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.
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.
The construction sector accounts for more than one-third of the global energy consumption. Ventilated roofs and facades are among the adopted strategies to improve the efficiency of the building envelope: air flowing in cavities under the cladding layer, in fact, is particularly effective in hot summers for the reduction of the incoming heat flow due to solar radiation. Regarding roofs, satisfying results were obtained through the realization of a 5-10 cm air gap under the covering layer which allows better thermal performances of the roof and a reduction of the energy consumption for air conditioning. Although most of products and techniques applied are based on the assumption that air enters only from the eaves line and exits at the ridge one, it is demonstrated that in case of discontinuous mantles, a great contribution derives from air entering from the overlaps. As a matter of fact, air entering from the eaves line is strictly dependent on the wind direction and benefits are evident only when the wind is perpendicular. In all the other cases, buoyancy forces due to air heating under the mantle cannot provide such a consistent contribution. Tiles overlaps’ air permeability allows the wind to enter from multiple directions with consequent greater ventilation of the substrate. Experimental research regarding the performances of pitched tiled roofs was conducted at the TekneHub laboratory of the University of Ferrara and the results are here presented. The tests carried out aimed at investigating the behaviour of different configurations of tiled roofs both from a thermal and an energetic point of view. Three configurations were compared: one was a completely sealed roof (sealed), one had sealed eaves and ridge lines but unsealed tiles overlaps (laid) and the last one was a ventilated roof (vented). The comparison between the sealed and the ventilated roof confirmed the improvement of the performances when in presence of an air cavity. The ventilated roof was then compared to the laid roof to assess the actual contribution of the air permeability of the tiles, and results clearly showed a great contribution, even in case of low wind.
The adoption of ventilated roofs and facades, as well as the integration of phase change materials (PCMs) in the building envelope, have proved to be effective as passive cooling techniques in reducing the solar heat gain through the building envelope during the summer period and, therefore, reduce the energy requirement for cooling. Even though much research focused on each of these strategies individually, their combination has not been deeply studied yet. Preliminary numerical studies were carried out on the application of PCMs on a pitched ventilated tiled roof and the most effective position turned out to be suspended in the middle of the above sheathing ventilation (ASV) channel. Based on this conclusion and exploiting an existing mock-up facility, two equivalent pitched ventilated roofs with an air gap of 4 cm were built as coverage of two identical rooms, each one equipped with a fan coil, one with a 0.007 m PCM layer suspended in the middle of the ASV and the other one without. They were then tested under real conditions at the TekneHub Laboratory at the University of Ferrara. The behaviour of the two configurations were compared in terms of temperature, velocity of the air in the ASV, heat flux, and energy requirement for cooling, which were monitored through T-type thermocouples, heat flow meter, anemometers and energy meters, respectively. The aim of the research was to validate the numerical results and confirm that the combination of the two strategies allows further improvement of roof performance.
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