Role of phase change materials in backfilling of flat-panels ground heat exchanger

The behaviour of a multi-source heat pump system coupled with phase change materials (PCMs) is discussed in this manuscript, as based on selected data collected during one-year testing at the TekneHub Laboratory of the University of Ferrara (Italy), as a synergic prototype setup of two European projects: IDEAS, an H2020 project, and CLIWAX, an EFDR project. Three geothermal loops of novel shallow FlatPanels ground heat exchangers (GHX) provide the coupling of a water-to-water heat pump with the ground, as backfilled with sand, a mixture of sand and granules with paraffins and containers filled in with hydrated salts. Furthermore, two hybrid photovoltaic panels and a dry-cooler complete the exploitable thermal sources landscape. Finally, a control unit manages all the elements for the exploitation of the different thermal sources. How the increased underground thermal energy storage is driven by PCMs has been investigated by means of specific tests, and compared with the standard case of backfilling sand. Results confirm that PCMs can compensate peak loads occurring during hard weather conditions. Good performances of the multi-source heat pump were found, with a winter coefficient of performance always higher than 5. Finally, the application of PCM in summer should be preferred in climatic zones with hot summers and cold winters, With evidence, latent heat, thermal conductivity and melting point of PCMs should be tuned accordingly to the energy requirements and the local ground thermal conditions. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

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

Granular PCM-Enhanced Plaster for Historical Buildings: Experimental Tests and Numerical Studies

none2The construction sector is among the major players responsible for global energy consumption and therefore related emissions, both because of the constantly increasing indoor air quality standard which requires increasingly higher energy demands as well as the great share of historical buildings which are now obsolete and are not up to date with current regulations. Phase change materials (PCMs) applied on the building envelope represent a feasible possibility to improve the performance of existing buildings, also the historical ones, increasing their thermal iner-tia without violating any legal restriction or causing further alterations to the structure. More specifically, focus of this research was on the addition of a granular paraffin PCM into a lime-based plaster. Experimental tests at lab scale and numerical simulations with COMSOL Multiphysics were carried out to characterize the plasters realized, namely one reference lime-based plaster and one with incorporated 10% by mass of granular PCM (named REFp and PCMp, respectively). The behavior of these plasters applied on the exterior side of a wall was then simulated and compared in terms of temperatures and heat fluxes. However, considering that the esti-mated thermal conductivity of the reference lime-based plaster was lower than the values found in literature, the simulations were carried out considering an additional plaster, namely a lime-based plaster (renamed LITp), whose properties were found in literature and considered quite representative of a consistent share of existing historical buildings. Great improvements were ob-served from the application of PCM into the plaster, with reductions of the incoming energy between 9% and 18%.openBaccega, Eleonora; Bottarelli, MicheleBaccega, Eleonora; Bottarelli, Michel

Numerical and experimental evaluation of a granular PCM-enhanced plaster for historic building application

The construction sector represents more than one-third of the global energy consumption, and a consistent part of the building stock is made of historical buildings. The application of phase change materials (PCMs) mixed within the plaster represents a tangible possibility to improve the performances of historical buildings without violating any legal restriction. In this study experimental tests and numerical simulations were carried out with the focus on lime plaster, suitable and reliable for the restoration of historic buildings, and on granular PCM, recently introduced after the European project TESSe2b (TESSe2b)

Tiled roofs air permeability: experimental and numerical investigation

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

Ventilazione intra-tegole per il raffreddamento dei tetti

A research promoted by the TekneHub Laboratory of the University of Ferrara has compared the summer performances of two different pitched roofs. Purpose was to evaluate the thermal flows due to solar radiation entering through the roofs and the consequent energy needed for air conditioning in order to maintain the temperature setpoint in the two rooms below the roofs and the same level of indoor comfort. It is well known that under tile air movement allows a temperature reduction of the air, a consequent reduction of the incoming heat flow and a reduction of energy needed for cooling. This research aimed to measure the benefits of the air moving from eaves to ridge line and the contribution of the air entering between the overlap lines of the tiles too. Two roofs were built, one with tiles laid on a normal dual wood battens layers, the second with tiles directly laid on the roof deck, eaves and ridge lines sealed with polyurethane foam and overlaps between tiles sealed with a membrane, so that to avoid any air circulation under the tiles. Data highlights how the simple presence of the air circulation in the free space under the tiles allow a great disposal of heat due to solar radiation

Tiled roofs air permeability: experimental and numerical investigation

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. An 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

Role of phase change materials in backfilling of shallow ground heat exchanger

The behaviour of a multi-source heat pump system coupled with phase change materials (PCMs) is discussed in this manuscript, as based on selected data collected during one-year testing at the TekneHub Laboratory of the University of Ferrara (Italy), as a synergic prototype setup of two European projects: IDEAS, an H2020 project, and CLIWAX, an EFDR project. Three geothermal loops of novel flat-panels ground heat exchangers provide the coupling of a water-to-water heat pump with the ground, as backfilled with sand, a mixture of sand and granules with paraffins and containers filled in with hydrated salts. Furthermore, two hybrid photovoltaic panels and a dry-cooler complete the exploitable thermal sources landscape. Finally, a control unit manages all the elements for the exploitation of the different thermal sources. How the increased underground thermal energy storage is driven by PCMs has been investigated by means of specific tests, and compared with the standard case of backfilling sand. Results confirm that PCMs can compensate peak loads occurring during hard weather conditions. With evidence, latent heat, thermal conductivity and melting point of PCMs should be tuned accordingly to the energy requirements and the local ground thermal conditions

Improving the Air Permeability of Ventilated Roofs

In hot climates, ventilated pitched roofs help dissipating the excess heat, thus reducing the cooling energy demand. The key factor is the so-called Above Sheathing Ventilation (ASV) that depends on the air entering and leaving at the eaves, ridge and the gaps among tiles. A strategy for increasing the ASV is the enhancement of the roof air permeability through the development of new tile shapes, as proposed in the European Life HEROTILE project. The performance of a ventilated pitched roof are experimentally analysed by comparing some covering options: the new tile shape designs against the standard ones, available in the market, and a metal cover. A real scale pitched roof mock-up was built and equipped with a comprehensive monitoring system. The air flow and temperature in the different roof layers, as well as the heat flux passing through the roof and the cooling energy demand, were monitored according to the local weather conditions during the summer season. The analysis showed that the new tile design increases the ASV in comparison with the standard ones, and better thermal performance was achieved by reducing the heat gain due to solar radiation

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