• Energy Research

The transition to a sustainable society and a carbon-neutral economy by 2050 requires extensive deployment of renewable energy sources that, due to the aleatority and non-programmability of most of them, may seriously affect the stability of existing power grids. In this context, buildings are increasingly being seen as a potential source of energy flexibility for the power grid. In literature, key performance indicators, allowing different aspects of the load management, are used to investigate buildings’ energy flexibility. The paper reviews existing indicators developed in the context of theoretical, experimental and numerical studies on flexible buildings, outlining the current status and the potential future perspective. Moreover, the paper briefly reviews the range of grid services that flexible buildings can provide to support the reliability of the electric power system which is potentially challenged by the increasing interconnection of distributed variable renewable generation.

Ventilated Façades integrated with photovoltaic panels have become a popular way to improve both the thermal-physical performances of the existing built environment. The increased usage of not-programmable renewable energy sources implies the adoption of energy storage systems to mitigate the mismatch between the power generation and the building's demand. Aiming at properly integrates a photovoltaic panel and a battery (Lithium based) as a module of an active ventilated façade, the prototype design has been carried out in terms of thermo-fluid dynamics performance. Based on experimental setup, a numerical study of flow through the air cavity of the active ventilated façade has been carried out by the fluid-dynamics Finite Volume code-Ansys-Fluent. The calibrated model was lastly used to perform a wide range of parametric analyses on different climate and boundary conditions to explore the viability of the prototype.

In this paper, cement mortar IN200 integrated with solid–solid PlusIce X25 commercial PCM was fully characterized for the first time via experimental tests and numerical simulations. An experimental setup was designed and built to evaluate the thermal performance of the composite. Experimental results confirmed the expected advantages of the PCM-loaded plaster in terms of inner surface temperature, inbound heat flux reduction, and the enhanced damping effect on the average temperature. The experimental results were used to validate and calibrate a finite element model implemented in COMSOL Multiphysics® 5.6. The model was adopted to carry out a parametric analysis assessing the influence of PCM mass fraction, phase transition temperature, and PCM mortar thickness. The composite thickness was the most influential parameter, resulting in an energy saving increase from 3.29% to 72.72% as it was increased from 10 mm to 30 mm. Moreover, the model was used in a set of dynamic simulations, reproducing real Mediterranean climatic conditions to capture the transition process for a long period in buildings. The PCM mortar located on the interior side exhibited the highest reduction in both heat flux and inner surface temperature, representing a simple approach to achieving the best thermal comfort conditions.

Ventilated Façades integrating photovoltaic panels are a promising way to improve efficiency and the thermal-physical performances of buildings. Due the inherent intermittence of the non-programmable renewable energy sources, their increasing usage implies the use of energy storage systems to mitigate the mismatch between power generation and the buildings' load demand. The main purpose of this paper is to investigate the thermo-fluid dynamic performances of a prototype integrating a photovoltaic cell and a battery as a module of an active ventilated façade. Based on an experimental setup, a numerical study in steady state conditions of flow through the air cavity of the module has been carried out and implemented in a fluid-dynamics Finite Volume code. In order to assess the viability of the prototype, the calibrated model was lastly used to predict thermal performance of the prototype on different climate conditions supporting its further improvement.

The building sector accounts for a relevant portion of the overall energy consumption and CO2 emissions. The type of construction materials used in the buildings as well as the characteristics of the envelope affect their energy consumption. The choice of appropriate building materials is a crucial challenge widely discussed in the context of the bioclimatic architecture concept. The implementation of phase change materials (PCMs) into the building envelope is among the investigated solutions to make the building sector more sustainable. In this paper, cement mortar integrated with solid/solid PlusIce X25 commercial PCM was characterized and tested. The main feature of the proposed composite is the use of the solid/solid phase change, which avoids typical PCMs' issues due to the leakage occurring when the material becomes liquid. The properties of the PCM material itself were investigated by measuring the latent heat and the phase change temperature through differential scanning calorimetry (DSC). Furthermore, in order to evaluate the performance of the realized samples, an experimental setup was designed and built. The main feature of the experimental setup is the possibility to test two different cement mortar bricks subjected contemporary to the same testing conditions. Experimental results confirmed the advantages of the PCM-loaded plaster. Thermal performances of the PCM were further compared to those ones of two specimens of cement mortar incorporating rubber and cork with the same experimental conditions. Experimental results were used to validate and calibrate a finite element model, implemented in COMSOL Multiphysics 5.6. Parametric simulations to investigate the effect of the PCM mass fraction were carried out. The results showed remarkable thermal performance improvements in terms of peak temperatures reduction with mass fraction of 25-50%. Furthermore, different placements of the PCM in the wall of a building were simulated and discussed.

The market of electric storage systems is widely dominated by Lithium ion batteries, whose peculiarity is the need for a thermal management system, whose proper design is complicated by the interaction. among different design and operating parameters. A specific methodology for carrying out the task is still lacking. In this context, the present paper proposes a systematic framework for the design of passive and hybrid thermal management systems (TMSs) of Li-ion batteries. Thermal tests were carried out on Lithium-Titanate-Oxide cells under realistic operating conditions in a controlled environment to characterize the electrical and thermal behaviour. A thermofluid dynamics model of the battery was implemented in COMSOL Multiphysics. The experimentally validated model was used to evaluate the influence of different design and operating parameters (ambient temperature, charge/discharge current, phase change material thickness and melting temperature) using the Taguchi method (orthogonal arrays), and discussing inter-related effects of the studied parameters via interaction plots. Air temperature (45 °C) and/or discharge current (69–92 A) were identified as critical operating conditions beyond which thermal runaway issues occur. Starting from the optimal design conditions for a passive TMS, the same methodology was used to assess a hybrid PCM-liquid cooling system as an alternative configuration. The results indicate that, compared to the baseline case of natural cooling, the optimal designs of standalone PCM and hybrid cooling system led to a reduction in maximum cell temperature of 11 and 22 °C, respectively, showing the high potential of these TMSs.