious concerns on potential violations of the 2nd law of thermodynamics reinforce the need for experimental demonstrations in future research

On the energy modulation of daytime radiative coolers: A review on infrared emissivity dynamic switch against overcooling

Passive daytime radiative cooling represents one of the boldest answers to tackle the future cooling needs of the built environment and to mitigate urban heat island effects. Recent developments in the field targeted subambience with several successful examples. On the other side, heating demands may get exacerbated unless effective countermeasures against overcooling are identified, especially in wintertime or heating-dominated climates. This review aims at collecting state-of-the-art technologies and techniques to dynamically control the heat transfer to and from the radiative emitter and ultimately modulate its cooling capacity. Potential solutions are selected from different applicative fields, including spacecraft thermal control, thermal camouflage and electronics. Environmentally-responsive solutions are analyzed in depth given their perfect match with radiative cooling design requirements. Among them, VO2-tuned Fabry-Perot resonators are given particular emphasis, owing to their proven applicability. Active solutions are presented for completeness, but in less detail. Underlying principles, structural composition and experimental/simulated results are detailed and discussed to identify prominent pathways towards technically and economically effective integration in the built environment

Upscaling of SMA film-based elastocaloric cooling

A new concept of upscaling a shape memory alloy (SMA) film based elastocaloric cooling device is presented by arranging SMA films in parallel to increase the specific cooling capacity at low actuation force, while maintaining the large surface-to-volume ratio needed for rapid heat transfer. Selected materials are cold-rolled TiNiFe films that exhibit maximum adiabatic temperature changes of 27.3 and -18.1 K upon loading and unloading, respectively. Demonstrators are designed, fabricated and characterized consisting of five free-standing TiNiFe film bridges that are coupled antagonistically for work recovery. Thermomechanical cycling is performed by out-of-plane deflection of the SMA bridges, while heat transfer is established through mechanical contact with solid heat sink/source elements. The cooling capacity of the demonstrators scales with the number of active SMA films, which confirms the concept of parallelization for upscaling. Investigated demonstrators reach a maximum cooling capacity of about 900 mW compared to a maximum of about 200 mW achieved for reference devices consisting of a single TiNiFe film. The investigation also reveals a number of open issues related to narrow fabrication tolerances upon upscaling, which may cause different plastic straining and varying inhomogeneous stress accumulation among the individual SMA films

A comprehensive environmental exposure indicator and respiratory health in asthmatic children: a case study

The primary goal of asthma management is to achieve and maintain asthma control, which can be influenced by environmental factors. This longitudinal study aimed to construct a comprehensive environmental indicator to predict asthma control in children with asthma in Palermo, Italy. The study included 179 asthmatic children aged 5–16 years. The Normalized Difference Vegetation Index (NDVI) was used to measure green cover, and the Coordination of Information on the Environment (CORINE) framework was used to assess land use based on each home address. A land use regression (LUR) model centered on the home address estimated NO2 exposure for each child using GIS. An environmental indicator, including environmental and personal exposure, was formulated using an additive value model approach. A logistic regression mixed model assessed the association between the environmental indicator and uncontrolled asthma. A probability map of uncontrolled asthma was constructed. In conclusion, a comprehensive environmental indicator proved effective in identifying areas at higher and lower risk of uncontrolled asthm

Optimization of random silica-polymethylpentene (TPX) radiative coolers towards substantial cooling capacity

In the context of global warming, radiative coolers with high solar reflectance and strong emissivity in the atmospheric window can cool the substrate as well as the ambient air. Silica at its nano or micro-scale being randomly dispersed into a uniform transparent polymer can form scalable radiative coolers for large-scale application. Promising cooling performance has been reported for silica-polymers compared with conventional cooling materials, but their performance can be largely influenced by various fabrication parameters. So far, how fabrication parameters influence the emissivity and the cooling performance has not been experimentally demonstrated and the cooling capacity of silica-polymers reported was not substantial compared to other superior radiative coolers. In this work, random silica-polymer has been optimized experimentally. Lab measurement and experimental testing of six fabricated silica-polymers under subtropical and desert climates indicated that due to the complexity of the thermo-radiative balance, high emissivity and strong selectivity are both indispensable in the production of high cooling power. If combined with superior reflectors with higher solar reflectance and especially the emissivity in 8–13 μm enhancing the heat dissipation ability, substantial cooling capacity can be achieved: under the harsh desert climate with average peak solar radiation over 1100 Wm-2, the combination presented sub-ambient temperature of maximum 4.7 ◦C when air temperature reached its peak and the maximum daytime and night-time sub-ambient temperatures were 12.5 ◦C and 15.9 ◦C respectively