• Energy Research

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.

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Optimizing the hydrogen value chain is essential to ensure hydrogen market uptake in replacing traditional fossil fuel energy and to achieve energy system decarbonization in the next years. The design of new plants and infrastructures will be the first step. However, wrong decisions would result in temporal, economic losses and, in the worst case, failures. Because huge investments are expected, decision makers have to be assisted for its success. Because no tools are available for the optimum design and geographical location of power to gas (P2G) and power to hydrogen (P2H) plants, the geographic information system (GIS) and mathematical optimization approaches were combined into a new tool developed by CNR-ITAE and the University of Bologna in the SuperP2G project, aiming to support the interested stakeholders in the investigation and selection of the optimum size, location, and operations of P2H and P2G industrial plants while minimizing the levelized cost of hydrogen (LCOH). In the present study, the tool has been applied to hydrogen mobility, specifically to investigate the conversion of the existing refuelling stations on Italian highways to hydrogen refuelling stations (HRSs). Middle-term (2030) and long-term (2050) scenarios were investigated. In 2030, a potential demand of between 7000 and 10,000 tons/year was estimated in Italy, increasing to between 32,600 and 72,500 tons/year in 2050. The optimum P2H plant configuration to supply the HRS was calculated in different scenarios. Despite the optimization, even if the levelized cost of hydrogen (LCOH) reduces from 7.0–7.5 €/kg in 2030 to 5.6–6.2 €/kg in 2050, the results demonstrate that the replacement of the traditional fuels, i.e., gasoline, diesel, and liquefied petroleum gases (LPGs), will be disadvantaged without incentives or any other economic supporting schemes.

This paper reports main criteria for design, realization and validation of a solar-powered hydrogen fueling station in a smart city application relevant to an on-site hydrogen production plant. The program has been developed by CNR-ITAE together with other industrial partners in the framework of the Italian research project called i-NEXT (innovation for greeN Energy and eXchange in Transportation). The i-NEXT hydrogen production plant is located in the Municipality of Capo d'Orlando, Sicily, it is fed by a microgrid able to receive energy from solar radiation by a 100 kW rooftop photovoltaic plant and connected with a battery energy storage of 300 kWh (composed by 16 sodium nickel chloride high temperature batteries). The plant is able to deliver hydrogen and electricity for an electric and hydrogen vehicles fleet. The hydrogen fueling station includes four subsystems: a hydrogen production system by electrolysis, a compression system, a high-pressure storage system and a hydrogen dispenser for automotive applications. It is able to generate in the hydrogen production subsystem through an alkaline electrolyzer of 30 kWh: 6.64 Nm3/h of H2 with a gas purity of 99.995% (O2 < 5 ppm and dew point < -60 °C). The compression subsystem has a three stage compressor with a rated gas flow rate of 5,2 Nm3/h and a delivery pressure of 360 bar. The compressed H2 gas is stored in a high-pressure tanks of 350 L capacity allowing, in this way, a supply through a dispenser system of two automotive's tanks of 150 L @ 350 bar in less than 30 min. This paper reports the design and the development results coming from a first test campaign. © 2017 Hydrogen Energy Publications LLC

Electrical energy storage systems are more and more investigated to increase efficiency in generation systems and to support power networks highly penetrated by renewables. Different kinds of batteries, with several features and performance are available on the market or in developing phase. CNR-ITAE is involved in a number of European and Italian research projects from one hand to develop smart energy devices, from the other hand to test and evaluating performance of existing technologies. This experience is reported in this work with the aim to highlight the key role of electrochemical batteries in the future energy scenario.

Lithium-ion batteries are increasingly used for the power network stabilization since renewable energy sources are massively exploited. Since the operating load profile has a strong impact on the degradation of lithium-ion cells, dedicated experimental tests can provide important information in this regard. Herein, a commercial high power 18,650-type LiCoO2-LiNiCoMnO2/Graphite cell was aged according to a standardized endurance test from IEC 61,427-2), which profile is formulated to simulate the primary frequency regulation service. In addition, accelerated ageing was obtained by increasing the ambient temperature to 45 °C. Then, a deep investigation was performed to assess the main degradation phenomena induced by the operating profile. For this purpose, incremental capacity (IC) and differential voltage (DV) analysis as well as electrochemical impedance spectroscopy (EIS) were performed at different state of health (SoH) of the cell. Moreover, in order to estimate the effects induced by the frequency regulation profile in comparison to the degradation phenomena caused by a typical full charge/discharge profile, an identical cell was also aged under this condition. Experimental evidences indicate that the operation under primary frequency regulation is less detrimental for the cell by capacity loss point of view, while larger internal impedance increase was observed in comparison to the typical full charge/discharge profile. Finally, a thermal acceleration coefficient was extrapolated to describe the cell capacity loss at room temperature under frequency regulation profile.

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.

Fifty-one percent of the world's population, approximately 3.5 billion people, reside in urban areas. Cities around the world emit almost 80% of global carbon dioxide as well as significant amounts of other greenhouse gases and this percentage is expected to grow further [1]. Energy use is responsible for approximately 70% of these emissions [2]. Climate change mitigation requirements, globalization of innovation networks and broadband services are the driving forces of new urban development paradigms towards cities which use technology and communication to create more efficient urban areas [3]. Pillars of the EU's overall policy are built upon the current context of climate change issues, increasing energy costs, concerns on security of energy supply and integrated sustainable urban development. The EU Smart Cities Initiative aims to improve energy efficiency and to step up the deployment of renewable energy in large cities going even further than the levels foreseen in the EU energy and climate change policy. It will bring the cities involved to the forefront of the development of the low-carbon economy [4]. Small renewable and non-renewable generators are increasingly becoming important components in the grid at distribution network levels. This creates an opportunity for network operators to balance large power plants, local small generators and demand side management systems with high flexibility, in real time. In this context fuel cells (as efficient power systems in transport), hydrogen (as a clean energy carrier), stationary and portable applications can play an important role within the European Initiative on Smart Cities [5-7]. On the other hand energy infrastructures are becoming co-dependent with information and communication technology (ICT) devices, so that all elements have to be integrated together with the aim to operate with synergy, optimizing efficiency and reducing consumptions [8].